Vision-based tactile sensing enhanced by microstructures and lightweight convolutional neural network.

Tactile sensing can provide a critical function in advanced interactive systems by emulating the human sense of touch to detect stimuli. Vision-based tactile sensors are promising for providing multimodal capabilities and high robustness, yet existing technologies still have limitations in sensitivity, spatial resolution and the high computational demands of deep learning-based image processing. This paper presents a comprehensive approach combining a novel microstructure-based sensor design and efficient image processing, demonstrating that carefully engineered microstructures can significantly enhance performance while reducing computational load. Without traditional tracking markers, our sensor incorporates a surface with micromachined trenches, as an example of microstructures which can modulate light transmission and amplify the visual response to applied force. The amplified image features can be extracted by an ultra-lightweight convolutional neural network to accurately infer contact location, displacement, and applied force with high precision. Through theoretical analysis, we demonstrate that the micro trenches significantly amplify the visual effects of surface deformation. Using only a commercial webcam, the sensor system effectively detected forces below 5 mN and achieved a millimetre-level single-point spatial resolution. Using a model with only one convolutional layer, a mean absolute error below 0.05 mm was achieved. The compliant sensor body and optical readout design make the system inherently compatible with soft robotic integration and immune to electrical crosstalk or electromagnetic interference that often affects electronic tactile arrays. These characteristics highlight its potential for reliable operation in complex human-machine environments.