Selection of UV-resins for nanostructured molds for thermal-NIL

Abstract

Nanoimprint molds made of soft polymeric materials have advantages of low demolding force and low fabrication cost over Si or metal-based hard molds. However, such advantages are often sacrificed by their reduced replication fidelity associated with the low mechanical strength. In this paper, we studied replication fidelity of different UV-resin molds copied from a Si master mold via UV nanoimprint lithography (NIL) and their thermal imprinting performance into a thermoplastic polymer. Four different UV-resins were studied: two were high surface energy UV-resins based on tripropyleneglycol diacrylate (TPGDA resin) and polypropyleneglycol diacrylate (PPGDA resin), and the other two were commercially available, low surface energy poly-urethane acrylate (PUA resin) and fluorine-containing (MD 700) UV-resins. The replication fidelity among the four UV-resins during UV nanoimprint lithograph from a Si master with sharp nanostructures was in the increasing order of (poorest) PUA resin < MD 700 < PPGDA resin < TPGDA resin (best). The results show that the high surface energy and small monomer size are keys to achieving good UV-resin filling into sharp nanostructures over the viscosity of the resin solution. When the four UV-resin molds were used for thermal-NIL into a thermoplastic polymer, the replication fidelity was in the increasing order of (poorest) MD 700 < TPGDA resin < PUA resin (best), which follows the same order of their Young's moduli. Our results indicate that the selection of an appropriate UV-resin for NIL molds requires consideration of the replication fidelities in the mold fabrication and the subsequent thermal-NIL into thermoplastic polymers.

High Aspect Ratio Polymeric Nanoneedle Arrays

“…These low chain length prepolymers were used to cast both primary and secondary molds as they produce high resolution replicas of nanometric features. [ 6,40,41 ] In addition, explorative experiments carried out by our group found that the difference in surface energy between photocured polypropylene glycol (PPG) and polyethylene glycol (PEG) molds was shown to aid mold separation of surfaces patterned with nanopillar arrays. However, it was expected that the features of the BCP 110 arrays would be more challenging to replicate than the BCP 440 arrays due to the higher feature density and smaller feature size.…”

“…To improve the understanding of the function of nano‐ and micro‐structured surfaces, as well as the limitations of these structures, extensive research has been carried out in imparting nanoscale topographies onto synthetic materials. [ 1–41 ] In particular, synthetic nanostructured surfaces significantly benefit many interdisciplinary fields including biomaterial engineering, antibacterial and antibiofouling, optics, controlling mammalian cell behavior and differentiation, and intracellular drug delivery. [ 2,8,14,18,41 ]…”

“…Conventional lithographic processes which fabricate silicon HAR nanostructures include photolithography and scanning beam processes such as e‐beam lithography and focused ion beam lithography. [ 6,31,33,38–40,51,52 ] While the advances in this area have been extremely noteworthy, in particular the work of the Steven's group, who have fabricated silicon nanoneedle arrays with tip diameters as low as 20 nm with micron scale heights and spacing, photolithography, and scanning beam lithography are not economically feasible options for many laboratories, meaning that it is often inaccessible to many research groups. [ 2,17,38 ] Moreover, scanning beam processes are difficult to scale and these patterning methods are generally limited for use with hard materials.…”

Nanohole array plasmonic biosensors: Emerging point-of-care applications

“…Fig. 7c, shows UV-curable resin used as NIL mold to replace hard molds, taking advantage of its lower Young's modulus and thus lower demolding force Jia et al 2018;Wu et al 2011). The expensive original Si master mold is only needed when the resin mold is damaged and needs to be remade.…”

Patterned Calcite Microneedle Arrays formed on Mollusk Shells via Oriented Dissolution and Their Application for Transdermal and Intracellular Delivery

“…[41,50] Silicon nanoneedle arrays are often used for penetration through cell interfaces due to its biocompatibility and stability in the cell culture environment. [40,61] Conventional processes to fabricate silicon and diamond nanoneedle arrays require expensive micromachining equipment and complicated manufacture methods, [62][63][64][65] which limit their applications.…”