A three-layer PMMA electrophoresis microchip with Pt microelectrodes insulated by a thin film for contactless conductivity detection

Abstract

A three-layer poly (methyl methacrylate) (PMMA) electrophoresis microchip integrated with Pt microelectrodes for contactless conductivity detection is presented. A 50 mm-thick PMMA film is used as the insulating layer and placed between the channel plate (containing the microchannel) and the electrode plate (containing the microelectrode). The three-layer structure facilitates the achievement of a thin insulating layer, obviates the difficulty of integrating microelectrodes on a thin film, and does not compromise the integration of microchips. To overcome the thermal and chemical incompatibilities of polymers and photolithographic techniques, a modified lift-off process was developed to integrate Pt microelectrodes onto the PMMA substrate. A novel two-step bonding method was created to assemble the complete PMMA microchip. A low limit of detection of 1.25 mg ml À1 for Na + and high separation efficiency of 77 000 and 48 000 plates/m for Na + and K + were obtained when operating the detector at a low excitation frequency of 60 kHz.

Contactless conductivity detection for analytical techniques: Developments from 2010 to 2012

“…The distance between the electrodes and the separation channel was given by the thickness of a dry film photoresist sheet, which was laminated over the electrodes, and was as thin as 17 μm. In a different approach, Pt sensing electrodes were prepared on a PMMA plate, which was subsequently bonded with a microchannel PMMA plate with a 50 μm thin PMMA film to achieve a minimum distance between the electrodes and the microchannel . A sidewall construction of detection electrodes, which were positioned at the side of the separation channel and were insulated from the channel with only a 1 μm thick silicon layer, was presented by Xu et al .…”

Fluid flow study of an AC electrothermal micropump consisting of multiple arrays of microelectrodes for biofluidic applications

“…In all cases the outer surfaces of the substrate were considered at a constant temperature condition equal to Tamb. Fluid viscosity was considered as thermally dependent by: 12,13 (0.19 W/mK) are among the most common substrate materials used for microelectrode fabrication in the literature. In order to study the effect of substrate material, different combinations of these materials in an ACET micropump were investigated (Fig.…”

Fabrication of PMMA nanofluidic electrochemical chips with integrated microelectrodes

“…Several methods have been reported for fabricating polymer nanochannels, such as sacrificial etching (Eijkel et al, 2004), proton beam writing (Shao et al, 2006), focused-ion beam milling (Cannon et al, 2004) and a variety of replication techniques (Liu et al, 2013;Studer et al, 2002;Zhang et al, 2008). Meanwhile, a few methods have been explored to fabricate microelectrodes on polymer substrates, including electrode microchannel method (Rossier et al, 1999), shadow mask method (Chen et al, 2001), screen printing (Kadara et al, 2009), electroless plating (McCarley et al, 2005, and photolithography techniques (Illa et al, 2010;Liu et al, 2011).…”

“…Photolithography is most widely used to fabricate microelectrodes due to the perfect control of shape and dimensions (Illa et al, 2010;Liu et al, 2011;Martins et al, 2013b). Plasma etching is compatible with photolithography techniques, and has been proved to be a good method for fabricating polymer microstructures, such as waveguides (Inoue et al, 2003), microchannels (Rossier et al, 2002), and even nanochannels (Liu et al, 2012).…”