An hourglass design with electrokinetic sampling and electrothermal actuation for micro biosensors

An hourglass design that enables electrokinetic sampling and electrothermal actuation for detecting waterborne pathogens with micro biosensors is presented. The hourglass component creates a large potential drop suitable for dielectrophoresis and serves as a V-shaped microelectrothermal actuator for structural measurements. Escherichia coli bacteria from a stagnant 5 μl sample were collected within 15 min with a signal of 5 V peak-to-peak (Vpp) at 1 kHz. The bacteria were detected by measuring resonant frequency shifts of the first eight modes of the microstructure, and a maximum sensitivity of 20.4 ± 5.3 fg/Hz was achieved with the seventh mode. The hourglass component is a unique design solution that combines structural excitation and electrokinetic sampling for micro biosensors.