On-chip integration of vector force sensor based on AlGaInP micro-LEDs with interface light coupling modulated by microstructures

Optical principle-based force sensors offer significant advantages in detection applications for surgical robots and wearable devices. With the rapid development in these fields, there is an increasingly urgent demand for improving sensor performance and reducing sensor size. Here, we present a monolithic micro-vector force sensor by integrating the sapphire based AlGaInP micro light-emitting diodes (micro-LEDs) and a surface micro-structured polydimethylsiloxane (PDMS) elastomer. The sensor primarily operates based on the overlapping between the emission spectra and the detection spectra of the multiple quantum well (MQW) structure in the micro-LEDs and the modulation of the reflectance of the sapphire interface by highly elastic microstructures. This monolithic micro-vector force sensor is characterized by its small footprint with a diameter of only similar to 7 mm, and it exhibits good real-time response performance with response sensitivities to normal force and shear force of 0.38 nA/mN (0-2 N) and 1.3 nA/mN (0-200 mN). Furthermore, this monolithic integrated device can be manufactured on a large scale and at low cost using wafer-level microfabrication processes. Additionally, the sensor operates in the biologically safe red light spectrum, thus offering broad prospects for applications in fields such as biomedicine and wearable devices.