Enhancing and Decoding the Performance of Muscle Actuators with Flexures

Abstract

Leveraging living muscle as an efficient and adaptive actuator for soft robots has been of increasing interest over the past decade, with a focus on proof‐of‐concept demonstrations of function. Reproducible design and scalable manufacturing of biohybrid machines requires methods to increase the stroke output of strain‐limited muscle actuators and enable accurate and precise quality control and performance monitoring. Compliant mechanical elements, termed flexures, are designed to enhance muscle contractile stroke to ≈5× previously reported values and decode contraction dynamics with high spatiotemporal resolution. Combining rigid and flexible elements within a linear elastic flexure enables us to outperform the sensitivity of gold standard elastomeric beam‐based measurements of muscle contraction at both low‐ and high‐frequency stimulations. Flexures are leveraged to make quantitative comparisons of force, work, and power outputs in muscle actuators, driving us to discover a new observation of frequency‐dependent fatigue in muscle, and also develop a novel method for tuning muscle contractile dynamics in a frequency‐independent manner. By enhancing the contractile stroke of muscle actuators and precisely tuning contractile dynamics and endurance with unprecedented precision, this study sets the stage for leveraging flexures to improve robust, reproducible, and predictive design and manufacturing of next‐generation biohybrid robots.