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Rapid droplet detachment from the surface in a "pancake rebound" has recently attracted abundant interest owing to the contact time control for applications in anti-icing and self-cleaning. Even though the pancake rebound on rigid substrates has been realized, the establishment of artificial structures on a flexible counterpart with droplet impact behavior studies has rarely been reported. Here, we introduced a facile approach to fabricating a flexible superhydrophobic film decorated with tunable hierarchical micro/nanostructures for water repellency. With the appropriately optimized architecture, the pancake rebound with reduced contact time can be realized when reaching a specific Weber number on the microcones. We also observed that the pancake rebound on microcilia could be realized by regulating the energy-transfer process on the flexible film during the droplet impact. A tightly stretched and suspended film can serve as the "spring" to store the elastic energy transferred from the kinetic energy of the penetrated droplet while converting back to kinetic energy during the emptying process with a reduced contact time of 5.2 ms. With the preserved water repellency on diverse curvatures, the study raises a new avenue to realize superhydrophobic surfaces and rapid droplet detachment with the potential for a broader spectrum toward practical scenarios in our daily life.
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The sensitivity and linearity are critical parameters that can preserve the high pressure-resolution across a wide range and simplify the signal processing process of flexible tactile sensors. Although extensive micro-structured dielectrics have been explored to improve the sensitivity of capacitive sensors, the attenuation of sensitivity with increasing pressure is yet to be fully resolved. Herein, a novel dielectric layer based on the gradient micro-dome architecture (GDA) is presented to simultaneously realize the high sensitivity and ultrabroad linearity range of capacitive sensors. The gradient micro-dome pixels with rationally collocated amount and height can effectively regulate the contact area and hence enable the linear variation in effective dielectric constant of the GDA dielectric layer under varying pressures. With systematical optimization, the sensor exhibits the high sensitivity of 0.065 kPa-1 in an ultrabroad linearity range up to 1700 kPa, which is first reported. Based on the excellent sensitivity and linearity, the high pressure-resolution can be preserved across the full scale of pressure spectrum. Therefore, potential applications such as all-round physiological signal detection in diverse scenarios, control instruction transmission with combinatorial force inputs, and convenient Morse code communication with non-overlapping capacitance signals are successfully demonstrated through a single sensor device.
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Dispositivos Electrónicos Vestibles , Capacidad Eléctrica , Fenómenos Mecánicos , Presión , TactoRESUMEN
Three-dimensional (3D) in vitro scaffolds that mimic the irregular fibrous structures of in vivo extracellular matrix (ECM) are critical for many important biological applications. However, structural properties modulation of fibrous 3D scaffolds remains a challenge. Here, we report the first highly modulable 3D fibrous scaffolds self-assembled by high-aspect-ratio (HAR) microfibers. The scaffolds structural properties can be easily tailored to incorporate various physical cues, including geometry, stiffness, heterogeneity and nanotopography. Moreover, the fibrous scaffolds are readily and accurately patterned on desired locations of the substrate. Cell culture exhibits that our scaffolds can elicit strong bidirectional cell-material interactions. Furthermore, a functional disparity between the two-dimensional substrate and our 3D scaffolds is identified by cell spreading and proliferation data. These results prove the potential of the proposed scaffold as a biomimetic extracellular microenvironment for cell study.
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Materiales Biomiméticos/química , Microambiente Celular , Matriz Extracelular/química , Andamios del Tejido/química , Animales , Humanos , Ratones , Células 3T3 NIHRESUMEN
The effect of the chain length of polyvinyl pyrrolidone (PVP) on the structures of silver nanowires (AgNWs) is explored in this study. It was found in the experiments that PVP, when serving as a capping agent, has a great impact on the morphology and structure of AgNWs. By means of a series of experiments and the inquiry of the growth mechanism, the critical minimum PVP chain length for the successful formation of uniform nanowires was discovered, below which only nanoparticles or short nanorods can be obtained. Surprisingly, a core-shell structure of a nanowire with a polycrystal was observed when PVP with a very long chain length was employed in the processing.
