Jing Zhang

An electric-field-assisted PECVD technique is developed to directly synthesize high-purity semiconducting single-walled carbon nanotube (SWNT) arrays. By leveraging the plasma sheath and charged particles in the PECVD system, this method induces negative charge accumulation on SWNTs, reducing the energy states of semiconducting SWNTs. It achieves a s-SWNT purity of 96%, advancing the development of carbon nanotube-based electronics.

Abstract

Semiconducting single-walled carbon nanotube (SWNT) horizontal arrays hold great promise for the development of next-generation, energy-efficient integrated circuits. While conventional chemical vapor deposition synthesis typically yields structurally diverse carbon nanotubes, achieving high-purity semiconducting SWNT horizontal arrays remains a major challenge. In this study, an electric-field-assisted plasma-enhanced chemical vapor deposition (PECVD) technique is introduced that enables the direct synthesis of high-purity semiconducting SWNT arrays. This method capitalizes on the inherent plasma sheath and the abundance of charged particles within the PECVD system to control charge accumulation on SWNTs. By inducing negative charge accumulation, the energy states of semiconducting nanotubes are effectively reduced, rendering them thermodynamically favored products, thereby enhancing semiconducting-tube purity in the resulting arrays. Additionally, the applied electric field modulates the growth kinetics of the SWNTs, ensuring efficient growth and high-density arrays. Utilizing this approach, semiconducting SWNT arrays are successfully synthesized with a purity of up to 96%. This electric-field-assisted PECVD technique represents a promising strategy for the controlled preparation of SWNTs, paving the way for advancements in carbon nanotube-based electronics.

Mechanochromic hydroxypropyl cellulose (HPC) integrated with microfluidic devices creates scalable, eco-friendly reflective color displays. We demonstrate mechanochromic displays with 500 µm pixel size and 5Hz switching rates with room for optimisation. The proposed mechanochromic HPC displays are an initial step toward more environmentally responsible color display and pixel technologies.

Abstract

Mechanochromic materials have garnered significant interest over the past decade due to their ability to change color in response to mechanical cues. While it is known that hydroxypropyl cellulose (HPC) self-assembles into biodegradable and low-cost mechanochromic materials, with a wide range of applications from edible colorants to optical strain sensors, mechanochromic HPC displays themselves are not reported. Here we address this challenge by combining thin mechanochromic HPC films with microfluidic arrays of inflatable microactuators that exert controlled forces. With these devices, the mechanochromic strain sensitivity, color resolution, response times, and operating frequencies of photonic aqueous HPC films are measured at decreasing length scales for the first time. Various pixel sizes, geometry, and input frequencies are also assessed to investigate mechanochromic HPC as a potential low-cost, biodegradable display. Potential applications range from dynamic color pixels for soft robotics to more environmentally responsible RGB display technology.

The highest experimentally determined focusing efficiency is reported here by using the direct imprinting of all-inorganic TiO₂ metalens arrays. Absolute efficiency greater than 80% and relative efficiency greater than 90% are achieved by optimization of all fabrication parameters controllable in the additive manufacturing process. The highest refractive index of 2.3 is demonstrated by a short post-imprint ALD process.

Abstract

Highly efficient metalens arrays designed for 550 nm are directly printed using UV-assisted nanoimprint lithography (UV-NIL) and a TiO₂ nanoparticle (NP)-based ink on 8″ optical wafers with imprint times less than 5 min. Approximately one-thousand 4-mm metalenses are fabricated per wafer with uniform optical performance using a reusable PDMS-based elastomeric stamp. The absolute and relative focusing efficiencies are as high as 81.2% and 90.4%, respectively, matching closely with the simulated maximum efficiencies of 83% and 91% achievable with the given master design, indicating that future improvements are possible, and efficiencies are not limited by materials or process. The imprinted metalenses are free from organics due to a post-imprint calcination step and exhibit outstanding dimensional and optical stabilities. The highest efficiencies are attained using imprint formulations comprised of mixtures of 10 and 20 nm TiO₂ NPs, whose denser packing not only increases the refractive index (RI) of the calcined lenses up to 2.0 but also reduces the feature shrinkage relative to the master. 25 cycles of atomic layer deposition of TiO₂ following imprinting increase the RI up to 2.3 without changing dimensions by uniform gap filling between NPs. This work opens a path for true, full-scale additive manufacturing of metaoptics.

