Micro-force measurement with high resolution, accuracy, and reliability is of interest in a broad range of applications including gravitational-wave detection, intelligent healthcare, bionic robotics, and micromanipulation. Herein, the researchand development in recent years of micro-force sensors based on various principles is reviewed thoroughly, presenting their characteristics and applications, as well as summarizing their advantages and limitations. The most indispensable component of force sensors, elastic sensitive elements, is underlined. Next, four kinds of not widely used but promising sensors are also introduced briefly. Finally, the traceable reference forces are analyzed, concluding with a future perspective into the corresponding challenges and opportunities of micro-force sensors for future research. This review aims at providing references for developing micro-force sensors and improving their performance.

Haptics plays an important role in grasping and manipulating objects for human hands and artificial robotic hands. The density of tactile receptors at the tips of the fingers is very high, reaching 140 units/cm ² . However, the density of the existing tactile sensors is very low. To increase the density of the 3-D tactile sensor, a novel high-density arrayed and curved 3-D tactile sensor based on bionic compound eye with the density up to 42 units/cm ² is proposed in this article. The tactile sensor can detect both normal force and shear force since it is isotropic. The force measurement setup has been successfully built with a sensitivity of 0.000280 mN/Gray for normal force and 0.0262 N/ μm for shear force. The sensor will provide a technical basis for force measurement of surgical robots and manipulators.

A micro/nano force can be traced to the International System of Units by means of an electrostatic force balance weight system. However, the micro/nano force measurement system is susceptible to environmental disturbances. Various methods have been proposed to reduce the effect of environmental disturbances and obtain high resolution and fast response. In this paper, we introduce a combination of air damping and inherent damping from the internal molecular friction of spring suspension. This will optimize system stability and improve environmental noise suppression. Results from the air damping model show that the damping ratio increases from 0.0005 to 0.1, which improves the vibration resistance. We found that the system with air damping has the advantages of fast response and low scatter.