Monday, March 29, 2010

Carbon Nanotube Gecko Inspired Dry Adhesives and Tape Suitable for MEMS, Electronics and Display Technologies, Licenses Available

In this research, gecko-inspired adhesives based on carbon nanotubes have been developed with frictional adhesive characteristics superior to that of the gecko in nature. The microstructure of the gecko footpad has been simulated using carbon nanotube bundles to replicate the microscale setae, while individual carbon nanotubes were used to replicate the nanoscale spatulae present within the setae.

Such gecko tapes can support a shear stress nearly four times higher than the gecko foot, and can allow for enhanced adhesion to a variety of substrates including mica, glass, acrylic, and Teflon®. Unlike conventional materials, gecko-based adhesives can adhere to nearly any surface, whether it be hard or soft, rough or smooth, wet or dry. Based on this technology, a flexible adhesive tape has been constructed which maintains its adhesive character and can be used repeatedly without deterioration of the adhesive performance.

With the proper design of size, shape, and pattern of the carbon nanotubes, it has been further discovered that these synthetic  gecko tapes can also be self-cleaning. Reversible adhesion and the self-cleaning effect can be  demonstrated through either rinsing with water, or by mechanical cleaning of the surface. The results show that the shear stress of the cleaned samples are 60- 90% of those for the pristine, unsoiled samples.

University of Akron research has shown that shown that carbon nanotube-based gecko tapes offer an excellent synthetic option as a dry, conductive, and reversible adhesive for use in microelectronics, robotics, and space applications.

The rapidly growing field of biomimetics has enabled a better understanding of the extraordinary adhesive properties and climbing abilities demonstrated by the gecko. The unique aspects of gecko adhesion result from the complex hierarchal structure of the microscopic hairs, or setae, present on the gecko’s footpads. Synthetic routes to mimic nature’s magic have been invented.

The carbon nanotube Geko glue was developed by Rice University Professor in Engineering, Materials Science and Nanotechnology  Pulickel M. Ajayan  and University of Akron Professor of Polymer Science Ali Dhinojwala.   

They developed carbon nanostructure composite systems which may be useful for various applications, including as dry adhesives, electronics and display technologies, or in a wide variety of other areas where organized nanostructures may be formed and integrated into a flexible substrate.

The University of Akron has filed Patent Application 20100075024 for “Aligned Carbon Nanotube-Polymer Materials, Systems and Methods” which encompasses the Gecko glue.  It also covers systems and methods wherein organized nanotube structures or other nanostructures are embedded within polymers or other flexible materials to provide a flexible skin-like material, with the properties and characteristics of the nanotubes or other nanostructures exploited for use in various applications.

Adhesives are typically wet and polymer-based, and have low thermal and electrical conductivity. For electronics, micro-electro-mechanical systems (MEMS), low or zero atmosphere environments, cryogenic or high temperature environments, or a variety of other areas, it would be desirable to provide a dry adhesive which is selectively attachable and detachable to/from a surface. It would also be desirable to provide an adhesive which has other beneficial properties, such as high electrical and thermal conductivity or high adhesion strengths while being selectively detachable. For example, the mechanism which allows a gecko lizard to climb a vertical surface or any other surface is based upon the anatomy of the gecko's feet and toes, wherein each five-toed foot is covered with microscopic elastic hairs called setae.

The ends of these hairs split into spatulas which come into contact with the surface and induce enough intermolecular (van der WAALS,[VdW]) forces to secure the toes to the surface. The gecko's foot anatomy allows them to selectively adhere to any surface which they touch. Although attempts have been made to provide synthetic systems which mimic the gecko's feet and toe anatomy, no such systems have generally been successful. It would be desirable to provide an adhesive which mimics these characteristics, and provides a surface which interacts with other surfaces via intermolecular or VdW forces, via nanostructure technologies.

In a variety of other areas, the use of organized carbon nanostructures in unique configurations may provide valuable functions in biocompatible or bioactive systems, electronic displays, functional films or skins, or other applications.

FIG. 2 is a schematic illustration of a method for preparing a carbon nanotube-polymer composite according to the  University of Akron invention. (click to enlarge) 

FIG. 3 is a schematic illustration of an alternative method for preparing a carbon nanotube-polymer composite according to the University of Akron invention.

FIG. 7 shows a scanning electron microscope image of the carbon nanotube architectures before being embedded into a polymer matrix. FIG. 8 is a scanning electron microscope image showing the nanotube architectures of FIG. 7 after polymer infiltration. (click to enlarge)

 FIG. 9 is a top view of nanotube walls prior to polymer infiltration. FIG. 10 shows a cross-sectional scanning electron microscope image of the nanotube walls shown in FIG. 9 after polymer infiltration.

The technology is available for licensing from the University of Akron Office of  Technology Transfer. 

University of Akron Office of Technology Transfer
Kenneth Preston, Director
Susan Dollinger, Marketing Director
Goodyear Polymer Center, Suite 312
Akron, Ohio 44325-2103
Phone: 330-972-7840
Fax: 330-972-2368
Title: Aligned Carbon Nanotube-Polymer Materials, Systems and Methods

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