Macromolecular Science and Engineering

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Macromolecular Science and Engineering

Ann Arbor, MI, United States

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News Article | April 17, 2017
Site: www.prweb.com

Park Systems, world leader in Atomic Force Microscopy (AFM) will be exhibiting at the Advanced Coatings and Characterization Conference in Houston, TX April 10 - 11, 2017. Park Systems will feature innovative Atomic Force Microscopy products and instrumentation at the exhibition, where industry experts in coatings, material and characterization will highlight the latest research and industry trends in Polymer Coatings and Nanostructured Materials, Corrosion and Characterization and Analytical Methods. “Park Systems’s unsurpassed AFM nanoscale imaging technology provides state-of-the-art characterization that meets the demanding needs of the smart coatings industry and excels in both reliability and accuracy,” comments Keibock Lee, President of Park Systems, who will give a presentation on advanced Analytical Methods with Atomic Force Microscopy on April 11 at 3pm. This year marks Park Systems 20 year anniversary since they began manufacturing AFM’s, and now recognized as a world-leader in Atomic Force Microscopes and AFM technology, Park has offices in the US, Korea, Japan, and Singapore, and distribution partners throughout Europe, Asia, and America. Development of new coatings is a continuously growing field in materials research and has numerous applications that affect the business roadmaps of various industries. Reports from NanoMarkets forecast that the market for such coatings will grow to $5.8 billion USD by 2020. Smart coatings augment products in the construction, automotive, energy, electronic goods, textile, and medical industries, enhancing performance by improving traits such as conductivity, tensile strength, and corrosion resistance amongst so many others. The Advanced Coatings two-day conference is an extensive training and premiere networking event attracting many industry experts from leading chemical companies, academic institutions, researchers, and industry coatings experts and formulators. Located in an attractive Houston setting, Advanced Coatings provides informative conference sessions that will cover a wide range of topics including coatings based on polymer nanocomposites, organic-inorganic hybrid materials, alloys, and 2-D nanomaterials, smart coatings capable of self-healing and much more. “The Advanced Coatings Conference is designed for both novice and highly trained researchers to gain new knowledge about the latest developments in coatings technologies and the use of smart additives and new nanomaterial formulation methods in a short amount of time,” comments Advanced Coatings organizer and Director of the Petro Case Consortium, Dr. Rigoberto Advincula, Professor with the Department of Macromolecular Science and Engineering at Case Western Reserve University. “The conference is highly valued for excellent networking opportunities both in industry and academia and for providing attendees the chance to meet with leading companies and solution providers in materials, formulations, analytical methods, and project services.” The Advanced Coatings conference will provide informative conference sessions that will cover a wide range of topics including coatings based on polymer nanocomposites, organic-inorganic hybrid materials, alloys, and 2-D nanomaterials, smart coatings capable of self-healing, superhydrophobicity, stimuli-responsiveness, sensory functions, and high performance under extreme conditions and much more. The conference will present information to understand not only the fundamentals of formulations, coatings, and curing methods but also the synergistic functionalities that contribute to overall long-term performance and cost-effectiveness and explore the commonalities and requirements in industrial coatings, architectural coatings, barrier packaging, optical, and solid state device coatings. Website and registration: http://www.parkafm.com/coating2017


Kim B.-G.,Macromolecular Science and Engineering | Park H.J.,Macromolecular Science and Engineering | Guo L.J.,Macromolecular Science and Engineering | Kim J.,Macromolecular Science and Engineering | Kim J.,University of Michigan
ACS Applied Materials and Interfaces | Year: 2011

To investigate the structure-dependent aggregation behavior of conjugated polymers and the effect of aggregation on the device performance of conjugated polymer photovoltaic cells, new conjugated polymers (PVTT and CN-PVTT) having the same regioregularity but different intermolecular packing were prepared and characterized by means of UV-vis spectroscopy and atomic force microscopy (AFM). Photovoltaic devices were prepared with these polymers under different polymer-aggregate conditions. Polymer aggregation induced by thermal annealing increases the short circuit current but provides no advantage in the overall power conversion efficiency because of a decrease in the open circuit voltage. The device fabricated from a pre-aggregated polymer suspension, acquired from ultrasonic agitation of a conjugated polymer gel, showed enhanced performance because of better phase separation and reduced recombination between polymer/PCBM. © 2011 American Chemical Society.


