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Perna L.E.,Massachusetts Institute of Technology | Hicks F.M.,Massachusetts Institute of Technology | Coffman C.S.,Massachusetts Institute of Technology | Li H.,Massachusetts Institute of Technology | And 2 more authors.
48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2012 | Year: 2012

As a solution to the problem of scalable propulsion in small satellite architectures, the microfabricated ion Electrospray Propulsion System (iEPS) developed by MIT's Space Propulsion Laboratory has progressed to a point where it is ready to be characterized on a realistic testbed. In this paper, developments in the iEPS thruster design and testing equipment are outlined. Design changes address the performance and testing issues encountered with the first version. These changes include features to mitigate the formation of liquid current paths and ease grid-to-tip alignment and grid removal. Additionally, a 1-DOF free-floating CubeSat testbed with an integrated autonomous remote control system and high-voltage PPU has been developed and tested for use as a thrust balance and attitude control demonstrator. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source


News Article
Site: http://news.mit.edu/topic/mitnanotech-rss.xml

“I’ve never experienced this!” The researcher from Mexico was referring to the 7 degrees Fahrenheit weather outside Building 39 at MIT last month, but his comment might also apply to the outright excitement he and seven colleagues conveyed in recent interviews about their stay at the Institute. The eight faculty and postdocs are here as part of the Tec de Monterrey and MIT Program, a formal relationship established between MIT and the Tecnológico de Monterrey in 2014 and launched in early 2015. The program aims to foster exchanges and collaborations among researchers at both institutions focused on the general area of nanotechnology and nanoscience with the ultimate goal of supporting the Tec in its quest to become a research university. Tecnológico de Monterrey, founded by MIT Class of 1914 graduate Eugenio Garza Sada in 1943 and initially directed by León Álvalos y Vez '29, is one of the largest universities in Latin America with more than 90,000 students. The Tec de Monterrey and MIT Program was established by a gift from the Garza family to honor the 100th anniversary of Eugenio Garza Sada’s graduation from MIT’s Department of Civil and Sanitary Engineering. The exchange program is housed at MIT’s Microsystems Technology Laboratories (MTL), under the leadership of Professor Jesús del Alamo of the Department of Electrical Engineering and Computer Science. A primary goal of the program is to pair professors and postdocs from Monterrey Tec with host faculty at MIT, creating opportunities for them to collaborate on world class-research at the leading edge of their fields. “We are hoping to get really smart, driven and enthusiastic young people,” said del Alamo, with “fruitful collaboration” as the benefit for both schools. As del Alamo described it, the program covers engineering of systems and structures at any scale, with initial emphasis on nanoscience and nanotechnology, “broadly construed.” The inaugural cohort of participants in the Monterrey Tec program includes three faculty and five postdocs who have come to MIT for visits ranging from a semester to the full academic year. In 2016, the program will expand to include graduate students. At the end of five years the program’s focus on nanotechnology will be reviewed, with modifications made as needed, del Alamo said. The visiting Monterrey Tec faculty and postdocs bring expertise in diverse fields, including telecommunications, biotechnology, chemical engineering, mechatronics, molecular biology, microfluidics, acoustics engineering, and more, but in separate interviews they described having similar goals. Many came with a desire to learn more about how their MIT peers think, how they use tools and logic, while others wanted to expand the reach of their own research and that of their home university; in a word, to “grow.” Most emphatically, the visitors expressed a strong desire to forge permanent connections between people at both institutions and to demonstrate the mutual value of these research collaborations. The researchers are working on a range of projects at MTL and MTL-affiliated labs and centers, and talked about their work with unqualified excitement. For example, acoustics engineer David Isaac Ibarra-Zarate described his experience working with Brian Anthony and others in the Medical Electronic Device Realization Center as “since the beginning wonderful.” The researcher’s main goal is to develop a micro-electric system that can deliver acoustic therapies to the ear, and he has been working with a Mexico City hospital to develop protocols for this therapy. Drawn to the project in part for personal reasons (his father has tinnitus), Ibarra-Zarate intends to develop a device, standards, and protocol, and perhaps bring it to market. While at MIT he hopes to complete the first step, which is constructing a prototype. With his signal processing experience, the researcher was also invited to join a project to devise an ultrasound pill that can be swallowed to yield an image of the intestines, and he is hopeful of reaching the prototype stage with this pill as well. Beyond these efforts, he is interested in exploring the brain-computer interface, he said, and in correlating encephalography signals with acoustic sensation and binaural sounds. José González-Valdez vividly described his work in Professor Scott Manalis’s lab at the Koch Institute in a similarly