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The Fano resonance induced by symmetry breaking could improve the sensitivity of localized surface plasmon resonance sensors. In this work, the spectra of gold nanocrescent arrays are measured and confirmed by simulation results through the finite element method (FEM). The Fano resonance presented in the spectra could be modulated by the symmetry breaking with different waist widths, which are understood through plasmonic hybridization theory with the help of surface charge distribution. Our results indicate the Fano lineshape is generated by the coherent coupling of the quadrupole plasmon mode QH of nanohole and the antibonding plasmon mode D(AB) of nanocrescent. Finally, the high figure of merit (FoM=1.6-3.5) of the Q mode in the visible region illustrates this nanocrescent Fano sensor is of great value in the biological and chemical scientific fields.
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Benefitting from the antenna effect and localized surface plasmon resonance (LSPR), a metal nanoparticle with a designed morphology has the amazing ability to confine light energy into the required extremely small volume, whose refractive index largely affects the optical properties of the whole metal nanoparticle. In this work, the optical spectra and near-field distribution of a gold nanocrescent array were investigated both experimentally and theoretically. To find out the LSPR wavelength and the enhancement using different morphologies of sharp tips, the spectra of gold nanocrescent arrays with different waist widths (d) were first measured, which were then confirmed and analyzed using the finite difference time-domain method and the hybridization theory. At last, the LSPR of this array with 100 nm diameter dielectric nanodisks was studied for sensing in subwavelength areas. Our results showed that because of its giant nanoantenna-enhanced electromagnetic field at the two tips, this gold nanocrescent array could be a suitable local senor to sense the variation of a local medium in a subwavelength area.
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Exploring flexible tactile sensors capable of recognizing surface information is significant for the development of virtual reality, artificial intelligence, soft robotics, and human-machine interactions (HMI). However, it is still a challenge for current tactile sensors to efficiently recognize the surface pattern information while maintaining the simplicity of the overall system. In this study, cantilever beam-like magnetized micropillars (MMPs) with height gradients are assembled as a position-registered array for rapid recognition of surface pattern information. After crossing the surface location with convex patterns, the deformed MMPs undergo an intrinsic oscillating process to induce damped electrical signals, which can then be converted to a frequency domain for eigenfrequency extraction. Via precisely defining the specific eigenfrequencies of different MMPs, position mapping is realized in crosstalk-free behavior even though all signals are processed by one communication channel and a pair of electrodes. With a customized LabVIEW program, the surface information (e.g., letters, numbers, and Braille) can be accurately reconstructed by the frequency sequence produced in a single scanning procedure. We expect that the proposed interface can be a convenient and powerful platform for intelligent surface information perception and an HMI system in the future.
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The current generation of wearable sensors often experiences signal interference and external corrosion, leading to device degradation and failure. To address these challenges, the biomimetic superhydrophobic approach has been developed, which offers self-cleaning, low adhesion, corrosion resistance, anti-interference, and other properties. Such surfaces possess hierarchical nanostructures and low surface energy, resulting in a smaller contact area with the skin or external environment. Liquid droplets can even become suspended outside the flexible electronics, reducing the risk of pollution and signal interference, which contributes to the long-term stability of the device in complex environments. Additionally, the coupling of superhydrophobic surfaces and flexible electronics can potentially enhance the device performance due to their large specific surface area and low surface energy. However, the fragility of layered textures in various scenarios and the lack of standardized evaluation and testing methods limit the industrial production of superhydrophobic wearable sensors. This review provides an overview of recent research on superhydrophobic flexible wearable sensors, including the fabrication methodology, evaluation, and specific application targets. The processing, performance, and characteristics of superhydrophobic surfaces are discussed, as well as the working mechanisms and potential challenges of superhydrophobic flexible electronics. Moreover, evaluation strategies for application-oriented superhydrophobic surfaces are presented.
