News Article | February 21, 2017
ALBUQUERQUE, N.M.--(BUSINESS WIRE)--Optomec, a leading global supplier of production grade additive manufacturing (AM) systems for 3D Printed Metals and 3D Printed Electronics, announced today that the company will feature its recently released LENS Machine Tool Series for metal AM applications at the Laser Institute of America’s (LIA), Laser Additive Manufacturing (LAM) Conference in Houston, Texas on February 21-22. The Machine Tool Series combines Optomec industry proven LENS Print Engine technology with conventional CNC Vertical Milling platforms making metal AM technology affordable to a broader market. Three models of the LENS Machine Tool Series are available, including an industry first Hybrid Controlled Atmosphere system for processing titanium and aluminum. The remaining two LENS Machine Tool Series models include a Hybrid Open Atmosphere and an Additive-only Open Atmosphere systems for processing non-reactive metals. All three standard configurations are designed to reduce manufacturing process times and costs while enabling improved end product performance and rapid design changes. Entry level pricing for the LENS Machine Tool Series starts at under $250,000. Click here more information. For over two decades, Optomec LENS 3D Metal Printers have been used to cost-effectively repair, rework and manufacture high-performance metal components in materials such as titanium, stainless steel, and super alloys. LENS printers use the energy from a high-power laser to build up structures one layer at a time directly from powdered metals. The resulting fully functional metal structures offer excellent mechanical properties, similar to forged components for many applications. LENS 3D printers are used throughout the entire product lifecycle for applications ranging from Materials Research to Repair and Rework to Low Volume Manufacturing. For more information on LENS printers, click here. The 2017 LAM workshop will feature presentations from researchers and industry presenters on when, where, and how to use laser additive manufacturing. Attendees will learn about additive manufacturing from design, materials, modelling, and manufacturing to applications. A new session on micro/nano laser additive manufacturing will cover the latest research in this rapidly rising area of laser manufacturing. Serving the industrial, medical, research and government communities for over 45 years, LIA offers technical information, training and networking opportunities to laser users from around the globe. For more information on the workshop, click here. Optomec is a privately-held, rapidly growing supplier of Additive Manufacturing systems. Optomec patented Aerosol Jet Systems for printed electronics and LENS 3D Printers for metal components are used by industry to reduce product cost and improve performance. Together, these unique printing solutions work with the broadest spectrum of functional materials, ranging from electronic inks to structural metals and even biological matter. Optomec has more than 200 marquee customers around the world, targeting production applications in the electronics, energy, life sciences and aerospace industries. For more information about Optomec, visit optomec.com. LENS is a registered trademark of Sandia National Labs; Aerosol Jet is a registered trademark of Optomec.
News Article | October 26, 2016
Ground-breaking work on synthetic organ transplants made Paolo Macchiarini one of the most famous doctors in the world. But some of his academic research is now seen as misleading, and most of the patients who received his revolutionary treatment have died. What went wrong? In July 2011, the world was told about a sensational medical breakthrough that had taken place in Stockholm, Sweden. The Italian surgeon Paolo Macchiarini had performed the world's first synthetic organ transplant, replacing a patient's trachea, or windpipe, with a plastic tube. The operation promised to reshape organ transplantation. No longer would patients have to wait for a donor organ, only to run the risk of biological rejection. Plastic tracheas - and possibly other organs - would be produced quickly, safely, and made-to-measure for each patient. It was a story that befitted the reputation of Dr Macchiarini's workplace, the prestigious Karolinska Institute, whose professors decide each year who will receive the Nobel Prize in Medicine. But five years on, Macchiarini's headline-making work has brought KI and its sister organisation, the Karolinska University Hospital, no glory. Of the nine patients that received the treatment, in Sweden and elsewhere, seven have died. The two still alive have had their synthetic tracheas removed and replaced with a windpipe from a donor. Last week, an independent report sharply criticised the three synthetic trachea operations that took place at Karolinska University Hospital. The investigation, led by Kjell Asplund, Chairman of the Swedish Council on Medical Ethics, found that the scientific foundation for the new operation was weak, and condemned the failure to carry out risk analyses before the patients received their operations, or seek the necessary ethical approval. On Monday, a separate investigation at KI identified mistakes made when Macchiarini was recruited and when allegations of misconduct were made against him two years ago. In the picture that emerges from these reports, we see a doctor persisting with a technique that showed few signs of working and able to take extraordinary risks with his patients, and a medical institution so attached to their star doctor that they ignore mounting evidence of his poor judgement. Macchiarini arrived in Stockholm in 2010, already a leader in the field of regenerative medicine - the project of growing tissue or organs to be implanted in sick patients. Not only was Macchiarini known as a brilliant surgeon, he was handsome and impressive - able to give press conferences in several languages. At the hospital, a "bandwagon effect" emerged around his work. "Regenerative medicine" was at the cutting edge of scientific fashion, and few colleagues raised questions or objections about the basic science underlying the procedures. The patient who received that first synthetic organ transplant, in 2011, was 36-year-old Andemariam Beyene, a graduate student from Eritrea living in Iceland. After unsuccessful treatment for a rare form of cancer, he had been referred by his Icelandic doctors to the experts at Karolinska University Hospital. Macchiarini told Beyene that the revolutionary surgery was his only chance of survival and persuaded him to agree to the new procedure. The synthetic "scaffold" for Beyene's new trachea was made in a lab in London. It was seeded with stem cells taken from the patient's bone marrow, then placed in a shoe-box sized machine called a bioreactor, where it rotated in a solution designed to encourage cell growth. The idea was that these cells would divide and turn into tracheal cells. Before the operation, Macchiarini also deposited slivers of cells from the patient's nose on the scaffold. It was hoped these would grow into a lining of epithelial cells. In effect, the doctors were trying to grow a new trachea inside Beyene's body. A month after the operation, reporters from around the world were able to interview Beyene in bed. He told the BBC: "I was very scared, very scared about the operation. But it was live or die." By the end of the year, Macchiarini and his colleagues were writing in the Lancet that Beyene had an "almost normal airway" that was free of infection and growing new tissue. The publication of this sent a signal to the medical community that the miraculous-sounding project of growing and implanting synthetic transplants was a viable treatment. By this time, two more synthetic tracheas had been implanted. In the first - an operation not overseen by Macchiarini - a young British woman in a serious condition received a trachea at University College London. In the second, Macchiarini himself fitted a 30-year-old American man with a new kind of scaffold. These two patients only survived for a few months. No autopsy was performed on the American man so his exact cause of death is unknown, but we know that the British woman's synthetic trachea did not function well. "The biggest problem with the materials used at that time was lack of integration into the surrounding bodily tissue, both outside it and at the ends where you join it on to the bronchi and the larynx," says one of the surgeons, Prof