enthusiastic vein. The group is “measuring the weights of exosomes “at a very precise, attogram, scale,” in order to characterize different exosome populations, he said. Exosomes are extracellular vesicles or tiny sacs filled with liquid. The intent is to link one of the exosome populations with the symptoms of patients who have what's known as vestibular schwannoma, a cancer of the cerebellum that can leave people blind or deaf. González-Valdez explained that a group he works with in Mexico has been using chromatography to separate molecules. “There’s a protocol,” he said, “but it’s not that efficient — it’s quite tough to do.” His hope, he continued, is to connect the “exosome people” (in Cambridge) and the “bio-separation people” in Mexico, to continue and broaden this critical effort. Biotechnologist Grissel Trujillo-de Santiago, whose PhD focused on biomaterials, described her work on tissue engineering in Professor Ali Khademhosseini’s lab at the Brigham and Women’s Hospital as “a very powerful experience.” The researcher used the analogy of homespun ingredients — milk and coffee — to explain how she is making use of chaotic flows to develop microstructures that become small pieces of tissue. Trujillo-de Santiago hopes to set up her own group for biomaterials and tissue engineering when she returns to Mexico. “The applications would be infinite — it’s a matter of imagination,” she exclaimed, opening a tablet computer and displaying slides of pink and green fluorescent particles in a polymer solution to illustrate these microstructure platforms. Professor Mario Moisés Alvarez, trained in chemical and biological engineering, is also working in the Khademhosseini Lab, focusing on biotechnology and on biomedical technology projects. His research group at Tecnológico de Monterrey had developed proteins that can be used to detect the Ebola virus, and he spoke of how elated he is to be part of a team here leveraging the use of those protein molecules, in combination with nanoparticles and a microfluidic chamber, to detect and capture Ebola viral particles from a patient’s circulating blood — “at the point at which you can still save a life!” A “microfluidics device designer” is how José Israel Martinez-López describes himself. Trained in electrical engineering and biotechnology and with a PhD in mechatronics and advanced materials, he is working with Professor Jongyoon Han’s group in the Research Laboratory of Electronics (RLE). The large-group environment allows him to “get a glimpse” of topics in related fields, and is proving “very helpful for professional growth,” he said. Martinez-López is helping to devise rapid microfabrication methodologies that will enable developing countries to manufacture devices for disease detection close to the site where the devices are needed, using off-the-shelf materials. The goal is “functionality at low cost,” he stated, stressing the enormous need for these tools. All program participants used high praise to describe their experience working with MIT mentors and lab mates. Daniel Olvera Trejo, a mechatronics engineer specializing in machine processes, vibrations, and tools, is working on projects in the MTL lab of Luis Fernando Velásquez-Garcia. Experienced in conventional microfabrication, the researcher is now exploring even more accurate technologies, such as 3-D printing and stereophotography, to design new devices; for example, tools to control drug release. “People always make time to get you what you need,” he said. One important aspect of his experience in the program has been to see how people at MIT work together across disciplines, said Olvera Trejo. Once home, he hopes to increase collaboration between researchers with expertise in mechanics, chemistry, and manufacturing, and the physicians in Monterrey’s hospital who have applications for new devices. The researchers will return to Mexico by the end of this semester, and they spoke eagerly of what they expect to bring back. “People here are very committed, they are very connected,” said Monterrey Tec Professor Rodrigo Balam Muñoz Soto of his experience in the RLE lab of Professor Joel Voldman, working with pairing-cell devices. A molecular biologist, Muñoz Soto noted that these devices have many potential diagnostic uses, and said that his microfluidics and microsystems work here will have “immediate application” in the molecular diagnostics and immunology courses he is teaching next semester. Monterrey Tec Professor Gerardo Antonio Castañón Avila, a telecommunications engineer by training, has been working on silicon photonics in the research laboratory of Professor Rajeev Ram, using concepts of electronics to design wave guides at the nano level. Researchers at MIT “are working with very relevant problems — and that is difficult to find,” he remarked. There are advantages in coupling photonics with electronics such as is being done here, Avila said, and he plans to set up a nanophotonics lab at Monterrey Tec, where fabrication can be done more easily and products can be tested. Researchers outlined many more goals, such as publishing journal articles on their work here; devising new courses in areas like silicon photonics; increasing the number of point-of-care applications in their work; and translating the experience of MIT’s cross-disciplinary thinking to Monterrey. Several said they plan to invite MIT faculty to Monterrey Tec to lecture on microsystems-related work, and to send ambitious Monterrey graduate students to MIT. Perhaps the most commonly mentioned plan was a human one. As Muñoz Soto emphatically said, “My next goal is to keep the relationship [with MIT] alive!”


