Biologically inspired fibrillar adhesion and friction on biological tissues: Modeling, fabrication, and applications

Biologists have long observed with awe the attachment capabilities of insects and small animals on smooth surfaces, marveling at how flies land on ceilings, watching beetles cling for their lives to leaves while ants try to pry them off, and wondering as geckos clamber up the vertical faces of rocks. As part of the natural day-to-day lives of these creatures, their attachment mechanisms must be robust, repeatable, and energy efficient. With so many desirable qualities, engineers have begun to look to these natural attachment mechanisms based on fibrillar microstructures for use in all manner of devices. Small robotics, in particular, stands to gain much from the added mobility and energy efficiency that a successful biomimetic adhesive could provide. A new, exciting application for small robots is work on or inside the human body. To be successful, these robots must have precise position control yet be gentle enough to prevent damage to the patient.;This thesis aims to provide an understanding of the natural attachment mechanisms and use that knowledge to guide the development of removable, repeatable, viscous oil-coated fibrillar adhesives for use in biomedical devices. Approximate models for dry and wet adhesion are presented. The wet adhesion model combines the static capillary force solution with a viscous squeeze film force. Low and high aspect ratio microstructures were fabricated out of poly(dimethylsiloxane) and polyurethane using standard molding techniques. A simple method of applying a thin silicone coating on the structures was implemented. Adhesion experiments using a rigid glass substrate verified the developed models. Adhesion experiments on a soft polyurethane susbtrate revealed limitations of the current microfiber design.;Two capsule designs that implement the biologically inspired fibrillar tissue adhesive on a tri-legged anchoring mechanism for enhancing the performance and capabilities of existing passive capsule endoscopes are presented. Mechanism modeling, prototype fabrication, and in vitro testing with porcine tissues were completed. Finally, integration of the tissue adhesive into gas masks as a means of improving their sealing performance is discussed.