News Article | October 28, 2016
Site: www.prweb.com

Park Systems congratulates Jean-Pierre Sauvage, James Fraser Stoddart and Bernard Feringa on being awarded the 2016 Nobel Prize in chemistry for their work on molecular machines. Their extraordinary work on molecular machines is expected to lead to the development of new nanomaterials, operating sensors, creating energy-storage mechanisms and much more. This award also highlights the need for advanced analytical tools to understand and manipulate materials at the atomic and molecular level. “Park Atomic Force Microscopes or AFMs advanced surface science and topography can observe and characterize these molecules, facilitating further discoveries in supramolecular chemistry,” comments Keibock Lee, President of Park Systems. “Park AFM uniquely excels in imaging and characterizing smart materials and nano-manipulation for various applications including nanomachines.” Sauvage, Stoddart, Feringa and other researchers have built about five dozen varieties of molecular machines including knots, switches, shuttles, rotors, pumps and chains, all at chemistry's smallest scale. Too tiny to see with naked eye, the supramolecular particles are 1,000 times less than the width of a human hair. AFM is one of the few methods available to directly visualize and manipulate these nano-objects by investigating topology and field response in flat surfaces and using specific cantilever-tip to molecule interactions. “AFM techniques based on contact and non-contact modes including scanning tunneling microscopy (STM) as well as field-responsive methods have enabled quantitative and visualized experiments to correlate with the dynamics of macromolecular and supramolecular chemistry,” commented Dr. Rigoberto Advincula, who was recently awarded a $300,000 grant from the National Science Foundation to develop methods for producing knots at an industrial level. Advincula’s research was lauded early by Noble Prize recipient Jean-Pierre Sauvage, who congratulated him saying “he looks forward to reading more papers from this group in this fascinating research field.” The researchers at Case Western will collaborate with polymer physicists, theorists, and rheologists to develop various knotted macromolecules with controlled entanglements with high yields and high molecular weight that can produce different physical and chemical properties in plastics, coatings, rubber, composites and more. ”Park AFM and users will be an important tool and community going forward in designing better analytical and characterization methods for investigating supramolecular chemistry and templating for organic molecules and nanoobjects,” commented Dr. Advincula, who is giving an upcoming webinar titled Supramolecular Chemistry, NanoMachines and AFM, hosted by Park Systems. “AFM can be used as a tool for directly visualizing supramolecular topologies with adequate surface fixation methods on atomically flat surfaces and the proper tip to nano-object interaction.” The webinar is schedule for Nov. 9 and is recommended for all researchers studying smart materials including supramolecular chemistry and nanomachines. Park Atomic Force Microscopy (AFM) state-of-the art microscopy equipment provides an important method for probing and harnessing the potential of supramolecular chemistry and other rapidly advancing nano scientific fields of study. The added value include their revolutionary and patented operating system, SmartScan, and many other advanced features such as PinPoint Nanomechanical, making it an essential tool for advanced research into interlocked molecules. To attend our webinar please register at: https://attendee.gotowebinar.com/register/8025694189710243076 Park Systems is a world-leading manufacturer of atomic force microscopy (AFM) systems with a complete range of products for researchers and industry engineers in chemistry, materials, physics, and life sciences, semiconductor, and data storage industries. Park's products are used by over a thousand organizations worldwide and provide the highest data accuracy at nanoscale resolution, superior productivity, and lowest operating cost thanks to its unique technology and innovative engineering. For its efforts to advance imaging methodologies and enhance the user experiences, Park has been awarded the Frost & Sullivan 2016 Global Enabling Technology Leadership Award. Park Systems, Inc. is headquartered in Santa Clara, California with its global manufacturing and R&D headquarters in Korea. Park’s products are sold and supported worldwide with regional headquarters in the US, Korea, Japan, and Singapore, and distribution partners throughout Europe, Asia, and the Americas. Please visit http://www.parkafm.com or email inquiry(at)parkafm(dot)com. Rigoberto Advincula is Professor at the Department of Macromolecular Science and Engineering, Case Western Reserve University in Cleveland, Ohio, USA. He is a Fellow of the American Chemical Society (ACS), Fellow of the Polymer Science and Engineering Division (ACS), Fellow of the Polymer Chemistry Division (ACS). He recently received the distinguished Herman Mark Scholar Award in 2013. He is Editor of Reactive and Functional Polymers and Associate Editor of Polymer Reviews. His group does research in polymer materials, nanocomposites, colloidal science, hybrid materials, and ultrathin films towards applications from smart coatings to biomedical devices.


