Lithiating magneto-ionics in a rechargeable battery.

Magneto-ionics, real-time ionic control of magnetism in solid-state materials, promise ultralow-power memory, computing, and ultralow-field sensor technologies. The real-time ion intercalation is also the key state-of-charge feature in rechargeable batteries. Here, we report that the reversible lithiation/delithiation in molecular magneto-ionic material, the cathode in a rechargeable lithium-ion battery, accurately monitors its real-time state of charge through a dynamic tunability of magnetic ordering. The electrochemical and magnetic studies confirm that the structural vacancy and hydrogen-bonding networks enable reversible lithiation and delithiation in the magnetic cathode. Coupling with microwave-excited spin wave at a low frequency (0.35 GHz) and a magnetic field of 100 Oe, we reveal a fast and reliable built-in magneto-ionic sensor monitoring state of charge in rechargeable batteries. The findings shown herein promise an integration of molecular magneto-ionic cathode and rechargeable batteries for real-time monitoring of state of charge.

A 3D-printed molecular ferroelectric metamaterial.

Molecular ferroelectrics combine electromechanical coupling and electric polarizabilities, offering immense promise in stimuli-dependent metamaterials. Despite such promise, current physical realizations of mechanical metamaterials remain hindered by the lack of rapid-prototyping ferroelectric metamaterial structures. Here, we present a continuous rapid printing strategy for the volumetric deposition of water-soluble molecular ferroelectric metamaterials with precise spatial control in virtually any three-dimensional (3D) geometry by means of an electric-field-assisted additive manufacturing. We demonstrate a scaffold-supported ferroelectric crystalline lattice that enables self-healing and a reprogrammable stiffness for dynamic tuning of mechanical metamaterials with a long lifetime and sustainability. A molecular ferroelectric architecture with resonant inclusions then exhibits adaptive mitigation of incident vibroacoustic dynamic loads via an electrically tunable subwavelength-frequency band gap. The findings shown here pave the way for the versatile additive manufacturing of molecular ferroelectric metamaterials.

Ultrahigh Temperature Copper-Ceramic Flexible Hybrid Electronics.

Advanced high-temperature materials, metals and ceramics, have been widely sought after for printed flexible electronics under extreme conditions. However, the thermal stability and electronic performance of these materials generally diminish under extreme environments. Additionally, printable electronics typically utilize nanoscale materials, which further exacerbate the problems with oxidation and corrosion at those extreme conditions. Here we report superior thermal and electronic stability of printed copper-flexible ceramic electronics by means of integral hybridization and passivation strategies. High electric conductivity (5.6 MS/m) and thermal stability above 400 °C are achieved in the printed graphene-passivated copper platelet features, while thermal management and stability above 1000 °C of printed electronics can be achieved by using either ultrathin alumina or flexible alumina aerogel sheets. The findings shown here provide a pathway toward printed, extreme electronic applications for harsh service conditions.

Printed copper-nanoplate conductor for electro-magnetic interference.

As one of the conductive ink materials with high electric conductivity, elemental copper (Cu) based nanocrystals promise for printable electronics. Here, single crystalline Cu nanoplates were synthesized using a facile hydrothermal method. Size engineering of Cu nanoplates can be rationalized by using the LaMer model and the versatile Cu conductive ink materials are suitable for different printing technologies. The printed Cu traces show high electric conductivity of 6 MS m-1, exhibiting electro-magnetic interference shielding efficiency value of 75 dB at an average thicknesses of 11µm. Together with flexible alumina ceramic aerogel substrates, it kept 87% conductivity at the environmental temperature of 400 °C, demonstrating the potential of Cu conductive ink for high-temperature printable electronics applications.

Printing conformal and flexible copper networks for multimodal pressure and flow sensing.

Flexible multimodal sensors with ultrasensitive detection capabilities are an indispensable component of wearable electronics and are highly sought-after involving a wide range of signal monitoring such as artificial skin and soft robotics. Here we report a flexible and wireless multimodal sensor using low-temperature additive manufacturing of copper nanoplates on elastic polyurethane substrates for temperature, pressure, and flow monitoring. The positive temperature coefficient and piezoresistive performance of the copper nanoplate network translates to a reliable temperature, steady-state and dynamic pressure/flow sensing for detecting pressures as small as 0.64 Pa with a response time of 130 ms, as well as velocity detection ranging from 2.5-6.8 m s-1. Additionally, by incorporating a printed antenna, it enables a self-powered, battery-free system, offering a wireless readout of printed multimodal sensors with superior real-time sensing performance in conjunction with wearable flexibility.

