Bio-Inspired Dry Adhesives

A new generation of bio-inspired adhesives is under development for controlling the face-seal leakage in respirator masks. While conventional pressure-sensitive adhesives rely on liquid-like fluidity under pressure to adapt to surface roughness, biological adhesion mechanisms employed by gecko, spider and insects rely upon the compliance of a fibrillar array to accommodate surface roughness for magnifying molecular-scale contacts. The fibrillar nature of biological adhesives distinguishes them from conventional pressure-sensitive adhesives in terms of adhesion to wet surfaces via capillary action, self-cleaning, stability under repeated use and in severe conditions, the ability to accommodate facial hair, dirt and skin irregularities, and removability. Bio-inspired adhesives, however, cannot match some key qualities of pressure-sensitive adhesives, including ductility and energy absorption capacity (reliability and immunity to excess size effect), density of the interface (sealing qualities), and accommodation of local (sub-micron-scale) roughness (adhesion capacity). Our approach makes complementary use of patterned bio-inspired adhesives and highly stable variations of pressure-sensitive adhesives to combine their corresponding advantages in a new generation of bio-inspired adhesives. The integrated theoretical/experimental work of Phase I project verified the balanced qualities and the commercial promise of the new bio-inspired adhesives. The proposed Phase II project will build upon the Phase I accomplishments towards full development and optimization of the new bio-inspired adhesives, their integration into the peripheral seal of full-facepiece respirator masks, thorough evaluation of the corresponding benefits to the face-seal leak resistance of respirators, and assessment of the commercial potential of the technology in application to respirator masks and also in other fields of application.