Abidian M.R.,University of Michigan | Corey J.M.,University of Michigan | Kipke D.R.,University of Michigan | Martin D.C.,Macromolecular Science and Engineering | Martin D.C.,University of Delaware
Small | Year: 2010

An in vitro comparison of conducting-polymer nanotubes of poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (pyrrole) (PPy) and to their film counterparts is reported. Impedance, charge-capacity density (CCD), tendency towards delamination and neunte outgrowth are compared. For the same deposition charge density, PPy films and nanotubes grow relatively faster vertically, while PEDOT films and nanotubes grow more laterally. For the same deposition charge density (1.44C cm-2), PPy nanotubes and PEDOT nanotubes have lower impedance (19.5±2.1 kΩ for PPy nanotubes and 2.5 ± 1.4 kΩ for PEDOT nanotubes at 1 kHz) and higher CCD (184 ± 5.3 mCcm-2 for PPy nanotubes and 392 ± 6.2 mC cm-2 for PEDOT nanotubes) compared to their film counterparts. However, PEDOT nanotubes decrease the impedance of neural-electrode sites by about two orders of magnitude (bare iridium 468.8 ± 13.3 kΩ at 1 kHz) and increase capacity of charge density by about three orders of magnitude (bare iridium 0.1 ± 0.5 mC cm-2). During cyclic voltammetry measurements, both PPy and PEDOT nanotubes remain adherent on the surface of the silicon dioxide while PPy and PEDOT films delaminate. In experiments of primary neurons with conducting-polymer nanotubes, cultured dorsal root ganglion expiants remain more intact and exhibit longer neuntes (1400 ± 95 μm for PPy nanotubes and 2100 ± 150 μm for PEDOT nanotubes) than their film counterparts. These findings suggest that conducting-polymer nanotubes may improve the long-term function of neural microelectrodes. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.


Lee J.,Macromolecular Science and Engineering | Kim J.,Macromolecular Science and Engineering | Kim J.,University of Michigan
Chemistry of Materials | Year: 2012

A novel fabrication method of monophasic, biphasic, and triphasic alginate microparticles having sensory polydiacetylene (PDA) liposomes has been developed to achieve selective and more sensitive multitargeting detection in solution. In this alginate microparticle based detection system, the sensory PDA liposomes are concentrated in the particles rather than being diluted in a solution, which is the case of a conventional solution based detection system, providing superior sensitivity and stability. The biphasic nature of the alginate microparticles was realized by coinjecting two different PDA liposome/alginate mixture solutions into a CaCl 2 solution using a simple combined needle injection system. The size and the constituent of the Janus particles and the extended triphasic particles could be independently manipulated by controlling a centrifugal force and formulating the composition of the PDA liposome solutions, respectively. The multitargeting capability of such mutiphasic alginate particles was demonstrated by fluorescence microscopy. The presented particle-based detection system has a great potential to be combined with a microfluidic device for the development of advanced biosensors having a high throughput screening capability. © 2012 American Chemical Society.