In situ liquid cell TEM provides real-time, atomic-level insights into catalyst evolution under operational conditions. This review focuses on how LC-TEM uncovers dynamic changes in morphology, phase structure, and active sites during electrochemical CO₂ reduction reaction (CO₂RR), shedding light on reaction mechanisms. It also discusses major challenges and explores exciting opportunities to advance LC-TEM's role in CO2RR research.

Abstract

The electrochemical carbon dioxide reduction reaction (CO₂RR), driven by renewable energy, represents a promising approach for converting CO₂ into valuable fuels and chemicals, addressing pressing energy and environmental challenges. However, the development of high-performance CO₂RR electrocatalysts remains constrained by a limited understanding of their dynamic evolution mechanisms, intrinsic stability factors, and activity origins under operational conditions. Transmission electron microscopy (TEM), with its unparalleled spatial resolution at the nanoscale and atomic level, combined with its microregional analytical capabilities, has become a vital tool for investigating heterogeneous electrocatalysis. Among these techniques, in situ liquid cell TEM (LC-TEM) enables real-time visualization of structural and morphological changes in catalysts during CO₂RR. This review critically examines recent advancements in in situ LC-TEM and its applications in CO₂RR, focusing on three key aspects of electrocatalysts: the dynamic evolution of morphology, transformation of phase structure, and the identification of active sites. It highlights the pivotal role of in situ LC-TEM in elucidating structure–activity relationships and the activation and deactivation mechanisms of electrocatalysts. Moreover, the review discusses the primary challenges facing in situ LC-TEM and outlines future directions for advancing its applications in CO₂ electrolysis research.

This review examines droplet interactions with heated surfaces, outlining boiling modes and Leidenfrost point determinants like surface characteristics, liquid properties, and external conditions. It analyzes droplet dynamics on structured surfaces (linear and rotation motion) and applications in heat transfer, self-cleaning, drag reduction, and energy conversion, concluding with future research directions.

Abstract

The interaction of droplets with high-temperature solid surfaces is critical in processes like machining cooling and internal combustion engine operations. As surface temperature rises, droplets transition through distinct boiling regimes: film evaporation, contact boiling, transition boiling, and film boiling. In the film boiling regime, droplets are suspended on a vapor layer formed by their evaporation, known as the Leidenfrost effect, which occurs above the Leidenfrost point-the minimum temperature for this phenomenon. While the vapors layer impairs heat transfer by acting as an insulator, it also facilitates droplet mobility, enabling applications in fluid motion control and driving research interest in this area. This review provides a comprehensive overview of droplet interactions with heated surfaces. It begins with a classification of boiling regimes and the criteria defining them, followed by an analysis of factors influencing the Leidenfrost point, including surface properties, liquid characteristics, and external conditions. The motion behaviors of droplets on high-temperature structured surfaces such as horizontal transport, vertical detachment, and rotation are then explored. Finally, potential applications for controlling droplet behavior on hot surfaces are discussed, including enhanced heat transfer, self-cleaning, drag reduction, and energy conversion, while highlighting emerging directions for future research.

An amorphous (ErAlCrZrTi)O high-entropy nanofilm is first fabricated and identified as an efficient and robust hydrogen barrier for hydrogen embrittlement prevention. The nanofilm, with thickness of only 270 nm, increases hydrogen resistance by 2738 times at 500 °C compared with that of the steel, achieving one of the highest reported hydrogen barrier efficiencies attributed to the unique amorphous high-entropy structure.

