Gray-scale photolithography using microfluidic photomasks

The ability to produce three-dimensional (3D) microstructures is of increasing importance in the miniaturization of mechanical or fluidic devices, optical elements, self-assembling components, and tissue-engineering scaffolds, among others. Traditional photolithography, the most widely used process for microdevice fabrication, is ill-suited for 3D fabrication, because it is based on the illumination of a photosensitive layer through a “photomask” (a transparent plate that contains opaque, unalterable solid-state features), which inevitably results in features of uniform height. We have devised photomasks in which the light-absorbing features are made of fluids. Unlike in conventional photomasks, the opacity of the photomask features can be tailored to an arbitrary number of gray-scale levels, and their spatial pattern can be reconfigured in the time scale of seconds. Here we demonstrate the inexpensive fabrication of photoresist patterns that contain features of multiple and/or smoothly varying heights. For a given microfluidic photomask, the developed photoresist pattern can be predicted as a function of the dye concentrations and photomask dimensions. For selected applications, microfluidic photomasks offer a low-cost alternative to present gray-scale photolithography approaches.

[1]  Hubert Lorenz,et al.  3D microfabrication by combining microstereolithography and thick resist UV lithography , 1999 .

[2]  P. Aebischer,et al.  Photoimmobilization of a bioactive laminin fragment and pattern-guided selective neuronal cell attachment. , 1995, Bioconjugate chemistry.

[3]  G. Whitesides,et al.  Fabrication of a configurable, single-use microfluidic device. , 2001, Analytical chemistry.

[4]  G. Whitesides,et al.  Micromolding of Polymers in Capillaries: Applications in Microfabrication , 1996 .

[5]  S. Herminghaus,et al.  Artificial liquid microstructures , 1999 .

[6]  G. Whitesides,et al.  Generation of Solution and Surface Gradients Using Microfluidic Systems , 2000 .

[7]  Hans Joachim Quenzer,et al.  Microfabrication of complex surface topographies using grey-tone lithography , 1995 .

[8]  G. Whitesides,et al.  Microfabrication inside capillaries using multiphase laminar flow patterning , 1999, Science.

[9]  David T. Burke,et al.  Microfabricated devices for genetic diagnostics , 1998, Proc. IEEE.

[10]  Sing H. Lee,et al.  Fabrication of diffractive optical elements using a single optical exposure with a gray level mask , 1995 .

[11]  M. Madou.  Fundamentals of microfabrication , 1997 .

[12]  D. Beebe,et al.  Three-dimensional micro-channel fabrication in polydimethylsiloxane (PDMS) elastomer , 2000, Journal of Microelectromechanical Systems.

[13]  George M. Whitesides,et al.  Reconfigurable diffraction gratings based on elastomeric microfluidic devices , 1999 .

[14]  Robin H. Liu,et al.  Functional hydrogel structures for autonomous flow control inside microfluidic channels , 2000, Nature.

[15]  G. Whitesides,et al.  Using an elastomeric phase mask for sub-100 nm photolithography in the optical near field , 1997 .

[16]  Stucky,et al.  Mirrorless lasing from mesostructured waveguides patterned by soft lithography , 2000, Science.

[17]  J. Michael Ramsey,et al.  Minimizing the number of voltage sources and fluid reservoirs for electrokinetic valving in microfluidic devices. , 1999, Analytical chemistry.

[18]  大房 健.  基礎講座 電気泳動(Electrophoresis) , 2005 .

[19]  G. Whitesides,et al.  Polymer microstructures formed by moulding in capillaries , 1995, Nature.

[20]  S. Quake,et al.  Monolithic microfabricated valves and pumps by multilayer soft lithography. , 2000, Science.

[21]  G. Whitesides,et al.  Patterned deposition of cells and proteins onto surfaces by using three-dimensional microfluidic systems. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[22]  M. Toner,et al.  Numerical model of fluid flow and oxygen transport in a radial-flow microchannel containing hepatocytes. , 1999, Journal of biomechanical engineering.

[23]  G M Whitesides,et al.  Manipulation of the Wettability of Surfaces on the 0.1- to 1 -Micrometer Scale Through Micromachining and Molecular Self-Assembly , 1992, Science.

[24]  G. Whitesides,et al.  Fabrication of microfluidic systems in poly(dimethylsiloxane) , 2000, Electrophoresis.

[25]  G M Whitesides,et al.  Patterning cells and their environments using multiple laminar fluid flows in capillary networks. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[26]  M. Gad-el-Hak,et al.  Micro Flows: Fundamentals and Simulation , 2002 .

[27]  Hongkai Wu,et al.  Reduction photolithography using microlens arrays: applications in gray scale photolithography. , 2002, Analytical chemistry.

[28]  N. Dontha,et al.  Generation of biotin/avidin/enzyme nanostructures with maskless photolithography. , 1997, Analytical chemistry.

[29]  George M. Whitesides,et al.  Active control of wetting using applied electrical potentials and self-assembled monolayers , 1995 .

[30]  G M Whitesides,et al.  Fabrication of topologically complex three-dimensional microfluidic systems in PDMS by rapid prototyping. , 2000, Analytical chemistry.

[31]  Jeffrey B. Sampsell,et al.  Digital micromirror device and its application to projection displays , 1994 .