Room temperature bonding of micromachined glass devices for capillary electrophoresis

We report a simple method to bond glass at room temperature for microfluidic applications, which is based on rigorous cleaning [K. Fluri, G. Fitzpatrick, N. Chiem, D.J. Harrison, Integrated capillary electrophoresis devices with an efficient postcolumn reactor in planar quartz and glass chips, Anal. Chem. 68 (1996) 4285–4290; N. Chiem, D.J. Harrison, Microchip-based capillary, Anal. Chem. 69 (1997) 373–378; D. Sobek, A.M. Young, M.L. Gray, S.D. Senturia, A microfabricated flow chamber for optical measurements influids, Proc. IEEE Micro-Electromechanical Systems Workshop, Fort Lauderdale, FL, Feb 7–10, 1993, pp. 219–224.] of the glass substrates before bonding. Low applied pressure on micromachined glass substrates contacted at 20°C provides devices, which are robustly bonded. These devices are able to withstand routine handling, and be used for capillary electrophoresis for as long as 2 years. Separation efficiencies as high as 90,000 theoretical plates were observed at 6–8 kV applied, comparable to 100,000 observed in devices bonded at 440–650°C. A wide range of the same or different types of commercially available glass can be bonded without heat treatment, alleviating the need for a good match in thermal expansion coefficients between the glasses.