Abstract

Hydrogen embrittlement in metals seriously threatens the safe and durable operation of hydrogen energy. Developing efficient and robust hydrogen barriers is a viable solution to solve this issue but remains a significant challenge. An amorphous (ErAlCrZrTi)O high-entropy nanofilm is successfully fabricated via sol-gel on steel and identified as highly efficient and robust hydrogen barrier. At 270 nm thickness, the nanofilm achieves ultra-low hydrogen permeability of 1.35 × 10⁻¹⁵ mol m⁻¹ s⁻¹ Pa^−0.5, enhancing hydrogen resistance by 2738 times at 500 °C compared with that of bare steel. Compared to Er₂O₃, Al₂O₃, Cr₂O₃, and ZrO₂, it improves hydrogen resistance by 5, 11, 26, and 90 times, respectively. Moreover, such a high hydrogen resistance can be satisfyingly retained even after the (ErAlCrZrTi)O nanofilm suffering 10 dpa irradiation. The nanofilm exhibits 37 MPa bonding strength and exceptional thermal shock resistance, attributed to the formation of Cr₂O₃ transition layer via precipitation and oxidation of Cr from the substrate during annealing. It strengthens adhesion and alleviates thermal expansion mismatch with the substrate. The mechanism for the high barrier efficiency is further revealed by this theoretical calculations. These results provide tremendous insights on the understanding and future design of high-performance hydrogen barriers for hydrogen embrittlement prevention.

A tetrahedral DNA nanostructure (TDN) coating system is developed to precisely functionalize titanium surfaces through hydroxylation, silanization, click chemistry, and base-pairing. Titanium modified with 30 nm TDNs showed stronger cellular responses and enhanced osteointegration effects compared to 7 nm TDNs. These improvements involve the focal adhesion pathway, highlighting the critical role of TDN size in cellular behavior and bone integration.

Abstract

Titanium (Ti) is extensively used in the medical field because of its excellent biomechanical properties; however, how to precisely fabricate Ti surfaces at a nanoscale remains challenging. In this study, a DNA nanocoating system to functionalize Ti surfaces via a series of sequential reactions involving hydroxylation, silanization, and click chemistry is developed. Tetrahedral DNA nanostructures (TDNs) of two different sizes (≈7 and 30 nm) are assembled and characterized for subsequent surface attachment. In vitro and in vivo assays demonstrated significantly enhanced cell adhesion, spreading, proliferation, osteogenesis, and osseointegration on Ti surfaces modified with 30-nm TDNs, compared to slightly improved effects with 7-nm TDNs. Mechanistic studies showed that the focal adhesion pathway contributed to the enhanced bioaffinity of the 30-nm TDNs, as evidenced by the upregulated expression of vinculin and activation of the Akt signaling pathway. Moreover, under inflammatory or hypoxic conditions, Ti surfaces modified with 30-nm TDNs maintained excellent cellular performance comparable to that under normal conditions, suggesting a broader adaptability for DNA nanoparticles. Thus, better performance is achieved following modification with 30-nm TDNs. In summary, the proposed DNA-guided nanocoating system provides a novel and efficient strategy for the surface nanofabrication of Ti.

The high gain-bandwidth product MXene-Si-MXene vdW photodetector is fabricated by using a synergistic photogating effect. The device exhibits an enhanced photogain of up to 7.2 × 10³ and a GBP of up to 1.45 GHz, enabling high-quality NIR single-pixel imaging with 512 × 512 pixels and a high signal-to-noise ratio of 72.3 dB.

