Surface-induced nano-generator utilizing a thermo-responsive smart window based on ionic liquid aqueous solution that exhibits lower critical solution temperature type phase separation

Abstract

We demonstrate a surface-induced nano-generator utilizing a thermo-responsive smart window based on ionic liquid aqueous solution that exhibits lower critical solution temperature (LCST) type phase separation. This smart window was fabricated by filling an aqueous solution of [${}^n$Bu${}_4$P][CF${}_3$COO] between the glass substrates coated with two different polymers: a polyimide with an alkyl side chain and an amorphous fluoropolymer. Below the LCST, the transmittance of the smart window was 87 %, nearly identical to that of a glass substrate. In contrast, when heated above the LCST, the [${}^n$Bu${}_4$P][CF${}_3$COO] aqueous solution undergoes phase separation, causing the [${}^n$Bu${}_4$P] cations and [CF${}_3$COO] anions to adsorb onto the polyimide with the alkyl side chain and the amorphous fluoropolymer facilitated by the surface pinning effect. This adsorption process results in the smart window generating electricity while transitioning to an opaque state. Therefore, the proposed smart window functions as an electricity-generating thermo-responsive device that can switch between transparent and opaque states in response to temperature changes.