ÿþWe recently reported a puma creepers new UV-curable polyurethane-methacrylate (PUMA) resin that has excellent qualities as a disposable microfluidic substrate for clinical diagnostic applications. This article discusses strategies to improve the production yield of PUMA chips that contain dense and high-aspect-ratio features, which presents unique challenges in demolding and bonding steps. These fabrication improvements were deployed to produce a microfiltration device that contained closely spaced and high-aspect-ratio columns.

Polydimethylsiloxane (PDMS) molds were prepared according to procedures described previously 18 from a molding master that was prepared by deep-reactive ion etching of silicon wafer and subsequently silanized with PUMA resin , CT) was dispensed to 3-mm thickness onto the PDMS mold, then covered with a sheet of cellophane tacked to a clear puma fenty polypropylene backing (8-mil thick) to prevent oxygen inhibition of the cross-linking reaction ( Fig. 1A ).

PUMA resin; 3 : PTFE posts; 4 : polypropylene sheet; 5 : cellophane (or Aclar). ( B ) Two methods of interfacing PUMA puma slides chip with external tubing: 1 : PUMA chip; 2 : barb elbow connector; 3 : polyurethane tubing; 4 : additional resin to seal leak (Dymax 186M); 5 : PTFE tubing; 6 : polyolefin heat-shrink; 7 : retaining ring.Fig. 1B shows two examples of interfacing a PUMA chip for external fluidic delivery. The left side of Fig. 1B illustrates the use of a barbed elbow connector.

The elbow connector was inserted into a thick-wall polyurethane (PU) tubing (1/8-in outer diameter (OD), puma rihanna 1/16-in inner diameter (ID)), which served as a mechanical anchor against shear. The PU tubing was then inserted into a 1/8-in hole, formed either by embedding PTFE posts or laser cutting, in the PUMA substrate and additional resin (Dymax 186M) was dispensed around the junction and cured for 2 4 min. A tubing (1/163 ID) was attached to the external end of the barbed elbow connector.

PDMS cannot be used as the material of fabrication because of low shear modulus; 6 the features would simply lean and topple over under gravity.Fig. 2 shows an example of features that can be fabricated in PUMA but not PDMS. Fig. 2A shows a scanning electron microscopy (SEM) image of a replica in PUMA resin; this test pattern for replication consists of densely spaced vertical columns alternating with solid walls. puma suede classic The feature height was ~40 ¼m and the aspect ratio of the vertical columns was ~3.5.

UMA replica taken under a stereoscope (same pattern as Fig. 2A ), released from the mold without the assistance of the pulling station. Two types of defects were evident: (1) wavy walls, and (2) irregular vertical column spacings. The waviness of the wall is generally attributable to improper cleaning of the PDMS mold between replication runs, which increases the adhesion between the mold and the resin. Consequently it is not possible to lift apart without some horizontal motion to counter the adhesive force.