Fig. 5: Potential applications in fluid physical property evaluation.

a Photograph of the sensor-equipped robotic arm with readout circuits for the application, scale bar, 2 cm. Inset: photograph of the sensor, scale bar, 0.5 cm. b Oscillation frequency of the sensor after conversion as a function of pressure. Inset: diagram of the readout circuit and photograph of the readout module. c Cyclic tests of the dynamics of the normalized frequency change, where Δf is the recorded frequency change during this process and f₀ is the initial recorded frequency of the sensor, involve being immersed and held in, and extracted from various fluids. The zoom-in (right) clearly shows the taken-out state, which is defined as the point when the sensor is just extracted from the fluid. d, Measured pressure change between the initial and immersion states after decoupling the effect of the dielectric constant, which is almost proportional to the density (water: ~1 g/mL; detergent: ~1.05 g/mL; yogurt: ~1.2 g/mL; honey: ~1.4 g/mL). The measure of center denotes the mean value, and the error bars indicate the standard deviation from 100 repeated measurements. e Measured pressure change between the initial and taken-out states after decoupling the effect of the dielectric constant. The measure of center denotes the mean value, and the error bars indicate the standard deviation from 20 repeated measurements. f, Dynamics of the normalized frequency change of the sensor when it is immersed and held in and removed from ketchup. The zoom-in (middle) clearly shows the small variations in pressure, and corresponding optical images (right) of the position of the sensor, scale bar, 1 cm. Source data are provided as a Source Data file.