• HUI ZHANG

Articles written in Bulletin of Materials Science

• Computational analyses for tunable solid lenses coupling polyacrylamide hydrogel electrodes

Electrically tunable lenses could change focus without motor-controlled translations of stiff lenses. Firstly, the lens system is enabled by stable polyacrylamide (PAM) hydrogel electrodes that are synthesized containing silicone oil, sodium chloride, etc. Two layers of the hydrogel are used as ionic conductors to sandwich a dielectric elastomer membrane. The maximum rupture stretch of the hydrogel was around 20 and the small strain Young’s modulus was about 0.5 kPa in experiments. Secondly, compact computational models are proposed based on the assumption of homogeneous deformation on materials, and the application of energy methods. Thickness-stretch curves of the PAM hydrogel are calculated, and the relation between electric field and stretch of a lens actuator is obtained by using the built mathematic models. Thirdly, a soft solid-body lens is described to obtain compact tunable results. The relationship between the applied voltage and the focus has also been given based on the derived equations. An increase in lens size produced larger tunable range variation. The new lens could find application in systems requiring large variations of focus with silent operation, low weight, shock tolerance, etc.

• Focus-tunable imaging analyses of the liquid lens based on dielectric elastomer actuator

In order to simulate the auto-focusing function of human eyes, a liquid lens is proposed based on dielectric elastomer actuator (DEA). The lens could realize rapid focusing under voltages. The structure and principle of the lens are described in detail. A novel fabricating method is presented for the lens, which is inspired by the negative pressure technology. A negative pressure region is made in the centre of the dielectric elastomer (DE) membrane, and the liquid is filled. Then the other layer of membrane is covered to seal the liquid. Around the lens is the DEA coupling carbon grease electrodes. The finite element analysis and simulation of the lens deformation are carried out by using the software of Abaqus. The relationship is explored among lens diameter, volume, pretension ratio, actuating voltage and focal length. Itis found that when the liquid volume is fixed in the soft lens, the larger the pre-stretching ratio is, the greater the lens deformation is. At the condition of the same lens diameter, focal-length changes are inversely proportional to the liquid volume. The correctness of built theoretical models is verified by experiments in the end.

• Carbon-doped titania-polymethylsilsesquioxane aerogels for the photocatalytic degradation of antibiotics

Removal of antibiotics detected in wastewater or natural aquatic systems by regular municipal treatment is challenging. Photocatalysis is considered to be the most well-known and green strategy for such removal. However, the catalytic efficiency is restricted by UV radiation dependence, fast electron-hole recombination, and low porosity/surface area of the photocatalyst. In this study, we have developed a highly porous anatase TiO$_2$-polymethylsilsesquioxane(PMSQ) aerogel with nonmetal carbon dopant, which can simultaneously enhance the adsorption ability and visible light photo-activity. And tetracycline hydrochloride (TCH) was selected as a model antibiotic. A high surface area (747 g cm$^{-3}$) C-TiO2-PMSQ aerogel can remove 91% TCH within 180 min under visible light. But the removal needs to be in an isopropyl alcohol/water co-solvent, due to the intrinsic hydrophobicity of PMSQ. After a heat treatment under 400°C, the surface area of C-TiO$_2$-PMSQ aerogel decreases to 618 g cm$^{-3}$, and the sample loses its hydrophobicity, the removal of TCH can be in aqueous condition and the efficiency increases to 98%. Moreover, both catalysts can be recycled 7 times and still maintain high removal efficiency (85 and 64% remained for hydrophobic and hydrophilic gels, respectively).

• # Bulletin of Materials Science

Volume 45, 2022
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020