Major Research Result

NEW Artificial Muscle Actuators: The Key to an Immersive Augmented Reality Experience

  • 2022-11-07
  • 152

Researchers use shape memory alloys to create compact, lightweight, and high power density actuators for wearable devices

Wearable optical devices find use in several fields, ranging from gaming to medicine. To improve on the immersive visual experience current devices offer, researchers from South Korea have developed an all-new compliant amplified shape memory alloy actuator (CASA). Its elliptic configuration and compliant structure amplify actuation strain and retain power density. Moreover, the artificial muscle-like actuator is light and compact. The researchers also demonstrate CASA-based prototype augmented reality glasses and two-way communication 3D-touch gloves.

Wearable technology is expected to utilize shape memory alloy-based actuators in the near future

Image source: Shutterstock

Wearable devices are a technology with gaming, medical, and communication applications. They require compact, lightweight, and high power density actuators—devices that move and control a mechanism—for smart operation. These criteria put a variety of design constraints from an engineering standpoint. Previous studies have considered using shape memory alloys (SMAs), amongst other materials, for actuators. However, they suffer from low energy efficiency and require additional heavy components.

Recently, a team of researchers from South Korea, led by Prof. Je-Sung Koh of Ajou University, have developed a compliant amplified SMA actuator (CASA) for wearable devices. It employs a minimal strain-amplification mechanism to compensate for the existing shortcomings. The findings were published in Nature Communications on 18th July 2022

Prof. Koh explains the fundamentals of CASA: “The actuator has an optimized elliptic configuration and a compliant structure: that of an artificial muscle. It consists of an SMA wire and elastic beams that amplify actuation strain and minimize power density reduction. The actuator weighs only 0.22 grams but is powerful enough to throw 10 grams of weight. Moreover, it has a relatively high power density of 1.7 kW/kg and an actuation strain of 300% under 80 grams of external payload.”

The researchers have integrated this actuator with a bistable parallelogram linear stage. It improves energy efficiency, making possible the development of compact devices. Prof. Koh’s team has utilized the artificial muscle actuator to demonstrate multi-focus augmented reality glasses and soft 3D-touch gloves. 

The prototype glasses are capable of image depth control to relieve visual fatigue. On the other hand, the haptic gloves generate high pressures to provide large skin-deformation sensations for the wearer. They can also detect external contact by utilizing the actuator as a resistance-type force sensor, establishing two-way communication. 

“The present research has demonstrated the practical use of smart materials in commercial wearable devices. CASA has distinguishing performance in terms of actuation strain, power density, weight, and form factor. I believe it can replace the commercially available motor-based actuators soon,” concludes Prof. Koh.



Dongjin Kim1, Baekgyeom Kim1, Bongsu Shin2,3, Dongwook Shin1, Chang-Kun Lee2,3, Jae-Seung Chung2,3, Juwon Seo2,3, Yun-Tae Kim2,3, Geeyoung Sung2,3, Wontaek Seo2, Sunil Kim2, Sunghoon Hong2, Sungwoo Hwang2,4, Seungyong Han1, Daeshik Kang1, Hong-Seok Lee2,5 and Je-Sung Koh1

Title of original paper:

Actuating compact wearable augmented reality devices by multifunctional artificial muscle


Nature Communications 



1Department of Mechanical Engineering, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16499, Republic of Korea. 

2Samsung Advanced Institute of Technology, Samsung Electronics, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea

3Samsung Electronics, 34, Seongchon-gil, Seocho-gu, Seoul 06765, Republic of Korea

4Samsung SDS, 125, Olympic-ro, 35-gil, Songpa-gu, Seoul 05510, Republic of Korea

5Department of Electrical and Computer Engineering, Seoul National University, 1, Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea

*Corresponding author’s email:

About Ajou University

Founded in 1973, Ajou University has quickly grown to become one of the top universities in the Republic of Korea. With over 15,000 students and 50 research centers in diverse fields, Ajou University partakes in the largest national research and graduate education project funded by the Korean Ministry of Education. In line with its recently reformed vision, Ajou University’s goal is to change society by connecting minds and carrying out high-impact research to improve the welfare of people in and outside Korea. 


About the author

Prof. Je-Sung Koh is an Associate Professor in Department of Mechanical Engineering at Ajou University, Republic of Korea. His research group is developing biologically inspired robotic technologies. These include abstracting principles of nature creatures and building a biologically inspired robot using smart materials. His research interests encompass design and fabrication with smart materials, robots based on foldable structure, and soft robotics for enabling human-robot interaction.