News Article | November 17, 2016
Site: www.cemag.us

Researchers from Case Western Reserve University, Dayton Air Force Research Laboratory, and China have developed a new dry adhesive that bonds in extreme temperatures — a quality that could make the product ideal for space exploration and beyond. The gecko-inspired adhesive loses no traction in temperatures as cold as liquid nitrogen or as hot as molten silver, and actually gets stickier as heat increases, the researchers report. The research, which builds on earlier development of a single-sided dry adhesive tape based on vertically aligned carbon nanotubes, is published in the journal Nature Communications. As far as the researchers know, no other dry adhesive is capable of working at such temperature extremes. Liming Dai, professor of macromolecular science and engineering at Case Western Reserve and an author of the study teamed with Ming Xu, a senior research associate at Case School of Engineering and visiting scholar from Huazhong University of Science and Technology; Feng Du, senior research associate in Case Western Reserve’s Department of Macromolecular Science and Engineering; and Sabyasachi Ganguli and Ajit Roy, of the Materials and Manufacturing Directorate, Air Force Research Laboratory. Vertically aligned carbon nanotubes with tops bundled into nodes replicate the microscopic hairs on the foot of the wall-walking reptile and remain stable from -320 degrees Fahrenheit to 1,832 degrees, the scientists say. “When you have aligned nanotubes with bundled tops penetrating into the cavities of the surface, you generate sufficient van der Waal’s forces to hold,” Xu says. “The dry adhesive doesn’t lose adhesion as it cools because the surface doesn’t change. But when you heat the surface, the surface becomes rougher, physically locking the nanotubes in place, leading to stronger adhesion as temperatures increase.” Because the adhesive remains useful over such a wide range of temperatures, the inventors say it is ideally suited for use in space, where the shade can be frigid and exposure to the sun blazing hot. In addition to range, the bonding agent offers properties that could add to its utility. The adhesive conducts heat and electricity, and these properties also increase with temperature. “When applied as a double-sided sticky tape, the adhesive can be used to link electrical components together and also for electrical and thermal management,” Roy says. “This adhesive can thus be used as connecting materials to enhance the performance of electronics at high temperatures,” Dai says. “At room temperature, the double-sided carbon nanotube tape held as strongly as commercial tape on various rough surfaces, including paper, wood, plastic films and painted walls, showing potential use as conducting adhesives in home appliances and wall-climbing robots.”


News Article | November 16, 2016
Site: www.rdmag.com

Researchers from Case Western Reserve University, Dayton Air Force Research Laboratory and China have developed a new dry adhesive that bonds in extreme temperatures--a quality that could make the product ideal for space exploration and beyond. The gecko-inspired adhesive loses no traction in temperatures as cold as liquid nitrogen or as hot as molten silver, and actually gets stickier as heat increases, the researchers report. The research, which builds on earlier development of a single-sided dry adhesive tape based on vertically aligned carbon nanotubes, is published in the journal Nature Communications. As far as the researchers know, no other dry adhesive is capable of working at such temperature extremes. Liming Dai, professor of macromolecular science and engineering at Case Western Reserve and an author of the study teamed with Ming Xu, a senior research associate at Case School of Engineering and visiting scholar from Huazhong University of Science and Technology; Feng Du, senior research associate in Case Western Reserve's Department of Macromolecular Science and Engineering; and Sabyasachi Ganguli and Ajit Roy, of the Materials and Manufacturing Directorate, Air Force Research Laboratory. Vertically aligned carbon nanotubes with tops bundled into nodes replicate the microscopic hairs on the foot of the wall-walking reptile and remain stable from -320 degrees Fahrenheit to 1,832 degrees, the scientists say. "When you have aligned nanotubes with bundled tops penetrating into the cavities of the surface, you generate sufficient van der Waal's forces to hold," Xu said. "The dry adhesive doesn't lose adhesion as it cools because the surface doesn't change. But when you heat the surface, the surface becomes rougher, physically locking the nanotubes in place, leading to stronger adhesion as temperatures increase." Because of the adhesive remains useful over such a wide range of temperatures, the inventors say it is ideally suited for use in space, where the shade can be frigid and exposure to the sun blazing hot. In addition to range, the bonding agent offers properties that could add to its utility. The adhesive conducts heat and electricity, and these properties also increase with temperature. "When applied as a double-sided sticky tape, the adhesive can be used to link electrical components together and also for electrical and thermal management," Roy said. "This adhesive can thus be used as connecting materials to enhance the performance of electronics at high temperatures," Dai said. "At room temperature, the double-sided carbon nanotube tape held as strongly as commercial tape on various rough surfaces, including paper, wood, plastic films and painted walls, showing potential use as conducting adhesives in home appliances and wall-climbing robots." In testing, a double-sided tape made with the carbon nanotubes (CNTs) applied between two layers of copper foil had an adhesive strength of about 37 newtons per cm-2 at room temperature, about the same as a commercial double-sided sticky tape. Unlike the commercial tape, which loses adhesion as it freezes or is heated, the CNT adhesive maintained its strength down to -320 degrees Fahrenheit. The adhesive strength more than doubled at 785 degrees Fahrenheit and was about six times as strong at 1891 degrees. Surprised by the increasing adhesive strength, the researchers used a scanning electron microscope to search for the cause. They found that, as the bundled nodes penetrate the surface cavities, the flexible nanotubes no longer remain vertically aligned but collapse into web-like structures. The action appears to enhance the van der Waal's forces due to an increased contact surface area with the collapsed nanotubes. Looking further, the researchers found that as the temperature increased above 392 degrees Fahrenheit, the surface of the copper foil became increasingly rough. The bundled ends and collapsed nanotubes appear to penetrate deeper into the heat-induced irregularities in the surface, increasing adhesion. The researchers dub this adhesion mechanism "nano-interlocking." The adhesive held strong during hundreds of temperature transition cycles between ambient temperature and -320 degrees then up to 1891 degrees and between the cold extreme and ambient temperature. Copper foil, which was used for many of the tests to demonstrate the potential for thermal management, is not unique. The surface of many other materials, including polymer films and other metal foils, roughen when heat is applied, making them good targets for this kind of adhesive, the team suggests.


