Enhancing Grasping Function with a Thermoresponsive Ionogel Adhesive Glove for Patients with Rheumatic Diseases

Abstract

Rheumatic diseases often result in joint deformities and peripheral nerve damage, leading to impaired hand function. Current wearable assistive gloves commonly rely on external forces to flex fingers for grasping, but they face limitations such as bulky hardware, complex finger manipulation, and a risk of joint injuries. This study presents a lightweight, portable, soft wearable adhesive glove based on thermoresponsive ionogels aimed at enhancing grasping function. The ionogel exhibits high adhesion (≈35 kPa to various materials) at 25 °C and low adhesion (≈6.8 kPa) at 45 °C. Smart adhesive pads use embedded flexible heaters and temperature sensors for closed-loop control of the ionogels' temperature, providing programmable adhesion. A rapid switch from high to low adhesion is achieved within 4 s at 4 V. Additionally, a hands-free control interface uses inertial measurement units to detect the user's intent to release, facilitating easy and intuitive detachment. Weighing only 47 g, the glove is 7.2 times lighter than existing assistive gloves. Notably, it empowers users to grasp and release a variety of objects that will otherwise be unmanageable. Evaluation of various activities of daily living demonstrates that the glove significantly enhances grasping ability and increases autonomy for patients with rheumatic diseases.

Keywords: hand exoskeleton; medical robotics; soft robotics; switchable adhesion; wearable robotics.

Figure 1

System overview. a) Schematic illustration showing the overall configuration and application of the portable grasp‐assist glove with soft switchable adhesives. b) Representative images of ADL tasks performed by a rheumatic patient with hand impairments using the glove, including playing Chinese chess, picking up a student card, and grasping a bottle for drinking.

Figure 2

Overall design of the portable grasp‐assist glove with switchable soft adhesives. a) Side view of the proposed wearable adhesive glove. b) Palmar view of the proposed wearable adhesive glove. c) Optical image of a fully integrated electronic system. d) Photograph of the FPCB. The white dashed boxes indicate the locations of the major integrated circuit components. 1. FPC connectors. 2. NMOS transistor. 3. IMU. 4. MCU. 5. LDO. 6. To 3.7 V lithium polymer battery. 7. Switch. 8. Bluetooth. 9. LEDs. 10. Analog switch. e) Block diagram of the electronic system of the proposed robotic glove. f) Comparison of the control interface and system weight between various wearable assistive gloves. The proposed soft wearable adhesive glove has the hands‐free control interface and the lightest system weight (47 g).

Figure 3

Design, mechanism, and characterization of thermoresponsive ionogels with switchable adhesion. a) The proposed mechanism of thermoresponsive ionogels with switchable adhesion. Left: photo of ionogel disc at 25 °C and optical microscopic image of the ionogel surface. Middle: schematic illustration showing thermoresponsive adhesion switching mechanism of ionogels. Right: photo of ionogel disc at 45 °C and optical microscopic image of the ionogel surface. b) Temperature‐dependent adhesion strengths of the ionogels with 60, 65, and 70 wt.% PBA contents against glass substrates. c) Adhesion strengths of the ionogel with 65 wt.% PBA content against various substrates at different temperatures. d) Cycling adhesion tests of the ionogels between 25 and 45 °C against glass substrates. e) The effects of contact time on adhesion strength for the ionogels at high and low temperatures against glass substrates. f) The effects of preload on adhesion strength for the ionogels at high and low temperatures against glass substrates. g) Thermoresponsive adhesion switching for the ionogels is available on various substrates.

Figure 4

Smart adhesive pads with the flexible heater and in situ temperature sensor embedded. a) Schematic illustration of fabrication steps for smart adhesive pads. b) Optical image and IR camera image of the smart adhesive pad. c) Photographs of the smart adhesive pad under bending and twisting. d) The temperature evolution of the smart adhesive pad measured via the in situ temperature sensor and the IR camera at different applied voltages (1, 2, 3, and 4 V). Recorded temperature traces of the in situ temperature sensor (solid lines) are in excellent agreement with data taken from IR images (dashed lines). e) Maximum temperature error between the in situ temperature sensor with and without thermally conductive silicone applied and the infrared camera during heating from room temperature to 45 °C under various voltages. f) Heating time required for the smart adhesive pad to heat from room temperature (25 °C) to 45 °C by the flexible heater at different applied voltages. g) Time‐dependent temperature profile of the smart adhesive pad programmed to modulate the temperature in a stepwise fashion realized by the PID controller at ambient temperature (25 °C). h) PID control scheme for closed‐loop temperature control.

Figure 5

Hand release intention detection via the hands‐free control interface based on IMU. a) IMU orientation and joint angle of the little finger. b) Detachment trigger mechanism. Detachment is triggered by two consecutive extensions and flexions of the little finger. c) Schematic flow diagram of data processing steps for detecting the user intention. d) RMSE between the IMUs estimated angles and the ground truth static angles. e) RMSE between the reference and measured angles under conditions where both IMUs were fixed at a 90° angle and rotated about the x, y, and z axes at an angular velocity of 100°/s. f) RMSE between the reference angles provided by the servo motor and those measured by the IMUs at rotation speeds of 200, 400, and 800°/s.

Figure 6

Example of performance of the drinking task performed by the rheumatic patient without and with assistance of the glove. a) Selected snapshot images showing the patient was not able to pick up the water bottle without the assistance of the glove. b) Demonstration of the patient to grip, lift, drink from, and release the water bottle with the assistance of the glove. The curves below show real‐time measurements of the little finger's angle and the temperature of other finger's smart adhesive pads during this process.

Figure 7

Different simulated ADL tasks performed by the patient with rheumatic disease for unassisted (without glove) and assisted (with glove) conditions. a) Picking up a coin and placing it into a money jar. b) Playing Chinese chess to kill the opponent. c) Picking up a metal spoon and placing it into a cutlery organizer. d) Grasping the bottle, drinking juice from the bottle through a straw, and placing it back on the table. Grasping various objects of different shapes and sizes and placing them in the storage box: e) student card, f) softball, g) metal box, h) mobile phone. Without the assistance of the glove, the subject was not able to complete the tasks, whereas with the glove's assistance, the subject could complete the tasks.