Chen Chihchen, Hirdes Danny, Folch Albert
Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.
Proc Natl Acad Sci U S A. 2003 Feb 18;100(4):1499-504. doi: 10.1073/pnas.0435755100. Epub 2003 Feb 6.
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.
制造三维（3D）微结构的能力在机械或流体装置、光学元件、自组装部件以及组织工程支架等的小型化过程中变得越来越重要。传统光刻技术是微器件制造中使用最广泛的工艺，但它并不适合3D制造，因为它是通过“光掩膜”（一块包含不透明、不可改变固态特征的透明板）对光敏层进行照射，这不可避免地会产生高度均匀的特征。我们设计了一种光掩膜，其吸光特征由流体构成。与传统光掩膜不同，这种光掩膜特征的不透明度可以定制为任意数量的灰度级，并且它们的空间图案可以在数秒的时间尺度内重新配置。在此，我们展示了包含多种高度特征和/或高度平滑变化特征的光刻胶图案的低成本制造方法。对于给定的微流体光掩膜，显影后的光刻胶图案可以根据染料浓度和光掩膜尺寸进行预测。对于某些特定应用，微流体光掩膜为当前的灰度光刻方法提供了一种低成本的替代方案。
