Hong Zhao

Smart textiles with temperature‐sensing capabilities have attracted much attention due to their facile temperature monitoring in healthcare and packaging industry. This study explores the deposition of thermochromic cholesteric liquid crystal (CLC) on PET nonwoven using direct ink writing (DIW), focusing on the influences of calendering and surface treatment, such as hydrophilic PVA and hydrophobic NeverWet coatings. Wetting studies show that the porous nonwoven promotes rapid CLC absorption, while calendering the uncoated nonwoven accelerates the ink absorption despite the reduced pores and air permeability. Surface chemistry further affects the CLC behavior, with PVA enhancing wetting and NeverWet suppressing both wetting and absorption. As a result, NeverWet coating significantly improves the thermochromic performance with a ~260% increase in the peak perceptual lightness (L*) for both calendered and non‐calendered substrates. PVA‐coated non‐calendered nonwoven shows a slightly lower peak L* (~12% decrease) compared to its uncoated counterparts, however, the synergistic effect of PVA coating and calendering results in an increase of ~160% in the peak L* value due to suppression of absorption. The color intensities of Red, Green, and Blue (RGB) follow similar trends. The findings highlight the importance of controlling CLC–substrate interactions and demonstrate its potential for wearable temperature sensing applications.

Covalent organic frameworks (COFs) have emerged as promising sulfur hosts for lithium-sulfur batteries; however, most studies rely on conventional two-dimensional cast cathodes, which restrict practical sulfur loading levels and areal capacity. Here, we report a 3D direct ink writing (DIW) strategy for fabricating metal-free, redox-active COF-based cathodes that enable electrodes with practical sulfur loadings essential for achieving high areal capacity. This study addresses the long-standing processing challenges associated with COF-based DIW to fabricate sulfur cathodes by carefully optimizing the ink rheology, printing parameters, and postprocessing conditions. A porous anthraquinone COF (DAAQ-TFP), synthesized via a scalable terracotta method, was used as the sulfur host and further formulated as a printable ink with shear-thinning behavior suitable for DIW. The free-standing 3D-printed cathodes delivered high sulfur loadings (up to 10 mg cm–2) and areal capacities (up to 11.1 mAh cm–2) at 0.05 C. Furthermore, battery cycling studies of a 5.1 mg cm–2 sulfur-loaded cathode-based coin cell demonstrated good cycling stability over 300 cycles with >95% Coulombic efficiency. These results support advancement in battery technology by offering promising solutions to improve active-site accessibility and enhance performance and reliability in metal-sulfur batteries under higher loading conditions.

Liquid crystals have gained significant attention worldwide for use in digital displays, sensing, smart textures, etc. Thermochromic liquid crystals, which respond to temperature, find applications in medical diagnostics and industrial monitoring through temperature sensing and mapping. Here, we deposited a thermochromic cholesteric liquid crystal (CLC) ink on surface-modified polyethylene terephthalate (PET) substrates using doctor blade coating and direct ink writing (DIW) methods, enabling its use for monitoring temperature changes in various applications. We investigated the thermochromic responses of the CLC ink films doctor blade-coated at different temperatures and analyzed how the processing temperature influences the surface characteristics, alignment of the liquid crystals, and their thermochromic behavior. Based on these observations, we identified the optimal printing temperature for the DIW process. We elucidated the interaction of CLCs with surface treatment, such as hydrophobic and hydrophilic coatings, and how they affect the spreading behavior and thermochromic response of CLCs printed on the coated PET substrates. The results demonstrate that the hydrophobic coating intensifies the temperature response of the CLC by drastically reducing ink spreading. This result is supported by the wetting studies of the CLC ink on various substrates and the wetting envelopes, which are developed to predict the contact angles of the ink on these surfaces. Direct ink writing of liquid crystals at elevated temperatures together with the surface treatment of substrates provides a facile way to pattern the liquid crystals with desirable alignment and robust thermochromic performance for temperature sensing applications.

The practical deployment of lithium–sulfur batteries (LSBs) is hindered by fundamental limitations in conventional slurry-cast cathodes, including poor sulfur utilization, sluggish ion transport, and low areal capacity, particularly in thick electrodes required for high energy density. To address these challenges, we present direct ink writing (DIW) as an additive manufacturing strategy to fabricate advanced current-collector-free, 3D-printed sulfur cathodes (3DP S@CoNi-DSACs/NC) with hierarchically porous architectures that enhance lithium-ion diffusion, promote electrolyte penetration, and reduce interfacial resistance. The synergistic effects of Co/Ni dual-atom sites accelerate redox kinetics and mitigate polysulfide shuttling. As a result, the optimized 3DP cathode with a sulfur loading of 5.4 mg cm⁻² demonstrated excellent rate capability, delivering a high reversible capacity of 1041.4 mAh g⁻¹ at 1C with 85.5% capacity retention after 1000 cycles, significantly outperforming its cast counterpart. Remarkably, even at a higher sulfur loading of 8.1 mg cm⁻², the 3DP cathode maintains outstanding performance, achieving a discharge capacity of 1538.4 mAh g⁻¹ and an areal capacity of 12.5 mAh cm⁻² at 0.1C. This study not only demonstrates the functional integration of catalytically active materials into 3D printable sulfur cathode architectures but also offers a scalable and transformative platform for building high-performance LSBs beyond conventional electrode manufacturing methods.

