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.
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 demonstrate the combination of a tunable lens and tunable aperture in a compact imaging system whose structure is inspired by the human eye. The concept is based on innovative optical materials ...and tuning mechanisms including an optofluidic iris for a tunable aperture and an elastomer lens for focal length tuning. Wavefront and modulation transfer function analysis reveals a high imaging performance of both the individual elements and the complete system. Most significantly, the wavefront is not degraded (ΔPV<λ/10) when tuning the focal length (Δf=5.36%).
The shape of liquid interfaces can be precisely controlled using electrowetting, an actuation mechanism which has been widely used for tunable optofluidic micro-optical components such as lenses or ...irises. We have expanded the considerable flexibility inherent in electrowetting actuation to realize a variable optofluidic slit, a tunable and reconfigurable two-dimensional aperture with no mechanically moving parts. This optofluidic slit is formed by precisely controlled movement of the liquid interfaces of two highly opaque ink droplets. The 1.5 mm long slit aperture, with controllably variable discrete widths down to 45 µm, may be scanned across a length of 1.5 mm with switching times between adjacent slit positions of less than 120 ms. In addition, for a fixed slit aperture position, the width may be tuned to a minimum of 3 µm with high uniformity and linearity over the entire slit length. This compact, purely fluidic device offers an electrically controlled aperture tuning range not achievable with extant mechanical alternatives of a similar size.
While high-throughput planar patch-clamp instruments are now established to perform whole-cell recordings for drug screening, the conventional micropipette-based approach remains the gold standard ...for performing cell-attached single-channel recordings. Generally, planar platforms are not well-suited for such studies due to excess noise resulting from low seal resistances and the use of substrates with poor dielectric properties. Since these platforms tend to use the same pore to position a cell by suction and establish a seal, biological debris from the cell suspension can contaminate the pore surface prior to seal formation, reducing the seal resistance. Here, femtosecond laser ablation was used to fabricate dual-pore glass chips optimized for use in cell-attached single-channel recordings that circumvent this problem by using different pores to position a cell and to establish a seal. This dual-pore design also permitted the use of a relatively small patch aperture (D ~ 150 to 300 nm) that is better-suited for establishing high-resistance seals than the micropores used typically in planar patch-clamp setups (D ~ 1 to 2 μm) without compromising the ability of the device to position a cell. Taking advantage of the high seal resistances and low capacitive and dielectric noise realized using glass substrates, patch-clamp experiments with these dual-pore chips consistently achieved high seal resistances (rate of gigaseal formation = 61%, mean seal resistance = 53 GΩ), maintained gigaseals for prolonged durations (up to 6 hours), achieved RMS noise values as low as 0.46 pA at 5 kHz bandwidth, and enabled single-channel recordings in the cell-attached configuration that are comparable to those obtained by conventional patch-clamp.
While high-throughput planar patch-clamp instruments are now established to perform whole-cell recordings for drug screening, the conventional micropipette-based approach remains the gold standard ...for performing cell-attached single-channel recordings. Generally, planar platforms are not well-suited for such studies due to excess noise resulting from low seal resistances and the use of substrates with poor dielectric properties. Since these platforms tend to use the same pore to position a cell by suction and establish a seal, biological debris from the cell suspension can contaminate the pore surface prior to seal formation, reducing the seal resistance. Here, femtosecond laser ablation was used to fabricate dual-pore glass chips optimized for use in cell-attached single-channel recordings that circumvent this problem by using different pores to position a cell and to establish a seal. This dual-pore design also permitted the use of a relatively small patch aperture (
D
~ 150 to 300 nm) that is better-suited for establishing high-resistance seals than the micropores used typically in planar patch-clamp setups (
D
~ 1 to 2 μm) without compromising the ability of the device to position a cell. Taking advantage of the high seal resistances and low capacitive and dielectric noise realized using glass substrates, patch-clamp experiments with these dual-pore chips consistently achieved high seal resistances (rate of gigaseal formation = 61%, mean seal resistance = 53 GΩ), maintained gigaseals for prolonged durations (up to 6 hours), achieved RMS noise values as low as 0.46 pA at 5 kHz bandwidth, and enabled single-channel recordings in the cell-attached configuration that are comparable to those obtained by conventional patch-clamp.
This automated dual-pore planar patch-clamp platform enables low-noise single-channel recordings with similar fidelity to conventional pipette-based patch-clamp experiments.
We present a liquid crystal elastomer (LCE) actuator with large stroke and fast reaction time. LCEs show a large macroscopic shape change when heated above the phase transition (≈120°C). Buried ...wafer-level fabricated micro-heaters offer optimal thermal reaction times and compact design of the actuators. A relative length change of λ = 1.28 was obtained with 320 mW power consumption. Heating the device from room temperature takes τ rise = 19.7 s, cooling below the phase transition temperature from the fully contracted state needs τ fall - 5.6s. We verify that the displacement may be accurately controlled by varying electrical input power.
IntroductionAs delineated in Chapter 2, many optical systems in nature are based on soft and pliable organic tissue. Technical implementations of tunable optical systems, as described in Chapters 1, ...3, 6, and 7, also benefit from the use of soft matter in the fabrication of optical components.Whereas in natural optical systems such as the human eye, actuation (for tuning the focal length) uses flexible muscle tissue, most technical optical systems are actuated with rigid metallic or crystalline semiconductor-based actuators, that are used to deform a pliable optical component. Now, a new family of materials, liquid crystal elastomers (LCEs), represent a useful and novel means for generating force and movement in a micromechanical system and may thus be used to tune an optical system. In this chapter, we show how LCE-based actuators may be conceived to realize compact tunable irises and tunable lenses, all fabricated with soft materials.The LCE is a polymer-based material that contracts and elongates significantly in direct dependence of temperature changes; it may thus be considered a thermal actuator characterized by a long stroke and able to generate significant force. By microstructuring the LCE and incorporating microfabricated heaters into the material, very compact actuators may be designed, allowing the realization of self-contained, highly miniaturized tunable optical systems.Bioinspired tunable optical components have been demonstrated before. In the example shown in Figure 14.1a, Carpi et al. (2011) uses a dielectric elastomer to tune a pliable lens, thus imitating the human eye. Alternatively, liquids can be used to realize a completely fluidic tunable iris (Müller et al. 2012), which can be seen in Figure 14.1b; this system is discussed in-depth in Chapter 6.Following the design of the human eye in both optics and actuation (Schuhladen et al. 2013), one challenge remained: the integration of individual components into a complete imaging system. In the following, we describe means for realizing actuation of soft-matter tunable optical devices using LCEs and the integration of these into an imaging system that includes a tunable lens and variable iris.We begin with an in-depth exposé of the chemistry, fabrication technology, and operating characteristics of LCEs. We then continue to characterize two optical components that rely on the characteristic behavior of this active material: an LCE-based iris and an LCE-actuated tunable lens. The chapter concludes with a discussion of the functionality of a complete imaging system that employs these components.
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