Abstract

Emerging near-infrared (NIR) single-pixel imaging (SPI) technology presents a promising alternative to conventional imaging systems, offering cost efficiency and enhanced durability. The high gain bandwidth product (GBP) of the single-pixel photodetector (PD) is the primary requirement for high resolution and high imaging speed in SPI. Here, a novel MXene-Si-MXene van der Waals (vdW) metal-semiconductor-metal (MSM) PD, is demonstrated fabricated via a facile solution process. By incorporating a Ti₃C₂T _x MXene film, the device exhibits a synergistic photogating effect, leading to an exceptional photogain of up to 7.2 × 10³ and a GBP of up to 1.45 GHz under 850 nm illumination at a bias voltage of 2 V, outperforming most currently reported silicon-based detectors and even many commercial avalanche photodiodes (APDs). Significantly, the high-quality 512 × 512-pixel image is successfully achieved at an even 1% sampling rate without any additional filter circuitry by using the PD. The signal-to-noise ratio (SNR) of 72.3 dB is the highest value reported to date for SPIs and prior to some NIR array detectors. Thereafter, a high-quality reconstruction image is also obtained with a SNR of 32.1 dB in visible opaque light. This work paves the way for easy fabrication of high GBP PD for high-quality NIR SPI.

This study develops a self-powered piezoelectric fish tag (SPFT) using a hybrid-mode piezoelectric nanogenerator (HM-PENG) to harvest strain energy and hydrodynamic impacts from fish-tailing. Validated on robotic and live crucian carp, the system enables real-time monitoring of fish locomotion via underwater acoustic communication, demonstrating sustainable aquatic behavioral tracking through self-powered operation.

Abstract

Acoustic fish tags are the primary method for tracking marine animal behavior. However, existing acoustic fish tags are typically rigid, invasive, and powered by batteries, which raises concerns about biocompatibility and limits the device's longevity. In this study, a self-powered piezoelectric fish tag (SPFT) is presented based on a hybrid-mode piezoelectric nanogenerator (HM-PENG). The HM-PENG efficiently harvests both flow impact energy and strain energy generated by fish-tailing, utilizing a cavity structure and an auxetic design. The flexible fish tag can monitor fish behavior and enable self-powered underwater acoustic transmission. These functions are demonstrated using a robotic fish and a living crucian carp. Through signal modulation and demodulation, detailed parameters of fish locomotion, such as oscillation angle, frequency, and typical movement patterns, are transmitted and decoded. This work advances the development of self-powered, flexible fish tags, contributing to animal behavioral studies and ocean exploration.

A computational method is proposed for predicting the 2D molecular packing in crystalline thin films of flexible organic molecules. The approach employs a grid search for molecular arrangements, achieving accurate predictions of 2D packing motifs with strongly reduced computational costs. The results show very good agreement with experimental structures, emphasizing the method's efficiency for optoelectronic applications.

Abstract

The large variety of structural morphologies realized in organic semiconductors is a big challenge for the microscopic modeling of such systems. A global computational solution is still out of reach due to prevalent molecular flexibility. However, the specific case of crystalline thin films that exhibit surface alignment of molecular π-systems for optoelectronic applications of high technological relevance, seems to be a simpler task. This study proposes an approach for the structure prediction of two-dimensional (2D) molecular layers as precursors for the three-dimensional (3D) structure of deposited crystalline thin films. Based on grid search sampling for the layer's degrees of freedom, it requires only a small number of trial structures to find complex packing motifs of layered molecular materials. It facilitates parallel screening among multiple molecular conformers, which is usually very difficult and expensive, using the latest 3D-based prediction methods. The study researches theoretically and experimentally a set of known and newly crystallized compounds of evaporable flexible molecules with interesting optoelectronic properties, predicts their packing in 2D layers, and compares them with experimentally resolved crystal structures, obtaining very good agreement in the packing of these molecules within layers. The computational costs are estimated to be several orders of magnitude lower than with 3D methods.

Inspired by Pleurotya caterpillar kinematics, a novel segmental soft crawling robot with adaptive, well-controlled locomotion is developed using advanced multi-material 4D printing. The combination of gradient alignment and a light-fueled strategy enables tunable curvature of the robot, facilitating multiple postures and adaptive locomotion, including bidirectional crawling, rolling, and self-righting. The robot demonstrates considerable potential for efficient navigation in complex environments.