Martin Birchall at UCL. "At those junctions it always seems to be loose and healing tissue can become an obstruction to breathing. "The second thing that seemed to happen was that you are putting the trachea on to a bed, which is made up of the oesophagus, the swallowing tube, and the synthetic material could press into the oesophagus. "Finally, the lining didn't seem to grow into the scaffolds either, so you are left with something chronically infected and unable to clear mucus properly." The patient was able to go home after the operation, but died two months later. Over the next three years, Macchiarini implanted six more synthetic tracheas, and four of these patients died. It is unknown whether their deaths were all related to the tracheas, or whether they were due to underlying illnesses or even unrelated events. Karolinska University Hospital stopped Macchiarini's work in November 2013, but he continued to perform the transplants as part of a clinical trial in Russia. Meanwhile, reports about the health of the first patient, Andemariam Beyene, remained positive. In a 2014 article published in the Journal of Biomedical Materials Research, Macchiarini reported that he had an "almost normal" airway a year after the operation, repeating the phrase from the Lancet article. But by the time that article appeared Beyene too had died. He had suffered repeated infections, and his trachea needed to be held open by a series of stents. His autopsy revealed the synthetic trachea had come loose. However, the questions that have dogged Paolo Macchiarini are related less to disappointing patient outcomes, and more to the decision-making around operations. Had the risk of each operation been properly assessed? Were the patients ill enough to require such drastic intervention? Did the patients understand the risks involved? Then there is a second set of questions that relate to the way Macchiarini has described the operations in academic publications. After Beyene's death, four doctors at the Karolinska Institute began to have doubts about synthetic transplants, and about Macchiarini himself. The group included Karl-Henrik Grinnemo, who had assisted Macchiarini in Beyene's organ transplant operation in 2011, and Thomas Fux, who was involved in the aftercare of Macchiarini's patients at the hospital. They alleged that Macchiarini had misrepresented the success of the operations, omitting or even fabricating data in his published articles. KI's vice chancellor at the time, Dr Anders Hamsten, called in an outside expert, Dr Bengt Gerdin, from Uppsala University Hospital, to lead an investigation. In May 2015, Gerdin reported back, concluding that by-and-large the whistleblowers were right: Macchiarini was guilty of scientific misconduct. But in August 2015 Hamsten and the KI management threw out Gerdin's report. Based on undisclosed evidence they had seen - which Gerdin had not - they reaffirmed their faith in the surgeon and extended his contract. In the end, it was not a scientist, doctor or lawyer that grounded Macchiarini's high-flying career, but a TV journalist. Bosse Lindquist followed the surgeon for months for a documentary series for the Swedish public broadcaster, SVT. Lindquist also scoured the world's media archives for footage of Macchiarini, and he was rewarded with a wealth of material. "It turned out that Macchiarini had always liked journalists and had often invited TV teams to his surgeries," Lindquist says. Some of the most striking moments of the series come from these archive rushes. For example, Lindquist uncovered footage of Andemariam Beyene undergoing bronchoscopies, the procedure in which doctors view a patient's airways with a miniature camera. The footage from the surgical camera seemed to conflict with the descriptions of the patient in Macchiarini's published articles. Instead of an "almost normal airway" the footage showed that a build-up of scar tissue was impeding the passage of air to the right lung. The clips also showed a fistula - a hole into the rest of the body - at the end of the trachea. The articles are currently the subject of yet another investigation. On Friday, the Central Ethical Review Board in Sweden ruled that a 2014 article by Macchiarini, published in the journal Nature Communications, involved research misconduct. The article described a transplant trial in rats, which, the committee ruled, was not as successful as had been implied. The Review Board will rule on the other contentious articles soon. The 2011 article in the Lancet now carries an "expression of concern". The senior editor of the Journal of Biomedical Materials Research tells the BBC that his journal will issue a similar warning soon. Macchiarini says that some mistakes were made in the preparation of the articles, but there was no intention to mislead. Lindquist agreed not to ask Macchiarini about the allegations against him until the outcome of KI's internal investigation in 2015, but eventually the two men sat down for a long and very awkward interview. The normally urbane Macchiarini becomes increasingly rattled as Lindquist presses him to answer why five human beings received plastic tracheas before any experiments checking the suitability of the scaffolds in animals were published. At first, Macchiarini says that his team conducted animal studies before 2011 at KI, but they have yet to be published. When Lindquist points out that he has found no official approvals for such research, Macchiarini changes tack, asking, "How do you know that we didn't do animal studies in Russia?" Finally the doctor admits in an irritated tone, "We didn't do any animal study that involves large animals - of course not, we didn't have the time. The material was proven, the material was studied. We used fibres that were approved by the FDA [the US Food and Drug Administration]. And now all the studies are coming." Lindquist called his documentary series The Experiments. The implication is that Macchiarini was treating humans as guinea pigs, instead of doing preliminary research on animals. When it was broadcast in Sweden in January, The Experiments caused a sensation, with about 15% of the population tuning in to watch this complicated medical story unfold. Anders Hamsten stood down as vice-chancellor of KI, as did Urban Lendahl, the general secretary of the Nobel Committee. Macchiarini was fired, and half a dozen inquiries launched. Last week, the Swedish government sacked all members of KI's board who remained in position. Bo Risberg, professor emeritus of surgery at the University of Gothenberg and a former chairman of the Swedish Ethics Council, has called for the Nobel Prize to be suspended for two years as an "apology" to Macchiarini's patients and their families. He has said the events amount to the biggest research scandal Sweden has experienced in modern times. "It is very strange that it should take a TV programme to make this public," Risberg said earlier this year. "Everything was swept under the carpet." The failure to do pre-clinical tests on animals, he said, was "the worst crime you can commit." In May, Macchiarini discussed his decision to operate on Andemariam Beyene on SVT. "We had a human being that we wanted to save," he said, "And in these circumstances what would you do? Do you just leave him dying at that young age? I don't think it's correct." This touches on the blurred distinction between trying out a new treatment as part of a clinical research programme, and innovating in an emergency to save or prolong a life. The Swedish government is investigating whether guidelines differentiating the different scenarios need to be clearer. Last week's report into the synthetic transplant operations that took place at Karolinska University Hospital concluded that while there was a compassionate element to the operations, they still involved clinical research. Therefore, Macchiarini should have sought approval from an ethical review board. "It is unlikely that the project would have been approved," the report notes. Moreover, it states that there was no immediate threat to life for Macchiarini's three patients before the operations. In an email to the BBC, Macchiarini says he accepts the findings of the report, but he adds that it was the responsibility of the hospital administration to apply for ethical permissions. "I would welcome international discussion and clarification of the ethical processes to be undertaken in such difficult circumstances as these - where experimental treatments are involved," he writes. "It