Bionic soft crystalline lens materials for MEMs applications based on self-assembling amphiphilic block copolymer/nanoparticle hybrids

• Published in: Microelectronic engineering 2011-08, Vol.88 (8), p.1737-1741
• Main Authors: Chang, Chun-Jie, Yang, Yi-Lung, Lee, Yu-Ping, Chiang, Chi-Ju, Dai, Chi-An, Chen, Jyh-Chien, Cheng, Yao-Yi, Chen, Chien-Chun, Liu, Ming-Wei, Shih, Wen-Pin, Yen, Jia-Yush
• Format: Article
• Language: English
• Subjects: Applied sciences; Artificial lens; Block copolymers; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronics; Exact sciences and technology; Human; Hydrogels; Lenses; Materials science; Methods of nanofabrication; Micro- and nanoelectromechanical devices (mems/nems); Nanoparticles; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Networks; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Self-assembly; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Soft materials; Titanium dioxide; UV crosslinking
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2010.12.024

In this study, a biomimetic crystalline lens with properties that combine the softness of a hydrogel comparable to that of a human lens for adjustable focus and the property for image aberration correction with gradient refractive index (GRIN) was developed by the self-organization of an amphiphilic block copolymer blended with high refractive index titanium nanoparticles (TiO2). The hydrogel lens was prepared by using a thermally responsive poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PPO–PEO–PPO) triblock copolymer (Poloxamer 407) with the lower-critical solution temperature (LCST) property that can be injectable into the eye capsule as a liquid below its LCST and solidifies as a soft gel above the LCST at the human body temperature. By chemical modification of the triblock copolymer with double bonds on its chain-ends (Poloxamer 407A), the soft lens network can be made by using UV crosslinking of the hydrogel. To further increase the refractive index (RI) of the hydrogel lens network and to match its RI to that of the human lens (=1.41), highly visible-light transparent titanium dioxide (TiO2) nanoparticles were introduced into the hydrogel lens network. To create a biomimetic GRIN lens as in the human’s eyes, an electric field method was also used to induce an axial diffusion of TiO2 nanoparticles from the center of the lens where TiO2 nanoparticles were first injected to the edge. The above method demonstrates the potential to use the hydrogel/nanoparticle hybrid as an injectable replacement for a soft optical lens system with an adjustable focus for future MEMs application.