A liquid-crystal elastomer (LCE) iris inspired by the human eye is demonstrated. With integrated polyimide-based platinum heaters, the LCE material is thermally actuated. The radial contraction direction, similar to a mammalian iris, is imprinted to the LCE by a custom-designed magnetic field. Actuation of the device is reproducible over multiple cycles and controllable at intermediate contraction states.

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Microlenses fabricated using flexible elastomers can be tuned in focal length by application of controlled strain. By varying the strain azimuthally, the lenses may be deformed asymmetrically such that aberrations may be controlled. This approach is used to tune the astigmatism of the tunable lenses, and it is shown that the generated wavefront may be accurately controlled. The lens presented here has an initial focal length of 32.6 mm and a tuning range of 12.3 mm for approximately 10% applied strain. The range of directly tunable Zernike polynomials representing astigmatism is about 3 mm, while the secondary lens errors, which cannot be tuned directly, vary only by about 0.2 mm. Light: Science & Applications (2013) 2, e98; doi:10.1038/lsa.2013.54; published online 13 September 2013Keywords: aberrations; active or adaptive optics; micro-optical devices; polymers INTRODUCTION A broad spectrum of tunable micro-optical components using a wide variety of physical effects has been proposed and demonstrated. 1 One approach with considerable potential is the mechanical deformation of microlenses entirely made of flexible elastomers: by controlled application of radial strain, resulting in a change in lens curvature, it has been shown that the focal length can be tuned over a considerable range. 2,3 To date, strain has only been applied symmetrically around these tunable elastomeric lenses, such that only refractive power (focal length), but not other optical properties, have been tuned. A number of other tunable devices have considered the astigmatism. For example, Beadie et al. 4 presented a tunable composite lens, one part being a fixed focal length lens made of poly(methylmetacrylate) and the tunable part using a membrane with a poly(dimethylsiloxane) (PDMS) elastomer as a filling; the surface profiles showed an inherent astigmatism.Alternatively, singlet polymer lenses with thermal actuation have been reported by Lee et al. 5 By choosing an anisotropic heater structure, Lee et al. were able to tune astigmatism along one axis, while the other axis remains fixed. A more versatile approach with a combination of several membrane lenses was pursued by Marks et al. 6 Here two perpendicularly oriented cylindrical lenses provide variable astigmatism, whose total focus is compensated with a rotational symmetric membrane lens.We show here that application of azimuthally varying strain to a deformable elastomer lens can result in controlled variation of aberrations, particularly astigmatism. As a result, the microlens is not only tunable in focal length, but the concomitant aberrations can be increased or decreased at will.

We demonstrate a tunable imaging system based on the functionality of the mammalian eye using soft-matter micro-optical components. Inspired by the structure of the eye, as well as by the means through which nature tunes its optical behavior, we show that the technologies of microsystems engineering and micro-optics may be used to realize a technical imaging system whose biomimetic functionality is entirely distinct from that of conventional optics. The engineered eyeball integrates a deformable elastomeric refractive structure whose shape is mechanically controlled through application of strain using liquid crystal elastomer (LCE) actuators; two forms of tunable iris, one based on optofluidics and the other on LCEs with embedded heaters; a fixed lens arrangement; and a commercial imaging sensor chip. The complete microsystem, optimized to yield optical characteristics close to those of the human eye, represents the first fully functional, soft-matter-based tunable single-aperture eye-like imager.

We present novel biconvex solid-body elastomer (polydimethylsiloxane) lenses, which can be tuned in focal length by using magnetic or mechanical actuation. The focal length change is induced by applying radial elastic strain and is investigated for different initial radii of curvature of the lenses and different actuation designs. In all cases, a linear correlation between induced strain and focal length tuning, in the range of about 10% (approximately 3 mm), is found. These results compare favorably with finite element simulations.