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In this study, the plasmonic Ag nanoparticles (Ag NPs) were uniformly anchored on the high conductivity Nb2CTx (MXene) nanosheets to construct an Ag/Nb2CTx substrate for surface-enhanced Raman spectroscopy (SERS) detection of polystyrene (PS) nanoplastics. The KI addition (0.15 mol/L), the volume ratio between substrate colloid and nanoplastic suspension (2:1), and the mass ratio of Nb2CTx in substrate (14%) on SERS performance were optimized. The EM hot spots of Ag/Nb2CTx are significantly enlarged and enhanced, elucidated by FDFD simulation. Then, the linear relationship between the PS nanoplastics concentration with three different sizes (50, 300, and 500 nm) and the SERS intensity was obtained (R2 > 0.976), wherein, the detection limit was as low as 10-4 mg/mL for PS nanoplastic. Owing to the fingerprint feature, the Ag/Nb2CTx-14% substrate successfully discerns the mixtures from two-component nanoplastics. Meanwhile, it exhibits excellent stability of PS nanoplastics on different detection sites. The recovery rates of PS nanoplastics with different sizes in lake water ranged from 94.74% to 107.29%, with the relative standard deviation (RSD) ranging from 2.88% to 8.30%. Based on this method, the expanded polystyrene (EPS) decomposition behavior was evaluated, and the PS concentrations in four water environments were analyzed. This work will pave the way for the accurate quantitative detection of low concentration of nanoplastics in aquatic environments.
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The recent development of wearable devices is revolutionizing the way of human-machine interaction (HMI). Nowadays, an interactive interface that carries more embedded information is desired to fulfill the increasing demand in era of Internet of Things. However, present approach normally relies on sensor arrays for memory expansion, which inevitably brings the concern of wiring complexity, signal differentiation, power consumption, and miniaturization. Herein, a one-channel based self-powered HMI interface, which uses the eigenfrequency of magnetized micropillar (MMP) as identification mechanism, is reported. When manually vibrated, the inherent recovery of the MMP causes a damped oscillation that generates current signals because of Faraday's Law of induction. The time-to-frequency conversion explores the MMP-related eigenfrequency, which provides a specific solution to allocate diverse commands in an interference-free behavior even with one electric channel. A cylindrical cantilever model is built to regulate the MMP eigenfrequencies via precisely designing the dimensional parameters and material properties. It is shown that using one device and two electrodes, high-capacity HMI interface can be realized when the magnetic micropillars (MMPs) with different eigenfrequencies have been integrated. This study provides the reference value to design the future HMI system especially for situations that require a more intuitive and intelligent communication experience with high-memory demand.
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In this study, leveraging the tunable surface groups of MXene, the two-dimensional (2D) Nb2CTx with OH terminal (NC) was synthesized. 2D ZnIn2S4 (ZIS) nanosheets were prepared with the aid of sodium citrate, enhancing the exposure ratio of active (110) facet. On this basis, 2D/2D ZnIn2S4/Nb2CTx heterojunctions were fabricated to improve photocatalytic hydrogen evolution reaction (HER) performance. The optimized 6 wt%Nb2CTx/ZnIn2S4-450 (6NC/ZIS-450) photocatalyt exhibits a remarkable HER rate of 3603 µmol g-1h-1, which is 10 times superior to that of the original ZnIn2S4. Its apparent quantum efficiency (AQE) at 380 nm reaches 14.9 %. Meanwhile, even after 5 rounds of HER, the activity of 2D/2D ZnIn2S4/Nb2CTx heterojunction remained at 90 %, far superior to that of pure ZnIn2S4 (34 % and 31 %). Energy band structure analysis and density functional theory (DFT) calculation indicate that Nb2CTx adsorbed with OH exhibit a low work function. By serving as a hole cocatalyst, it effectively boosts the photocatalytic HER rate of ZnIn2S4/Nb2CTx heterojunction and inhibits the photocorrosion of ZnIn2S4. This unique insight, via hole transport highways and increased exposure of active facets, effectively enhances the activity and stability of sulfides photocatalysts.
