Capturing individual charged microparticles and cells with microelectrodes in a circular microfluidic channel

Capture and, subsequently, in situ characterization of microparticles generally require complex fabrication processes and sophisticated techniques in microfluidic devices. In this paper, we present a simple and inexpensive technique for capturing and applying chemical agents to individual charged microparticles with the same glass microelectrode in a circular microfluidic channel. The microfluidic device features a thin poly-dimethyl-siloxane (PDMS) layer (100 µm, thickness) above the circular channel (diameter, 50 µm) so that the tip of the glass microelectrode can enter into the channel by penetrating through the thin PDMS layer. When an electric field is applied across the tip of the microelectrodes, the tip can capture charged microparticles or living cells that are flowing through the channel. Meanwhile, the same glass microelectrode can be used to apply chemical agents to the captured particles or living cells by filling the solution of the chemical agent into its tip. This simple design method offered simple fabrication without the need for any specialized equipment for the manipulation of charged particles or living cells in controlled microenvironments.