Ali Hashmi, Jie Xu
Washington State University
University of Washington
Why is this useful?
Previously we presented a method for connecting inlets and outlets to an external source that involved tubing and needles . However, the process involves the use of needles which could be a safety concern. The process is also somewhat time-consuming. We have now developed a more convenient and rapid method for fabricating inlets/outlets in a PDMS chip without the need for needles.
What do I need?
- A puncher, for example, we use a Schmidt punch press (Syneo, LLC)
- Connectors with barbs and corresponding tubings, for example, we use elbow tube fitting with classic series barbs for 1/16” (1.6 mm) ID tubing (Valueplastic.com)
What do I do?
1. When the PDMS device has been cured, punch inlets and outlets from the top of the device.
Figure 1: (a) Schmidt Press; (b) punching through holes at desired locations on the device; (c) device with a set of three punched holes.
2. After sealing the device, insert the connectors (“Elbow Tube Fitting with classic series Barbs, 1/16”, (1.6 mm) ID Tubing, White Nylon”) into the inlets and outlet.
3.Tubing can then be connected to the connectors at one end, and to a syringe pump at the other end.
What else should I know?
The diameter of the punched holes is specific to the nominal cutting edge diameter of the punch. The punch, connectors, and tubing can be any size as long as they correspond to each other so that the connection does not leak. The connectors and tubing can be ordered from Value Plastics, INC.
The height of the Schmidt press can be adjusted according to the thickness of the PDMS device to ensure a through hole.
The maximum pressure we have tried with this type of connection is about 240 kPa, beyond which other parts of the chip fail (such as the PDMS/glass).
 P. Li., W. Xue, and J. Xu, The fabrication of PDMS interconnecting interface assisted by tubing fixation, Lab Chip, Chips and Tips, 10 June 2011