News Article | November 18, 2016
Site: www.sciencedaily.com

Researchers from Case Western Reserve University, Dayton Air Force Research Laboratory and China have developed a new dry adhesive that bonds in extreme temperatures -- a quality that could make the product ideal for space exploration and beyond. The gecko-inspired adhesive loses no traction in temperatures as cold as liquid nitrogen or as hot as molten silver, and actually gets stickier as heat increases, the researchers report. The research, which builds on earlier development of a single-sided dry adhesive tape based on vertically aligned carbon nanotubes, is published in the journal Nature Communications. As far as the researchers know, no other dry adhesive is capable of working at such temperature extremes. Liming Dai, professor of macromolecular science and engineering at Case Western Reserve and an author of the study teamed with Ming Xu, a senior research associate at Case School of Engineering and visiting scholar from Huazhong University of Science and Technology; Feng Du, senior research associate in Case Western Reserve's Department of Macromolecular Science and Engineering; and Sabyasachi Ganguli and Ajit Roy, of the Materials and Manufacturing Directorate, Air Force Research Laboratory. Vertically aligned carbon nanotubes with tops bundled into nodes replicate the microscopic hairs on the foot of the wall-walking reptile and remain stable from -320 degrees Fahrenheit to 1,832 degrees, the scientists say. "When you have aligned nanotubes with bundled tops penetrating into the cavities of the surface, you generate sufficient van der Waal's forces to hold," Xu said. "The dry adhesive doesn't lose adhesion as it cools because the surface doesn't change. But when you heat the surface, the surface becomes rougher, physically locking the nanotubes in place, leading to stronger adhesion as temperatures increase." Because of the adhesive remains useful over such a wide range of temperatures, the inventors say it is ideally suited for use in space, where the shade can be frigid and exposure to the sun blazing hot. In addition to range, the bonding agent offers properties that could add to its utility. The adhesive conducts heat and electricity, and these properties also increase with temperature. "When applied as a double-sided sticky tape, the adhesive can be used to link electrical components together and also for electrical and thermal management," Roy said. "This adhesive can thus be used as connecting materials to enhance the performance of electronics at high temperatures," Dai said. "At room temperature, the double-sided carbon nanotube tape held as strongly as commercial tape on various rough surfaces, including paper, wood, plastic films and painted walls, showing potential use as conducting adhesives in home appliances and wall-climbing robots." In testing, a double-sided tape made with the carbon nanotubes (CNTs) applied between two layers of copper foil had an adhesive strength of about 37 newtons per cm-2 at room temperature, about the same as a commercial double-sided sticky tape. Unlike the commercial tape, which loses adhesion as it freezes or is heated, the CNT adhesive maintained its strength down to -320 degrees Fahrenheit. The adhesive strength more than doubled at 785 degrees Fahrenheit and was about six times as strong at 1891 degrees. Surprised by the increasing adhesive strength, the researchers used a scanning electron microscope to search for the cause. They found that, as the bundled nodes penetrate the surface cavities, the flexible nanotubes no longer remain vertically aligned but collapse into web-like structures. The action appears to enhance the van der Waal's forces due to an increased contact surface area with the collapsed nanotubes. Looking further, the researchers found that as the temperature increased above 392 degrees Fahrenheit, the surface of the copper foil became increasingly rough. The bundled ends and collapsed nanotubes appear to penetrate deeper into the heat-induced irregularities in the surface, increasing adhesion. The researchers dub this adhesion mechanism "nano-interlocking." The adhesive held strong during hundreds of temperature transition cycles between ambient temperature and -320 degrees then up to 1891 degrees and between the cold extreme and ambient temperature. Copper foil, which was used for many of the tests to demonstrate the potential for thermal management, is not unique. The surface of many other materials, including polymer films and other metal foils, roughen when heat is applied, making them good targets for this kind of adhesive, the team suggests.


