MotorSkins—a bio-inspired design approach towards an interactive soft-robotic exosuit

Abstract

The work presents a bio-inspired design approach to a soft-robotic solution for assisting the knee-bending in users with reduced mobility in lower limbs. Exosuits and fluid-driven actuators are fabric-based devices that are gaining increasing relevance as alternatives assistive technologies that can provide simpler, more flexible solutions in comparison with the rigid exoskeletons. These devices, however, commonly require an external energy supply or a pressurized-fluid reservoir, which considerably constrain the autonomy of such solutions. In this work, we introduce an event-based energy cycle (EBEC) design concept, that can harvest, store, and release the required energy for assisting the knee-bending, in a synchronised interaction with the user and the environment, thus eliminating any need for external energy or control input. Ice-plant hydro-actuation system served as the source of inspiration to address the specific requirements of such interactive exosuit through a fluid-driven material system. Based on the EBEC design concepts and the abstracted bio-inspired principles, a series of (material and process driven) design experimentations helped to address the challenges of realising various functionalities of the harvest, storage, actuation and control instances within a closed hydraulic circuit. Sealing and defining various areas of water-tight seam made out of thermoplastic elastomers provided the base material system to program various chambers, channels, flow-check valves etc of such EBEC system. The resulting fluid-driven EBEC-skin served as a proof of concept for such active exosuit, that brings these functionalities into an integrated ‘sense-acting’ material system, realising an auto-synchronised energy and information cycles. The proposed design concept can serve as a model for development of similar fluid-driven EBEC soft-machines for further applications. On the more general scheme, the work presents an interdisciplinary design-science approach to bio-inspiration and showcases how biological material solutions can be looked at from a design/designer perspective to bridge the bottom–up and top–down approach to bio-inspiration.