Biomimetic Polymer Film with Brilliant Brightness Using a One‐Step Water Vapor–Induced Phase Separation Method. (25th February 2019)

• Record Type: Journal Article
• Authors: Zou, Weizhi; Pattelli, Lorenzo; Guo, Jing; Yang, Shijia; Yang, Meng; Zhao, Ning; Xu, Jian; Wiersma, Diederik S.
• Is Part Of: Advanced functional materials. Volume 29:Number 23(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-02-25
• Subjects: biomimicry -- Cyphochilus -- Monte Carlo simulation -- phase separation -- polymer; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201808885
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: The scales of the white Cyphochilus beetles are endowed with unusual whiteness arising from the exceptional scattering efficiency of their disordered ultrastructure optimized through millions of years of evolution. Here, a simple, one‐step method based on water vapor–induced phase separation is developed to prepare thin polystyrene films with similar microstructure and comparable optical performance. A typical biomimetic 3.5 µm PS film exhibits a diffuse reflectance of 61% at 500 nm wavelength, which translates into a transport mean free path below 1 µm. A complete optical characterization through Monte Carlo simulations reveals how such a scattering performance arises from the scattering coefficient and scattering anisotropy, whose interplay provides insight into the morphological properties of the material. The potential of bright‐white coatings as smart sensors or wearable devices is highlighted using a treated 3.5 µm film as a real‐time sensor for human exhalation. Abstract : A one‐step water vapor–induced phase separation method is developed to fabricate thin, freestanding polymeric films with brilliant brightness, flexibility, and activatable superhydrophilicity as a new smart bright‐white coating. Complete optical characterization based on a Monte Carlo solution of the radiative transfer model and analysis of formation mechanism provide useful guidance to design surfaces with advanced scattering properties.