is clearly a difficult area for clinicians and researchers to be involved in, and yet vitally important that new treatments are developed and tried…" Macchiarini says that the report highlights "the very great amount of pre-clinical research that has been done into synthetic tracheal scaffolds", though he concedes that Andemariam Beyene was the recipient of an untested procedure. "I would like to add that the welfare of patients has always been my driving concern. Although there may be criticisms of decision-making processes and administrative processes, and these may have had tragic consequences that with hindsight are deeply regrettable, everyone involved in the clinical care of these patients felt that they were doing their very best for these individuals. That should never be overlooked." When asked about the transplants, Macchiarini has often mentioned that he was not the only one responsible for the decision to operate, but discussed his patients in multidisciplinary conferences. "There were 30 or more professionals involved in the decision-making process," he told SVT, "and then even in the inter-operative and postoperative care of the patient." Yet one of the most critical issues was not discussed in the meetings - whether there was enough scientific evidence to support the procedure. Some experts claim that the entire project of growing human organs, although appealing to popular science journalists, is flawed. Dr Pierre Delaere, a professor of respiratory surgery at KU Leuven in Belgium, has said that it is impossible for surgeons to establish a new blood supply to a trachea - donated or synthetic. Delaere has called Macchiarini's method "one of the biggest lies in medical history, because you are doing something that is impossible from a theoretical point of view". The use of bone marrow cells has also come under scrutiny. "There is absolutely no evidence that these cells differentiate into mucosal epithelia (lining tissue) or blood vessels," says Leonid Schneider, a science blogger who trained as a molecular cell biologist and used to work in stem cell research. "This claim that bone marrow cells can create any kind of tissue is based on old papers, which are long discredited by science, and every single stem cell scientist will tell you they cannot do it." He adds: "Everybody switched off their brain. The stem cell scientists switched off their brains to the science, and the clinicians switched off their brains to the use of the plastic, which couldn't even be sutured into patients, and everybody went along with it." Macchiarini maintains, in his email to the BBC, that "there is no doubt that it is a viable technology". He adds that he is continuing his work with biological scaffolds, expanding his focus from the trachea to other organs. A public prosecutor in Stockholm is currently gathering as much information as she can about the three operations that took place at Karolinska University Hospital, and says she will decide next year whether to press charges equivalent to manslaughter and grievous bodily harm. The hospital is already the subject of two police investigations, triggered last year by complaints from government healthcare agencies. Despite his many appearances in the media, the man at the centre of the scandal remains something of an enigma. By chance, the transmission of The Experiments in Sweden coincided with the publication of an article in Vanity Fair in which it was alleged that Macchiarini had had a relationship with a television producer who was making a film about him. The story alleged that the producer had ordered her wedding dress before learning that Macchiarini was married with children. Macchiarini has declined to comment on the story. "He's an exceptional person for sure, and he has this faculty for stretching the truth just the right amount," says Bosse Lindquist. "But in order to be able to seduce the medical community you need to have a whole host of professors who would like to be seduced and who would like to believe that the Nobel prize is very close, or you can make lots of patent money, for example, or corporate money. "I think he has an acute ability to suss out the faults and cracks in the system where he could manoeuvre." Additional reporting from Christine Westerhaus. Listen to Christine Westerhaus's report on the Macchiarini scandal, which was originally broadcast in February 2016 on the BBC World Service. The Experiments will be broadcast in the UK in BBC4's Storyville strand in October. Subscribe to the BBC News Magazine's email newsletter to get articles sent to your inbox.
News Article | February 20, 2017
The coiled thread on a screw is among the 'chiral' structures' whose mirror image is different from the original. When reduced to the nanometer scale, these structures could have an important role in nanosensor technology. However, making a screw out of a straight wire is no small task, even in the macroscopic world. Making it on the nanoscale has previously used bottom-up methods that grow or assemble the structure in a gas or solution. But such approaches can be complicated, slow and expensive. Jun Wei from A*STAR's Singapore Institute of Manufacturing Technology and co-workers from the A*STAR Institute of Materials Research and Engineering, Nanyang Technological University and Nanjing Tech University in China, developed a simpler method that uses etching techniques to convert a straight nanowire into a screw. The team created 10-micrometer silver nanowires, 80 nanometers in diameter and with five sides. The structures were attached to a silicon substrate and then placed into a solution of silver nitride in ethylene glycol at 80 degrees Celsius for 20 minutes. The sample was then rinsed clean and the process repeated five times. When the resultant wires were imaged using a scanning transmission electron microscope the team observed smooth ridges and grooves reminiscent of screw threads. Interestingly, such a structure was not evident when a single-step etch was used. Etching usually works along specific crystallographic directions, leading to symmetric structures, so the team wanted to know how equivalent crystal facets could be etched in an anisotropic way. They propose that this unusual etching mode might begin with the creation of pits at the boundaries between the five crystallographic regions that make up the pentagonal nanowire. These pits merge at an angle, driven by the propensity to minimize the surface energy, and thus create ridges and grooves that spiral around the nanowire. "This selective etching is driven by a faster etching rate at some defect locations on the silver nanowire," says Wei. "Thus, we can convert a regular structure into non-symmetrical one." Such chiral nanostructures have a much larger surface area than a straight nanowire of similar size. This makes them potentially useful for sensing applications. "We next hope to use the nanoscrews in the fabrication of sensors and transparent conductors," says Wei. The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Manufacturing Technology and the Institute of Materials Research and Engineering. More information: Rachel Lee Siew Tan et al. Nanoscrews: Asymmetrical Etching of Silver Nanowires, Journal of the American Chemical Society (2016). DOI: 10.1021/jacs.6b06250
News Article | March 9, 2016