News Article
Site: http://phys.org/technology-news/

That's because manufacturing MEMS has traditionally required sophisticated semiconductor fabrication facilities, which cost tens of millions of dollars to build. Potentially useful MEMS have languished in development because they don't have markets large enough to justify the initial capital investment in production. Two recent papers from researchers at MIT's Microsystems Technologies Laboratories offer hope that that might change. In one, the researchers show that a MEMS-based gas sensor manufactured with a desktop device performs at least as well as commercial sensors built at conventional production facilities. In the other paper, they show that the central component of the desktop fabrication device can itself be built with a 3-D printer. Together, the papers suggest that a widely used type of MEMS gas sensor could be produced at one-hundredth the cost with no loss of quality. The researchers' fabrication device sidesteps many of the requirements that make conventional MEMS manufacture expensive. "The additive manufacturing we're doing is based on low temperature and no vacuum," says Luis Fernando Velásquez-García, a principal research scientist in MIT's Microsystems Technology Laboratories and senior author on both papers. "The highest temperature we've used is probably 60 degrees Celsius. In a chip, you probably need to grow oxide, which grows at around 1,000 degrees Celsius. And in many cases the reactors require these high vacuums to prevent contamination. We also make the devices very quickly. The devices we reported are made in a matter of hours from beginning to end." For years, Velásquez-García has been researching manufacturing techniques that involve dense arrays of emitters that eject microscopic streams of fluid when subjected to strong electric fields. For the gas sensors, Velásquez-García and Anthony Taylor, a visiting researcher from the British company Edwards Vacuum, use so-called "internally fed emitters." These are emitters with cylindrical bores that allow fluid to pass through them. In this case, the fluid contained tiny flakes of graphene oxide. Discovered in 2004, graphene is an atom-thick form of carbon with remarkable electrical properties. Velásquez-García and Taylor used their emitters to spray the fluid in a prescribed pattern on a silicon substrate. The fluid quickly evaporated, leaving a coating of graphene oxide flakes only a few tens of nanometers thick. The flakes are so thin that interaction with gas molecules changes their resistance in a measurable way, making them useful for sensing. "We ran the gas sensors head to head with a commercial product that cost hundreds of dollars," Velásquez-García says. "What we showed is that they are as precise, and they are faster. We make at a very low cost—probably cents—something that works as well as or better than the commercial counterparts." To produce those sensors, Velásquez-García and Taylor used electrospray emitters that had been built using conventional processes. However, in the December issue of the Journal of Microelectromechanical Systems, Velásquez-García reports using an affordable, high-quality 3-D printer to produce plastic electrospray emitters whose size and performance match those of the emitters that yielded the gas sensors. In addition to making electrospray devices more cost-effective, Velásquez-García says, 3-D printing also makes it easier to customize them for particular applications. "When we started designing them, we didn't know anything," Velásquez-García says. "But at the end of the week, we had maybe 15 generations of devices, where each design worked better than the previous versions." Indeed, Velásquez-García says, the advantages of electrospray are not so much in enabling existing MEMS devices to be made more cheaply as in enabling wholly new devices. Besides making small-market MEMS products cost-effective, electrospray could enable products incompatible with existing manufacturing techniques. "In some cases, MEMS manufacturers have to compromise between what they intended to make, based on the models, and what you can make based on the microfabrication techniques," Velásquez-García says. "Only a few devices that fit into the description of having large markets and not having subpar performance are the ones that have made it." Electrospray could also lead to novel biological sensors, Velásquez-García says. "It allows us to deposit materials that would not be compatible with high-temperature semiconductor manufacturing, like biological molecules," he says. "For sure, the paper opens new technical paths to making gas microsensors," says Jan Dziuban, head of the Division of Microengineering at Wroclaw University of Technology in Poland. "From a technical point of view, the process may be easily adapted to mass fabrication." "But promising results must be proved statistically," he cautions. "Personal experience tells me that plenty of very promising materials for new sensors, utilizing nanostructured materials, which have been published in high-level scientific papers, haven't resulted in reliable products."