Molecular copper decomposition ink for printable electronics.

Nanostructured metal materials are the frontrunners of numerous electronic advancements. While realizing such potential, it is indispensable to address their oxidation and stability drawbacks, which are due to their high surface energies. Here, we report printable and air-stable molecular metal ink materials from metal-organic decomposition by using copper ions, including both copper formate and aqueous copper-amine complexes. By complexing copper formate with amines, the decomposition temperature of the printed molecular copper ink can be achieved at 100 °C, while maintaining its electric conductivity. The printed copper conductors exhibit a high electric conductivity of 35 MS m-1 (>50% of bulk copper's electric conductivity at room temperature) and an electromagnetic interference shielding effectiveness of 63 dB. The findings shown here of the molecular decomposition ink are promising for applications in printable electronics.

Surface-passivated Cu conductors for high-temperature sulfurous environments.

Advanced materials capable of withstanding extreme environments garner extensive interest in the development of next-generation advanced anti-corrosion electronics. Herein, we report that the surface passivation of printed copper conductors imparts corrosion resistance in high-temperature sulfurous environments while maintaining a high electrical conductivity of 4.42 MS m-1 when subjected to a sulfur-containing environment at 350 °C for 12 h. This study provides potential for the development of surface-passivated copper conductors that are resistant to the sulfidizing environments found in several applications of modern technology.

Recent Advancement of Emerging Nano Copper-Based Printable Flexible Hybrid Electronics.

Printed copper materials have been attracting significant attention prominently due to their electric, mechanical, and thermal properties. The emerging copper-based flexible electronics and energy-critical applications rely on the control of electric conductivity, current-carrying capacity, and reliability of copper nanostructures and their printable ink materials. In this review, we describe the growth of copper nanostructures as the building blocks for printable ink materials on which a variety of conductive features can be additively manufactured to achieve high electric conductivity and stability. Accordingly, the copper-based flexible hybrid electronics and energy-critical devices printed by different printing techniques are reviewed for emerging applications.

Solution-shearing of dielectric polymer with high thermal conductivity and electric insulation.

Polymer dielectrics, an insulating material ubiquitous in electrical power systems, must be ultralight, mechanically and dielectrically strong, and very thermally conductive. However, electric and thermal transport parameters are intercorrelated in a way that works against the occurrence of thermally conductive polymer electric insulators. Here, we describe how solution gel-shearing­strained polyethylene yields an electric insulating material with an outstanding in-plane thermal conductivity of 10.74 W m−1 K−1 and an average dielectric constant of 4.1. The dielectric constant and loss of such sheared polymer electric insulators are nearly independent of the frequency and a wide temperature range. The gel-shearing aligns ultrahigh­molecular weight polymer crystalline chains for the formation of separated and aligned nanoscale fibrous arrays. Together with lattice strains and the presence of boron nitride nanosheets, the dielectric polymer shows high current density carrying and high operating temperature, which is attributed to greatly enhanced heat conduction.

Ductile cooling phase change material.

Cooling represents a considerable fraction of energy consumption. However, it is indispensable to develop eco-friendly, biocompatible, and ductile cooling materials for personal applications. In this study, we demonstrate the ductile cooling ability with phase change of thermally passivated hydrogel composite materials with additive manufacturing ability. Thermal evaluation of such water-based composites indicates a superior cold retention capacity with a cooling comfort over 6 hours, while the composite displays a full recovery when strained up to 80% in uniaxial compression tests as a result of the intertwining between covalent and ionic bonds. A three-layered rectangular model was utilized to simulate the problem in a steady-state thermal analysis to study the cooling effect. Our findings indicate the potential of hydrogel as a cooling phase-change medium and its contribution towards ductile cooling applications.

Flexible and printable dielectric polymer composite with tunable permittivity and thermal stability.

Lightweight and printable polymer dielectrics are ubiquitous in flexible hybrid electronics, exhibiting high breakdown strength and mechanical reliability. However, their advanced electronic applications are limited due to their relatively low permittivity, compared to their ceramic counterparts. Here, we report flexible all organic percolative nanocomposites that contain in situ grown conductive polymer networks and dielectric polymer matrix, in which their dielectric properties can be designed and guided from the percolation theory. High dielectric constant of all organic percolative nanocomposites is shown over a broad frequency range under intensive bending cycles, while their thermal stability is attributed to thermally conductive 2D montmorillonite nanosheets. The printable polymer composites with high dielectric performance and thermal stability will find broader interest in flexible hybrid electronics and radio frequency devices.