Micro devices integrated with microchannels and electrospray nozzles using PDMS casting techniques

The design, fabrication, and analytical utility of a polydimethylsiloxane (PDMS)-based microfluidic device for electrospray ionization mass spectrometry (ESI-MS) are described. The microdevice is composed of a one-dimensional (1D), or three-dimensional (3D) channel integrated with sample reservoirs, built-in electrodes and silica capillaries as electrospray nozzles. Several innovative fabrication features have been reported in the present study. First, there is no dead-volume region in the connection of the microchannels and capillary nozzles using PDMS casting techniques. Furthermore, there is no bonding process required to form a sealed microchannel, resulting in a simpler fabrication process and providing higher mechanical strength for high-pressure applications. Another advantage of the developed method is the feasibility to fabricate genuine 3D channels integrated with electrospray nozzles such that chip size can be minimized. Electrical contact to apply required high drive voltage for generation of the electrosprays can be also integrated on the microfluidic chip. The micro devices could be mass-produced at low costs and used as a disposable device to generate ESI-MS signals for protein identification from low amounts of protein samples. Compared with commercially available nanospray capillary tips, the microfluidic module gives comparable signal quality for ESI-MS and also offers advantages in convenience and easiness in operation, permitting repeated usages and disposability.