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1. Mechanically tunable elastic modulus of freestanding Ba1− x Sr x TiO3 membranes via phase-field simulation

   https://doi.org/10.1063/5.0099772  

   Zhang, Kena; Ren, Yao; Cao, Ye (October 2022, Applied Physics Letters)

   The freestanding ferroelectric membranes with super-elasticity show promising applications in flexible electronic devices such as transducers, memories, etc. While there have been recent studies on the effect of mechanical bending on the domain structure evolutions and phase transitions in ferroelectric membranes, its influence on Young's modulus of these freestanding membranes is less explored, which is crucial for the design and application of flexible electronics. Here, a phase-field model is developed to simulate the tunability of Young's modulus of freestanding Ba1−xSrxTiO3 membranes under mechanical bending. It is demonstrated that the bended membrane shows a uniform Young's modulus compared with unbended membrane. By increasing the bending angle, Young's modulus tunability is enhanced, which can be attributed to the vortex-like domain structures induced by the mechanical bending. These vortex-like domains with large domain wall energy inhibit the subsequent domain switching under externally applied tensile strain and reduce the eigenstrain variation, which leads to a large Young's modulus. In addition, the formation of vortex domain structure is suppressed with increasing Sr2+ content in Ba1−xSrxTiO3 membranes at the same bending degree, resulting in a decrease in Young's modulus tunability. Our work reveals that the tunability of Young's modulus of freestanding ferroelectric membranes can be achieved by mechanical bending, which provides guidance for designing flexible electronic devices. 

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2. Superhydrophobic inkjet printed flexible graphene circuits via direct-pulsed laser writing

   https://doi.org/10.1039/c7nr06213c  

   Das, Suprem R.; Srinivasan, Srilok; Stromberg, Loreen R.; He, Qing; Garland, Nathaniel; Straszheim, Warren E.; Ajayan, Pulickel M.; Balasubramanian, Ganesh; Claussen, Jonathan C. (January 2017, Nanoscale)

   Solution-phase printing of exfoliated graphene flakes is emerging as a low-cost means to create flexible electronics for numerous applications. The electrical conductivity and electrochemical reactivity of printed graphene has been shown to improve with post-print processing methods such as thermal, photonic, and laser annealing. However, to date no reports have shown the manipulation of surface wettability via post-print processing of printed graphene. Herein, we demonstrate how the energy density of a direct-pulsed laser writing (DPLW) technique can be varied to tune the hydrophobicity and electrical conductivity of the inkjet-printed graphene (IPG). Experimental results demonstrate that the DPLW process can convert the IPG surface from one that is initially hydrophilic (contact angle ∼47.7°) and electrically resistive (sheet resistance ∼21 MΩ □ −1 ) to one that is superhydrophobic (CA ∼157.2°) and electrically conductive (sheet resistance ∼1.1 kΩ □ −1 ). Molecular dynamic (MD) simulations reveal that both the nanoscale graphene flake orientation and surface chemistry of the IPG after DPLW processing induce these changes in surface wettability. Moreover, DPLW can be performed with IPG printed on thermally and chemically sensitive substrates such as flexible paper and polymers. Hence, the developed, flexible IPG electrodes treated with DPLW could be useful for a wide range of applications such as self-cleaning, wearable, or washable electronics. 

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3. Inkjet‐printed flexible MXetronics : Present status and future prospects

   https://doi.org/10.1002/appl.202300085  

   Krishnamoorthy, Rajavel; Das, Suprem R. (February 2024, Applied Research)

   Abstract Over the past several years, atomically thin two‐dimensional carbides, nitrides, and carbonitrides, otherwise known asMXenes, have been expanded into over fifty material candidates that are experimentally produced, and over one hundred fifty more candidates that have been theoretically predicted. They have demonstrated transformative properties such as metallic‐type electrical conductivities, optical properties such as plasmonics and optical nonlinearity, and key surface properties such as hydrophilicity, and unique surface chemistry. In terms of their applications, they are poised to transform technological areas such as energy storage, electromagnetic shielding, electronics, photonics, optoelectronics, sensing, and bioelectronics. One of the most promising aspects ofMXene'sfuture application in all the above areas of interest, we believe, is reliably developing their flexible and bendable electronics and optoelectronics by printing methods (henceforth, termed asprinted flexible MXetronics). Designing and manipulatingMXeneconductive inks according to the application requirements will therefore be a transformative goal for future printed flexible MXetronics.MXene'scombined property of high electrical conductivity and water‐friendly nature to easily disperse its micro/nano‐flakes in an aqueous medium without any binder paves the way for designing additive‐free highly conductiveMXene ink. However, the chemical and/or structural and hence functional stability of water basedMXeneinks over time is not reliable, opening research avenues for further development of stable and conductiveMXeneinks. Such priorities will enable applications requiring high‐resolution and highly reliable printedMXeneelectronics using state‐of‐the art printing methods. EngineeringMXenestructural and surface functional properties while tuningMXeneink rheology in benign solvents of choice will be a key for ink developments. This review article summarizes the present status and prospects ofMXeneinks and their use in inkjet‐printed (IJP) technology for future flexible and bendableMXetronics. 

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4. Synergetic Effect of In Situ Formed TiO ₂ in MXene for Enhanced Energy Storage in High-Performance Supercapacitors

   https://doi.org/10.1021/acsaem.4c02769  

   Jadhav, Sarika; Ramana, C V; Tan, Susheng; Gosavi, Suresh; Haram, Santosh (January 2025, ACS Applied Energy Materials)

   This study explores and presents a comprehensive understanding of the synergistic effect of in situ formed TiO2 in Ti2C MXene (TTMXene) nanomaterials to derive enhanced energy characteristics in high-performance flexible symmetric supercapacitors. The TTMXene two-dimensional (2D) (nanocomposite) materials were synthesized by a simple single-step chemical etching method. The TTMXene thus formed exhibits a layered structure with an average particle size in the range of 10−50 nm. The electrochemical studies demonstrate that the TTMXene nanocomposite exhibits a specific capacitance of 729 F g−1 at a current density of 0.5 A g−1 . This enhanced performance is due to utilizationofa highactivesurfaceareaand excellentelectronicconductivityofthe in-situ formed TiO2 in Ti2C MXene. The prototype of a flexible symmetric TTMXene supercapacitor was fabricated and characterized. The TTMXene// TTMXenedemonstratedanexcellentenergydensityof152.3Whkg−1 atapower density of 0.215 kW kg−1 and retained 88% specific capacitance after 10,000 cycles. These findings highlight that the TTMXene nanocomposites are exceptional candidates for future flexible supercapacitor devices with long-term and superior performance. 

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5. Incorporation of density scaling constraint in density functional design via contrastive representation learning

   https://doi.org/10.1039/D3DD00114H  

   Gong, Weiyi; Sun, Tao; Bai, Hexin; Chowdhury, Shah Tanvir; Chu, Peng; Aryal, Anoj; Yu, Jie; Ling, Haibin; Perdew, John P.; Yan, Qimin (October 2023, Digital Discovery)

   We demonstrate that contrastive representation learning is a computationally efficient and flexible method to incorporate physical constraints, especially those defined by equalities, in machine-learning-based density functional design. 

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