Stretchable R-G-B haptic soft optical sensor for human-robot interaction

Polymer-based optical sensors, renowned for their flexibility and stretchability, have found extensive application as displacement sensors in the soft robotics and wearable robotics. Emitting from LEDs, light traverses through a transparent and flexible polymer core, thereby modulating the intensity of light detected by photodiodes contingent upon alterations in the core's cross-sectional area induced by sensor deformation. Due to its polymer composition, it offers flexibility, enabling free deformation, while its ability to measure light intensity demonstrates immunity to external magnetic and electric fields. In this study, a novel haptic sensor was devised by integrating color filters into polymer-based optical sensors to detect specific wavelengths from the LED's initial spectrum. Pressing of Red, Green, and Blue color filters enclosing the core enables light transmission through the filters. The spectrometer detects wavelengths ranging from 415nm to 680nm through eight channels, sufficiently covering the visible spectrum. Furthermore, it was ascertained that wavelength classification by color filters remains unaffected even with a decrease in initial intensity of light due to sensor deformation. Hence, the application of this sensor in wearable robotics or soft robotics is envisaged to facilitate simultaneous displacement measurement and haptic feedback, enhancing control and measurement capabilities.