State of Utah Center of Excellence for Biomedical Microfluidics
|
|
| Students Involved: David Chang-Yen and Andrew Christensen A simple and cost effective packaging technique for PDMS microfluidic and microoptical systems has been developed. The technique involves the novel method of drilling a small hole in the PDMS to access the micro channels using a modified 20 gauge needle. An unmodified needle is then inserted into the hole, creating a direct connection to the microchannel that requires no bonding or molding. The interface can than be removed and reinserted multiple times. The luer fitting on the needles is be easily connected to standard fluid fittings. The optical packaging involves traditional tapered interfaces to bring the fiber optics in contact with PDMS waveguides. Packaging for microsystems has
historically been a challenge due to size and cost.
Microfluidic devices typically require multiple interconnects and in many
cases the packaging components are much larger then the microsystems they
interface. Common PDMS packaging
techniques require tubing to be glued or molded to the substrate The microfluidic packaging technique is implemented by creating a coring tool from a 20 gage blunt needle. Using a Dremel tool the needle is filed down on the outer edge to create a beveled edge (see Figure 2). Using a twisting motion, the coring tool is used to cut a hole through the PDMS to the channel. The hole created has a diameter identical to the inner diameter of the 20 gauge needle (610μm). When a second unaltered 20 gage needle is inserted a compression seal is formed around the needle since the outer diameter of the needle is 950μm, 340μm larger than the hole (see Figure 1). The technique should be easily automated and can be done in parallel. The optical packaging technique uses a V-shaped guide to direct the fiber optics directly to the waveguide (Figure5). Combined with the integrated optics, microfluidics, and the microfluidics packaging, a simple, inexpensive and robust system is generated [2]. The microfluidic packaging was
tested by creating channels in a 6 mm layer of PDMS using an SU-8 mold.
The ports were created using the coring tool and the channel layer was
then bonded to another layer of PDMS using liquid PDMS as the bonding agent (see
Figures 3 & 4). In each of the
four tests conducted, the system leaked at the bond between the PDMS layers
before leaking at the needle port. During testing, pressure reached up to 489
kPa psi (see Table 1). The holes are
extremely flexible and durable allowing the needle to be pushed at least 30
degrees in any directing without leaking. In
most cases, the seals held at these pressures even after inserting and removing
the needle over 100 times. The
thickness of PDMS has some effect on the allowable flexure angles and maximum
pressures. The coring tool’s
rotation speed and pitch also affect the surface roughness of the hole which in
turn affects the leakage pressure. These
techniques REFERENCES [1] Jaeggi, D., Gray, Proceedings of the Solid-State Sensor and Actuator Workshop, Hilton Head, South Carolina, June 8 - 11, 1998, pp. 112 - 115. [2] David A. Chang-yen and Bruce K. Gale, “Integrated
optical glucose sensor fabricated using PDMS waveguides on a PDMS substrate,”
Proc. Of SPIE: Microfluidics, BioMEMS, and Medical Microsystems II,
Figure 1: Manufacturing Process Figure 2: Needle and Coring Tool
Figure 3: Interface Setup Figure 4: Setup for pressure measurements
Andrew M. Christensen, David A. Chang-Yen, and Bruce K. Gale, “Characterization Of Interconnects Used In PDMS Microfluidic Systems,” Journal of Micromechanics and Microengineering, Vol. 15, pp. 928-935, 2005.
| |||||||||||||||
Send mail to
bruce.gale@utah.edu with
questions or comments about this web site.
|
