Two-dimensional Force Sensing Whisker Based on a WGM Microbubble Resonator

We present an all-optical two-dimensional (2D) force sensor utilizing cascaded whispering gallery mode (WGM) microbubble resonators (MBRs). The 2D force sensing system is composed of two MBRs formed along a single microcapillary (a sensing “whisker”), two glass supports, and two tapered fibers. By using a characteristic sensing matrix to decouple the cross sensitivity to forces in orthogonal directions, the sensor achieves force sensitivities of 118.14 pm/mN (x-axis) and 177.12 pm/mN (y- axis). To the best of our knowledge, this is the first demonstration of a WGM-based sensor capable of sensing 2D forces on the lateral plane, highlighting its potential for robotics and biomedical applications that require high-precision vectorial force measurements.