Design and development of functional dry adhesives and their applications

Functional dry adhesives are dry adhesives that rely on dry adhesive structures for adhesion but also include additional functionality that enables adhesion switching or sensing capabilities. This thesis describes the design and testing of functional dry adhesives. Electro-dry-adhesives with flexible electrodes were fabricated. When a high voltage was applied to the flexible electrodes, fabricated from mixing and curing Carbon Black (CB) and polydimethylsiloxane (PDMS), an electrostatic field was generated between opposing electrodes and between the Electro-dry-adhesive and the surface it was attached to. The generated electrostatic field resulted in an increased shear adhesion force over the shear adhesion measured without the applied electrostatic field applied as well as the ability to self-preload. Magnetic field switchable dry adhesives were designed with a backing layer composed of iron oxide particles embedded within PDMS. The design of the dry adhesive backing layer allowed increased or decreased measured adhesion forces when the magnetic field was present during only the pull-off portion of the normal dry adhesion test cycle depending on the orientation of the magnetic field. Decreased adhesion was observed when the magnetic field was present during either the entire adhesion test cycle or when the magnetic field was present during only the preload portion of the dry adhesion test cycle regardless of the orientation of the magnetic field. Force and torque sensing dry adhesives were designed and fabricated by molding CB-PDMS. Force sensing was observed when the device was both compressed and extended by measuring a change in the resistance across the device terminals. Torque sensing was observed when the dry adhesive backing layer was twisted again by comparing resistance changes across the device terminals. The design of the force and torque sensing dry adhesives allowed the user to differentiate between forces in compression and extension as well as torques. Finally, a low cost method of fabricating dry adhesives was developed that utilizes commercially available meshes as a mold. The ability to utilize commercially available meshes instead of cleanroom fabrication techniques may save on overall fabrication costs and allow dry adhesives to be fabricated in large sheets.