Abstract
Humidity-sensitive poly(ethylene glycol) (PEG) inverse opals with micropatterns of 2 μm wide anti-swell-broken grooves were prepared using polystyrene (PS) colloidal crystals as templates and colloidal lithography. Monodisperse PS colloids were deposited in an ordered manner onto glass slides using a double-substrate vertical deposition method to form colloidal crystal templates. Poly(ethylene glycol) diacrylate (PEGDA) with photoinitiator was infiltrated into the interspaces of the colloidal crystals and photo-crosslinked by UV irradiation through a photomask. After removal the PS templates and unexposed PEGDA by tetrahydrofuran (THF), PEG hydrogel micropatterns with three-dimensional ordered porous structures were obtained. The band gaps of the PS colloidal crystals and corresponding PEG hydrogel inverse opals were measured by UV-VIS reflection spectrometer, calculated by Bragg law and simulated by Band SOLVE. The obtained PEG hydrogel inverse opal micropatterns can be used as sensors for humidity sensing due to absorption and desorption of moisture in the band gap structures. The sensor had a very reliable performance after repeated humidity sensing, and could be mass produced facilely with very low cost. The photopatterned anti-swell-broken grooves play an important role in the reliability of the sensors.
Highlights
In past decade, three-dimensional ordered porous materials have attracted great attention for wide potential applications in different areas such as band gap materials, biomedical materials, energy storage, and conversion materials [1,2]
Compared with the poly(ethylene glycol) (PEG) hydrogel inverse opal without micropatterns of anti-swell-broken grooves (Figure 9b), we can see that the photopatterned micropatterns of anti-swell-broken grooves (Figure 9b), we can see that the photopatterned antianti-swell-broken grooves play an important role in the reliability of the sensors
PEG hydrogel inverse opal sensors without antianti-swell-broken grooves will be irreversibly damaged caused by excessive squeeze
Summary
Three-dimensional ordered porous materials have attracted great attention for wide potential applications in different areas such as band gap materials, biomedical materials, energy storage, and conversion materials [1,2]. Materials 2017, 10, 1035 replicas of the templates with pores distributed in a three-dimensionally ordered way, can cause Bragg diffraction of lights [17,18] Both organic and inorganic ordered porous materials are very interesting for theoretical research and practical applications such as making optical filters, switches, photonic crystals and chemical sensors [19,20,21]. Wiltzius et al created a polyacrylamide inverse opal hydrogel structure to from a colloidal crystal template. This material can respond to various humidity conditions by shifting its optical reflection peak noticeably within the visible wavelength range [26]. The performance of the sensors with and without micropatterns of anti-swell-broken grooves was studied and discussed preliminarily
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