Electro-Permanent Artificial Muscles

What it does

A low-power, muscle-like actuator that uses magnetic forces to create motion and hold force with minimal energy. It solves the bulk, inefficiency, and tethering of current artificial muscles, enabling compact, wearable, and bio-inspired assistive technologies.

Your inspiration

From childhood afternoons glued to animal documentaries and evenings dismantling toys, I became obsessed with how creatures move and how machines work. A degree in mechanical design armed me with tools, and a Master’s in Bionic Engineering fused those passions. Yet millions of people with limb loss still rely on bulky, rigid, power-hungry prosthetics, so I pursued a leaner answer. Biological muscles contract cleanly, without gears or linkages; inspired by this, I turned to magnetism, dedicating my PhD to developing compliant, power-efficient magnetic artificial muscles to power life-restoring limbs and wearable assistive technology.

How it works

The actuator works by harnessing magnetic interactions between two types of materials: soft-magnetic and hard-magnetic. A soft-magnetic core is wrapped in a solenoid; when a short electrical pulse is applied, it flips the core’s magnetic polarity. This change creates controlled attraction or repulsion with nearby hard-magnetic (permanent magnet) elements, which are unaffected by the pulse. The resulting force produces motion and mechanical work. Because these magnetic states are bistable, no energy is needed to maintain force, enabling zero-energy holding of objects when used in a prosthetic hand. The movement and output force depend on the geometry, the electromagnetic and material properties of its elements, as well as the electrical characteristics of the pulse. This simple yet powerful concept converts discrete electrical inputs into continuous mechanical force, mimicking muscle-like behavior with low-power, compliant components.

Design process

The project began with a central question: how can we improve the state of the art in artificial muscles for wearable devices? Literature reviews pointed to the need for lower driving voltages, higher power efficiency, and solutions that avoid pumps or tethered systems. I explored electro-permanent magnet principles to generate controllable attraction and repulsion between magnetic materials. The design process followed four stages: ideation, prototyping, iteration, and validation. I tested combinations of solenoids and magnets, focusing on switching the polarity of AlNiCo-5 (a soft magnetic material) to interact with NIB permanent magnets. Key design parameters, such as the geometry and configuration of magnets and solenoids, their electrical and magnetic properties, and the forces generated between them, were characterized and analyzed to uncover the design principles governing this technology. These insights guided performance optimization in microsecond energy pulse switching and magnet sizing. Final testing showed improved power efficiency, portability, and low-voltage operation, with stress and strain values comparable to natural muscles. Feedback from 35 interviews across healthcare and robotics confirmed the need for compact, compliant actuators in wearable tech.

How it is different

Unlike other artificial muscles, our actuator uniquely offers zero-energy force holding, able to maintain load without consuming power or using additional mechanisms. It operates at low voltage, is electrically driven, and remains untethered. This overcomes common limitations in other systems that require high voltage, are tethered to pumps, or suffer from low efficiency. Compared to traditional motors, it avoids bulky transmissions, is inherently compliant, and conforms naturally to the human body. Unlike standard solenoids, it doesn’t require continuous current to hold force. Instead, a brief electrical pulse magnetizes a soft-magnetic core, triggering stable attraction or repulsion with a set of permanent magnets. This creates motion and allows the actuator to perform work and sustain force for long periods without additional energy input. The result is a compact, efficient, and bio-inspired solution ideal for wearable, assistive, and robotic applications.

Future plans

Next steps include miniaturizing the actuator’s driving electronics for integration into wearable assistive devices, along with embedding flexible sensors and electronics. We’re developing multi-actuator arrays for modular motion and exploring commercialization in smart garments, exosuits, robotics, and haptics. To diversify applications, we’re also testing these actuators in efficient, untethered robots with diverse locomotion modes. In parallel, we aim to validate scalable manufacturing to support market adoption. Our goal is to deliver compact, efficient, and human-safe artificial muscles for real-world wearable and robotic technologies.

Awards

This project received a commercialization grant (GAP funding) under the ARISE Program at the Singapore University of Technology and Design (SUTD) through the Venture, Innovation & Entrepreneurship (VIE) office, supporting the development of smart assistive wearables using this registered technology.