Abstract

Soft crawling robots capable of adjusting postures and generating adaptive locomotion modes are in high demand for autonomous adaptation to varying environments. Appropriate postures generated by robots’ deformation are crucial for diverse target locomotion. However, achieving multiple postures for integrating bidirectional crawling, crawling-to-rolling mode switching, and self-righting capability remains challenging. Herein, inspired by the kinematics of Pleurotya caterpillars, dynamic curvature controllability, which is realized through combining segmental structures and high curvature bending of each segment, is an effective strategy for active shape adaptation and attaining multiple postures. Segmental soft crawling robots, termed CRAWL, are fabricated by incorporating soft liquid crystal elastomers (LCEs) and rigid acrylic resin via multi-material 4D printing. The high curvature bending of each segment is attributed to the gradient alignment of mesogens induced by the non-uniform shear forces. The tunable curvature of the CRAWL is achieved through light-fueled bending of designated LCEs within the segmental structure on demand. This enables the CRAWL to obtain multiple postures and thus perform adaptive locomotion, including bidirectional crawling, curling into a loop, and rolling downhill, as well as correcting their postures through self-righting behavior when losing balance. This work provides new insights for designing soft robots with enhanced environmental adaptability.

Liquid Metal Photothermal Actuators

In article number 2416991, Xingyou Tian, Xian Zhang, and co-workers present a novel design for programmable liquid metal photothermal actuators using laser etching, overcoming the trade-off between load-carrying capacity and response speed. Featuring high stability, rapid oscillation, and robust performance, these actuators show promise in advanced robotics, enabling versatile smart devices like photothermally actuated robotic dogs for diverse terrains.

3D-printed picoliter droplet networks have been fabricated that control gene expression in bacterial populations by releasing chemical signals with precise spatial definition and high temporal resolution. This system of effector release is widely applicable, offering diverse applications in biology and medicine.

Abstract

Synthetic cells, such as giant unilamellar vesicles, can be engineered to detect and release chemical signals to control target cell behavior. However, control over the targeting of cell populations is limited due to poor spatial or temporal resolution and the inability of synthetic cells to deliver patterned signals. Here, 3D-printed picoliter droplet networks are described that direct gene expression in underlying bacterial populations by patterned release of a chemical signal with temporal control. Shrinkage of the droplet networks prior to use achieves spatial control over gene expression with ≈50 µm resolution. Ways to store chemical signals in the droplet networks and to activate release at controlled points in time are also demonstrated. Finally, it is shown that the spatially-controlled delivery system can regulate competition between bacteria by inducing the patterned expression of toxic bacteriocins. This system provides the groundwork for the use of picoliter droplet networks in fundamental biology and in medicine in applications that require the controlled formation of chemical gradients (i.e., for the purpose of local control of gene expression) within a target group of cells.

Nature, Published online: 29 April 2025; doi:10.1038/d41586-025-01329-z

Cell classification should be based on more than just DNA

A scalable method for direct laser patterning of 2D films on transparent substrates like polycarbonate and glass is presented. This technique eliminates the need for photolithography and solvents, enabling the fabrication of functional devices like strain gauges, supercapacitors, and photodetector arrays. The approach is demonstrated using a WSe₂/graphite photodetector array, showcasing its potential for flexible, semi-transparent imaging applications.

