Fig. 3: Circuit architecture and optimal coupling regime.
a A circuit diagram describing our wireless DEP and impedance sensing architecture. Power is inserted at VIN (using a function generator with an internal resistance Rint) and drives current, IP, through the primary inductor LP, relative to ground, GND. This power is coupled to the secondary inductor, LS, via mutual inductance, M, with a coupling coefficient, k, which depends on the distance of separation, x, between the two solenoid inductors. A variable load impedance, ZL, models the trapping of particles and can be detected on the primary circuit as a change in reflected impedance. The primary capacitor, CP, and device capacitance, CDEP, define the resonant frequency needed for optimal coupling. b–f A demonstration of strong coupling and the importance in finding the optimal coupling regime for efficient wireless power transfer. The wireless voltage gain over the coplanar nanogap was measured as a function of frequency as the distance, x, between the primary and secondary coil was decreased. As the distance was reduced, a larger voltage gain was observed until frequency splitting occurred due to strong coupling. This splitting in resonance from the coupled primary and secondary circuit effectively reduces the voltage at the target 1 MHz frequency needed for wireless particle trapping.
