Ga2O3 has emerged as a promising material for the wide-bandgap industry aiming at devices beyond the limits of conventional silicon. Amorphous Ga2O3 is widely being used for flexible electronics, but suffers from very high resistivity. Conventional methods of doping like ion implantation require high temperatures post-processing, thereby limiting their use. Herein, an unconventional method of doping Ga2O3 films with Si, thereby enhancing its electrical properties, is reported. Ion-beam sputtering (500 eV Ar+) is utilized to nanopattern SiO2-coated Si substrate leaving the topmost part rich in elemental Si. This helps in enhancing the carrier conduction by increasing n-type doping of the subsequently coated 5 nm amorphous Ga2O3 films, corroborated by room-temperature resistivity measurement and valence band spectra, respectively, while the nanopatterns formed help in better light management. Finally, as proof of concept, metal-semiconductor-metal (MSM) photoconductor devices fabricated on doped, rippled films show superior properties with responsivity increasing from 6 to 433 mA W-1 while having fast detection speeds of 861 µs/710 µs (rise/fall time) as opposed to non-rippled devices (377 ms/392 ms). The results demonstrate a facile, cost-effective, and large-area method to dope amorphous Ga2O3 films in a bottom-up approach which may be employed for increasing the electrical conductivity of other amorphous oxide semiconductors as well.

Microparticles have been applied in many areas, ranging from drug delivery, diagnostics, cosmetics, personal care, and the food industry to chemical and catalytic reactions, sensing, and environmental remediation. Coating further provides additional functionality to the microparticles, such as controlled release, surface modification, bio-fouling resistance, stability, protection, etc. In this study, the conformal coating of microparticles with a positively charged polyelectrolyte (polyallylamine hydrochloride, PAH) by utilizing an acoustofluidic microchip was proposed and demonstrated. The multiple laminar streams, including the PAH solution, were formed inside the microchannel, and, under the traveling surface acoustic wave, the microparticles traversed through the streams, where they were coated with PAH. The results showed that the coating of microparticles can be achieved in a rapid fashion via a microfluidic approach compared to that obtained by the batch method. Moreover, the zeta potentials of the microparticles coated via the microfluidic approach were more uniform. For the unfunctionalized microparticles, the charge reversal occurred after coating, and the zeta potential increased as the width of the microchannel or the concentration of the PAH solution increased. As for the carboxylate-conjugated microparticles, the charge reversal again occurred after coating; however, the magnitudes of the zeta potentials were similar when using the microchannels with different widths or different concentrations of PAH solution.

Beta cell replacement therapies can restore glycemic control to select individuals living with type 1 diabetes. However, the obligation of lifelong immunosuppression restricts cell therapies from replacing exogenous insulin administration. Encapsulation strategies can reduce the inherent adaptive immune response; however, few are successfully translated into clinical testing. Herein, we evaluated if the conformal coating of islets with poly(N-vinylpyrrolidone) (PVPON) and tannic acid (TA) (PVPON/TA) could preserve murine and human islet function while conferring islet allograft protection. In vitro function was evaluated using static glucose-stimulated insulin secretion, oxygen consumption rates, and islet membrane integrity. In vivo function was evaluated by transplanting human islets into diabetic immunodeficient B6.129S7-Rag1tm1Mom/J (Rag-/-) mice. The immunoprotective capacity of the PVPON/TA-coating was assessed by transplanting BALB/c islets into diabetic C57BL/6 mice. Graft function was evaluated by non-fasting blood glucose measurements and glucose tolerance testing. Both coated and non-coated murine and human islets exhibited indistinguishable in vitro potency. PVPON/TA-coated and control human islets were able to restore euglycemia post-transplant. The PVPON/TA-coating as monotherapy and adjuvant to systemic immunosuppression reduced intragraft inflammation and delayed murine allograft rejection. This study demonstrates that PVPON/TA-coated islets may be clinically relevant as they retain their in vitro and in vivo function while modulating post-transplant immune responses.

A novel methodology, based on wetting and electromigration, for transporting liquid metal, over long distances, at micro-and nano-scale using a stylus is reported. The mechanism is analogous to a dropper that uses \'suction and release\' actions to \'collect and dispense\' liquid. In our methodology, a stylus coated with a thin metal film acts like the dropper that collects liquid metal from a reservoir upon application of an electric current, holds the liquid metal via wetting while carrying the liquid metal over large distances away from the reservoir and drops it on the target location by reversing the direction of electric current. Essentially, the working principle of the technique relies on the directionality of electromigration force and adhesive force due to wetting. The working of the technique is demonstrated by using an Au-coated Si micropillar as the stylus, liquid Ga as the liquid metal to be transported, and a Kleindiek-based position micro-manipulator to traverse the stylus from the liquid reservoir to the target location. For demonstrating the potential applications, the technique is utilized for closing a micro-gap by dispensing a minuscule amount of liquid Ga and conformally coating the desired segment of the patterned thin films with liquid Ga. This study confirms the promising potential of the developed technique for reversible, controlled manipulation of liquid metal at small length scales.

Silicon (Si) photovoltaic devices present possible avenues for overcoming global energy and environmental challenges. The high reflection and surface recombination losses caused by the Si interface and its nanofabrication process are the main hurdles for pursuing a high energy conversion efficiency. However, recent advances have demonstrated great success in improving device performance via proper Si interface modification with the optical and electrical features of two-dimensional (2D) materials. Firmly integrating large-area 2D materials with 3D Si nanostructures with no gap in between, which is essential for optimizing device performance, has rarely been achieved by any technique due to the complex 3D morphology of the nanostructures. Here we propose the concept of a 3D conformal coating of graphene metamaterials, in which the 2D graphene layers perfectly adapt to the 3D Si curvatures, leading to a universal 20% optical reflection decrease and a 60% surface passivation improvement. In a further application of this metamaterial 3D conformal coating methodology to standard Si solar cells, an overall 23% enhancement of the solar energy conversion efficiency is achieved. The 3D conformal coating strategy could be readily extended to various optoelectronic and semiconductor device systems with peculiar performance, offering a pathway for highly efficient energy-harvesting and storage solutions.

