Samsung Electronics Publishes Paper in Nature Communications on Multifunctional Artificial Muscle Actuator

Samsung Electronics announced that Dr. Bongsu Shin (co-first author) at Samsung Research¹ published a paper titled “Actuating Compact Wearable Augmented Reality Devices by Multifunctional Artificial Muscle” in the world-renowned journal ‘Nature Communications.’

This project was carried out in partnership with the Ajou University’s team of Mechanical Engineering, led by Professor Je-Sung Koh (corresponding author) based in Korea. The joint research team developed an artificial muscle actuator that can be applied on augmented reality (AR) glasses and naturally fit haptic gloves.

With the increasing popularity of the metaverse, actuator and sensor technologies are evolving rapidly to create even more immersive experience in virtual worlds. Actuators and sensors integrated into wearable devices must be compact and lightweight as the devices are worn by users and often require mobility. The conventional actuator had certain limitations as to the realization of more advanced functionalities, as thin form factor and high-power density would be difficult for conventional types to achieve.

The research team suggests an artificial muscle actuator that resolves the challenges in practical engineering, which are limited to conventional types such as electromagnetic actuators. An artificial muscle actuator can function as a small-scale, high-power actuating system with a sensing capability for developing wearable devices such as multi-focus AR glasses and naturally fit haptic gloves. The research team designed a shape memory alloy (SMA)-based lightweight and high-power artificial muscle actuator, the so-called compliant amplified SMA actuator (CASA). The newly developed version is lightweight (0.22g) but durable enough to lift a weight that is 800 times heavier than itself.

“This new actuator that we suggest is lightweight, compact yet powerful in terms of force-to-weight ratio. It is significant that the new actuator has overcome the limitations of the conventional actuators, while bringing the potential for its expanded applications ranging from robotics to wearable devices,” Dr. Bongsu Shin at Samsung Research said. “We anticipate that the outcome of our latest research will be the core hardware technology for more immersive and interactive experience for the next generation.” 

The team also demonstrated how the actuator enables image depth control. Binary depth switching is adopted to reduce vergence accommodation conflict (VAC), which can cause visual fatigue to some of AR glasses users, by directly adjusting distance between the display and the optical system of the AR glasses prototype based on the focusing distance of the object to be projected.

Furthermore, non-vibrating mechanotactile outputs are important to generate natural and expressive tactile sensations on skin through haptic devices. To convey the sensation of a large skin deformation, haptic devices require actuators with a high force-to-weight ratio and a large displacement. Combining multiple actuators in the limited area of the haptic device prototype also enables more expressive tactile experiences.

CASA triggers an action to an object with pressure and measures pressure without a sensor by using a characteristic of the artificial muscle of which electrical resistance varies in response to outside pressure. The haptic glove prototype equipped with CASA is so slim and pressure-sensitive that it has the potential to be applied to telehaptics which recognizes expressions made by the tactile writing system and converts them into electric signals.

¹ Samsung Research, acting as Samsung Electronics’ advanced R&D hub, leads the development of future technologies for the company’s Device eXperience (DX) Division.