Novel Compact Tactile Stimulator with Sensing: Designed for Individuals with a Brain Injury and MRI

Existing tactile assessments indicate that greater than half of individuals living with a brain injury experience tactile impairments, which impede their recovery. Yet, these tactile assessments lack sensitivity, reliability, and ergonomic compatibility for the millions of individuals who experience a clenched hand posture following their brain injury. We present a novel compact, automated tactile stimulator with real-time force estimation, which we designed for use in brain injury and magnetic resonance imaging (MRI). The system interfaces with the finger through a compact-sized stimulator (9 mm height - 18 mm outer diameter) that uses pneumatic actuation to inflate a silicone membrane. The membrane indents a Kirigami cutout, maintaining a constant 6 mm contact area on the finger and enabling precise force application down to 0.01 N with increments as low as 0.01 N. Integrated fiber optic displacement and pressure sensors provide real-time measurement of the indentation of the skin and estimation of forces applied. A physical model and a neural network each estimated the applied forces, with the latter achieving higher accuracy. This novel tactile stimulator system addresses critical limitations of existing devices, enabling accurate, low-force tactile stimulation and measurement, while maintaining a compact size to investigate the neural processes governing tactile perception, including following a brain injury.