The three-dimensional (3D) structure of batteries nowadays obtains a lot of attention because it provides the electrodes a vast surface area to accommodate and employ more active material, resulting in a notable increase in areal capacity. However, the integration of polymer electrolytes to complicated three-dimensional structures without defects is appealing. This paper presents the creation of a flawless conformal coating for a distinctive 3D-structured NiO/Ni anode using a simple thermal oxidation technique and a polymer electrolyte consisting of three layers of PAN-(PAN-PVA)-PVA with the addition of Al2O3 nanoparticles as nanofillers. Such a composition with a unique combination of polymers demonstrated superior electrode performance. PAN in the polymer matrix provides mechanical stability and corrosion resistance, while PVA contributes to excellent ionic conductivity. As a result, NiO/Ni@PAN-(PAN-PVA)-PVA with 0.5 wt% Al2O3 NPs configuration demonstrated enhanced cycling stability and superior electrochemical performance, reaching 546 mAh g-1 at a 0.1 C rate.

Soft, conformal and wearable epidermal fuel cells may offer promising energy solutions to power next-generation on-skin electronics on-demand anytime anywhere. However, it is non-trivial to design intrinsically stretchable electrode in order to maintain the fuel cell performance under real-world and dynamic mechanical deformations. Here, we present a tattoo-like epidermal fuel cell based on Pd conformally-coated, one-end-embedded percolation gold nanowire (EP-AuNW/EP-AuPdNW) networks, which are in essence the combination of in-plane percolation conductivity and out-plane anisotropic conductivity. Both EP-AuNW and EP-AuPdNW are intrinsically stretchable conductors for anode and cathode in fuel cell. Compared to non-conformal counterparts, a 6-times greater power density was achieved for conformal system. Importantly, EP-NW based fuel cell can function under various mechanical deformations including stretching, compression, bending, and twisting; the power density showed negligible changes to the tensile strain up to ∼50% and could maintain its 75% performance even under 80% strain. Furthermore, a dragon-tattoo epidermal fuel cell was fabricated, demonstrating on-demand power generation with real-world ethanol sources.

Contractility is one of the most crucial functions of the heart because it is directly related to the maintenance of blood perfusion throughout the body. Both increase and decrease in contractility may cause fatal consequences. Therefore, drug discovery would benefit greatly from reliable testing of candidate molecule effects on contractility capacity. In this study, we further developed a dual-axis piezoelectric force sensor together with our human cell-based vascularized cardiac tissue constructs for cardiac contraction force measurements. The capability to detect drug-induced inotropic effects was tested with a set of known positive and negative inotropic compounds of isoprenaline, milrinone, omecamtiv mecarbil, propranolol, or verapamil in different concentrations. Both positive and negative inotropic effects were measurable, showing that our cardiac contraction force measurement system including a piezoelectric cantilever sensor and a human cell-based cardiac tissue constructs has the potential to be used for testing of inotropic drug effects.

Transition metal oxides are considered promising anode materials for next-generation lithium-ion and sodium-ion batteries (LIBs and SIBs) because of their high theoretical capacities; however, their practical application is limited by the detrimental large volume expansion that occurs upon cycling. In this work, a rationally designed TiO2 @Fe@FeOx nanocomposite encapsulated by a TiO2 shell with unique core-shell structure is synthesized and exhibits outstanding electrochemical performance as an anode in LIBs and SIBs. The nanocomposite exhibits a reversible capacity of 619.2 mAh g-1 at 1 A g-1 with a coulombic efficiency over 99.5% after 1000 cycles when used as a LIB anode. The nanocomposite also exhibits superior sodium storage performance (267 mAh g-1 at 50 mA g-1 , capacity retention of 65.4% after 1000 cycles at 200 mA g-1 ). The TiO2 shell serves as a strong conformal layer and soft matrix that can tolerate the volume expansion and maintain the structural integrity of the anode during discharging and charging. Moreover, the open active diffusion channels of the shell contribute to high ion diffusivity and improved ionic, and electronic diffusion. These findings indicate that adoption of TiO2 coating is an effective strategy to optimize the electrochemical performance of transition metal oxide anode materials.

Silver nanowire (AgNW) networks have been intensively investigated in recent years. Thanks to their attractive physical properties in terms of optical transparency and electrical conductivity, as well as their mechanical performance, AgNW networks are promising transparent electrodes (TE) for several devices, such as solar cells, transparent heaters, touch screens or light-emitting devices. However, morphological instabilities, low adhesion to the substrate, surface roughness and ageing issues may limit their broader use and need to be tackled for a successful performance and long working lifetime. The aim of the present work is to highlight efficient strategies to optimize the physical properties of AgNW networks. In order to situate our work in relation to existing literature, we briefly reported recent studies which investigated physical properties of AgNW networks. First, we investigated the optimization of optical transparency and electrical conductivity by comparing two types of AgNWs with different morphologies, including PVP layer and AgNW dimensions. In addition, their response to thermal treatment was deeply investigated. Then, zinc oxide (ZnO) and tin oxide (SnO2) protective films deposited by Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD) were compared for one type of AgNW. We clearly demonstrated that coating AgNW networks with these thin oxide layers is an efficient approach to enhance the morphological stability of AgNWs when subjected to thermal stress. Finally, we discussed the main future challenges linked with AgNW networks optimization processes.