# A Smart Rehabilitation Glove Based on Shape-Memory Alloys for Stroke Recovery
However, traditional rehabilitation methods are time-consuming, and the frequency and intensity of recovery cannot be well controlled [8; 9; 10]. Nowadays, exoskeleton-assisted rehabilitation machines effectively help patients to repeat hand movements periodically to complete therapy [11]. Currently, rehabilitation gloves are mainly divided into pneumatic and motor-driven types [12; 13; 14; 15]. A micro-motor-driven rehabilitation glove developed by [PERSON] et al. leverages machine learning to recognize the gestures of the sensing glove [16]. However, the glove driven by the motor is bulky. Additionally, a hydraulically actuated rehabilitation glove designed by [PERSON] et al. uses soft, segmented elastic actuators reinforced with fiber materials, facilitating specific bending, twisting, and stretching motions. Although it is effective for achieving sports rehabilitation, the pneumatic-driven glove is not easy to control, and the gas is difficult to seal [17]. In contrast to conventional approaches, shape-memory alloys (SMAs) have emerged as a significant research focus for rehabilitation exoskeleton devices due to their unique intelligent characteristics. The most remarkable feature of these materials is the shape-memory effect (SME), enabling recovery of their preset configuration under specific stimuli (e.g., mechanical stress or thermal activation). This behavior originates from a reversible martensitic transformation (MT) between an austenite phase (B2 cubic structure) at high temperature and a martensite phase (B19' monoclinic structure) at low temperature. Cooling below the martensite finish temperature (M\({}_{\ell}\)) induces the forward transformation (B2\(\rightarrow\)B19'), allowing deformability at low stresses. Subsequent heating above the austenite start temperature (A\({}_{\mathrm{s}}\)) triggers the reverse transformation (B19'\(\rightarrow\)B2), recovering the original shape [18; 19; 20; 21; 22; 23; 24]. When electrified, SMA wires generate Joule heating that elevates the temperature above A\({}_{\mathrm{s}}\), driving the martensite-to-austenite transformation. This phase change produces characteristic \"low-temperature compliance and high-temperature contraction\" behavior. The B2-to-B19' notation explicitly references the crystallographic restructuring during MT, which underlies the actuation mechanism in this study. Some studies have shown the feasibility of SMA for use in rehabilitation devices [6; 25; 26; 27; 28; 29]. For example, [PERSON] et al. developed a wearable hand-rehabilitation robotic arm, driven by SMA wires with corresponding joints equipped with sensors on the glove, to fix the path of SMA contraction [18]. The force generated by SMA contraction is used to compensate for insufficient finger-muscle force. Additionally, a variable-stiffness robot finger has been developed where the finger is driven by three embedded SMA wires [19]. Additionally, our research team previously filed a patent (CN 216,908,523 U) for an SMA-based rehabilitation glove, which laid the foundation for the amplified actuation structure described in this study [30]. Currently, commonly used SMAs include NiTi and NiTi-based alloys, Cu-based shape-memory alloys, and Fe-based shape-memory alloys. Among these, near-equiatomic NiTi alloys are widely used for their excellent mechanical properties and fatigue performance. But the recoverable strain of NiTi alloys is typically less than 8%; thus, a long SMA wire is required to provide sufficient contraction length for recovery treatment, which increases the volume of devices [20; 21; 22; 23; 24]. This study proposes a lightweight, small-volume, and portable rehabilitation glove based on SMA wires, facilitating repetitive recovery motion of disabled fingers for stroke treatment. This smart rehabilitation glove is equipped with an amplifier that amplifies the stroke of the glove six times through multiple windings of SMA wires, capable of accommodating 960 mm of wires within a 160 mm amplifier.