Traditional nanoimprint lithography is a simple and versatile method
for producing devices with a large range of possible feature sizes.
Within this class of methods, direct nanoimprinting has been used to
pattern materials that are suspended in solvents directly, allowing for
simple deposition and patterning of materials on substrates with low
waste. However, this direct nanoimprinting process inevitably leaves a
residual layer that must be etched away in subsequent steps, adding
complexity to the process, and often results in features with
non-uniform aspect ratios.
Investigators at the University of California at Berkeley are addressing these challenges by developing a microfabrication method that allows for the direct patterning of materials on a variety of substrates using microcapillaries. This very simple patterning method results in features with a controllable aspect ratio and zero residual layer. First, a bare solvent or secondary fluid is spread on the substrate. A soft, porous elastomer mold, patterned using traditional photolithography, is pressed on the substrate to pattern the fluid. A nanoparticle ink or other functional or structural material is introduced to the resulting microcapillaries through dedicated filling ports and flows into the microcapillaries as the bare solvent or secondary fluid evaporates though the porous mold. The nanoparticle ink or dissolved material self-concentrates as the solvent evaporates, eventually leaving only the patterned material on the substrate.