Most people would be happy to get rid of excess body fat. Even better: Trade the spare tire for something useful — say, better-functioning knees or hips, or a fix for an ailing heart or a broken bone. The idea is not far-fetched, some scientists say. Researchers worldwide are repurposing discarded fat to repair body parts damaged by injury, disease or age. Recent studies in lab animals and humans show that the much-maligned material can be a source of cells useful for treating a wide range of ills. At the University of Pittsburgh, bioengineer Rocky Tuan and colleagues extract buckets full of yellow fat from volunteers’ bellies and thighs and turn the liposuctioned material into tissue that resembles shock-absorbing cartilage. If the cartilage works as well in people as it has in animals, Tuan’s approach might someday offer a kind of self-repair for osteoarthritis, the painful degeneration of cartilage in the joints. He’s also using fat cells to grow replacement parts for the tendons and ligaments that support the joints. Foremost among fat’s virtues is its richness of stem cells, which have the ability to divide and grow into a wide variety of tissue types. Fat stem cells — also known as adipose-derived stem cells — can be coerced to grow into bone, cartilage, muscle tissue or, of course, more fat. Cells from fat are being tested to mend tissues found in damaged joints, hearts and muscle, and to regrow bone and heal wounds. The stem cells in fat share the medical-worthy spotlight with a few other cells. Along with the fat-filled adipocytes that store energy, fat tissue has its own blood supply and supporting connective tissue, called stroma. The stroma contains blood cells, immune cells, endothelial cells that line the inner surface of blood vessels and pericytes, which line the outer surface. These other fat-derived cells are proving to have therapeutic value as well. Plastic surgeon J. Peter Rubin, also at Pitt, says that the multitalented cells found in fat could prove to be the ultimate body repair kit, providing replacement tissue or inspiring repair of body parts that can’t mend themselves. Much of the research — more than a decade of studies — has been in lab animals, but a few applications are being tested in human volunteers. Current clinical studies under way aim to provide replacement tissue to treat chronic wounds and diabetic sores, or conditions such as Parkinson’s disease, multiple sclerosis, chronic obstructive pulmonary disease and type 1 diabetes. Most clinical studies use the simplest approach: Harvest cells from a patient, then inject them in a single procedure. In more complex approaches still in lab and animal testing, various cells in fat are extracted and manipulated to create custom treatments for worn-out or damaged tissues or to generate blood flow after a heart attack or replace bone in large fractures. Questions remain, however, about how the cells do their regenerative magic. Scientists and regulators still have plenty to figure out, such as what cell characteristics work best for each application. Stem cells can develop into various cell types, which makes them the focus of studies that aim to replace cells that fail because of disease, accident or age. Stem cells taken from embryos are more versatile than other types of stem cells, but their use is controversial. For that reason, researchers have studied stem cells from sources other than embryos, including bone marrow, muscle and blood. Fat tissue comes from the same embryonic tissue as bone marrow, a traditional stem cell source, so scientists reasoned that fat might contain similar cells. In 2002, UCLA researchers discovered stem cells in human fat. They were surprised to find vast quantities. Stem cells make up 2 to 10 percent of fat tissue. A cubic centimeter of liposuctioned fat (about one-fifth of a teaspoon) yields 100 times as many stem cells as does the same amount of bone marrow, Tuan says. And fat cells are easy to harvest — much easier than bone marrow. One pound of fat removed from a patient’s abdomen can yield up to 200 million stem cells, a more than adequate supply for treatments. Why fat produces so many stem cells isn’t clear, but Rubin points out that fat tissue serves several important functions. In addition to storing and releasing energy, it helps insulate and protect the body’s internal organs. “Like most tissues in the body, fat has a reservoir of stem cells to replenish cells as they die off or create new cells in response to growth or the need for more cells,” he says. Fat produces so many stem cells, in fact, that for some applications — such as tissue-replacement or “fat grafting” — there’s no need to grow more of them in the lab. Once harvested, liposuctioned material is treated with enzymes to remove cells from the surrounding tissue, then put into a centrifuge to separate the stem cells from other cell types. In about an hour, the stem cells are ready to be injected back into the patient to plump skin or round out fat tissue lost to injury or disease. Rubin has used this method to treat patients who have lost tissue during breast cancer surgery or have been injured in war. His lab is conducting a clinical trial on the use of fat stem cells to plump up tissue at the site of an amputation to improve the comfort and fit of a prosthetic arm or leg or to make it easier to tolerate sitting for long periods in a wheelchair. Already, Rubin’s team has treated five military patients, extracting fat from each patient’s abdomen and injecting the stem cells back into the patient at the injury site. He and other scientists think that the fat stem cells remodel tissue by releasing growth factors and communicating with surrounding cells in their new location — sending and receiving signals through chemical cues. As a result, the stem cells enhance the growth of new fat tissue and boost blood supply to surrounding tissue. Over a period of several weeks, the cells he injects form a mound of fat tissue, allowing patients to fit a prosthesis or sit without pain. So far, all of the patients have benefited from the stem cell injections, he says, though his group is still working on how much to inject for each patient. Fat is an organ with a complex assembly of cells. In addition to fat cells, or adipocytes, and blood vessels, fat tissue contains stem cells, pericytes (cells that stabilize blood vessel walls), pre-adipocytes (precursors to fat cells), macrophages (immune cells) and endothelial cells, which form the inner lining of blood vessels. Other applications require manipulating cells in the lab, placing fat stem cells in a specific environment — and sometimes putting mechanical pressure on them — to direct the cells to transform into certain cell types. Tuan’s group at Pitt places fat stem cells on scaffolds that help guide the growth of the cells, developing treatments to regenerate anterior cruciate ligament tissue or to repair rotator cuff injuries and Achilles tendon ruptures. Injury to ligaments and tendons is common, especially among athletes, but tears or worn-down areas generally don’t heal completely by themselves. Efforts to create substitute tissues have largely failed, Tuan says, because re-creating the structure of a tendon or ligament remains a challenge. Tendons are the cables that connect muscle to bone, allowing arms to rotate at the shoulder, knees to bend or fists to clench. Cells in tendons, called tenocytes, line up along long fibers of collagen, creating molecular bridges that reach across and intertwine with collagen cables to help give them strength and flexibility. This structure allows tendons to be stretched up to 15 or 20 percent beyond their original length and snap back into shape. Tuan’s group has discovered a trick for turning fat stem cells into tenocytes that grow in the same organized way. In 2013, the researchers outlined the method in Biomaterials. To replicate the structure of natural tissues, the scientists created scaffolds of biodegradable nano-sized fibers. Fat cells were then combined with bovine collagen and placed, or seeded, into the scaffold. The tiny fibers interacted with the stem cells, sending and receiving instructions that guided the stem cells’ growth. Over seven days, as the stem cells differentiated into tenocytes, the scientists applied mechanical force on the ends of the scaffold — pulling the structure to keep the cells under tension just like a natural tendon would do during motion. By tugging on fat stem cells, Tuan says, the group can create replacement tendons that are strong, stiff and resilient, like natural human tendons. Tuan’s group is also exploring 3-D printing to create artificial cartilage from fat stem cells. Cartilage is a flexible tissue that serves as padding between bones, allowing knees, fingers, hips and shoulders to move freely. When cartilage wears down, the result is osteoarthritis, a painful condition that affects one in four people, often those over age 65. Once cartilage is damaged, it continues to deteriorate, forming what Tuan calls “potholes.” Over time, the potholes grow, eventually reaching the bone. The standard solution is a joint replacement. In the United States, more than 1 million people get knee or hip replacements each year. Tuan calls the process “rebuilding the road.” The invasive procedure requires surgically replacing the joint with plastic and metal parts that generally last 10 to 15 years. Because an increasing number of people get new joints in their 40s or 50s, many require more than one round of surgery. “But there’s a limit to the number of times you can do that,” he says. Tuan’s 3-D printing method builds thin layers of fat stem cells into a custom-sized scaffold to create new cartilage in the size