Dead Lithium Growth
In article number 2301902, Michel Armand, Andrea Paolella, and co-workers plan-view monitor the nucleation and growth of dendritic and dead Li using a novel anode-free coin cell set-up equipped with a transparent optical window. Operando optical microscopy and computer vision calculations are synergistically combined to observe the evolution of Li metal from a mossy morphology to needle aggregates at low currents, whereas hollow structures are detected at high currents.
Nanothermometry explores the use of temperature-dependent properties of materials for remote and sensitive thermal readout at the nanoscale. The currently established nanothermometers are largely limited by uncontrollable nanoparticle flocculation, complex experimental setup, and narrow working temperature range. Here it is shown that gold nanoparticles (e.g., spheres, rods) embedded in a hydrogel can afford sensitive, durable, and range-tunable temperature sensing via the terminal breathing of the nanoparticle surface-grafted DNA. The realization of the plasmonic hydrogel thermometer with a thermal sensitivity of ≤2 °C relies on the dynamically modulable interparticle spacing by thermo-responsive terminal base pairing/unpairing of the surface DNA. By altering the alcoholic ratio of the hydrogel, the temperature-response range can be continuously regulated based on solvent-mediated DNA base pairing. Compared with the colloidal counterpart, importantly, the hydrogel thermometer exhibits greatly improved thermal sensing capability (e.g., repeatability ≥50 times) while possessing excellent durability. Given the excellent durability, high sensitivity, and programmable temperature response range, the thermometers actuated by DNA breathing for advanced uses in human sensing and optoelectronics are within reach.
Infrared (IR) neuromodulation holds an increasing potential in brain research, which is fueled by novel neuroengineering approaches facilitating the exploration of the biophysical mechanism in the microscale. The group lays down the fundamentals of spatially controlled optical manipulation of inherently temperature-sensitive neuronal populations. The concept and in vivo validation of a multifunctional, optical stimulation microdevice is presented, which expands the capabilities of conventional optrodes by coupling IR light through a monolithically integrated parabolic micromirror. Heat distribution in the irradiated volume is experimentally analyzed, and the performance of the integrated electrophysiological recording components of the device is tested in the neocortex of anesthetized rodents. Evoked single-cell responses upon IR irradiation through the novel microtool are evaluated in multiple trials. The safe operation of the implanted device is also presented using immunohistological methods. The results confirm that shift in temperature distribution in the vicinity of the optrode tip can be controlled by the integrated photonic components, and in parallel with the optical stimulation, the device is suitable to interrogate the evoked electrophysiological activity at the single neuron level. The customizable and scalable optrode system provides a new pathway to tailor the location of the heat maximum during infrared neural stimulation.
Regenerative therapies, including the transplantation of spinal cord progenitor cells (SCPCs) derived from induced pluripotent stem cells (iPSCs), are promising treatment strategies for spinal cord injuries. However, the risk of tumorigenicity from residual iPSCs advocates an unmet need for rapid SCPCs safety profiling. Herein, a rapid (≈3000 cells min-1) electrical-based microfluidic biophysical cytometer is reported to detect low-abundance iPSCs from SCPCs at single-cell resolution. Based on multifrequency impedance measurements (0.3 to 12 MHz), biophysical features including cell size, deformability, membrane, and nucleus dielectric properties are simultaneously quantified as a cell is hydrodynamically stretched at a cross junction under continuous flow. A supervised uniform manifold approximation and projection (UMAP) model is further developed for impedance-based quantification of undifferentiated iPSCs with high sensitivity (≈1% spiked iPSCs) and shows good correlations with SCPCs differentiation outcomes using two iPSC lines. Cell membrane opacity (day 1) is also identified as a novel early intrinsic predictive biomarker that exhibits a strong correlation with SCPC differentiation efficiency (day 10). Overall, it is envisioned that this label-free and optic-free platform technology can be further developed as a versatile cost-effective process analytical tool to monitor or assess stem cell quality and safety in regenerative medicine.
Direct-current triboelectric nanogenerators (DC-TENGs) arising from electrostatic breakdown have garnered significant attention due to their advantages of rectification-free operation, constant current output, and high output power density. Previous studies have primarily concentrated on improving its performance through structural design and parameter optimization, neglecting the potential benefits of external charge excitation. Here, a facile and universal strategy coupling charge pump and electric field enhancing effect with DC-TENG (CE-DC-TENG) is proposed to improve the output performance of DC-TENG. An alternating current TENG is used as the charge pump. A field-enhancing conductive layer, which is introduced under the main DC-TENG, is connected with the pump TENG to accumulate the charge and enhance the electric field for electrostatic breakdown. The effectiveness of this method is demonstrated by linear and rotary sliding mode TENGs. Furthermore, a fully integrated rotary sliding mode CE-DC-TENG is designed and fabricated, and it exhibits impressive performance with a 13-fold higher power density of 1.56 W m−2 compared to conventional DC-TENG. Moreover, it can directly power small electronics or be combined with a designed power management circuit for more efficient energy conversion. This work presents a new design strategy for improving the performance of DC-TENG and facilitating its practical applications.
