Researchers have developed valves in microfluidic chips from fabricated from sticky tape.
Scientists based at the National Institute of Standards and Technology (NIST; MD, USA) have developed working valves in microfluidic chips made from sticky tape. The NIST-based researchers first utilized sticky tape as a cheaper microfluidic fabrication alternative to the current technique of etching glass or plastic with photolithography.
The scientists have previously fabricated sticky tape microfluidic devices by cutting narrow slits and holes in specific places on a strip of sticky tape, before folding over the tape so it sticks together, and then covering the whole structure in a plastic film that contains holes in the same places as the tape. Gregory Cooksey and Javia Atencia (NIST) were able to fabricate 2D and 3D microfluidic devices by joining together multiple strips of these sticky tapes.
In their recent publication, Cooksey and Atencia have managed to create valves in the sticky tape devices, increasing the complexity of possible devices. Valves are traditionally made from silicones; however in this case, a thin membrane of polydimethylsiloxane (PDMS), a flexible polymer, was placed between the folded ends of the sticky tape. Therefore if two channels are lying on top of each other, applied air pressure will cause the PDMS to block off the bottom channel, acting as a valve.
The authors state in their publication that, “The time required from conception to full fabrication of functional devices is within a few hours. A key characteristic of this technology is that devices are thin (typically less than 0.5 mm in thickness), which allows for the fabrication of devices with many layers. This feature also permits folding of devices into 3D structures having fully functional valves.”
Sources: Cooksey G, Atencia J. Pneumatic valves in folded 2D and 3D fluidic devices made from plastic films and tapes. Lab Chip, DOI: 10.1039/C4LC00173G (Epub ahead of print) (2014); NIST’s simple microfluidic devices now have valves.