A Microforce Sensor Incorporating a Flexible Force-Sensitive Mechanism and Interferometric Displacement Measurement

Measuring the deformation of an elastic element to obtain the exerted force is a typical design paradigm for force sensors. Even though the laser interferometric displacement measurement method has a lot of advantages, such as a large range, high accuracy, and noncontact, it is still seldom seen in the construction of microforce sensing systems. This article presents the design of a uniaxial microforce sensor that integrates a flexible force-sensitive mechanism and a commercially available laser interferometer. Adopting commercial interferometric instruments has effectively improved the deformation monitoring performance and sensor development efficiency. The well-designed flexible force-sensitive mechanism based on multistage parallelogram mechanisms has an excellent linear force-deformation relationship, which has been verified by theoretical analysis, simulation investigation, and experimental testing. A prototype was fabricated and characterized in the laboratory. The force sensor demonstrated 1.66-N/mm sensitivity, 1.53% nonlinearity, 64.40- $\mu $ N resolution, and 8.50-N range. Puncture experiments and palpation experiments confirmed its preliminary application potential. This work provides a new insight into the rapid development of high-performance force sensors.