Document Type

Article

Publication Date

2026

DOI

10.1371/journal.pone.0356385

Publication Title

PLoS One

Volume

21

Issue

8

Pages

e0356385

Abstract

Silicones are elastomers that have a wide variety of uses, including biomedical applications such as the coating of biomedical devices and as implants. Soft silicones with mechanical properties similar to those of biological tissues have particularly gained use as substrates for cell culture in mechanobiology studies. In this context, it would be desirable to be able to alter their surface mechanical properties with a relatively simple physical treatment. While deep ultraviolet (deep UV) or ultraviolet C (UV-C) treatment has been previously used as a surface treatment method for stiffer silicones formulations, the effect of this treatment on soft silicones relevant for mechanobiology applications is still uncharacterized. We first used nanoindentation to determine the Young’s modulus of two types of soft silicones, Qgel and GEL-8100/Syl (GEL-8100 with Sylgard-184 crosslinker), both with initial moduli in the kilopascal range. We show that nanoindentation in the presence of 1% sodium dodecyl sulfate avoids adhesion between the nanoindentation glass probe and the soft silicones. After deep UV exposure in the presence of air, nanoindentation revealed that the apparent Young’s moduli of the soft silicones Qgel and GEL-8100/Syl increased by 70% and 33%, respectively. The bulk rheology of the soft silicones were not affected, suggesting that this corresponds to a surface stiffening effect with a topical stiffening of at least several hundred kilopascals. Energy-dispersive X-ray spectroscopy results show an increase in the mole fraction of oxygen, consistent with oxidation of the surface. Attenuated total reflectance Fourier transform infrared spectra show evidence of Si-OH group formation in GEL-8100/Syl and silicon sub-oxide formation in Qgel. Consistent with this, water contact angle measurements show enhanced hydrophilicity after deep UV treatment. Our results have implications for using soft silicones as substrates in mechanobiology studies and in processes where deep UV light is used in the surface treatment of soft silicones.

Rights

© 2026 Wilder et al.

This is an open access article distributed under the terms of the Creative Commons Attribution  4.0 International (CC BY 4.0) License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability

Article states: "All relevant data files that underly figures are available from the figshare database, DOI below: https://doi.org/10.6084/m9.figshare.29175788.v2."

Original Publication Citation

Wilder, A., Booth, Z., Obermeyer, C., Sharmin, S., & Maruthamuthu, V. (2026). Stiffening of soft silicone upon deep UV treatment as characterized using nanoindentation. PLoS One, 21(8), Article e0356385. https://doi.org/10.1371/journal.pone.0356385

ORCID

0000-0002-6565-1125 (Booth), 0009-0005-8503-3374 (Obermeyer), 0009-0001-2614-8383 (Sharmin), 0000-0002-3470-5274 (Maruthamuthu)

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