BONDING
US Researchers have developed a rapid method for bonding thermoplastic microchannel plates. Suitable for volume production, the technique takes advantage of the minute network of channels within the plates to deliver solvent adhesives.
A research team from the National Institute of Standards and Technology (Gaithersburg, MD, USA), George Mason University (Fairfax, VA, USA), and Sequoyah Technology (Olney, MD, USA) describes the bonding procedure in the article “Capillarity Induced Solvent-Actuated Bonding of Polymeric Microfluidic Devices,” published in the 1 April 2006 issue of Analytical Chemistry. The team clamped together two polymethyl methacrylate microchannel plates, injected a minute amount of acetone solvent at one end of the microchannels, and applied a vacuum at the opposite end. As the solvent moved through the channels, capillary forces drew it into a space between the two polymeric substrates. The process was sufficiently rapid to prevent clogging of the microchannels. After aspiration, the clamped plates were incubated while remaining clamped for 5 minutes. The complete procedure creates a strong bond between the plates in less than 8 minutes.
To demonstrate the effectiveness of the technique, the team used the microchannel plates to successfully perform high-efficiency electrophoretic separation of 400-base single-strand DNA ladders—a typical microfluidics application.
The technique shows promise for the rapid, volume production of lab-on-a-chip devices because it creates a secure bond, can be performed quickly, and does not block the microchannels. Alternative bonding methods for microchannel plates include clamping the plates together and heating the plastic until the polymer chains begin to diffuse. This method has the drawback of requiring a precise combination of time, pressure, and temperature that must be modified for each lot of plastic. Another method requires welding the pieces together with a solvent-based glue, which sometimes can inadvertently close the microchannels. By using the channels themselves to deliver adhesive, the research team found an unexpected solution for bonding the plates without clogging their internal microchannel network.
