EPSCoR Research Fellows: NSF: Enhanced Functional Deformation Transfer in Elastomer-Shape Memory Alloy Composite Actuators for Soft Robotics

Shape memory alloys (SMAs) possess the unique ability to recover large deformations either upon heating (shape memory effect) or unloading (superelasticity). This characteristic makes them ideal for use as skeletal backbones in lightweight actuators or grippers for robotics. However, one significant obstacle to their broader adoption lies in the difficulty of machining them into novel shapes.

This project addresses this challenge by utilizing laser micromachining to create SMA geometries that were previously unattainable. Laser micromachining is particularly attractive as it can be scaled up for mass production. The project proposes to use these innovative 2D lattice SMA geometries and embed them in rubbery polymers to enable locomotion in soft robotics.

Soft robotics, which utilizes compliant materials instead of rigid links, mimics movement mechanisms found in nature. This soft system, fabricated through mass production techniques, aims to expand the practical applications of SMAs in areas such as artificial muscles, soft grippers, wearables, medical devices, and haptic devices, all of which offer societal benefits.

The use of SMAs' functional behaviors, such as the shape memory effect and superelasticity, remains limited due to challenges in machining. As a result, novel geometries like auxetics, which enhance functional deformations, are underutilized. Over the past year and a half, the project has applied laser ablation, a micromachining technique suitable for mass production, to create auxetic SMA meshes that demonstrate enhanced 2D functionality.

These geometries are intended to serve as backbones in elastomers, enabling 2D actuation for soft robotics. The proposal aims to develop 2D auxetic lattice actuators that successfully transfer the functional shape memory deformation from the SMA backbones to the surrounding elastomer. This composite system is designed to serve as a testbed for thermally driven actuation devices in soft robotics.

The project will utilize the advanced materials analysis and imaging facilities at the University of Michigan’s Michigan Center for Materials Characterization (MC)². In-situ and ex-situ scanning electron microscopy (SEM) with heating capabilities will be employed to analyze surface topology, chemistry, phase contrast imaging, and full-field deformations using digital image correlation (DIC).

The principal investigator (PI) will collaborate with Dr. Abdon Pena-Francesch, an expert in functional polymers and soft robotics. By addressing a gap in research expertise in polymer characterization, both in macroscale thermomechanical characterization and micro/nanoscale analysis of polymers, this effort will build on the PI’s existing work in polymer/composite characterization and SMA applications, positioning the PI for future utilization of (MC)² facilities.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.