Superhydrophilic hydrogel-enhanced conductive MOF-based wearable sweat sensors with anti-lipid biofouling capability

Hydrogel patches are highly promising for application in wearable sweat sensors because of their excellent sweat absorption abilities. Additionally, the hydrophilic nature of hydrogels offers an ideal platform for tackling the problem of lipid biofouling in sweat analysis. The superhydrophilic hydrogel patches can integrate the functions of rapid sweat sampling, lipid filtration, and sweat transport to the sensing region, effectively improving sensor detection efficiency and preventing electrode contamination by lipids. Herein, polyacrylamide (PAM) and polyvinyl alcohol (PVA) were selected to coat cotton cloth and produce hydrogel patches. Furthermore, inspired by mussels, catechol functional moieties were introduced to improve the hydrophilicity and lipophobicity, resulting in polydopamine-polyacrylamide (PDA-PAM) and polydopamine-polyvinyl alcohol (PDA-PVA) hydrogels. The optimal PDA-PAM hydrogel with the best anti-lipid interference ability was screened out for integration into sweat detection patches. Meanwhile, a highly sensitive sensing patch was fabricated using a conductive metal-organic framework (MOF), namely Ni-HAB (HAB = hexaiminobenzene), electrode for detecting dopamine (DA) in sweat. When combined with PDA-PAM hydrogel patches, the Ni-HAB electrode exhibits good sensitivity, anti-interference ability, and reusability. This hydrogel-assisted anti-lipid interference strategy not only allows for rapid collection and filtration of sweat, but also ensures the accuracy and durability of the conductive MOF electrodes, guaranteeing the practical application ability of wearable sensors for analyzing human sweat components