Cylindrical microlens arrays (CMLAs) play a key role in many optoelectronic devices, and 100% fill-factor CMLAs also have the advantage of improving the signal-to-noise ratio and avoiding stray-light effects. However, the existing preparation technologies are complicated and costly, which are not suitable for mass production. Herein, we propose a simple, efficient, and lowcost manufacturing method for CMLAs with a high fill-factor via the electric-field-driven (EFD) microscale 3D printing of polydimethylsiloxane (PDMS). By adjusting the printing parameters, the profile and the fill-factor of the CMLAs can be controlled to improve their optical performance. The optical performance test results show that the printed PDMS CMLAs have good imageprojecting and light-diffraction properties. Using the two printing modes of this EFD microscale 3D-printing technology, a cylindrical dual-microlens array with a double-focusing function is simply prepared. At the same time, we print a series of specially shaped microlenses, proving the flexible manufacturing capabilities of this technology. The results show that the prepared CMLAs have good morphology and optical properties. The proposed method may provide a viable route for manufacturing large-area CMLAs with 100% fill-factor in a very simple, efficient, and low-cost manner.
flexible devices has received widespread attention. Among them, flexible strain sensors have attracted great interest from the industry and academia due to their promising applications in wearable devices, [1][2][3] electronic skin, [4,5] intelligent robots, [6] healthcare monitoring, [7] and humanmachine interfaces. [8,9] The three primary categories of strain sensors are resistive, [10] capacitive, [11] and piezoelectric. [12] The advantages of capacitive-type strain sensors are high sensitivity, rapid response, and high linearity, but the sensor has poor response performance on various strains due to their structural limitations. The performance of the piezoelectric-type strain sensor mainly focuses on the piezoelectric material, which requires excellent piezoelectricity of the material, but the piezoelectric material is more expensive and the measurable range is narrower. Compared to the above two types of sensors, resistivetype strain sensors have the advantages of a wider strain sensing range, relatively simple reading mechanism and easy fabrication, which have received wide attention in recent years in the fields of wearable devices and electronic skins. Therefore, this paper will focus on the resistive-type strain sensors. The working principle is that the structure of the conductive material changes when the device is stretched, bent, and twisted, causing the resistance of Flexible strain sensors have received widespread attention because of their great potential in many fields. Carbon nanotubes (CNTs) have been used as conductive materials for flexible strain sensors due to their excellent electrical and mechanical properties, and the fabricated flexible strain sensors have excellent sensing performance. This paper systematically summarizes the advances in flexible resistance-type strain sensors based on CNTs. The strain sensing mechanisms are introduced, including crack extension, tunneling effect, and disconnection of overlapping materials. The performance parameters of the sensors, including sensitivity, stretchability, linearity, hysteresis, dynamic durability, and transparency, are discussed comprehensively. The coating methods, 3D printing techniques, chemical vapor deposition, transfer methods, and spinning processes used to fabricate CNT strain sensors are highlighted. The effect of isolated and porous internal conductive structures, folded and microcracked surface structures, films and fabrics macroscopic structures on sensor performance were systematically analyzed. The applications of the sensors in medical health, motion monitoring, gesture recognition, human-computer interaction, and soft robotics are provided in detail. Finally, the future challenges of CNT flexible strain sensors are summarized and the outlook is presented. Although CNT strain sensors have made great progress so far, there are still many problems that need researchers' attention and solutions.
Flexible transparent electrodes (FTEs) with embedded metal mesh composed of composite materials or structures have excellent comprehensive performance, which has attracted extensive attention, but it also brings great challenges to its manufacturing. Herein, a simple and cost‐effective fabrication process free of template, vacuum processes is proposed for high‐performance FTEs with ultra‐fine embedded Cu/Ag(shell)–P4VP(core) conductive grid via a microscale hybrid additive manufacturing technique. The produced FTE exhibits excellent properties with a sheet resistance of 2.5 Ω, a transmittance of 93% at a line pitch of 250 µm, and an ultra‐fine line width of 4 µm, low surface roughness (Ra ≈ 5.28 nm), and excellent mechanical stability (no change in Rs after 100 adhesion and 150 scratch tests). The FTEs expose only a few conductive areas, which make it excellent environmental stability (no change in Rs after exposure to humidity environment for 72 h). The flexible electroluminescent device fabricated with this FTE has good bending and luminescent properties, showing great potential for flexible optoelectronic applications.
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