All PDMS pneumatic microfinger with bidirectional motion and its application

This paper describes the experimental results on static and dynamic bending motions of all polydimethylsiloxane (PDMS) pneumatic microfinger. The proposed pneumatic microfinger consists of two PDMS diaphragms with different thicknesses or material properties. The microfinger is fabricated through PDMS molding process and the PDMS-to-PDMS bonding process. The out-of-plane motion of the microfinger is achieved by using the pulling force of the inflated actuator diaphragms while the square wave pneumatic force is supplied to the balloon actuators. In the case of the microfinger with different thickness of two diaphragms, the pressure-dependent dual-bending motion of the microfinger is available. The proposed working principle is confirmed from the steady-state bending angle measurement of the two types of the microfingers with different thicknesses of the bottom PDMS layers. While the pneumatic force is less than 20 kPa, the top diaphragm of Type A microfinger is fully inflated and the microfinger moves downward. Around 20 kPa, the bending direction of the microfinger starts to be changed from downward to upward. The microfinger with two types of PDMS films with different mixing ratio of base polymer and curing agent is also proposed for the improvement of the PDMS-to-PDMS bonding strength, the material property change, and the rapid manufacturing process. The microfinger moves only upward because the top PDMS diaphragm with excess of silicon hydride group is relatively stiffer than the bottom PDMS diaphragm with excess of vinyl group. The dynamic bending motion of the single microfinger and the object-lifting motion of the microfinger array are observed to evaluate their performance. The dynamic bending angle of the microfinger with golden air bone length is about 179deg at 1 Hz, while the square wave input pressure of 250 kPa is supplied to finger structure