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Superhydrophobic fabrics have recently attracted extensive interest not only in the fields of water-repellent clothing but also for the emerging functional fabrics due to their intrinsic flexibility and excellent stability. In this work, we proposed a simple, cost-effective, and environmentally friendly method to fabricate superhydrophobic fabrics with a broad application scope for textiles of different apertures. The flexible, breathable, and superhydrophobic fabric was realized via a three-step process, including polydimethylsiloxane (PDMS) encapsulation, in situ microcilia array formation, and silica nanoparticle decoration. With an adhesive PDMS layer and additive NdFeB particles, the hierarchical structures can tightly attach to the fabric substrate to provide robustness and durability. Specifically, the optimization of microcilia architecture was achieved via tuning the composite mass ratios so that suitable morphologies can be produced for robust nonwetting behavior. The superhydrophobic fabrics possess a contact angle and sliding angle of â¼155 and â¼3°, respectively, with excellent durability against 650 cycles' periodic mechanical abrasion, 130 cycles' tape-peeling test, washing evaluation, and chemical corrosions. Furthermore, the superhydrophobic fabric shows outstanding breathability and flexibility to be adaptive to surfaces with curvature or irregular shapes. The presented superhydrophobic strategy was considered to be feasible for multiple fabric substrates, revealing the broad application potential for fields of healthcare production, outdoor goods, catering industry, etc.
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Rather than using longitudinal "muscle" as in biological inchworm, the existing magnetic active elastomer (MAE)-based inchworm robots utilize magnetic torque to pull and push the soft body, which hinders its locomotion mobility. In this paper, a new pre-strained MAE inchworm millirobot with micropillars is proposed. The pre-strained elastomer serves as a pre-load muscle to contract the soft body, and the micropillars act as tiny feet to anchor the body during the locomotion. The proposed magnetic inchworm robot features a simple fabrication process that does not require special magnetization equipment. For the first time, the pre-load muscle is introduced in the design of magnetic inchworm robots, making it more like a real inchworm in terms of locomotion mechanism. The locomotion principle and parametric design for the desired locomotion performance have been investigated. Experimental results show that the fabricated magnetic inchworm robot (size: 10 mm × 5 mm, micropillars length: 200 µm, and mass: 262 g) can locomote on a smooth acrylic surface (roughness of 0.3 µm) at the speed of 0.125 body lengths per second, which is comparable with the existing magnetic inchworm robots. Moreover, the locomotion capabilities of the inchworm robot on wet surfaces and inclined planes have been verified via experimental studies.
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Researchers have struggled to develop highly reliable and sensitive surface-enhanced Raman scattering (SERS) substrates for detecting compounds in complicated systems. In this work, a strategy by constructing Au cores with incompletely wrapped Prussian blue (PB) for highly reliable and sensitive SERS substrate is proposed. The wrapped PB layers can provide the internal standard (IS) to calibrate the SERS signal floatation, whereas the exposed surface of Au cores offers the enhancement effect. The balance between the signal self-calibration and enhancement (hence the trade-off between SERS reliability and sensitivity) is obtained by the approximate semi-wrapping configuration of PB layers on Au cores (i.e., SW-Au@PB). The proposed SW-Au@PB nanoparticles (NPs) exhibit the similar enhancement factor as the pristine Au NPs and contribute to the ultralow RSD (8.55%) of calibrated SERS signals using R6G as probe molecules. The simultaneously realized reliability and sensitivity of SW-Au@PB NPs also enables the detection of hazardous pesticide residues such as paraquat and thiram in herbal plants, with the average detection accuracy up to 92%. Overall, this work mainly provides a controllable synthetic strategy for incompletely wrapped NPs, and most importantly, explores the potential with a proof-of-concept practical application in accurate and sensitive Raman detection of hazardous substances with varying solubility.
