Air-permeable hydrogels through viscoelastic phase separation of aerogels.

Yan, Xiao-Yun; Li, Shucong; Song, Won Jun; Li, Runze; Dahal, Aarosh; Aymon, Bastien F G; Hu, Haodong; Malu, Deep K et al. · Nature · 2026

basic_science · Level V

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Abstract

Hydrogels are widely used in biomedical interfaces, in which effective gas exchange (for example, O<sub>2</sub>, CO<sub>2</sub>) within a water-rich environment is essential. However, hydrogels show intrinsically limited air exchange efficiency, owing to the low solubility (C) and diffusivity (D) of non-polar gases in the polar water medium<sup>1</sup>. This limitation poses a substantial bottleneck in long-term applications, such as wearable health monitors<sup>2-7</sup> and tissue engineering<sup>8-12</sup>. Existing methods<sup>13-16</sup> to enhance air permeability suffer from poor robustness and/or an inherent trade-off between permeability and water content (for example, <50 vol%). Here we introduce a viscoelastic phase separation<sup>17</sup> (VPS)-enabled strategy to create a non-collapsible, air-rich network in high-water-content hydrogels, achieving a record-high oxygen permeability of 185 barrer with 70 vol% water-a tenfold increase compared with pristine hydrogels. VPS, a ubiquitous phenomenon in soft matter, is used to drive hydrophobic, dry gas particles within a hydrophilic, wet medium into a thin, stable three-dimensional network. This approach allows the facile and scalable fabrication of air-permeable hydrogels across diverse chemistries and form factors. Physiological tests over a 10-day continuous wear condition confirmed their effectiveness in preventing fluid accumulation and maintaining skin health. This strategy paves the way for hydrogels in long-term biomedical applications in which efficient and sustained air exchange becomes critical.