We designed a shape memory alloy-based lightweight and high-power artificial muscle actuator, the so-called compliant amplified shape memory alloy actuator (CASA). Despite its light weight (0.22 g), the actuator has a high power density of 1.7 kW/kg, an actuation strain of 300% under 80 g of external payload. This actuator can be also designed to weigh ~ 17 mg, demonstrating its scalability.

 A haptic glove equipped with CASAs provides a high-pressure tactile experience with a relatively high continuous contact pressure compared to high-frequency actuators (vibration) under a limited volume. Despite its thin form factor, the haptic glove is so powerful as to throw a 10 g weight, about 45 times heavier than the single actuator. The haptic glove can, thus, convey the highly impulsive pressure as well as gradually increasing and static pressure to the user.

 The CASA with the embedded smart material has a favorable characteristic to couple sensing and actuation for applications such as communication for deaf-blind people through the haptic glove. The electrical resistance of the SMA can be varied by changing the strain. The SMA-based device can be controlled through resistance-based self-sensing techniques.

 We designed a prototype pair of AR glasses capable of image depth control using CASAs to relieve visual fatigue. The actuators in the glasses are mechanically adjusting the display allowing natural focus cues for users. This approach can resolve the vergence-accommodation confilict (VAC), a major source of discomfort in AR systems.

 The combination of SMAs and a bistable structure which only requires input energy to shift its state and no energy to maintain each state is suitable for energy efficient long-term use. Each SMA wire triggers snap-through bistable transition between the beam’s downward and upward stable states, opening and closing a breathable chamber.