Patent ID: 8188438

Claim:
An electrokinetic microfluidic flow cytometer apparatus comprising: a substrate having defined therein an input port, an output port, and a microchannel that fluidly connects the input port and the output port to allow fluid to flow therebetween; a pair of signal and noise detection channels that are defined in the substrate and fluidly connected to the microchannel from locations adjacent to each other and which extend in opposite directions away from the microchannel to receive ambient electrical noise; and a particle detection circuit that is electrically connected to the signal and noise detection channels and generates a particle detection signal in response to a differential voltage across the signal and noise detection channels, which tracks changes in resistivity across an adjacent portion of the microchannel as particles within the fluid move responsive to an electric field along that portion of the microchannel, while at least substantially canceling a common component of the ambient electrical noise received by the signal and noise detection channels; and a sensing gate that reduces the cross sectional area of the microchannel through which fluid carrying particles can flow, wherein the signal and noise detection channels are fluidly connected to the microchannel adjacent to the sensing gate, and wherein the particle detection circuit generates the particle detection signal responsive to resistivity changes that occur across the sensing gate as particles flow through the sensing gate under electrokinetic force, wherein the sensing gate reduces the width of the microchannel through which fluid can flow to less than about ten times a width of individual particles that are to be sensed as they flow within fluid through the sensing gate.