Reactive inkjet (RIJ) printing represents an important approach for printed electronics. Different from the traditional inkjet printing of colloidal inks with nanosized metal particles, RIJ prints the solution of metal organic compound, that is, metal‐organic decomposition (MOD) ink, and reduces it to the pure metal during the post‐treatment to form conductive electrodes. Successful RIJ printing of MOD inks has been demonstrated; however, the fundamental understanding of droplet deposition involved in RIJ printing is lacking. Herein, the effect of substrate temperature and nozzle temperature during inkjet printing of copper MOD ink on the deposition morphology is investigated. It exhibits distinct behaviors in the deposition morphology at elevated temperatures when compared with the ones at room temperature. The different deposition morphology of the copper ink at various temperatures is attributed to the generation of a localized seeding layer which attracts the copper ions to deposit. In addition, the copper MOD ink printing is compared with a silver MOD ink. The different deposition morphology between the copper ink and silver ink is due to the solvent system. Understanding the deposition mechanism for reactive inks provides valuable information and guidance in the fabrication of printed functional devices using particle‐free reactive inks.

A significant barrier to the commercialization of magnetic heat pumping is the lack of scalable, low-cost manufacturing techniques that enable shaping brittle magnetocaloric materials into heat exchange structures with porous geometries, controlled chemical gradients, and advantageous anisotropic microstructures. Though direct ink writing additive manufacturing has the potential to expand into a viable net-shaping technology for functional magnetic alloys, it is typically challenging to fabricate dense parts—an observation ascribed to the constraint on powder particle size that inevitably impacts both green density of 3D printed parts and shrinkage during sintering. To this end, we report a comprehensive study on the influence of precursor powder characteristics on the magnetic and structural properties of 3D printed test coupons produced using La_0.67Ca_0.33MnO₃ magnetocaloric particles. Ink formulations comprising powders with nano-scaled, micron-scaled, and bimodal size distributions were printed and sintered. The impact of particle size on part quality and magnetofunctional response was examined, and it was found that test coupon fabricated using nano-scaled powders (∼100–200 nm) demonstrated the lowest part porosity (∼17%) and the highest magnetocaloric response (8 J kg⁻¹·K⁻¹ at μ ₀H = 5T). The results presented in this work address critical technical questions about the process feasibility of making magnetic heat pumps with additive manufacturing schemes.

Materials that generate structural color may be promising alternatives to dyes and pigments due to their relative long-term stability and environmentally benign properties. Liquid crystal (LC) mixtures of cholesteryl esters demonstrate structural color due to light reflected from the helical structure of the self-assembled molecules. The apparent color depends on the pitch length of the liquid crystal. While a wide range of colors have been achieved with such LC formulations, the nature of the pitch–concentration relationship has been difficult to define. In this work, various machine learning approaches to predict the reflected wavelength, i.e., the position of the selective reflection band, based on LC composition are compared to a Scheffe cubic model. The neural network regression model had a higher root mean squared error (RMSE) than the Scheffe cubic model with improved predictions for formulations not included in the dataset. Decision tree regression provided the best overall performance with the lowest RMSE and predicted position of the selective reflection band within 0.8% of the measured values for LC formulations not included in the dataset. The predicted values using the decision tree were over two-fold more accurate than the Scheffe cubic model. These results demonstrate the utility of machine learning models for predicting physical properties of LC formulations.

Excellent electrical performance of assemblies of 1D silver nanowires (AgNWs) has been demonstrated in the past years. Up to now, however, there are limited approaches to realize simultaneously deterministic assembly with dense arrangement of AgNWs and desired functional layouts. Herein, an assembly strategy from compressed air‐modulated alignment of AgNWs to heterogeneous integration of stretchable sensing devices through printing transfer is proposed. In this process, a convective flow induced by compressed air brings the AgNWs to the air–droplet interface, where the AgNWs are assembled with excellent alignment and packing due to the surface flow, van der Waals, and capillary interactions. Compared with those random AgNWs networks, the oriented, densely packed AgNWs exhibit a lower and uniform electrical sheet resistance. To incorporate the AgNWs to an elastomer substrate, direct ink writing is employed to transfer the assembled AgNW network to the printed silicone elastomer with desirable patterns. Excellent electrical property is demonstrated including a wide electrical response range from 10% to 120% strain, and high electrical repeatability. An antibacterial property is confirmed, notifying additional benefit as wearable sensors. The printing transfer of preassembled AgNW networks to the printed elastomer patterns provides a facile strategy to construct stretchable electronic devices.