Hydrogen sensors are important in a hydrogen-driven society to prevent explosions caused by hydrogen leaks into the atmosphere. In previous studies, resistive hydrogen sensors on polymer films have metal oxide nanostructures decorated with novel metals that enable good responses at room temperature. However, the in situ growth process of sensing nanostructures has the disadvantage of ineffective fabrication, particularly when preparing a thick catalyst layer to produce reliable readouts from the catalytic hydrogen combustion. This work presents a catalytic combustion hydrogen sensor with a thick catalyst layer anchored in a UV resin layer on polyimide film. Catalyst anchoring channels are made by UV imprinting with a glass mold. The sensor consists of a sensing electrode and a microheater, both made of Au within an area of 1.2 mm diameter. UV imprinting produces a UV resin layer of 27 µm thick and catalyst anchoring channels of 14 µm deep and 20–30 µm wide, which are filled with Pt/TiO2 as a catalyst. The sensing response is 7.9% for 1% H2 under ambient conditions, and the detection range is 0.1–3% H2. The UV-resin microstructures can effectively retain a thick catalyst layer to enhance sensitivity, and their low thermal conductivity reduces heat loss.
Development of artificial opto-electronic synaptic devices plays a crucial role for the practical implementation of energy-efficient, parallel processing of human brain. In this article, two terminal inter-digitated devices are fabricated on Gallium oxide (Ga2O3) thin films grown on sapphire substrates by pulsed laser deposition (PLD) technique to study its ability to mimic biological synaptic behaviors. The layers are found to exhibit long persistent photo-conductivity (PPC) effect, which is identified to be the key parameter to replicate the behavior of biological synapses. Channel resistance and PPC time constants should also be optimized to improve the efficiency of response and energy consumption of synaptic devices. It has been observed that both conductivity and the PPC decay time of Ga2O3-films can be controlled by varying oxygen pressure and growth temperature (TG). These devices demonstrate their ability to perform paired pulse facilitation (PPF) at very low applied bias in mV-range. They can mimic biological synapses showing short-to-long-term memory transition (STM-to-LTM) and learning-forgetting behavior. One of these devices is found to show synaptic behavior with the energy consumption of as low as 71fJ electrical and 21nJ optical per synaptic event. These findings thus strengthen the candidature of Ga2O3 films for the development of next-generation opto-electronic neuromorphic devices and systems.
The array of tactile information processing capabilities is an important index for modern intelligent devices advancing toward a humanoid form, and it greatly improves the recognition of different objects in human-computer interactions. Herein, a deep-learning-assisted intelligent grasping recognition system based on a piezoresistive sensing glove, hardware conditioning, and acquisition circuits, and a multibranch deep-capsule network is reported. Owing to the multiscale 3D structure of carbon nanotube (CNTs)/carbon fiber (CFs) embedded in polydimethylsiloxane (PDMS), the piezoresistive sensing glove is highly sensitive to the pressure exerted by external objects. The acquired signals are reflected on a hand-like background map, and a combination of multiple subgraphs is used to build the dataset. A multibranch deep-capsule network is constructed to encode spatial information while realizing object recognition with an accuracy of 99.4%. Therefore, the proposed intelligent grasping recognition system possesses good human-robot interaction capabilities, providing a new approach for the development of intelligent robots in the field of perceptual recognition applications.
Radiative cooling has been recently intensively explored for thermal management and enhancing energy efficiency. Yet, traditional materials with singular emissivity fall short in dynamic thermal management, highlighting the need for materials that can adjust their thermal radiation in real time. Active modulation methods, requiring external stimuli such as mechanical stretch, electric potential, or humidity change, offer adaptability but can increase energy use and complexity. Passive approaches, using materials' inherent thermal-responsive properties, face manufacturing and scalability challenges. Here, a scalable yet effective passive approach is introduced for adaptive thermal modulation based on gold (Au) and liquid crystal elastomer (LCE) with a reversible response to environmental temperature changes. This modulator enables a “low thermal resistance” state through actuation-induced microcracks that expose a high-emissivity polymer substrate, and a “high thermal resistance” state by closing these microcracks and forming a high thermal resistance air gap between the modulator and the target object. The flexible design and fixed external dimensions of the Au-LCE thermal modulator make it adaptable to various surface geometries. Furthermore, by adjusting the LCE's chemical composition, the modulator's transition temperature can be tailored, broadening its applications from enhancing building energy efficiency to improving clothing thermal comfort.
To date, new prototype device for directly converting chemical energy into electricity is still the most important pursuit although various types of fuel cells have been developed/commercialized. In this work, a novel () orientated ZnO single crystal device is reported that generates electricity using the usual redox reactions. The principle of the device is similar to that of a photovoltaic device, known as a chem-voltaic device. The air-KBH4 chem-voltaic device has an open-circuit voltage (Voc) of 2.14 ± 0.007 mV and a short-circuit current (Isc) of 1.44 ± 0.007 µA. The Voc and Isc increase to 2.24 mV and 2.81 µA, respectively, by preadding H2O2. A similar phenomenon is also observed when glucose is used to substitute KBH4. When KBH4 or glucose solution is added to the ZnO () surface, it reacts with chemisorbed oxygen to produce free electrons. Due to the presence of the spontaneous electric field (Es) in the polar [0001] azimuth of ZnO, these free electrons move along the [0001] direction, producing an electric current. So chemical energy is converted into electricity. This finding opens up research on the chem-voltaic cell.
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