Biomimetic Contact Behavior Inspired Tactile Sensing Array with Programmable Microdomes Pattern by Scalable and Consistent Fabrication.

Flexible sensor arrays have attracted extensive attention in human-computer interaction. However, realizing high-performance sensor units with programmable properties, and expanding them to multi-pixel flexible arrays to maintain high sensing consistency is still struggling. Inspired by the contact behavior of octopus antenna, this paper proposes a programmable multistage dome structure-based flexible sensing array with robust sensing stability and high array consistency. The biomimetic multistage dome structure is pressurized to gradually contact the electrode to achieve high sensitivity and a large pressure range. By adjusting the arrangement of the multistage dome structure, the pressure range and sensitivity can be customized. More importantly, this biomimetic structure can be expanded to a multi-pixel sensor array at the wafer level with high consistency through scalable and high-precision imprinting technologies. In the imprinting process, the conductive layer is conformally embedded into the multistage dome structure to improve the stability (maintain stability over 22 000 cycles). In addition, the braced isolation structure is designed to effectively improve the anti-crosstalk performance of the sensor array (crosstalk coefficient: 26.62 dB). Benefitting from the programmable structural design and high-precision manufacturing process, the sensor array can be customized and is demonstrated to detect human musculation in medical rehabilitation applications.

Efficient Fabrication of Disordered Graphene with Improved Ion Accessibility, Ion Conductivity, and Density for High-Performance Compact Capacitive Energy Storage.

High-performance compact capacitive energy storage is vital for many modern application fields, including grid power buffers, electric vehicles, and portable electronics. However, achieving exceptional volumetric performance in supercapacitors is still challenging and requires effective fabrication of electrode films with high ion-accessible surface area and fast ion diffusion capability while simultaneously maintaining high density. Herein, a facile, efficient, and scalable method is developed for the fabrication of dense, porous, and disordered graphene through spark-induced disorderly opening of graphene stacks combined with mechanical compression. The obtained disordered graphene achieves a high density of 1.18 g cm-3, sixfold enhanced ion conductivity compared to common laminar graphene, and an ultrahigh volumetric capacitance of 297 F cm-3 in ionic liquid electrolyte. The fabricated stack cells deliver a volumetric energy density of 94.2 Wh L-1 and a power density of 13.7 kW L-1, representing a critical breakthrough in capacitive energy storage. Moreover, the proposed disordered graphene electrodes are assembled into ionogel-based all-solid-state pouch cells with high mechanical stability and multiple optional outputs, demonstrating great potential for flexible energy storage in practical applications.

Optimizing high-temperature energy storage in tungsten bronze-structured ceramics via high-entropy strategy and bandgap engineering.

As a vital material utilized in energy storage capacitors, dielectric ceramics have widespread applications in high-power pulse devices. However, the development of dielectric ceramics with both high energy density and efficiency at high temperatures poses a significant challenge. In this study, we employ high-entropy strategy and band gap engineering to enhance the energy storage performance in tetragonal tungsten bronze-structured dielectric ceramics. The high-entropy strategy fosters cation disorder and disrupts long-range ordering, consequently regulating relaxation behavior. Simultaneously, the reduction in grain size, elevation of conductivity activation energy, and increase in band gap collectively bolster the breakdown electric strength. This cascade effect results in outstanding energy storage performance, ultimately achieving a recoverable energy density of 8.9 J cm-3 and an efficiency of 93% in Ba0.4Sr0.3Ca0.3Nb1.7Ta0.3O6 ceramics, which also exhibit superior temperature stability across a broad temperature range up to 180 °C and excellent cycling reliability up to 105. This research presents an effective method for designing tetragonal tungsten bronze dielectric ceramics with ultra-high comprehensive energy storage performance.

Bidirectional, Multilayer MXene/Polyimide Aerogels for Ultra-Broadband Microwave Absorption.

To obtain high-performance electromagnetic microwave (EM) absorption materials with broad effective absorption bandwidth (EAB) and reduced thickness, designing structures has proved to be a promising way. Herein, ultra-broadband multilayer bidirectional MXene/polyimide EM absorption aerogels containing multi-structures on scales ranging from the micro- to the macroscale are produced with the aid of electric and temperature fields. On the microscale, under the action of electric force and temperature gradient, the ordered structures made of aligned Ti3C2Tx MXene nanosheets and the microscale layered aerogel walls enable the bidirectional aerogel to achieve a wide EAB of 8.58 GHz at a thickness of 2.1 mm. This is ascribed to the numerous aligned nanosheets and layered aerogel walls perpendicular to the incident EMs, facilitating the conversion of electromagnetic energy into electrical energy. Furthermore, on the macroscale, the multilayer bidirectional aerogel with non-gradient structures effectively resolves the conflict between impedance matching and energy loss, resulting in an ultrawide EAB of 9.41 GHz at a thickness of 3 mm. This innovative design of electric-field-assisted multilayer bidirectional aerogels with multiscale structural coupling may provide feasible and effective pathways for the development of advanced EM absorption materials.

