A method includes providing a fluid to a structure including an aperture, applying a voltage signal to a circuit that includes the fluid, applying a substantially periodic pressure signal to the fluid, detecting a current signal in the circuit as an analyte passes through the aperture in response to the substantially periodic pressure signal, and processing the current signal and the substantially periodic pressure signal to determine a switch time and a release time for the analyte. An apparatus includes a structure including an aperture to receive a fluid, a voltage source to provide a voltage signal to an electronic circuit having a path that includes the aperture, a pressure signal generator to provide a substantially periodic pressure signal to the fluid, and a system to process the periodic pressure signal and a current signal induced in the electronic circuit.