nature, and harsh processing conditions of the ITO and the scarcity of the indium limit the further application for the THs. [3,4] As such, recent studies have proposed several emerging materials for the next-generation TCF to replace ITO, including carbon-based materials, [5][6][7][8] metal nanowires (NWs) or nanofibers (NFs), [9][10][11][12][13][14][15] metal meshes, [16][17][18] conductive polymers, [19] and hybrid materials. [1,[20][21][22] However, the cost, mechanical robustness, and trade-off between transmittance (T) and sheet resistance (R s ) of these TCFs remain limited and inconsistent across applications.The R s of carbon-based materials and conductive polymers is higher than that of ITO, [23] which restricts their use in high-performance TGHs. [4] Metal NWs or NFs and metal meshes have been studied extensively in recent years and have been described as the most promising TCF materials due to excellent electrical and optical properties (in some cases superior to ITO). Metal NWs and NFs have been demonstrated as an ITO substitute in flexible optoelectronic applications because of their mechanical flexibility and preferable T-R s trade-off. However, the resulting THs or TGHs have struggled to achieve T > 90% and R s < 10 Ω sq −1 . [24] Hsu et al. reported a high-performance TCF with R s = 0.36 Ω sq −1 at T = 92% by combining mesoscale NFs with metal NWs, [25] and An et al. produced a copper NF with T > 90% and R s < 0.5 Ω sq −1 using electrospinning and electroplating methods. [21] These NWs and NFs exhibit limitations such as excessive surface roughness, low uniformity, high material cost, and unavoidable haze. [13,26] In addition, adhesion between NWs and commonly-employed substrates is often poor, which makes it difficult to use NWs in harsh environments for extended time periods. [27] These characteristics hinder the production of low-cost high-performance TGHs, which require low R s , high T, and strong TCF adhesion.Metal mesh is considered to be an ideal TCF because of its inherently high T, low haze, high electrical conductivity, good mechanical properties, and low cost. [17] The T-R s trade-off in metal meshes can be further optimized by increasing the intrinsic conductivity or the aspect-ratio (AR) of the metal wire Great challenges remain concerning the cost-effective manufacture of highperformance metal meshes for transparent glass heaters (TGHs). Here, a high-performance silver mesh fabrication technique is proposed for TGHs using electric-field-driven microscale 3D printing and a UV-assisted microtransfer process. The results show a more optimal trade-off in sheet resistance (R s = 0.21 Ω sq −1 ) and transmittance (T = 93.9%) than for indium tin oxide (ITO) and ITO substitutes. The fabricated representative TGH also exhibits homogeneous and stable heating performance, remarkable environmental adaptability (constant R s for 90 days), superior mechanical robustness (R s increase of only 0.04 in harsh conditions-sonication at 100 °C), and strong adhesion force with a negligible increase in R...

performance, transparent conductive oxides, as represented by indium tin oxide (ITO), have been mostly used widely for transparent electrodes (TEs) in the past few decades. However, the inherent properties of ITO such as brittleness and poor flexibility hinder its applications for flexible and stretchable optoelectronic products. [10] Hence, many alternatives to ITO have been developed to address these challenges for the next generation of FTEs, such as graphene, [11] carbon nanotubes, [12,13] conductive polymers, [14][15][16][17][18] transparent thin metal films, [19,20] random metal nanowires, [2,21] regular metalmesh, [22,23] and hybrid materials. [24,25] Among these FTEs, metal-mesh possesses excellent mechanical flexibility and optoelectronic properties. In particular, the trade-off between low sheet resistance and the high transmittance of TEs can be parametrically designed and further optimized by simply changing the line width, pitch, aspect ratio (AR), shape, and arrangement of the mesh. The metal mesh can be fabricated with a low-cost and large-area manufacturing process (such as solution-process), which can be carried out in a vacuum-free environment and usually requires only a low temperature process. [26][27][28][29][30] So far, FTEs based on metal mesh Flexible transparent electrodes (FTEs) with an embedded metal mesh are considered a promising alternative to traditional indium tin oxide (ITO) due to their excellent photoelectric performance, surface roughness, and mechanical and environmental stability. However, great challenges remain for achieving simple, cost-effective, and environmentally friendly manufacturing of high-performance FTEs with embedded metal mesh. Herein, a maskless, templateless, and plating-free fabrication technique is proposed for FTEs with embedded silver mesh by combining an electric-field-driven (EFD) microscale 3D printing technique and a newly developed hybrid hot-embossing process. The final fabricated FTE exhibits superior optoelectronic properties with a transmittance of 85.79%, a sheet resistance of 0.75 Ω sq −1 , a smooth surface of silver mesh (R a ≈ 18.8 nm) without any polishing treatment, and remarkable mechanical stability and environmental adaptability with a negligible increase in sheet resistance under diverse cyclic tests and harsh working conditions (1000 bending cycles, 80 adhesion tests, 120 scratch tests, 100 min ultrasonic test, and 72 h chemical attack). The practical viability of this FTE is successfully demonstrated with a flexible transparent heater applied to deicing. The technique proposed offers a promising fabrication strategy with a cost-effective and environmentally friendly process for high-performance FTE.

Flexible transparent electrodes (FTEs) with embedded metal meshes play an indispensable role in many optoelectronic devices due to their excellent mechanical stability and environmental adaptability. However, low-cost, simple, efficient, and environmental friendly integrated manufacturing of high-performance embedded metal meshes remains a huge challenge. Here, a facile and novel fabrication method is proposed for FTEs with an embedded metal mesh via liquid substrateelectric-field-driven microscale 3D printing process. This direct printing strategy avoids tedious processes and offers low-cost and high-volume production, enabling the fabrication of high-resolution, high-aspect ratio embedded metal meshes without sacrificing transparency. The final manufactured FTEs with 80 mm × 80 mm embedded metal mesh offers excellent optoelectronic performance with a sheet resistance (R s ) of 6 𝛀 sq −1 and a transmittance (T) of 85.79%. The embedded metal structure still has excellent mechanical stability and good environmental suitability under different harsh working conditions. The practical feasibility of the FTEs is successfully demonstrated with a thermally driven 4D printing structure and a resistive transparent strain sensor. This method can be used to manufacture large areas with facile, high-efficiency, low-cost, and high-performance FTEs.

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.