and shape needed. The “ink” is made of fat stem cells plus gelatin, which consists of proteins found in living tissue. The scientists chemically modify the gelatin so that the ink remains fluid during printing. Once printed, the material is irradiated with light so that enzymes in the mixture form bonds, cross-linking to create stiffer, cartilage-like material. The procedure has been used to create cartilage implants for rabbits and goats. Animals that once hobbled were able to hop, trot and otherwise move about, according to a report last August in Frontiers in Bioengineering and Biotechnology. “Because the engineered cartilage is a living tissue … unlike a metal or polymer implant, it is expected to continue to grow into its natural shape and function once it is implanted into the joint,” Tuan says. “No replacement is therefore necessary.” Still, it’s not the ideal solution, Tuan admits. “The problem is that’s not how tissues are formed,” he says. “Tissues form when cells migrate to a place, make themselves at home and build their own support structure, or matrix.” His group is now devising ways to allow fat stem cells to set up their home right at the site of the pothole. The vision is to create a minimally invasive procedure, giving doctors a tool they can thread through a catheter to print the fat-derived stem cell cartilage at the site of the damage, inside the joint. Fat stem cells could then settle in and multiply directly in the joint. Additional arthroscopic instruments, also under development in Tuan’s lab, will allow physicians to guide the injection and smooth out newly printed cartilage to create a perfect fit that closely resembles the real thing. So far, each step in the new approach has been developed. The next step is to tie all the pieces together in animal studies. The body does a better job of healing broken bone than healing cartilage. But if the fracture is large or a significant amount of bone is lost, the bone may not heal. In such cases, surgeons can take bone from another part of the patient’s body, or use bone from a cadaver, to fill in the gap. Biomedical engineer Warren Grayson of Johns Hopkins University says more than 1 million bone replacement procedures are performed each year in the United States, often after accidents or tumor removal. The surgery is invasive and carries risks of rejection, infection and lingering pain. A better option, Grayson says, is to help patients grow bone from their own fat cells. Because the bone-growing material comes from the patient’s body, the grafts are less likely to get rejected than cells from donor tissue. What’s more, the bone may later grow with the patient, potentially eliminating the need for multiple surgeries in children who receive grafts but still have growing to do. Since 2010, Grayson’s team has been growing bone from liposuctioned fat and successfully implanting the bone in animals. Stem cells taken from fat are placed in a bioreactor, an incubator--like device that nourishes cells as they grow on a scaffold for five weeks. Added nutrients and growth factors help the cells transform into bone cells. Already, fat stem cells have been used in a few trials to help regenerate bone in people. In 2004, German doctors successfully used stem cells collected from a 7-year-old’s fat, along with other cells, to repair damage to her skull. Five years later, scientists at Cincinnati Children’s Hospital Medical Center seeded a bone graft with fat stem cells to replace a teen’s missing facial bones. In the case of the teen, fat stem cells were injected onto a scaffold from donor bone. But such bone grafts require multiple surgeries and don’t come with a ready blood supply to nourish the new bone as it grows. Grayson’s group aims to make the repair process easier on the patient. He and his team are growing fully functioning bone — with its own blood supply — from fat. Each graft can be custom-designed, using 3-D modeling and printing, to fit precisely where needed. His team is experimenting with different formulas — and two different cell types from fat — to find the best ways to form all the cell types needed. More recently, his group tested fat-derived stem cells against bone marrow cells in creating new bone. The fat stem cells outperformed the bone marrow stem cells. The findings, published in the September 2015 Stem Cells, show that in the presence of specific growth factors over a period of weeks, fat stem cells produced more calcium and bone mineral deposits per cell than did the bone marrow stem cells. The current challenge is to produce tissue that has its own system of blood vessels to supply nutrients needed for the new bone to grow. In the Journal of Biomedical Materials Research Part A in 2014, Grayson’s group outlined a method for printing bone grafts with internal pore structures that would allow blood vessels to grow through the graft while maintaining the structure of the scaffold. The team is now investigating ways to help spur such growth by seeding the structure with endothelial cells or blood-vessel forming cells from fat. Endothelial cells and other cells in fat are the lifeblood of efforts to develop a patch that can be applied to damaged heart tissue following a heart attack. Stuart Williams, a cardiologist at the University of Louisville in Kentucky, is creating a cell-infused patch seeded with a mixture of smooth muscle cells, endothelial cells and blood cells, all obtained from fat tissue. “This fat tissue contains a huge number of blood vessel–forming cells,” Williams says. The idea for the patch, outlined in 2013 in Stem Cells Translational Medicine, is to harvest fat from a patient, pull out the vessel-forming cells and seed the cells onto a biomaterial that can be immediately implanted. The whole process, from start to finish, will take about an hour. The fat-cell patch works particularly well to promote healing in very small blood vessels, Williams says, a feature that may be especially beneficial for women, who often have more problems with their small blood vessels and fewer problems with the large ones. Rats treated with a patch seeded with endothelial cells from fat tissue two weeks after a heart attack (MI SVF) show more new blood vessels (green) in the damaged area of the heart, compared with untreated rats (MI) and rats treated with an unseeded patch (MI Vicryl). Four weeks after treatment, the MI SVF rats had better heart function and less tissue damage. Total vessel density (vessels per square millimeter) was determined through staining methods. “The interesting thing is, there’s really no stem-ness to these cells at this point,” Williams says. “They don’t have to differentiate. All they have to do is reconnect with each other to form these new blood vessels.” The patches could be created in the operating room during surgical bypass, he says. Such patches might also be applied to other areas of the body, such as legs, hands or feet, where patients have limited blood flow, Williams says. In wounds that aren’t healing well, cells could be injected directly into the area to promote blood flow and healing. While Williams has shown his technology works in animals, he hasn’t yet tested it on people. Getting the federal go-ahead to pursue studies in humans remains a challenge for the heart patch and many other new applications of fat cells. Current guidelines issued by the U.S. Food and Drug Administration allow trials for treatments in which cells are harvested and injected back into the same patient in a single surgery. But the FDA, and regulatory agencies worldwide, are wrangling with questions on how to test and assess new types of therapies in which cells are grown on scaffolds or manipulated in the lab. Questions remain, for example, on how to best handle cells in the lab to ensure safety and purity of a product, and how to package and transport products once they are made. Fat stem cells, for example, may change or dedifferentiate when growing in a lab dish, sitting on a warehouse shelf or even following injection into the body, Tuan says. Later this year, the FDA plans to hold a public hearing to solicit comments from scientists, manufacturers and others on how to proceed. Meanwhile, scientists in the field agree that the potential for fat to do good is here. “Fat may actually be a natural storehouse of regenerative cells,” Williams says. “When applied correctly, these cells may someday help repair bodies on an as-needed basis.” This story appears in the March 19, 2016, issue with the headline, "Fat as a fixer."
