Heat-sensitive mode-localized current sensor with ultra-high sensitivity

Mode-localized sensors are a class of ultra-sensitive resonant sensors that leverage the mode localization effect of weakly coupled systems for signal detection. In this study, a high sensitivity MEMS current sensor based on mode localization is proposed, utilizing a heat-sensitive structure to enhance sensitivity. The heat-sensitive V-shaped beam generates thermal expansion forces in response to current-induced Joule heating, altering the stiffness of weakly coupled resonators and leading to a change in amplitude ratio. The current sensor based on the mode localization principle achieves the highest current resolution in the field of MEMS current sensors. Compared to previous mode-localized current sensors employing shunt resistors, the proposed design achieves a 10-times improvement in amplitude ratio sensitivity. Through rigorous experiments, the sensor demonstrates a noise floor of 2.7 nA/$\sqrt{\text{Hz}}$ and a resolution of 5.9 nA, achieving a 30-times enhancement over previous designs. The proposed sensor achieves the highest resolution among reported microelectromechanical system current sensors and outperforms handheld digital multimeters, laying a strong foundation for the development of next-generation miniaturized, high-precision current sensing technologies.