A nanoscale patterned hydrogel that’s hard to resist

Carbon paper has saved people from making tedious handwritten copies for centuries. There is an analog for electronics: resists, light-sensitive materials that can be photoengraved, then washed with chemical solvents to transfer intricate designs. But etching patterns onto such materials requires numerous steps and harsh solvents, developers, and removers. The thinnest patterns can also collapse or malform.

Devin Brown found that electron beam lithography could create patterns in a polyacrylic acid hydrogel film. The hydrogel is biodegradable and biocompatible, with potential uses in drug delivery and sensing. The technique enables patterns fewer than 100 nanometers in dimension.

“Other methods to achieve these patterns [have been] more indirect, more complex, take more steps, and cost more,” said Brown. “This is just more direct, simpler, and smaller.”

The research followed from previous work Brown conducted using water-based hydrogels as sacrificial layers, where he discovered that they were sensitive to electron beams. He then tried to synthesize thinner gels, but the pattern resolution was fuzzy. He moderated the hydrogels’ developing temperature, also yielding unsuccessful results. Finally, he varied the molecular weight of the gels from 50,000 to 5000. The electron patterns were then clear at 30 nanometers. Since the hydrogel’s solvent, developer, and remover are all water, the process could be compatible with materials requiring resists but unable to tolerate acids or bases.

In the future, Brown envisions the hydrogel as a specialized coating for drugs that dissolve at precise times, or as a smart film on chips to detect pH or biomarkers.

“Continuing to demonstrate its capability and try to proliferate this to other people who would be able to benefit from it would be really rewarding,” he said.

Source: “All water based nanoscale electron beam lithography using poly acrylic acid hydrogel as a resist,” by Devin K. Brown, Journal of Vacuum Science & Technology: B (2026). The article can be accessed at https://doi.org/10.1116/6.0004947 .

This paper is part of the Papers from the 68th International Conference on Electron, Ion and Photon Beam Technology and Nanofabrication (EIPBN 2025), learn more here .