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Proceedings Paper

Polymer micromolds with near optical quality surface finishes
Author(s): Pun-Pang Shiu; George K. Knopf; Suwas Nikumb
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Paper Abstract

Disposable microfluidic systems are used to avoid sample contamination in a variety of medical and environmental monitoring applications. A contactless hot intrusion (HI) process for fabricating reusable polymer micromolds with near "optical quality" surface finishes is described in this paper. A metallic hot intrusion mask with the desired microchannels and related passive components is first machined using a tightly focused beam from a diode-pumped solid-state (DPSS) laser. The polymer mold master is then created by pressing the 2D metallic mask onto a polymethylmethacrylate (PMMA) substrate. Since it is a contactless fabrication process the resultant 3D micro-reliefs have near optical quality surface finishes. Unfortunately, the desired micro-relief dimensions (height and width) are not easily related to the hot intrusion process parameters of pressure, temperature, and time exposure profile. A finite element model is introduced to assist the manufacturing engineer in predicting the behavior of the PMMA substrate material as it deforms under heat and pressure during micromold manufacture. The FEM model assumes that thermo-plastics like PMMA become "rubber like" when heated to a temperature slightly above the glass transition temperature. By controlling the material temperature and maintaining its malleable state, it is possible to use the stress-strain relationship to predict the profile dimensions of the imprinted microfeature. Examples of curved microchannels fabricated using PMMA mold masters are presented to illustrate the proposed methodology and verify the finite element model. In addition, the non-contact formation of the micro-reliefs simplifies the demolding process and helps to preserve the high quality surface finishes.

Paper Details

Date Published: 14 February 2012
PDF: 10 pages
Proc. SPIE 8251, Microfluidics, BioMEMS, and Medical Microsystems X, 82510H (14 February 2012); doi: 10.1117/12.908098
Show Author Affiliations
Pun-Pang Shiu, The Univ. of Western Ontario (Canada)
George K. Knopf, The Univ. of Western Ontario (Canada)
Suwas Nikumb, National Research Council Canada (Canada)

Published in SPIE Proceedings Vol. 8251:
Microfluidics, BioMEMS, and Medical Microsystems X
Holger Becker; Bonnie L. Gray, Editor(s)

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