Abstract

A scalable method is presented for direct patterning of graphite and transition metal dichalcogenide (TMD) films on polycarbonate (PC) and other transparent substrates using fiber laser ablation. This process facilitates the fabrication of various functional devices, including strain gauges, supercapacitors, and photodetector arrays, without the need for photolithography or solvents, thereby simplifying device production and enhancing environmental sustainability. Utilizing roll-to-roll mechanical exfoliation, homogeneous nanosheet films are created and then patterned with a laser engraving system. Electrical and optical characterization confirms that the laser-processed films maintain their crystallinity, with no observable damage to the underlying substrate. The scalability of this approach is demonstrated by constructing a WSe₂/graphite photodetector array on PC, which exhibits high sensitivity, low noise, and uniform photocurrent response across its active channels. As a proof-of-concept, this array is used as an image sensor to capture light patterns, showcasing its potential for flexible and semi-transparent imaging applications. These findings open up new avenues for incorporating all-van der Waals devices into wearable electronics, optoelectronics, and imaging technologies.

To achieve a coupled enhancement of catalytic and transport properties, and further unlock interfacial dynamics of the electrode, vertical-aligned bismuth-nanosheets are in situ decorated on the surface of the porous electrode in this paper. This advanced method can greatly release the performance of the electrode, improve battery performance, and enhance the application potential of vanadium redox flow batteries.

Abstract

Insufficient electrochemical activity and mass transport have been a longstanding issue hindering the development of high-performance electrode for vanadium redox flow batteries. In this work, vertical-aligned bismuth-nanosheets that unlock interfacial dynamics with enhanced catalytic and transport properties are decorated on the electrode surface. The vertical-aligned structures form highways to guide reactants transport from bulk solution to electrode surface, reducing transport resistance and optimizing active sites utilization. Meanwhile, the bismuth-nanosheets, dominated by (012) planes with large amounts of unsaturated bismuth atoms, boost the number of electroactive sites and catalytic activity. Full-cell EIS tests show that the charge transfer resistance and the finite diffusion resistance with prepared electrode are 49.4 and 47.7 mΩ cm⁻², 71.3%, and 6.7% lower than those with traditional electrode. In full-cell tests, the battery delivers a peak power density of 1340 mW cm⁻² and achieves an energy efficiency of 85.8% at 200 mA cm⁻², which is 4.4% higher than that with traditional electrodes. Remarkably, the battery can maintain an energy efficiency of 82.4% at 300 mA cm⁻² and be stably cycled for over 2000 cycles with an only 0.0016% efficiency decay per cycle. This work paves a feasible platform to fabricate advanced electrode for vanadium redox flow batteries.

Light: Science & Applications, Published online: 25 April 2025; doi:10.1038/s41377-025-01821-1

Wafer-level InP-LiNbO₃ heterogeneous integration platform enables large-scale, multifunctional, and high-performance lithium niobate photonic integrated circuits for Pbit/s hyperscale data center interconnects and mmwave/THz photonics.

Using nitrogen-doped graphyne with diamond cavities as support, a site-defined tellurium single-atom nanozyme (Te SAN) with excellent peroxidase-like activity is designed. The dual-channel sensor array based on Te SAN not only achieves the successful identification of five bisphenols but also provides a reference for research on compounds with similar structures.

Abstract

Single-atom nanozymes exhibit unique enzymatic activity due to their active centers, which resemble those of natural metalloenzymes. The design of the anchoring sites of single-atom active centers is an important factor that affects the loading capacity and catalytic activity. Herein, para-nitrogen-doped graphyne with diamond cavity is used as support, and single-atom tellurium atoms are then anchored in the nitrogen-containing graphyne cavities, akin to chess pieces placed on a chessboard grid. Due to the pre-designed regular anchoring sites, the site-defined tellurium single-atom nanozyme (Te SAN) achieves a high Te loading of 19.21 wt.%. Therefore, Te SAN shows good peroxidase-like activity. To explain the enhanced peroxidase-like activity, density functional theory calculations are performed and the results demonstrate that Te doping enhances catalytic activity by lower Gibbs free energy barrier for formation of •OH, a key intermediate in peroxidase-like activity. Finally, based on the inhibitory effect of bisphenols on nanozyme activity, the Te SAN-based sensor array successfully identifies five bisphenols, holding potential for on-site food safety monitoring. The design of the anchoring sites of single atoms in this work provides new ideas for precisely controlling the synthesis of nanozymes, exploring their action mechanisms, and enhancing their activities.