News Article | August 22, 2016
Undergraduate interns selected for this year’s Summer Scholars program come from Montana to Florida and Puerto Rico and have a diverse set of scientific accomplishments and personal interests. “I’m excited to use this internship as an opportunity to step out of my comfort zone. Interning at MIT will give me a chance to adapt to a new environment, cope with new subject matter, and meet new people,” says Justin Cheng, a Rutgers University junior majoring in materials science and engineering. He’d like to tackle a project related to electronic or photonic materials. “My fun fact is that I received a black belt in karate (Okinawan Shuri-Ryu) when I was in high school,” Florida State University junior Alexandra T. Barth says. She is pursuing a double major in chemistry and physical science and hopes to conduct research in the area of materials chemistry and pursue a doctorate in the field. Cheng and Barth are two of 11 outstanding undergraduates who will conduct graduate level research at MIT in Cambridge, Massachusetts, from June 7 through Aug. 6. The group’s interests range from condensed matter physics and materials science to biotechnology and bioinformatics. “MIT is very fortunate to have this very talented group of students with us, and the faculty all hope that one of them will work with their group,” says Carl V. Thompson, director of the Materials Processing Center and Stavros Salapatas Professor of Materials Science and Engineering at MIT. Center for Materials Science and Engineering Director Michael Rubner adds, "This is an amazingly successful program that will no doubt continue far into the future." Interns will have the opportunity to choose from a multitude of on-campus research opportunities. The scholars will hear faculty, postdocs, and graduate students outline their summer projects in the morning and then tour their labs in the afternoon on Wednesday, June 8, through Friday, June 10. The program is sponsored jointly by the Materials Processing Center and the Center for Materials Science and Engineering at MIT. Suna Njie, a junior at historically black Alabama State University, has lived on three continents and visited seven countries. “Traveling and living in different areas of the world at an early age has opened my eyes to many traditions and lifestyles,” she says. “It is my ultimate dream to become a research professional in the biochemistry field. This will allow me to have an immense impact on the scientific and general community.” “I’m excited to learn more about materials science and engineering and other scientific disciplines through talking with faculty and students alike,” says University of Massachusetts at Amherst junior chemical engineering major Ashley Kaiser. “I hope to research nanostructured materials, especially 2-D materials, and their role in energy and electronics applications.” Kaiser is a gymnast who is challenging herself by learning the still rings, an event that only appears in men’s gymnastics because it requires tremendous upper body strength. “Fascinated with this physical challenge, I worked hard to learn the basics. Today, I still seek advice for this event from my gymnastics coaches and male gymnasts, who always seem surprised to see a girl up on the rings,” she says. Physics major Grant Smith won the Bert Elsbach Honors Scholarship in Physics at Pennsylvania State University last year for exceptional achievement. He has minors in both mathematics and electronic and photonic materials. “I am exposed to coursework dealing with [the] most fundamental natural behaviors punctuated by coursework focused on the application of these concepts to engineering problems,” Smith says. His work under Professor Nitin Samarth at Penn State focuses on topological insulators. He hopes his lab experience at MIT will provide broader experience in the electronic properties of materials. Michael Concepción Santana, a junior at Polytechnic University in San Juan, Puerto Rico, is interested in the pharmaceutical industry, specifically in synthesizing ligands that can deliver drugs to attack disease cells and cure illnesses. He has participated in several research projects including experimental green synthesis and characterization of Podophyllotoxin, a plant-derived organic polymer and potential anti-cancer agent, under Ajay Kumar at Metropolitan University in San Juan. He participated in the Air Force Junior ROTC program during high school and won three military-themed scholarships. “Having that experience during high school developed in me the leadership, character and integrity that is necessary in the field of science and engineering,” Concepción says. Johns Hopkins University junior Michael Porter hopes to pursue research in polymeric biomaterials and drug delivery. “Through this program, I hope to refine and confirm my research interests for graduate school and for a career in research,” he says. Porter, whose father is white and mother is Japanese, recalls difficulty communicating as he grew up in Ohio trying to learn two languages and attending the local Japanese school. “I still find that communication is as fundamental as ever in building and maintaining meaningful relationships,” he says. He previously participated in a summer research internship at UMass Amherst, where he studied the bacterial collection potential of cellulose fiber mats, and how changing their surface charge and topography could impact their effectiveness. As the daughter of a U.S. military employee, Erica Eggleton lived in Germany for six years, attending an American school on base from 7th to 12th grade. “These were my forming years, so I believe that living in Germany helped shape me into the person I grew up to become,” she says. Eggleton, a chemical engineering major at Montana State University, plays mellophone in the university’s Spirit of the West Marching Band as well as French horn in the brass quintet. She is interested in fuel cell research and is a co-author of an International Journal of Hydrogen Energy paper analyzing gas-liquid flow mechanisms in proton exchange membrane fuel cells. “I live in Montana, where the mountains are my backyard and I am surrounded by outdoor activities. Seeing the beauty of our world everyday motivates me to help conserve it for generations to come,” Eggleton says. She hopes her summer internship will offer the opportunity to do work related to renewable energy or sustainable materials. University of Puerto Rico at Mayaguez sophomore Ashley Del Valle Morales is looking forward to exchanging new and exciting concepts about energy and sustainability with diverse scholars, as well taking advantage of the opportunity to acquire and enhance her research skills. “By learning about and implementing new materials, we can minimize pollution, increase the use of recycled and renewable materials and have recycling-friendly designs. My passion lies in creating and generating energy in an efficient, cost-effective and sustainable manner,” she says. Del Valle says she learned to do crochet when she was eight years old, and it has become one of her passions ever since. “All my family says I am a young woman with the soul of a grandmother, because in every free time I get I do crochet,” she says. Vanderbilt University sophomore Victoria Yao also is interested in exploring new ways to affect environmental change and sustainability. She hopes to conduct research from the perspective of her major, chemical engineering. Yao tutors elementary school students in math through the Pencil Projects club and mentors nearby high school Key Clubs through Circle K. “I enjoyed building a relationship with these kids, and I hope to continue this in the future,” she says. Jennifer Coulter, a Rutgers junior physics major, serves as the outreach coordinator for the Society of Physics Students and as a program co-coordinator and frequent mentor for the Douglass Project for Women in STEM. “Through both of these appointments, I feel I have been able to use science education to significantly better the careers of the future researchers of Rutgers,” she says. Coulter hopes to participate in condensed matter physics at MIT during her internship. “I have confidence that this program will allow me to develop my skills in solid state physics and hopefully help me determine my direction as I apply to graduate school,” she says. At Rutgers, Coulter has participated in research under materials science and engineering Professor Dunbar Birnie that led to several publications on solar cell material growth. The Materials Processing Center and Center for Materials Science and Engineering sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from the National Science Foundation's Materials Research Science and Engineering Centers program (grant number DMR-14-19807).
News Article | January 28, 2016
« DOE announces SBIR/STTR FY16 Phase 1 Release 1 awards; four for fuel cell membrane development | Main | Intelligent Energy signs LOI with drone manufacturer to develop fuel cell drones » A team from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory has developed a new practical, high-energy-capacity lithium-ion battery anode out of silicon by encapsulating Si microparticles (∼1–3 µm) using conformally synthesized cages of multilayered graphene. The graphene cage acts as a mechanically strong and flexible buffer during deep cycling, allowing the silicon microparticles to expand and fracture within the cage while retaining electrical connectivity on both the particle and electrode level. The chemically inert graphene cage also forms a stable solid electrolyte interface, minimizing irreversible consumption of lithium ions and rapidly increasing the Coulombic efficiency in the early cycles. In a paper published in Nature Energy, the team, led by Professor Yi Cui, reported that even in a full-cell electrochemical test, for which the requirements of stable cycling are stringent, stable cycling (100 cycles; 90% capacity retention) is achieved with the graphene-caged Si microparticles. Si is an attractive anode material for next-generation lithium-ion batteries, offering ten times the theoretical capacity of commercial graphite anodes. Cui and his collaborators have been working for years on different approaches to resolving the practical challenges preventing the commercialization of silicon-based anodes. These include large volume expansion of silicon (∼300%) during battery operation, which causes mechanical fracture; loss of inter-particle electrical contact; and repeated chemical side reactions with the electrolyte. The quest first led to anodes made of silicon nanowires or nanoparticles, which are so small that they are much less likely to break apart. The team came up with a variety of ways to confine and protect silicon nanoparticles, from structures that resemble pomegranates to coatings made of self-healing polymers or conductive polymer hydrogels like those used in soft contact lenses. Despite these advances in producing Si anodes, critical challenges remained: heavy reliance on expensive nanostructured Si for stable cycling and the poor first- and later-cycle Coulombic efficiencies. For the graphene cages to work, they have to fit the silicon particles exactly. The scientists accomplished this in a series of steps: First they coated silicon particles with nickel, which can be applied in just the right thickness. Then they grew layers of graphene on top of the nickel; the nickel acts as a catalyst to promote graphene growth. Finally they etched the nickel away, leaving just enough space within the graphene cage for the silicon particle to expand. This new method allows us to use much larger silicon particles that are one to three microns, or millionths of a meter, in diameter, which are cheap and widely available. In fact, the particles we used are very similar to the waste created by milling silicon ingots to make semiconductor chips; they’re like bits of sawdust of all shapes and sizes. Particles this big have never performed well in battery anodes before, so this is a very exciting new achievement, and we think it offers a practical solution. Now the team will work on fine-tuning the process and on producing caged silicon particles in large enough quantities to build commercial-scale batteries for testing. The research was carried out by SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC, and funded by the Battery Materials Research program of the DOE’s Vehicle Technologies Office.
