Enhanced two-dimensional superelasticity in a laser micromachined auxetic NiTiNOL geometry

• Laser micromachining is mass production technology that can be used to create novel geometries that are not possible via other technologies. • We showcase an example of superelastic enhancement in a novel auxetic geometry in a thin nitinol sheet. The superelastic effect in nitinol allows it to accommodate and recover large amounts of deformation. Despite possessing this incredible ability, their use in applications remains limited due to the difficulty in machining into novel geometries like auxetics. Laser-micromachining is an attractive solution to this problem, with the ability to micromachine geometries not conventionally possible. Such geometries, like auxetics, could be used to enhance the simultaneous two-dimensional accommodation and recovery of superelastic strain. We showcase an example of this enhancement in a laser-micromachined auxetic geometry that has minimal material removal. The recoverable strain in the auxetic geometry represents an enhancement of 86% increase over the bulk failure strain in the loading direction, and an absolute increase of 70% over the bulk failure strain in the transverse direction. Such geometries with enhanced two-dimensional functionality could serve as functional backbones on elastomeric composite testbeds with potential applications in soft robotics, stretch-triggered drug delivery, stretchable electronics, adaptive filters and controlled adhesion.