News Article
Site: http://news.mit.edu/topic/mitmechanical-engineering-rss.xml

Nanofibers — polymer filaments only a couple of hundred nanometers in diameter — have a huge range of potential applications, from solar cells to water filtration to fuel cells. But so far, their high cost of manufacture has relegated them to just a few niche industries. In the latest issue of the journal Nanotechnology, MIT researchers describe a new technique for producing nanofibers that increases the rate of production fourfold while reducing energy consumption by more than 90 percent, holding out the prospect of cheap, efficient nanofiber production. “We have demonstrated a systematic way to produce nanofibers through electrospinning that surpasses the state of the art,” says Luis Fernando Velásquez-García, a principal research scientist in MIT’s Microsystems Technology Laboratories, who led the new work. “But the way that it’s done opens a very interesting possibility. Our group and many other groups are working to push 3-D printing further, to make it possible to print components that transduce, that actuate, that exchange energy between different domains, like solar to electrical or mechanical. We have something that naturally fits into that picture. We have an array of emitters that can be thought of as a dot-matrix printer, where you would be able to individually control each emitter to print deposits of nanofibers.” Nanofibers are useful for any application that benefits from a high ratio of surface area to volume — solar cells, for instance, which try to maximize exposure to sunlight, or fuel cell electrodes, which catalyze reactions at their surfaces. Nanofibers can also yield materials that are permeable only at very small scales, like water filters, or that are remarkably tough for their weight, like body armor. The standard technique for manufacturing nanofibers is called electrospinning, and it comes in two varieties. In the first, a polymer solution is pumped through a small nozzle, and then a strong electric field stretches it out.  The process is slow, however, and the number of nozzles per unit area is limited by the size of the pump hydraulics. The other approach is to apply a voltage between a rotating drum covered by metal cones and a collector electrode. The cones are dipped in a polymer solution, and the electric field causes the solution to travel to the top of the cones, where it’s emitted toward the electrode as a fiber. That approach is erratic, however, and produces fibers of uneven lengths; it also requires voltages as high as 100,000 volts. Velásquez-García and his co-authors — Philip Ponce de Leon, a former master’s student in mechanical engineering; Frances Hill, a former postdoc in Velásquez-García’s group who’s now at KLA-Tencor; and Eric Heubel, a current postdoc — adapt the second approach, but on a much smaller scale, using techniques common in the manufacture of microelectromechanical systems to produce dense arrays of tiny emitters. The emitters’ small size reduces the voltage necessary to drive them and allows more of them to be packed together, increasing production rate. At the same time, a nubbly texture etched into the emitters’ sides regulates the rate at which fluid flows toward their tips, yielding uniform fibers even at high manufacturing rates. “We did all kinds of experiments, and all of them show that the emission is uniform,” Velásquez-García says. To build their emitters, Velásquez-García and his colleagues use a technique called deep reactive-ion etching. On either face of a silicon wafer, they etch dense arrays of tiny rectangular columns — tens of micrometers across — which will regulate the flow of fluid up the sides of the emitters. Then they cut sawtooth patterns out of the wafer. The sawteeth are mounted vertically, and their bases are immersed in a solution of deionized water, ethanol, and a dissolved polymer. When an electrode is mounted opposite the sawteeth and a voltage applied between them, the water-ethanol mixture streams upward, dragging chains of polymer with it. The water and ethanol quickly dissolve, leaving a tangle of polymer filaments opposite each emitter, on the electrode. The researchers were able to pack 225 emitters, several millimeters long, on a square chip about 35 millimeters on a side. At the relatively low voltage of 8,000 volts, that device yielded four times as much fiber per unit area as the best commercial electrospinning devices. The work is “an elegant and creative way of demonstrating the strong capability of traditional MEMS [microelectromechanical-systems] fabrication processes toward parallel nanomanufacturing,” says Reza Ghodssi, a professor of electrical engineering at the University of Maryland. Relative to other approaches, he adds, there is “an increased potential to scale it up while maintaining the integrity and accuracy by which the processing method is applied.”