News Article | November 2, 2016
Currently, computers use binary logic, in which each binary unit - or bit - is in one of two states: 1 or 0. Quantum computing makes use of superposition and entanglement, allowing the creation of quantum bits - or qubits - which can have a vast number of possible states. Quantum computing has the potential to significantly increase computing power and speed. A number of options have been explored for creating quantum computing systems, including the use of diamonds that have "nitrogen-vacancy" centers. That's where this research comes in. Normally, diamond has a very specific crystalline structure, consisting of repeated diamond tetrahedrons, or cubes. Each cube contains five carbon atoms. The NC State research team has developed a new technique for creating diamond tetrahedrons that have two carbon atoms; one vacancy, where an atom is missing; one carbon-13 atom (a stable carbon isotope that has six protons and seven neutrons); and one nitrogen atom. This is called the NV center. Each NV-doped nanodiamond contains thousands of atoms, but has only one NV center; the remainder of the tetrahedrons in the nanodiamond are made solely of carbon. It's an atomically small distinction, but it makes a big difference. "That little dot, the NV center, turns the nanodiamond into a qubit," says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and lead author of a paper describing the work. "Each NV center has two transitions: NV0 and NV-. We can go back and forth between these two states using electric current or laser. These nanodiamonds could serve as the basic building blocks of a quantum computer." To create these NV-doped nanodiamonds, the researchers start with a substrate, such as such as sapphire, glass or a plastic polymer. The substrate is then coated with amorphous carbon - elemental carbon that, unlike graphite or diamond, does not have a regular, well-defined crystalline structure. While depositing the film of amorphous carbon, the researchers bombard it with nitrogen ions and carbon-13 ions. The carbon is then hit with a laser pulse that raises the temperature of the carbon to approximately 4,000 Kelvin (or around 3,727 degrees Celsius) and is then rapidly quenched. The operation is completed within a millionth of a second and takes place at one atmosphere - the same pressure as the surrounding air. By using different substrates and changing the duration of the laser pulse, the researchers can control how quickly the carbon cools, which allows them to create the nanodiamond structures. "Our approach reduces impurities; controls the size of the NV-doped nanodiamond; allows us to place the nanodiamonds with a fair amount of precision; and directly incorporates carbon-13 into the material, which is necessary for creating the entanglement required in quantum computing," Narayan says. "All of the nanodiamonds are exactly aligned through the paradigm of domain matching epitaxy, which is a significant advance over existing techniques for creating NV-doped nanodiamonds." "The new technique not only offers unprecedented control and uniformity in the NV-doped nanodiamonds, it is also less expensive than existing techniques," Narayan says. "Hopefully, this will enable significant advances in the field of quantum computing." The researchers are currently talking with government and private sector groups about how to move forward. One area of interest is to develop a means of creating self-assembling systems that incorporate entangled NV-doped nanodiamonds for quantum computing. The paper, "Novel synthesis and properties of pure and NV-doped nanodiamonds and other nanostructures," is published in the journal Materials Research Letters. Explore further: Electron 'spin control' of levitated nanodiamonds could bring advances in sensors, quantum information processing More information: Jagdish Narayan et al, Novel synthesis and properties of pure and NV-doped nanodiamonds and other nanostructures, Materials Research Letters (2016). DOI: 10.1080/21663831.2016.1249805
News Article | November 2, 2016
Researchers at North Carolina State University have developed a new technique for creating NV-doped single-crystal nanodiamonds, only four to eight nanometers wide, which could serve as components in room-temperature quantum computing technologies. These doped nanodiamonds also hold promise for use in single-photon sensors and nontoxic, fluorescent biomarkers. Currently, computers use binary logic, in which each binary unit - or bit - is in one of two states: 1 or 0. Quantum computing makes use of superposition and entanglement, allowing the creation of quantum bits - or qubits - which can have a vast number of possible states. Quantum computing has the potential to significantly increase computing power and speed. A number of options have been explored for creating quantum computing systems, including the use of diamonds that have "nitrogen-vacancy" centers. That's where this research comes in. Normally, diamond has a very specific crystalline structure, consisting of repeated diamond tetrahedrons, or cubes. Each cube contains five carbon atoms. The NC State research team has developed a new technique for creating diamond tetrahedrons that have two carbon atoms; one vacancy, where an atom is missing; one carbon-13 atom (a stable carbon isotope that has six protons and seven neutrons); and one nitrogen atom. This is called the NV center. Each NV-doped nanodiamond contains thousands of atoms, but has only one NV center; the remainder of the tetrahedrons in the nanodiamond are made solely of carbon. It's an atomically small distinction, but it makes a big difference. "That little dot, the NV center, turns the nanodiamond into a qubit," says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and lead author of a paper describing the work. "Each NV center has two transitions: NV0 and NV-. We can go back and forth between these two states using electric current or laser. These nanodiamonds could serve as the basic building blocks of a quantum computer." To create these NV-doped nanodiamonds, the researchers start with a substrate, such as such as sapphire, glass or a plastic polymer. The substrate is then coated with amorphous carbon - elemental carbon that, unlike graphite or diamond, does not have a regular, well-defined crystalline structure. While depositing the film of amorphous carbon, the researchers bombard it with nitrogen ions and carbon-13 ions. The carbon is then hit with a laser pulse that raises the temperature of the carbon to approximately 4,000 Kelvin (or around 3,727 degrees Celsius) and is then rapidly quenched. The operation is completed within a millionth of a second and takes place at one atmosphere - the same pressure as the surrounding air. By using different substrates and changing the duration of the laser pulse, the researchers can control how quickly the carbon cools, which allows them to create the nanodiamond structures. "Our approach reduces impurities; controls the size of the NV-doped nanodiamond; allows us to place the nanodiamonds with a fair amount of precision; and directly incorporates carbon-13 into the material, which is necessary for creating the entanglement required in quantum computing," Narayan says. "All of the nanodiamonds are exactly aligned through the paradigm of domain matching epitaxy, which is a significant advance over existing techniques for creating NV-doped nanodiamonds." "The new technique not only offers unprecedented control and uniformity in the NV-doped nanodiamonds, it is also less expensive than existing techniques," Narayan says. "Hopefully, this will enable significant advances in the field of quantum computing." The researchers are currently talking with government and private sector groups about how to move forward. One area of interest is to develop a means of creating self-assembling systems that incorporate entangled NV-doped nanodiamonds for quantum computing. The paper, "Novel synthesis and properties of pure and NV-doped nanodiamonds and other nanostructures," is published in the journal Materials Research Letters. The paper was co-authored by Anagh Bhaumik, a Ph.D. student at NC State. The work was supported by the U.S. Army Research Office under grant W911NF-12-R-0012-03.