Modulation of wetting state switching of droplets on superhydrophobic microstructured surfaces by external electric field.

HYPOTHESIS: Electrowetting on conventional dielectrics requires direct fluid-electrode contact to generate strong electric fields at the three-phase contact line to modulate the wetting. Since the electric field alters wetting, the modulation of wetting can be achieved by applying an external electric field through insulated electrodes, preventing the liquid from contacting the electrodes. EXPERIMENT: A simple and efficient method for non-contact between the fluid and the electrode external electric field modulation of fluid wetting was proposed. The switching ability of droplets on microgroove surfaces from Cassie-Baxter to Wenzel wetting state under an external electric field was used to drive and quantify the relationship between wetting, contact angle, and the applied voltage. FINDINGS: Applying an external electric field modulates the wetting of deionized water, ionic liquids, and high-viscosity liquids on microgrooves. The wetting degree of liquid can be controlled by adjusting the external voltage parameters. The finite element simulations revealed that the Maxwell force drove this process. The effects of substrate size and liquid properties on wetting behavior were also examined. Post-application cross-sectional imaging showed the formation of a conformal interface, highlighting the relevance of the proposed method in advanced adaptive shape fabrication and microfluidic control, among other applications.

Ice-Enabled Transfer of Graphene on Copper Substrates Enhanced by Electric Field and Cu2O.

Graphene films grown by the chemical vapor deposition (CVD) method suffer from contamination and damage during transfer. Herein, an innovative ice-enabled transfer method under an applied electric field and in the presence of Cu2O (or Cu2O-Electric-field Ice Transfer, abbreviated as CEIT) is developed. Ice serves as a pollution-free transfer medium while water molecules under the electric field fully wet the graphene surface for a bolstered adhesion force between the ice and graphene. Cu2O is used to reduce the adhesion force between graphene and copper. The combined methodology in CEIT ensures complete separation and clean transfer of graphene, resulting in successfully transferred graphene to various substrates, including polydimethylsiloxane (PDMS), Teflon, and C4F8 without pollution. The graphene obtained via CEIT is utilized to fabricate field-effect transistors with electrical performances comparable to that of intrinsic graphene characterized by small Dirac points and high carrier mobility. The carrier mobility of the transferred graphene reaches 9090 cm2 V-1 s-1, demonstrating a superior carrier mobility over that from other dry transfer methods. In a nutshell, the proposed clean and efficient transfer method holds great potential for future applications of graphene.

Treefrog-Inspired Flexible Electrode with High Permeability, Stable Adhesion, and Robust Durability.

Long-term continuous monitoring (LTCM) of physiological electrical signals is an effective means for detecting several cardiovascular diseases. However, the integrated challenges of stable adhesion, low impedance, and robust durability under different skin conditions significantly hinder the application of flexible electrodes in LTCM. This paper proposes a structured electrode inspired by the treefrog web, comprising dispersed pillars at the bottom and asymmetric cone holes at the top. Attachment structures with a dispersed pillar improve the contact stability (adhesion increases 2.79/13.16 times in dry/wet conditions compared to an electrode without structure). Improved permeable duct structure provides high permeability (12 times compared to cotton). Due to high adhesion and permeability, the electrode's durability is 40 times larger than commercial Ag/AgCl electrodes. The treefrog web-like electrode has great advantages in permeability, adhesion, and durability, resulting in prospects for application in physiological electrical signal detection and a new design idea for LTCM wearable dry electrodes.

Bioinspired Suspended Sensing Membrane Array with Modulable Wedged-Conductive Channels for Crosstalk-Free and High-Resolution Detection.