Home > Press > Nanodevices at one-hundredth the cost: New techniques for building microelectromechanical systems show promise Abstract: Microelectromechanical systems -- or MEMS -- were a $12 billion business in 2014. But that market is dominated by just a handful of devices, such as the accelerometers that reorient the screens of most smartphones. Two recent papers from researchers at MIT's Microsystems Technologies Laboratories offer hope that that might change. In one, the researchers show that a MEMS-based gas sensor manufactured with a desktop device performs at least as well as commercial sensors built at conventional production facilities. In the other paper, they show that the central component of the desktop fabrication device can itself be built with a 3-D printer. Together, the papers suggest that a widely used type of MEMS gas sensor could be produced at one-hundredth the cost with no loss of quality. The researchers' fabrication device sidesteps many of the requirements that make conventional MEMS manufacture expensive. "The additive manufacturing we're doing is based on low temperature and no vacuum," says Luis Fernando Velásquez-García, a principal research scientist in MIT's Microsystems Technology Laboratories and senior author on both papers. "The highest temperature we've used is probably 60 degrees Celsius. In a chip, you probably need to grow oxide, which grows at around 1,000 degrees Celsius. And in many cases the reactors require these high vacuums to prevent contamination. We also make the devices very quickly. The devices we reported are made in a matter of hours from beginning to end." Welcome resistance For years, Velásquez-García has been researching manufacturing techniques that involve dense arrays of emitters that eject microscopic streams of fluid when subjected to strong electric fields. For the gas sensors, Velásquez-García and Anthony Taylor, a visiting researcher from the British company Edwards Vacuum, use so-called "internally fed emitters." These are emitters with cylindrical bores that allow fluid to pass through them. In this case, the fluid contained tiny flakes of graphene oxide. Discovered in 2004, graphene is an atom-thick form of carbon with remarkable electrical properties. Velásquez-García and Taylor used their emitters to spray the fluid in a prescribed pattern on a silicon substrate. The fluid quickly evaporated, leaving a coating of graphene oxide flakes only a few tens of nanometers thick. The flakes are so thin that interaction with gas molecules changes their resistance in a measurable way, making them useful for sensing. "We ran the gas sensors head to head with a commercial product that cost hundreds of dollars," Velásquez-García says. "What we showed is that they are as precise, and they are faster. We make at a very low cost -- probably cents -- something that works as well as or better than the commercial counterparts." To produce those sensors, Velásquez-García and Taylor used electrospray emitters that had been built using conventional processes. However, in the December issue of the Journal of Microelectromechanical Systems, Velásquez-García reports using an affordable, high-quality 3-D printer to produce plastic electrospray emitters whose size and performance match those of the emitters that yielded the gas sensors. Made to order In addition to making electrospray devices more cost-effective, Velásquez-García says, 3-D printing also makes it easier to customize them for particular applications. "When we started designing them, we didn't know anything," Velásquez-García says. "But at the end of the week, we had maybe 15 generations of devices, where each design worked better than the previous versions." Indeed, Velásquez-García says, the advantages of electrospray are not so much in enabling existing MEMS devices to be made more cheaply as in enabling wholly new devices. Besides making small-market MEMS products cost-effective, electrospray could enable products incompatible with existing manufacturing techniques. "In some cases, MEMS manufacturers have to compromise between what they intended to make, based on the models, and what you can make based on the microfabrication techniques," Velásquez-García says. "Only a few devices that fit into the description of having large markets and not having subpar performance are the ones that have made it." Electrospray could also lead to novel biological sensors, Velásquez-García says. "It allows us to deposit materials that would not be compatible with high-temperature semiconductor manufacturing, like biological molecules," he says. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

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