News Article | September 9, 2016
Ordered patterns of gold nanoparticles on a silicon base can be stimulated to produce collective electron waves known as plasmons that absorb only certain narrow bands of light, making them promising for a wide range of arrays and display technologies in medicine, industry, and science. Materials Processing Center (MPC)-Center for Materials Science and Engineering (CMSE) Summer Scholar Justin Cheng worked this summer in MIT professor of electrical engineering Karl K. Berggren’s Quantum Nanostructures and Nanofabrication Group to develop specialized techniques for forming these patterns in gold on silicon. “Ideally, we’d want to be able to get arrays of gold nanoparticles to be completely ordered,” says Cheng, a rising senior at Rutgers University. “My work deals with the fundamentals of how to write a pattern using electron-beam lithography, how to deposit the gold, and how to heat up the substrate so we can get completely regular arrays of particles,” Cheng explains. In MIT’s NanoStructures Laboratory, Cheng wrote code to produce a pattern that will guide the dewetting of a thin gold film into nanoparticles, examined partially ordered grids with an electron microscope, and worked in a clean room to develop a polymer resist, spin coat the resist onto samples, and plasma clean the samples. He is part of a team that includes graduate student Sarah Goodman and postdoctoral associate Mostafa Bedewy. He was also assisted by the NanoStructures Lab manager James Daley. “Plasmons are collective oscillations of the free-electron density at the surface of a material, and they give metal nanostructures amazing properties that are very useful in applications like sensing, optics and various devices,” Goodman explained in a presentation to Summer Scholars in June. “Plasmonic arrays are very good for visible displays, for example, because their color can be tuned based on size and geometry.” This multi-step fabrication process begins with spin coating hydrogen silsesquioxane (HSQ), which is a special electron-beam resist, or mask, onto a silicon substrate. Cheng worked on software used to write a pattern onto the resist through electron-beam lithography. Unlike some resists, HSQ becomes more chemically resistant as you expose it to electron beams, he says. The entire substrate is about 1 centimeter by 1 centimeter, he notes, and the write area is about 100 microns (or 0.0001 centimeter) wide. After the electron-beam lithography step, the resist is put through an aqueous (water-based) developer solution of sodium hydroxide and sodium chloride, which leaves behind an ordered array of posts on top of the silicon layer. “When we put the sample in the developer solution, all of the less chemically resistant areas of the HSQ mask come off, and only the posts remain,” Cheng says. Then, Daley deposits a gold layer on top of the posts with physical vapor deposition. Next, the sample is heat treated until the gold layer decomposes into droplets that self-assemble into nanoparticles guided by the posts. A key underlying materials science phenomenon at work in this self-assembly, Cheng says, is known as solid-state dewetting. “Self-assembly is a process where you apply certain conditions to a material that allow it to undergo a transformation over a large area. So it’s a very efficient patterning technique,” Goodman explains. Because of repulsive interaction between the silicon and gold layers, the gold tends to form droplets, which can be coaxed into patterns around the posts. The Berggren group is working collaboratively with Carl V. Thompson, the Stavros Salapatas Professor of Materials Science and Engineering and the director of the Materials Processing Center, who is an expert in solid-state dewetting. Using a scanning electron microscope, Cheng examines these patterns to determine their quality and consistency. “The gold naturally forms droplets because there is a driving force for it to decrease the surface area it shares with the silicon. It doesn’t look completely ordered but you can see beginnings of some order in the dewetting,” he says, while showing an SEM image on a computer. “[In] other pictures you can clearly see the beginnings of patterning.” “When we take the posts and we make them closer together, you can see that the gold likes to dewet into somewhat regular patterns. These aren’t completely regular in all cases, but for certain post sizes and spacings, we start to see regular arrays. Our goal is to successfully fabricate a plasmonic array of ordered, monodisperse [equally sized] gold nanoparticles,” Cheng says. Goodman notes that Thompson's group has demonstrated exquisite control over dewetting in single crystalline films at the micron scale, but the Berggren group hopes to extend this control down to the nanoscale. “This will be a really key result if we’re able to bring this dewetting that’s beautifully controlled on the micro scale and enable that on the nanoscale,” Goodman says. Cheng says that during his summer internship in Berggren’s lab, he learned to operate the scanning electron microscope and learned about nanofabrication processes. “I have learned a lot. Aside from the lab work that I’m doing, I’ve been scripting for the [LayoutEditor] CAD program that I use, and I’ve been using Matlab, too,” he says. “I actually learned a lot about image analysis because there are a lot of steps that go into image analysis. Since we have so much data and so many images to analyze, I’m doing it quantitatively and automatically to make sure I have repeatability.” MPC and CMSE sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships, with support from NSF’s Materials Research Science and Engineering Centers program. The program ran from June 7 through Aug. 6.
News Article | February 15, 2017
The transmission of light by electrochromic materials alters in response to brief bursts of electrical charge. They have optical uses ranging from the windows in Boeing 787-9 Dreamliners which change color at the touch of a button, to privacy glass around hotel bathrooms which switch between clear and opaque, to auto-dimming rear view car mirrors. To feasibly expand the potential uses for these materials, scientists must reduce the amount of electrical power needed to modulate their optical property changes, explains team leader Sing Yang Chiam from the A*STAR Institute of Materials Research and Engineering. To achieve this, "devices will require a greater surface area of contact for enhanced interaction", he says. "If you use nanoparticles for a large surface area, scattering makes for poor optical properties. Using a film with controlled cracks allows us to increase the surface area for better electrical efficiency, without sacrifice of the optical properties." Chiam's team's first step was to grow a thin NiO/Ni(OH)2 film on top of a regular array of pillars fixed to a rigid substrate. Such a structure introduced strain at pre-determined and regular points on the film. For example, spots with no support from any pillars were mechanically weak. The team found that briefly air-drying the newly-formed films was sufficient to trigger the crack formation at these locations. Further dehydration in a furnace caused the material to shrink and cause significant crack propagation. Electron microscopy images showed that the cracking pattern on the surface was so ordered that it looked "artificially squarish" (see image), Chiam says. An unprecedented level of fragmentation control at the submicron and nanometer scale had been achieved. Finally the team checked the electrochromic performance of the films using cyclic voltammetry measurements to measure their switching and optical properties. "The resultant structures yielded excellent electrochromic performance with high-coloration efficiency and stable cycling stability," Chaim confirms. "While the demonstrated enhancement is in electrochromics, I think the significance of the work is in the discovery of a method to order and control fragmentation at such a scale," he adds. Explore further: Understanding how hydration affects color-changing windows can boost their efficiency More information: L. Guo et al. Ordered fragmentation of oxide thin films at submicron scale, Nature Communications (2016). DOI: 10.1038/ncomms13148