Polymer micromolds with near optical quality surface finishes

Pun-Pang Shiu; George K. Knopf; Suwas Nikumb

doi:10.1117/12.908098

14 February 2012 Polymer micromolds with near optical quality surface finishes

Pun-Pang Shiu, George K. Knopf, Suwas Nikumb

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Proceedings Volume 8251, Microfluidics, BioMEMS, and Medical Microsystems X; 82510H (2012) https://doi.org/10.1117/12.908098
Event: SPIE MOEMS-MEMS, 2012, San Francisco, California, United States

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.

Citation Download Citation

Pun-Pang Shiu, George K. Knopf, and Suwas Nikumb "Polymer micromolds with near optical quality surface finishes", Proc. SPIE 8251, Microfluidics, BioMEMS, and Medical Microsystems X, 82510H (14 February 2012); https://doi.org/10.1117/12.908098

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KEYWORDS

Finite element methods

Polymethylmethacrylate

Polymers

Microfluidics

Surface finishing

Photomasks

Glasses

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