However, it still should utilize complicated mechanical parts to realize tunable focal lengths. This procedure was conducted 10, times. The sagittal shape of the plano-convex PVC gel lens is regulated by applying the electric fields and thus the focal length can be tuned as shown in Fig.This behavior is believed to be the electrode polarization caused by the increase of conductivity in the dielectric material 21 as the DBA molecules are charged and polarized in the electric field and the polarized DBA plasticizer facilitates the free dipole re-orientation of the PVC chain molecules in the physically-cross-linked PVC gel networks under a limited frequency range The response times at the on state and at the off state for the adaptive PVCH11 gel micro-lenses are 0. Utilizing the PVC gels responsive to an electric field, we previously reported an innovative approach to realize focus-variable micro-lenses 18 , 19 , which are operated by an electric-field-induced deformation of PVC gel toward the anode. The focal length increases from 3. The human lens has an asymmetric biconvex structure 20 , which is stretched or relaxed by the ciliary muscle to adjust the focal length Fig. In this paper, we exploit these ideas and mimic the design of the crystalline lens and ciliary muscle of the human eye to introduce a bio-inspired adaptive PVC gel micro-lens with electrically tunable focus. In particular, the PVCH11 gel used here is optimal in terms of optical, electrical, dielectric, and mechanical properties to facilitate a large electrically tunable range of focal lengths for fast responses. As the applied field was changed, the detection screen was moved until the smallest fine spot of collimated light could be observed again, which was indicative of the focal plane. Because a parabolic curvature of the gel micro-lens was formed, the compressed pressure in the gel caused the image to lose its focus and become blurry. Higher mechanical force can results in higher sagittal height of the plano-convex PVC gel lens. Micro-lens Performance The focal length experiments of the PVC gel micro-lens were carried out in a dedicated custom-built optical apparatus, composed of a collimated laser, a plano-convex PVC gel micro-lens, and a detection screen with a graph paper. This resulted in the conversion of the flat PVC gel to a plano-convex lens with the initial sagitta of 0. S1 to optimize the mechanical, electrical, and dielectric properties of the plasticized PVC gels. The 10,actuation cycles of the PVCH11 gel micro-lens were also reproducible under the experimental conditions Supplementary Fig. The PVC gel micro-lens was located between the microscope and the character object and the images were acquired by the microscope with a fixed-focus lens.
Afterwards, a 1-mm-thick printed circuit board PCBhaving a Cu-plated through-hole structure of 1. However, in comparison with other alternative technologies 30the operating speed of the electroactive PVCH11 gel micro-lens is relatively fast for applications in consumer electronic devices with completely reversible, silent, and stable operations over repeated measurements.The slight slower time response was due to the lag time required to physically deform the PVCH11 gel. From the simultaneous behavior of dielectric and electric characteristics in the PVC gels, it is concluded that PVC gels with high micro-crystallization induced by the high-molecular-weight PVC allow more free dipole re-orientation of the PVC chain by the DBA plasticizer with lower leakage current, while the non-ionic PVC gel shows the dielectric characteristics for the direct charge transfer. The focal length measurement was performed by a custom-built optical layout Fig. In this paper, we exploit these ideas and mimic the design of the crystalline lens and ciliary muscle of the human eye to introduce a bio-inspired adaptive PVC gel micro-lens with electrically tunable focus. Full size image Conclusions The bio-inspired, PVC gel-based micro-lens system is compact, lightweight, electro-responsive, and silent with low power consumptions. However, the PVC gel showed poor elasticity or even crushing under a certain pressure due to the lower physical crosslinking network, formed by insufficiently entangled anchored polymer chains and few microcrystallites, resulting in deterioration of the focal length variation. However, the PVCL5 gel became unfocused and significantly blurred in spite of the same electric field. Afterwards, a 1-mm-thick printed circuit board PCB , having a Cu-plated through-hole structure of 1. The conductivity changes in the dielectric material also appear in the results of the dielectric loss in the PVC gels Fig.
The PVC gel micro-lens was located between the microscope and the character object and the images were acquired by the microscope with a fixed-focus lens. The slight slower time response was due to the lag time required to physically deform the PVCH11 gel.
The response time of the micro-lens in the on or off state of the electrical activation increased with the applied electric field Fig. We first characterized the variations of the apparent focal length of the micro-lens with increasing the electric field.
These results demonstrate the suitability of the described approach for a new type of low-power consumption optical devices with variable focal lengths.