News Article | November 16, 2016
Site: phys.org

The gecko-inspired adhesive loses no traction in temperatures as cold as liquid nitrogen or as hot as molten silver, and actually gets stickier as heat increases, the researchers report. The research, which builds on earlier development of a single-sided dry adhesive tape based on vertically aligned carbon nanotubes, is published in the journal Nature Communications. As far as the researchers know, no other dry adhesive is capable of working at such temperature extremes. Liming Dai, professor of macromolecular science and engineering at Case Western Reserve and an author of the study teamed with Ming Xu, a senior research associate at Case School of Engineering and visiting scholar from Huazhong University of Science and Technology; Feng Du, senior research associate in Case Western Reserve's Department of Macromolecular Science and Engineering; and Sabyasachi Ganguli and Ajit Roy, of the Materials and Manufacturing Directorate, Air Force Research Laboratory. Vertically aligned carbon nanotubes with tops bundled into nodes replicate the microscopic hairs on the foot of the wall-walking reptile and remain stable from -320 degrees Fahrenheit to 1,832 degrees, the scientists say. "When you have aligned nanotubes with bundled tops penetrating into the cavities of the surface, you generate sufficient van der Waal's forces to hold," Xu said. "The dry adhesive doesn't lose adhesion as it cools because the surface doesn't change. But when you heat the surface, the surface becomes rougher, physically locking the nanotubes in place, leading to stronger adhesion as temperatures increase." Because of the adhesive remains useful over such a wide range of temperatures, the inventors say it is ideally suited for use in space, where the shade can be frigid and exposure to the sun blazing hot. In addition to range, the bonding agent offers properties that could add to its utility. The adhesive conducts heat and electricity, and these properties also increase with temperature. "When applied as a double-sided sticky tape, the adhesive can be used to link electrical components together and also for electrical and thermal management," Roy said. "This adhesive can thus be used as connecting materials to enhance the performance of electronics at high temperatures," Dai said. "At room temperature, the double-sided carbon nanotube tape held as strongly as commercial tape on various rough surfaces, including paper, wood, plastic films and painted walls, showing potential use as conducting adhesives in home appliances and wall-climbing robots." In testing, a double-sided tape made with the carbon nanotubes (CNTs) applied between two layers of copper foil had an adhesive strength of about 37 newtons per cm-2 at room temperature, about the same as a commercial double-sided sticky tape. Unlike the commercial tape, which loses adhesion as it freezes or is heated, the CNT adhesive maintained its strength down to -320 degrees Fahrenheit. The adhesive strength more than doubled at 785 degrees Fahrenheit and was about six times as strong at 1891 degrees. Surprised by the increasing adhesive strength, the researchers used a scanning electron microscope to search for the cause. They found that, as the bundled nodes penetrate the surface cavities, the flexible nanotubes no longer remain vertically aligned but collapse into web-like structures. The action appears to enhance the van der Waal's forces due to an increased contact surface area with the collapsed nanotubes. Looking further, the researchers found that as the temperature increased above 392 degrees Fahrenheit, the surface of the copper foil became increasingly rough. The bundled ends and collapsed nanotubes appear to penetrate deeper into the heat-induced irregularities in the surface, increasing adhesion. The researchers dub this adhesion mechanism "nano-interlocking." The adhesive held strong during hundreds of temperature transition cycles between ambient temperature and -320 degrees then up to 1891 degrees and between the cold extreme and ambient temperature. Copper foil, which was used for many of the tests to demonstrate the potential for thermal management, is not unique. The surface of many other materials, including polymer films and other metal foils, roughen when heat is applied, making them good targets for this kind of adhesive, the team suggests. Explore further: Nanotube adhesive sticks better than a gecko's foot


