Extended Data Fig. 4: Biodegradable sensors characterization.

a, Stretchable meanders of zinc foil serve as conductors on biogels (G1730). b, Repeated stretching and increase of the maximum strain does not affect the conductivity of the zinc meanders. Mean resistance changes (solid line) during stretch-release cycles (data envelope) are shown. c, Those are durable for over 1000 stretching cycles, when stretched to a maximum strain of 20 %. d, Humidity sensors are realized with structured zinc foil on biogels (G2430). e, The magnitude of the impedance Z is measured as function of frequency at different climatic conditions, showing a change of two orders of magnitude. f, The sensor response is below 1 % when stretched repeatedly to a maximum strain of 10 %. g, Temperature sensors are realized with a conductive paste between two stretchable conductors on a biogel (G3030). h, The conductive pastes, fabricated on glass substrates, show a change larger than a factor of 2 over a range of 30 °C. Error bars, standard deviation for a measurement period >10 min. i, Strain sensors are designed with 5 fingers total to allow displacement of the electrodes. j, The sensor signals follow the applied strain profile linearly. Repeated cycles are tested between 20 % and 40 % strain, to account for irreversible mechanical deformation of the substrate during the first stretch-release cycle. Scale bars, 5 mm.