Figure 4: Tuning of hydrochromic response.
From: Hydrochromic conjugated polymers for human sweat pore mapping

(a) Chemical structures of diacetylenic lipids: PCDA, TCDA, HCDA (8,10-heneicosadiynoic acid). (b) Colorimetric response of PDA films derived from various combinations of diacetylene monomers and ions under different humidity conditions. (c) Red intensity of the hydrochromic PDA films shown in b as a function of relative humidity. It is evident from the figures that colorimetric response of PDA films can be manipulated by choosing proper diacetylene monomers and cations.