This study investigates thin-film stacks combining organic and inorganic materials as conformal packaging coatings for CMOS microchips in next-generation neural implants. Using advanced material analysis, two coatings—an inorganic 100 nm hafnium-based ALD multilayer and a hybrid ParC-titanium-based ALD stack—were evaluated after a 7-month in vivo animal study. Results demonstrate excellent biostability and barrier properties, offering critical insights for future neural implant designs.

Abstract

Miniaturization of next-generation active neural implants requires novel micro-packaging solutions that can maintain their long-term coating performance in the body. This work presents two thin-film coatings and evaluates their biostability and in vivo performance over a 7-month animal study. To evaluate the coatings on representative surfaces, two silicon microchips with different surface microtopography are used. Microchips are coated with either a ≈100 nm thick inorganic hafnium-based multilayer deposited via atomic layer deposition (ALD-ML), or a ≈6 µm thick hybrid organic–inorganic Parylene C and titanium-based ALD multilayer stack (ParC-ALD-ML). After 7 months of direct exposure to the body environment, the multilayer coatings are evaluated using optical and cross-sectional scanning electron microscopy. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is also used to evaluate the chemical stability and barrier performance of the layers after long-term exposure to body media. Results showed the excellent biostability of the 100 nm ALD-ML coating with no ionic penetration within the layer. For the ParC-ALD-ML, concurrent surface degradation and ion ingress are detected within the top ≈70 nm of the outer Parylene C layer. The results and evaluation techniques presented here can enable future material selection, packaging, and analysis, enhancing the functional stability of future chip-embedded neural implants.

Nature, Published online: 23 April 2025; doi:10.1038/d41586-025-01131-x

An origami-inspired ‘metamaterial’ has been engineered to have properties not found in natural materials — enabling it to undergo large, reversible deformations.

Nature, Published online: 23 April 2025; doi:10.1038/d41586-025-01284-9

Bendy, twisty and collapsable origami towers could make temperature controlling panels, or, dancing robots.

Optical tweezers enable precise micro- and nanoscale particle manipulation and force measurement with piconewton accuracy, surpassing other techniques. This review explores their role in measuring forces in quantum mechanics and biophysical applications involving DNA, cells, and proteins, and assesses their potential and limitations in biophysics and biophotonics.

Abstract

Optical tweezers have found extensive applications across the realms of biophysics and nanoscience due to its ability to capture particles at both micro- and nanoscales. Serving as nanoscale force sensors, optical tweezers are capable of measuring physical properties of nanoparticles with piconewton-level precision, offering significantly higher accuracy compared to other measurement techniques, particularly for the biological samples. Given the rapid advancements in optical tweezers, a comprehensive review of their role in force measurement is imperative. This review begins with the fundamental interactions in biophysics, exploring how optical tweezers measure a variety of forces, such as the Casimir force, van der Waals force, and double-layer forces. Subsequently, the recent development in the application of optical tweezers across biomedical fields is focused on, including studies of cells, nucleic acids, proteins, and quantum mechanics. Finally, a detailed assessment of the potential and limitations of force measurement utilizing advanced optical tweezer technologies, emphasizing their impact and future applicability in the fields of biophysics and biophotonics, is offered.

This study uses a thin-film, high channel-count microelectrode array to deliver focal spinal cord stimulation to selectively activate lower limb muscles in rats. Both computational modeling and in vivo experiments demonstrate that this array significantly improves stimulation focality and muscle recruitment selectivity compared to traditional low channel-count arrays.

