Fig. 3: Multimodal sensing capabilities and mechanisms.

a Schematic illustration of the thermogalvanic effect as the temperature sensing mechanism. b MD simulation of the PVA chain structure and its solvation behavior around Fe²⁺/Fe³⁺ ions, with inset images showing the first solvation shell. c Radial distribution function g(r) (solid lines) and coordination number N(r) (dotted lines) of oxygen atoms surrounding Fe³⁺ and Fe²⁺ ions in the PVA hydrogel. d Output voltage-current curves and corresponding power densities under various temperature gradients. e Output current and current density as a function of temperature difference. f Schematic of the piezoionic effect for pressure sensing. g Enhancement of ionic piezoelectric output in d₃₃ mode using a prismatic architecture. h COMSOL simulation of ion concentration gradients and potential distributions under pressure. i COMSOL simulation of stress distributions in PVA gels at increasing deformation. j Relative current change as a function of applied pressure. k Waveform signals measured from radial artery pulses. l Contact angle measurement of various carbon paper surfaces: Pristine, PDMS-coated, Perforated, and Hydrochloric acid soaked. m Top view of the sweat transport electrode and its transport capacity (scale bar: 1 mm). n Schematic of the diffusion effect for sweat detection. o Current responses to different sweat Na⁺ concentrations. p Repeated current responses over 10 alternating cycles of NaCl addition and water dilution.