University of Alberta,
Keywords: kirigami, thin-film, composites, soft robotics, stretchable electronics, biomimetics, adhesive
Summary:In this talk I cover our group’s long-term goals of producing adaptive materials and composites through the blending of two distinct, but complementary micro and nanotechnologies: kirigami engineering and bioinspired adhesives. Kirigami is the art of papercutting to create functional structures or art from thin materials through a combination of cuts and bending. In many cases, it is directly analogous to surface micromachining devices which often have very low aspect ratios of thickness to overall dimension, and kirigami provides inspiration to designers in how to work with thin film electronics, MEMS, and other microsystems. The act of adding thin cuts to stiff sheet can create springs and material compliance while maintaining the original material properties such as inherent modulus, temperature, and processing compatibilities. Attractively, kirigami is material agnostic – the design rules and functionality can work with everything from graphene to sheet metals, making the technology scalable from macro to nano. A completely different, but extremely complimentary technology we have long-term manufacturing expertise in is the use of microstructured biomimetic adhesives for applications ranging from climbing robots to MEMS pick and place. These adhesive materials, which take inspiration from geckos and spiders, can leverage van der Waals forces, which can normally cause catastrophic failure in MEMS, and make them significant enough to produce useful macroscale forces – on the order of 1 MPa when well designed. Despite the two decades of research into these biomimetic adhesives, there is a relatively minor economic impact to date, as they compete in a crowded commercial space with existing adhesive solutions and have yet to find a key niche. Entirely new classes of composite materials can be created when both kirigami techniques and bioinspired adhesive mechanisms are combined. The synergy can convert regular materials into springs via kirigami techniques, and then reversibly “turn off” the cuts with van der Waals forces or other reversible adhesion mechanisms. As the number of layers increase, and the ratio of surface area inside a composite compared to its volume increases, the viability of creating composites held together by van der Waals adhesion or other biomimetic mechanisms becomes a practical reality. We cover two proof-of-principle designs that allow stiffness and shape tuning with both reversibly adhered gecko composites and kirigami, and discuss how these distinct but complementary techniques for altering material properties can open the door to mass production of new classes of customizable and healing composite materials.