The ability to fabricate materials, structures, devices, and systems with nanometer-scale precision is the key to obtain superior properties and performance. The scalability of lithographic approaches can promote them from research implementation to practical applications. My graduate research focuses on several unconventional lithographic techniques we have developed, which can create high-precision nanoscale patterns and three-dimensional (3D) hierarchical structures with high reproducibility, low cost, high throughput, and high precision.
A hybrid patterning strategy called polymer-pen chemical lift-off lithography (PPCLL) was developed. We used pyramidal and v-shaped polymer-pen arrays for the sub-micron chemical patterning. By introducing the stamp support system and height gradients, we obtained linear-arrays of chemical patterns with linewidths ranging from sub-50 nm to sub-500 nm in sub-20 nm increments. We also showed our capability to tune feature size by controlling the compression distance. In doing so, we extended the patterning capability of PPCLL to generate more complex hollow patterns and gold nanorings. Self-collapse lithography (SCL) was another chemical lift-off lithography (CLL) based patterning technique. When elastomeric stamps with microscale relief features contacted with the self-assembled monolayer (SAM) functionalized substrates, the roof of the stamp collapses, resulting in the removal of SAM molecules in contact regions. With this technique, chemical patterns with feature size from ~2 ï¿½m to below 30 nm were obtained by decreasing stamp relief heights.
We developed a robust and general strategy called multiple-patterning nanosphere lithography (MP-NSL) to fabricate periodic 3D hierarchical nanostructures in a highly scalable and tunable manner. The application of MP-NSL enables the fabrication of silicon nanotubes at the wafer scale with nanometer-scale control of outer diameter, inner diameter, height, hole-depth, and pitch. By adopting a multiple-patterning nanosphere lithography strategy, we are able to fabricate mechanically stable volcano-shaped nanostructures, called "nanovolcanos" with controllable heights, hole diameters/depths, and pitches. The sub-20-nm sharp features of nanovolcanos enable penetration of cell membranes and minimize disruption of cell functions. Biomolecular payloads containing the gene-editing packages are assembled and encapsulated into supramolecular nanoparticles. The holes (calderas) of the nanovolcanos can carry high payloads of biomolecular cargos that are readily accessed once cell membranes are penetrated.