This work presents a three-dimensional flexible polyimide (PI) probe array with biodegradable polymer that offers desirable insertion capability. In order to avoid the recording sites position shifts slightly and damage neuron cells when the body moves, the flexible neural probes are more preferable than traditional Si-based neural probes. A sufficient buckling strength of flexible probe is critical for inserting flexible probe into the brain. Here, we used a biodegradable polymer, polyethylene glycol (PEG), to improve the mechanical stiffness of flexible probe. PEG, which is solid state at room temperature and dissolves when immersing in water, was coated onto the flexible probe and the mechanical stiffness of the flexible probe was increased before insertion into the biological tissue. The buckling strength of different probes was simulated using finite element analysis and measured by compression tester. The coated PEG flexible probe maintains sufficient stiffness to facilitate tissue penetration with solid PEG elastic modulus of 660±19 MPa but loses its strength within 25 minutes once immersed in saline. A microassembly method of three-dimensional flexible probe array was also proposed to integrate the flexible probe and their interconnections. In vitro test, the coated PEG flexible probe regained their original impedance of 12.8 kΩ at 1 kHz within 30 minutes of immersing in saline via water absorption and polymer’s biodegradable response.

In this paper, a tilt sensing mechanism based on the capacitive micromachined ultrasound transducers (CMUTs) is presented. By measuring the difference in the time of flight of various pulse-echo signals from different CMUT transmitting elements to one common receiving element in the oil bath, the tilt angle of the oil surface can be determined. With the proposed device, the maximum tilt angles of 20° and 28° have been measured in the clockwise and counterclockwise directions, respectively, and the difference between the measured and the theoretical values of the tilt angle was found to be within 0.05° during the whole test.

In this paper, the dynamic mechanical stability of the liquid-filled lenses was studied, in which acoustic excitation was used as broad band perturbation sources and the resultant response of the lens was characterized using non-contact laser Doppler vibrometer. To the best of our knowledge, it's the first time that the mechanical stability of liquid-filled lenses was experimentally reported. Both experimental results and theoretical analysis demonstrate that the resonance of the lens will shift to higher frequency while the vibration velocity as well as its magnitude will be reduced accordingly when the pressure in the lens cavity is increased to shorten the focal length. All of these results will provide useful references to help researchers design their own liquid-filled lenses for various applications.