Fig. 4

(a) Swelling tests of the gel in aqueous solution of fluorescent stain. (b) The swelling rate was calculated by swelling the gel in water for 24 h, and the inset shows the PVAC-30 gel before and after 30 d of swelling. (c) Tensile strength test of the gel after 24 h swelling. (d) Relative resistance change \(\varDelta \text{R}/{\text{R}}_{0}\) of the gel after 24 h swelling at different tensile levels. (e) Conductive gel ring design. (f) Detection of balloon size underwater in a conductive gel ring.