Figure 2. Physical properties of the electrode composite.

(a) Information on the structure of the composite and its interface with the skin and the contact pad of the external (or wearable) device. (b) SEM image of ferromagnetic (carbonyl iron) particles in an elastomer matrix; scale bar is 4 µm. (c) Magnetization curve of carbonyl iron powder. (d) Comparison of adhesion strength of the electrode composite to the skin and the magnet. Inset: image of the ferromagnetic properties of the electrode composite. (e, f) Effect of hydration on the proposed composite and on a commercially available hydrogel electrode. (g) Elastic modulus as a function of volume fraction of CI particles in the ferromagnetic composite. (h) Mechanical responses of the composite and a commercial hydrogel to applied strain. (i) Optical image of the electrode composite under stretching; scale bar is 1 mm. (j) Finite element study for uniaxial stretching (left), biaxial stretching (center), and folding (right); scale bars are 1 mm.