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Técnicas Biosensibles , Nanopartículas del Metal , Nanopartículas del Metal/química , Oro/química , Espectrometría Raman , Reproducibilidad de los Resultados , Plata/químicaRESUMEN
Manipulation of micro-objects have been playing an essential role in biochemical analysis or clinical diagnostics. Among the diverse technologies for micromanipulation, acoustic methods show the advantages of good biocompatibility, wide tunability, a label-free and contactless manner. Thus, acoustic micromanipulations have been widely exploited in micro-analysis systems. In this article, we reviewed the acoustic micromanipulation systems that were actuated by sub-MHz acoustic waves. In contrast to the high-frequency range, the acoustic microsystems operating at sub-MHz acoustic frequency are more accessible, whose acoustic sources are at low cost and even available from daily acoustic devices (e.g. buzzers, speakers, piezoelectric plates). The broad availability, with the addition of the advantages of acoustic micromanipulation, make sub-MHz microsystems promising for a variety of biomedical applications. Here, we review recent progresses in sub-MHz acoustic micromanipulation technologies, focusing on their applications in biomedical fields. These technologies are based on the basic acoustic phenomenon, such as cavitation, acoustic radiation force, and acoustic streaming. And categorized by their applications, we introduce these systems for mixing, pumping and droplet generation, separation and enrichment, patterning, rotation, propulsion and actuation. The diverse applications of these systems hold great promise for a wide range of enhancements in biomedicines and attract increasing interest for further investigation.
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Sonido , Vibración , Acústica , Micromanipulación/métodos , TecnologíaRESUMEN
Ensuring accessible and high-quality healthcare worldwide requires field-deployable and affordable clinical diagnostic tools with high performance. In recent years, flexible electronics with wearable and implantable capabilities have garnered significant attention from researchers, which functioned as vital clinical diagnostic-assisted tools by real-time signal transmission from interested targets in vivo. As the most crucial and complex system of human body, cardiocerebral vascular system together with heart-brain network attracts researchers inputting profuse and indefatigable efforts on proper flexible electronics design and materials selection, trying to overcome the impassable gulf between vivid organisms and rigid inorganic units. This article reviews recent breakthroughs in flexible electronics specifically applied to cardiocerebral vascular system and heart-brain network. Relevant sensor types and working principles, electronics materials selection and treatment methods are expounded. Applications of flexible electronics related to these interested organs and systems are specially highlighted. Through precedent great working studies, we conclude their merits and point out some limitations in this emerging field, thus will help to pave the way for revolutionary flexible electronics and diagnosis assisted tools development.
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Micropillars have emerged as promising tools for a wide range of biological applications, while the influence of magnetic fields on cell behavior regulation has been increasingly recognized. However, the combined effect of micropillars and magnetic fields on cell behaviors remains poorly understood. In this study, we investigated the responses of H9c2 cells to ultramicromagnetic micropillar arrays using NdFeB as the tuned magnetic particles. We conducted a comparative analysis between PDMS micropillars and NdFeB/PDMS micropillars to assess their impact on cell function. Our results revealed that H9c2 cells exhibited significantly enhanced proliferation and notable cytoskeletal rearrangements on the ultramicromagnetic micropillars, surpassing the effects observed with pure PDMS micropillars. Immunostaining further indicated that cells cultured on ultramicromagnetic micropillars displayed heightened contractility compared to those on PDMS micropillars. Remarkably, the ultramicromagnetic micropillars also demonstrated the ability to decrease reactive oxygen species (ROS) levels, thereby preventing F-actin degeneration. Consequently, this study introduces ultramicromagnetic micropillars as a novel tool for the regulation and detection of cell behaviors, thus paving the way for advanced investigations in tissue engineering, single-cell analysis, and the development of flexible sensors for cellular-level studies.
