Photoembossing is a solvent‐free photolithographic technique for the production of polymeric relief microstructures (see Figure). A combinatorial methodology to explore the influence of different parameters (e.g., processing temperature, binder content, photoinitiator content) on the resultant relief structure is presented using an acrylate‐based model system. Results are discussed in the framework of a diffusion‐polymerization model.

Methodologies for the rapid screening of coating systems were developed and applied to photopolymer lacquers for photoembossing applications. Continuous and discrete gradient libraries were prepared with a gradient in grating period along the short axis and along the long axis, a gradient in exposure energy, development temperature, film thickness, photoinitiator concentration, or monomer to polymer mass ratio. Discrete gradient libraries consisted of arrays of rectangular films made by pipetting a certain amount of sample onto a chemically patterned substrate consisting of hydrophilic patches surrounded by hydrophobic, fluorinated barriers. The shape and height of the photoembossed gratings were measured using an automated AFM. Optimum grating height was obtained for a 20-microm period at intermediate exposure energies, photoinitiator concentrations, or both. Height improves with development temperature (max 110 degrees C), monomer-to-polymer ratio (max 55 wt % monomer), and film thickness. Surface topography can also be optimized, depending on any specific application.

A methodology for the rapid design, screening, and optimization of coating systems with surface relief structures, using a combination of statistical experimental design, high-throughput experimentation, data mining, and graphical and mathematical optimization routines was developed. The methodology was applied to photopolymers used in photoembossing applications. A library of 72 films was prepared by dispensing a given amount of sample onto a chemically patterned substrate consisting of hydrophilic areas separated by fluorinated hydrophobic barriers. Film composition and film processing conditions were determined using statistical experimental design. The surface topology of the films was characterized by automated AFM. Subsequently, models explaining the dependence of surface topologies on sample composition and processing parameters were developed and used for screening a virtual 4000-membered in silico library of photopolymer lacquers. Simple graphical optimization or Pareto algorithms were subsequently used to find an ensemble of formulations, which were optimal with respect to a predefined set of properties, such as aspect ratio and shape of the relief structures.