Science & Technology (Commonwealth Union) – Novel modular, spring-like mechanisms optimize the utilization of live muscle fibers, enabling their integration into biohybrid robots for enhanced power generation.
Muscles stand out as nature’s ultimate actuators, efficiently converting energy into motion with unparalleled strength and precision relative to their size. Moreover, their remarkable ability to self-repair and strengthen through exercise adds to their allure.
Recognizing these advantages, engineers are delving into the prospect of leveraging natural muscles to energize robots. Several biohybrid prototypes have emerged, employing muscle-based actuators to propel artificial skeletons in various tasks such as walking, swimming, pumping, and grasping. However, each creation follows a unique design path, lacking a standardized approach to maximize muscle efficiency across diverse robot configurations.
Enter MIT’s latest innovation: a spring-like component poised to serve as a foundational module for a myriad of muscle-driven robots. This innovative “flexure” is meticulously crafted to extract optimal performance from attached muscle tissues, akin to finely tuning a leg press to achieve maximum output. By leveraging this device, engineers can amplify the inherent movement capabilities of muscles, unlocking their full potential.
The research team’s experiments demonstrated significant efficacy as they affixed a ring of muscle tissue onto the flexure, akin to stretching a rubber band between two posts. Remarkably, the muscle consistently and robustly pulled on the spring, stretching it fivefold more than prior designs.
This flexure design emerges as a versatile building block, adaptable for diverse configurations of artificial skeletons. Engineers can seamlessly integrate these components, outfitting them with muscle tissues to propel a range of movements, heralding a new era in biohybrid robotics.
Ritu Raman, the Brit and Alex d’Arbeloff Career Development Professor in Engineering Design at MIT, describes the flexures as akin to a skeletal framework that enables the conversion of muscle actuation into diverse degrees of motion in a highly predictable manner. She also pointed out that they are essentially offering roboticists a fresh playbook for crafting robust and precise muscle-driven robots capable of performing intriguing tasks.
In a paper published recently in Advanced Intelligent Systems, Raman and her team outline the intricacies of this innovative flexure design. Collaborating with her at MIT are co-authors Naomi Lynch ’12, SM ’23; undergraduate Tara Sheehan; graduate students Nicolas Castro, Laura Rosado, and Brandon Rios; along with Professor of Mechanical Engineering Martin Culpepper.
When muscle tissue is isolated in a petri dish under favorable conditions, it exhibits spontaneous contraction, albeit in unpredictable directions and with limited utility, according to the researchers of the study.
Raman pointed out that when the muscle is unanchored, its movement is erratic, akin to flailing in a liquid medium.
To harness muscle as a mechanical actuator, engineers commonly affix a strip of muscle tissue between two pliable posts. As the muscle contracts naturally, it bends the posts and draws them closer, generating movement intended to power components of a robotic framework. However, these setups yield restricted movement due to the inherent variability in muscle-tissue interaction with the posts. Depending on placement and contact area, muscles may intermittently succeed in pulling the posts together, yet at other times, they may exhibit uncontrolled oscillations.
Raman’s team endeavored to devise a framework that optimizes muscle contractions, irrespective of placement or orientation, to yield and predictable and dependable movement.
Raman poses a critical query: How can we craft a skeletal structure that optimally harnesses the force generated by muscles?” The researchers began by examining the diverse directions muscles can naturally maneuver. Their logic followed that if a muscle intends to draw two posts together along a certain path, those posts ought to be linked to a spring permitting movement solely in that direction as it is pulled.
“We need a device that is very soft and flexible in one direction, and very stiff in all other directions, so that when a muscle contracts, all that force gets efficiently converted into motion in one direction,” explained Raman.
It so happened that Raman discovered numerous similar gadgets within Professor Martin Culpepper’s laboratory. Culpepper’s team at MIT focuses on crafting and designing machine components like miniature actuators, bearings, and various mechanisms. These components are integrated into machines and systems to facilitate extremely precise movement, measurement, and control across a diverse range of applications. Within the assortment of precision machined elements crafted by the group are flexures—spring-like structures typically formed from parallel beams capable of flexing and stretching with nanometer precision.
