A polydimethylsiloxane electrophoresis microchip with a thickness controllable insulating layer for capacitatively coupled contactless conductivity detection

A polydimethylsiloxane (PDMS) electrophoresis microchip with a thickness-controllable insulating layer for capacitatively coupled contactless conductivity detection is presented. A PDMS film is spin-coated on a glass slide with Pt microelectrodes to be the insulating layer, and then permanently bonded with a PDMS channel plate to make the whole microchip. The thickness of PDMS films can be precisely controlled down to submicrometers. With a microchip with a 0.6 mu m-thick PDMS insulating layer, a superior limit of detection (LOD) of 0.07 mu M for Na+ was obtained. For comparison, another two microchips with the same design but different insulating layer thicknesses (15 mu m and 50 mu m) were tested, and LODs were 1 mu M and 3 mu M respectively, which are almost two orders of magnitude higher. Moreover, the microchip detector also exhibited excellent linearity, reproducibilities and separation efficiencies. (C) 2012 Elsevier B.V. All rights reserved.