The research objective of this award is to understand how arrays of nanofibers can capture and release nanometer to micrometer size particles. The research will result in methods which are general enough to apply across a wide range of particle sizes and materials, and which are relevant to diverse applications. In nature, the nanofibers in natural gecko adhere to surfaces, yet shed dirt particles. The research will first develop a model for particle capture and release in both natural and synthetic fiber arrays. Using the developed self-cleaning model, arrays of nanofibers will be created to control particle adhesion, transport, and removal. The research results will be compared on a wide range of particle sizes and materials using both the natural gecko and synthesized nanofibers to validate models. Deliverables include models of particle capture and release mechanisms, demonstration particle cleaning surfaces, documentation of research results, engineering student and post-doc education, and research experiences for undergraduates.
If successful, the results of this research will provide the understanding to create dry self-cleaning surfaces, and adhesives which work reusably in dirty environments. These dry self-cleaning surfaces could be used for applications such as coatings which keep surfaces clean without water, surfaces which shed bacteria to stay sterile, air cleaning systems, and dirt shedding apparel. Electrically controlled fibers will allow particles to be captured and released when desired. Results of this research will be disseminated to allow the creation of commercial devices in which surfaces can self-clean without water. The project will educate undergraduate and graduate students in both biomimetics and nanotechnology. Through a summer research program, under-represented students in science and engineering will be provided an opportunity to experience research. Through the popular press, biomimetic research will be presented to the general public.
The research objective of this award was to understand how arrays of nanofibers can capture and release nanometer to micrometer size particles. In nature, the nanofibers in natural gecko adhere to surfaces, yet shed dirt particles, remaining clean. This work has focused on the understanding of the dry-self cleaning mechanics of fibrillar systems, with the ultimate aim of developing a method by which particles or contaminants could be captured or controlled. Future applications could include dry self-cleaning surfaces, or adhesives which work reusably in dirty environments. These dry self-cleaning surfaces could be used for applications such as coatings which keep surfaces clean without water, surfaces which shed bacteria to stay sterile, air cleaning systems, and dirt shedding apparel. In this project, we made magnetically controlled microfiber arrays with necessary geometry and motion patterns to control particle adhesion, removal, and transport for a wide range of particle sizes and materials. We demonstrated controllable adhesion to glass spheres with a magnetically actuated synthetic gecko adhesive. Results show adhesion forces can be increased 10-fold by changing the ridge orientation via the external magnetic field. The work was published in a high impact journal, and featured on the issue cover of Advanced Functional Materials. We also studied self-cleaning in gecko-inspired adhesives made from hard plastic nanofibers. An analysis of the contact strength between fibers, particles and substrates of various dimensions and elasticity reveals that dry self-cleaning will be more effective for gecko-inspired adhesives fabricated with smaller fiber diameters and from materials such as hard thermoplastics. This project resulted in three archival journal publications, and the project has provided training for one graduate and 2 undergraduate students. For education, a laboratory module on gecko adhesion was created for the UCB course IB C135L/EE C145O: Laboratory in the Mechanics of Organisms, in which students examine the relationship between contact area and loading for a silicone rubber gecko inspired adhesive. For other outreach, in a joint project with Dr. Rashmi Nanjundaswamy of Lawrence Hall of Science,fabrication methods for silicone rubber gecko adhesive have been described for junior and senior high school students at the Nanoscale Informal Science Education web site: www.nisenet.org/catalog/programs/synthetic_gecko_tape_through_nanomolding which has been online since June 2010.