News Article | November 16, 2016
Site: www.eurekalert.org

Researchers from Case Western Reserve University, Dayton Air Force Research Laboratory and China have developed a new dry adhesive that bonds in extreme temperatures--a quality that could make the product ideal for space exploration and beyond. The gecko-inspired adhesive loses no traction in temperatures as cold as liquid nitrogen or as hot as molten silver, and actually gets stickier as heat increases, the researchers report. The research, which builds on earlier development of a single-sided dry adhesive tape based on vertically aligned carbon nanotubes, is published in the journal Nature Communications. As far as the researchers know, no other dry adhesive is capable of working at such temperature extremes. Liming Dai, professor of macromolecular science and engineering at Case Western Reserve and an author of the study teamed with Ming Xu, a senior research associate at Case School of Engineering and visiting scholar from Huazhong University of Science and Technology; Feng Du, senior research associate in Case Western Reserve's Department of Macromolecular Science and Engineering; and Sabyasachi Ganguli and Ajit Roy, of the Materials and Manufacturing Directorate, Air Force Research Laboratory. Vertically aligned carbon nanotubes with tops bundled into nodes replicate the microscopic hairs on the foot of the wall-walking reptile and remain stable from -320 degrees Fahrenheit to 1,832 degrees, the scientists say. "When you have aligned nanotubes with bundled tops penetrating into the cavities of the surface, you generate sufficient van der Waal's forces to hold," Xu said. "The dry adhesive doesn't lose adhesion as it cools because the surface doesn't change. But when you heat the surface, the surface becomes rougher, physically locking the nanotubes in place, leading to stronger adhesion as temperatures increase." Because of the adhesive remains useful over such a wide range of temperatures, the inventors say it is ideally suited for use in space, where the shade can be frigid and exposure to the sun blazing hot. In addition to range, the bonding agent offers properties that could add to its utility. The adhesive conducts heat and electricity, and these properties also increase with temperature. "When applied as a double-sided sticky tape, the adhesive can be used to link electrical components together and also for electrical and thermal management," Roy said. "This adhesive can thus be used as connecting materials to enhance the performance of electronics at high temperatures," Dai said. "At room temperature, the double-sided carbon nanotube tape held as strongly as commercial tape on various rough surfaces, including paper, wood, plastic films and painted walls, showing potential use as conducting adhesives in home appliances and wall-climbing robots." In testing, a double-sided tape made with the carbon nanotubes (CNTs) applied between two layers of copper foil had an adhesive strength of about 37 newtons per cm-2 at room temperature, about the same as a commercial double-sided sticky tape. Unlike the commercial tape, which loses adhesion as it freezes or is heated, the CNT adhesive maintained its strength down to -320 degrees Fahrenheit. The adhesive strength more than doubled at 785 degrees Fahrenheit and was about six times as strong at 1891 degrees. Surprised by the increasing adhesive strength, the researchers used a scanning electron microscope to search for the cause. They found that, as the bundled nodes penetrate the surface cavities, the flexible nanotubes no longer remain vertically aligned but collapse into web-like structures. The action appears to enhance the van der Waal's forces due to an increased contact surface area with the collapsed nanotubes. Looking further, the researchers found that as the temperature increased above 392 degrees Fahrenheit, the surface of the copper foil became increasingly rough. The bundled ends and collapsed nanotubes appear to penetrate deeper into the heat-induced irregularities in the surface, increasing adhesion. The researchers dub this adhesion mechanism "nano-interlocking." The adhesive held strong during hundreds of temperature transition cycles between ambient temperature and -320 degrees then up to 1891 degrees and between the cold extreme and ambient temperature. Copper foil, which was used for many of the tests to demonstrate the potential for thermal management, is not unique. The surface of many other materials, including polymer films and other metal foils, roughen when heat is applied, making them good targets for this kind of adhesive, the team suggests. This work is mainly supported by the Department of Defense Air Force Office of Scientific Research Multidisciplinary Research Program of the University Research Initiative and the National Science Foundation.

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