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Wearable sensors have recently attracted extensive interest not only in the field of healthcare monitoring but also for convenient and intelligent human-machine interactions. However, challenges such as wearable comfort, multiple applicable conditions, and differentiation of mechanical stimuli are yet to be fully addressed. Herein, we developed a breathable and waterproof electronic skin (E-skin) that can perceive pressure/strain with nonoverlapping signals. The synergistic effect from magnetic attraction and nanoscaled aggregation renders the E-skin with microscaled pores for breathability and three-dimensional microcilia for superhydrophobicity. Upon applied pressure, the bending of conductive microcilia enables sufficient contacts for resistance decrease, while the stretching causes increased resistance due to the separation of conductive materials. The optimized E-skin exhibits a high gauge factor of 7.747 for small strain (0-80%) and a detection limit down to 0.04%. The three-dimensional microcilia also exhibit a sensitivity of -0.0198 kPa-1 (0-3 kPa) and a broad detection range up to 200 kPa with robustness. The E-skin can reliably and precisely distinguish kinds of the human joint motions, covering a broad spectrum including bending, stretching, and pressure. With the nonoverlapping readouts, ternary inputs "1", "0", and "-1" could be produced with different stimuli, which expands the command capacity for logic outputs such as effective Morse code and intuitive robotic control. Owing to the rapid response, long-term stability (10â¯000 cycles), breathability, and superhydrophobicity, we believe that the E-skin can be widely applied as wearable devices from body motion monitoring to human-machine interactions toward a more convenient and intelligent future.
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Dispositivos Electrónicos Vestibles , Humanos , Conductividad Eléctrica , Movimiento (Física)RESUMEN
Cracks play an important role in strain sensors. However, a systematic analysis of how cracks influence the strain sensors has not been proposed. In this work, an intelligent and highly sensitive strain sensor based on indium tin oxide (ITO)/polyurethane (PU) micromesh is realized. The micromesh has good skin compatibility, water vapor permeability, and stability. Due to the color of the ITO/PU micromesh, it can be invisible on the skin. Based on the fragility of ITO, the density and resistance of cracks in the micromesh are greatly improved. Therefore, the ITO/PU micromesh strain sensor (IMSS) has an ultrahigh gauge factor (744.3). In addition, a finite element model based on four resistance layers is proposed to explain the performance of the IMSS and show the importance of high-density cracks. Compared with other strain sensors based on low-density cracks, the IMSS based on high-density cracks has larger sensitivity and better linearity. Physiological signals, such as respiration, pulse, and joint motion, can be monitored using the IMSS self-fixed on the skin. Finally, an invisible and artificial throat has been realized by combining the IMSS with a convolutional neural network algorithm. The artificial throat can translate the throat vibrations of the tester automatically with an accuracy of 86.5%. This work has great potential in health care and language function reconstruction.
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Surface enhanced Raman scattering (SERS) is a rapid and nondestructive technique that is capable of detecting and identifying chemical or biological compounds. Sensitive SERS quantification is vital for practical applications, particularly for portable detection of biomolecules such as amino acids and nucleotides. However, few approaches can achieve sensitive and quantitative Raman detection of these most fundamental components in biology. Herein, a noble-metal-free single-atom site on a chip strategy was applied to modify single tungsten atom oxide on a lead halide perovskite, which provides sensitive SERS quantification for various analytes, including rhodamine, tyrosine and cytosine. The single-atom site on a chip can enable quantitative linear SERS responses of rhodamine (10-6-1 mmol L-1), tyrosine (0.06-1 mmol L-1) and cytosine (0.2-45 mmol L-1), respectively, which all achieve record-high enhancement factors among plasmonic-free semiconductors. The experimental test and theoretical simulation both reveal that the enhanced mechanism can be ascribed to the controllable single-atom site, which can not only trap photoinduced electrons from the perovskite substrate but also enhance the highly efficient and quantitative charge transfer to analytes. Furthermore, the label-free strategy of single-atom sites on a chip can be applied in a portable Raman platform to obtain a sensitivity similar to that on a benchtop instrument, which can be readily extended to various biomolecules for low-cost, widely demanded and more precise point-of-care testing or in-vitro detection. Electronic Supplementary Material: Supplementary material is available for this article at 10.1007/s40843-022-1968-5 and is accessible for authorized users.