GoKawiilPhotos of DFP printing and cross-sectional SEM images of the foams are given for different polymer systems: polycarbonate (PC) (a, f), cellulose triacetate (CTA) (b, e), polyethylene terephthalate (PET) (c, g), polysulfone (PSU) (d, h), and poly(methyl methacrylate) (PMMA) (i). Scale bars, 5 mm for the macrolens photos and 1 μm for the SEM cross-sections. 2.5-μm-thick polymer film was prepared by spin-casting a polymer solution (solvent: trifluoroacetic acid for PET and chloroform for the others) on cover glass. The photoinitiator (thioxanthone) to polymer ratio was maintained at 9 wt% for all the polymers. The films were illuminated using a custom LED chamber (Thorlabs, λ i : 385 nm) at an energy dosage of 600 J cm−2. Photomask was made using an OHP sheet. Development was performed at room temperature (22 ± 1 °C) for all polymers: 10 min for 1-proponal: toluene (v/v: 8/2) for the PET film, 130 s in acetic acid for the PC film, 120 s in acetone: acetic acid (v/v: 6/5) for the PSU film, and 60 s in 1-propanol: acetone (v/v: 7/3) for the CTA film, and 60 s in acetic acid: H 2 O (v/v, 5/3) for PMMA film. All films were dried using an air blower upon completion of development. Note we have also successfully realized formation of DFP structures via a diverse set of photoinitiators, which includes thioxanthone, benzophenone and its derivatives e.g., 2-methylbenzophenone, 4,4′-bis-(diethylamino)-benzophenone, etc., anthraquinone, and phenanthrenequinone. These photoinitiators have a broad absorption window in the wavelength range of 300–400 nm.
Foaming photopolymers as a high-resolution biomimetic printing platform
This work describes a light-driven method for foaming standard, commodity polymers \u2014 PC, PET, PMMA, PSU and cellulose triacetate \u2014 into patterned micro-porous structures using nothing more than a photoinitiator, UV LEDs, a printed transparency photomask and a brief solvent development step. Because it works across many polymers and several common photoinitiators absorbing in the 300\u2013400 nm range, it suggests a low-cost, broadly compatible route to biomimetic, high-resolution surface structures without specialized resins or printers.
- A single photofoaming process patterned five common polymers (PC, CTA, PET, PSU, PMMA) with sub-micron foam features in thin ~2.5 \u00b5m films.
- The setup is deliberately cheap and accessible: a custom 385 nm LED chamber, an OHP-sheet photomask, and room-temperature solvent development of 60 s to 10 min.
- Multiple photoinitiators work \u2014 thioxanthone, benzophenones, anthraquinone, phenanthrenequinone \u2014 indicating the method is chemistry-agnostic rather than tied to one proprietary formulation.
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