Abstract

Epidural electrical stimulation (EES) of the spinal cord is widely applied for pain management and as a possible route to functional restoration after spinal cord injury. Currently, EES employs bulky, nonconformal paddle arrays with low channel counts. This limits stimulation effectiveness by requiring high stimulation currents, reduces selectivity of muscle recruitment, and requires subject-specific designs to accommodate varied neuroanatomy across the patient population. Here, on a thin-film, high-channel count microelectrode array, termed SpineWrap is reported, which wraps around the dorsolateral aspect of the rat spinal cord. SpineWrap delivers focal stimulation to selectively activate muscles due to its thin substrate, high conformability, high channel count, on-device ground, and the material properties of its platinum nanorod contacts. Through computational and in vivo studies, the SpineWrap can selectively recruit muscles in the rat lower limb and identify stimulation hotspots at a submillimeter resolution, maximizing muscle recruitment selectivity. The effect of channel count and density on muscle recruitment selectivity is also investigated and show that rat spinal cord arrays require submillimeter pitches to achieve maximal selectivity. SpineWrap represents an advancement in EES technology and, when adapted to be used chronically, has the potential to improve SCI treatment by providing more refined stimulation.

Temperature and stress sensing based on flexible optical fibers may be the key to future artificial intelligence's perception of the world, here an optical fiber sensor capable of realizing such dual mode sensing is preliminary confirmed based on CaZnOS:Nd³⁺,Er³⁺.

Abstract

Mechanoluminescence (ML) and upconversion luminescence (UCL) materials exhibit significant potential in advanced optical sensing applications. However, single-function luminescent materials often fail to meet the increased complexity and precision demands of modern application scenarios. Here, flexible optical fiber based on ML and UCL dual-mode luminescence is demonstrated in Ca/SrZnOS: Nd³⁺, Er³⁺, which can be integrated into potential dual-mode stress and temperature sensing devices. After 4200 cycles of 2 N load, the ML intensity remaines at ≈67% of its initial value. Additionally, such device has a temperature sensitivity of 1.423% K⁻¹ at 273.15 K, with a detection accuracy of 1.1990 °C. The device maintained excellent cycling stability over a broad temperature range (0–80 °C), as evidenced by the unchanged FIR values after 10 cycles. The device demonstrates potential applications in remote stress and temperature monitoring, particularly in high-temperature, high-pressure, or hazardous environments, where optical fiber transmission ensures both safety and accuracy.

Piezoelectric transduction in monolayer MoS₂ is demonstrated using an ultrasound tip ( 100 kHz) from a wire bonder. Transient current measurements reveal sharp peaks with high peak-to-base ratios, tunable via gate voltage and ultrasound power. Multiple acoustic wave reflections enhance signal linewidth, validated by microacoustic simulations, establishing a robust platform for ultrasound-driven piezoelectric sensing.

Abstract

The interaction of ultrasonic waves with piezoelectric materials provides a quantitative route to enhance electrical and mechanical coupling in van der Waals (vdW) heterostructures. Here, wire-bonding tip-assisted ultrasound (≈100 kHz) is presented as an effective approach to achieve piezoelectric transduction in monolayer MoS₂ on Si/SiO₂ substrates. Transient current measurements show reproducible sharp peaks with a peak-to-base ratio (I _peak /I _base ≈ 12) unique to monolayer MoS₂, under an impact duration of 10–100 ms. Electrostatic gate voltage (V _g ) and ultrasound power (W _P ) tunable piezocurrent exhibit 3–5 times higher sensitivity in the ON-state (V _g ⩾ 0) compared to the OFF-state. Multiple reflections of acoustic waves at source-drain electrodes, with an increment in reflection coefficients, enhance the linewidth of peak currents, validated by microacoustic simulations of surface acoustic wave (SAW) propagation in submicron geometries. The localized strain and Joule heating under ultrasonic excitation may generate a temperature rise of ≈20 K, which reduces activation energy barriers, potentially enhancing reaction rates in temperature-sensitive chemical processes, such as hydrogen peroxide decomposition. This thermal-damage-free method integrates with silicon-based fabrication, establishing a robust platform for on-chip catalysis and energy harvesting in FET-based piezotransducers.