In Situ Formation of Conductive Epidermal Electrodes Using a Fully Integrated Flexible System and Injectable Photocurable Ink

In situ fabrication of wearable devicesthroughcoating approaches is a promising solution for the fast deploymentof wearable devices and more adaptable devices for different sensingdemands. However, heat, solvent, and mechanical sensitivity of biologicaltissues, along with personal compliance, pose strict requirementsfor coating materials and methods. To address this, a biocompatibleand biodegradable light-curable conductive ink and an all-in-one flexiblesystem that conducts in situ injection and photoniccuring of the ink as well as monitoring of biophysiological informationhave been developed. The ink can be solidified through spontaneousphase changes and photonic cured to achieve a high mechanical strengthof 7.48 MPa and an excellent electrical conductivity of 3.57 x10(5) S/m. The flexible system contains elastic injectionchambers embedded with specially designed optical waveguides to uniformlydissipate visible LED light throughout the chambers and rapidly curethe ink in 5 min. The resulting conductive electrodes offer intimateskin contact even with the existence of hair and work stably evenunder an acceleration of 8 g, leading to a robust wearable systemcapable of working under intense motion, heavy sweating, and variedsurface morphology. Similar concepts may lead to various rapidly deployablewearable systems that offer excellent adaptability to different monitoringdemands for the health tracking of large populations.