High spatial-resolution detection is essential for biomedical applications and human-machine interaction. However, as the sensor array density increases, the miniaturization will lead to interference between adjacent units and deterioration in sensing performance. Here, inspired by the cochlea's sensing structure, a high-density flexible pressure sensor array featuring with suspended sensing membrane with sensitivity-enhanced customized channels is presented for crosstalk-free and high-resolution detection. By imitating the basilar membrane attached to spiral ligaments, a sensing membrane is fixed onto a high-stiffness substrate with cavities, forming a stable braced isolation to provide an excellent crosstalk-free capability (crosstalk coefficient: 47.24 dB) with high-density integration (100 units within 1 cm2). Similar to the opening of ion channels in hair cells, the wedge-type expansion of the embedded cracks introduced by stress concentration structures enables a high sensitivity (0.19 kPa-1) and a large measuring range (400 kPa). Finally, it demonstrates promising applications in distributed displays and the condition monitoring of medical-surgical intubation.

Flexible Grid Graphene Electrothermal Films for Real-Time Monitoring Applications.

Flexible electrothermal films are crucial for protecting equipment and systems in cold weather, such as ice blockages in natural gas pipelines and icing on aircraft wings. Therefore, a flexible electric heater is one of the essential devices in industrial operations. One of the main challenges is to develop flexible electrothermal films with low operating voltage, high steady-state temperature, and good mechanical stability. In this study, a flexible electrothermal film based on graphene-patterned structures was manufactured by combining the laser induction method and the transfer printing process. The grid structure design provides accurate real-time monitoring for the application of electrothermal films and shows potential in solving problems related to deicing and clearing ice blockages in pipelines. The flexible electrothermal film can reach a high heating temperature of 165 °C at 15 V and exhibits sufficient heating stability. By employing a simple and efficient method to create a flexible, high-performance electrothermal film, we provide a reliable solution for deicing and monitoring applications.

Design Criteria for Architected Materials with Programmable Mechanical Properties Within Theoretical Limit Ranges.

Architected materials comprising periodic arrangements of cells have attracted considerable interest in various fields because of their unconventional properties and versatile functionality. Although some better properties may be exhibited when this homogeneous layout is broken, most such studies rely on a fixed material geometry, which limits the design space for material properties. Here, combining heterogeneous and homogeneous assembly of cells to generate tunable geometries, a hierarchically architected material (HAM) capable of significantly enhancing mechanical properties is proposed. Guided by the theoretical model and 745 752 simulation cases, generic design criteria are introduced, including dual screening for unique mechanical properties and careful assembly of specific spatial layouts, to identify the geometry of materials with extreme properties. Such criteria facilitate the potential for unprecedented properties such as Young's modulus at the theoretical limit and tunable positive and negative Poisson's ratios in an ultra-large range. Therefore, this study opens a new paradigm for materials with extreme mechanical properties.

Ultrahigh Energy Storage in Tungsten Bronze Dielectric Ceramics Through a Weakly Coupled Relaxor Design.

Dielectric energy-storage capacitors, known for their ultrafast discharge time and high-power density, find widespread applications in high-power pulse devices. However, ceramics featuring a tetragonal tungsten bronze structure (TTBs) have received limited attention due to their lower energy-storage capacity compared to perovskite counterparts. Herein, a TTBs relaxor ferroelectric ceramic based on the Gd0.03 Ba0.47 Sr0.485-1.5 x Smx Nb2 O6 composition, exhibiting an ultrahigh recoverable energy density of 9 J cm-3 and an efficiency of 84% under an electric field of 660 kV cm-1 is reported. Notably, the energy storage performance of this ceramic shows remarkable stability against frequency, temperature, and cycling electric field. The introduction of Sm3+ doping is found to create weakly coupled polar nanoregions in the Gd0.03 Ba0.47 Sr0.485 Nb2 O6 ceramic. Structural characterizations reveal that the incommensurability parameter increases with higher Sm3+ content, indicative of a highly disordered A-site structure. Simultaneously, the breakdown strength is also enhanced by raising the conduction activation energy, widening the bandgap, and reducing the electric field-induced strain. This work presents a significant improvement on the energy storage capabilities of TTBs-based capacitors, expanding the material choice for high-power pulse device applications.

Memristor-Based Artificial Chips.

Memristors, promising nanoelectronic devices with in-memory resistive switching behavior that is assembled with a physically integrated core processing unit (CPU) and memory unit and even possesses highly possible multistate electrical behavior, could avoid the von Neumann bottleneck of traditional computing devices and show a highly efficient ability of parallel computation and high information storage. These advantages position them as potential candidates for future data-centric computing requirements and add remarkable vigor to the research of next-generation artificial intelligence (AI) systems, particularly those that involve brain-like intelligence applications. This work provides an overview of the evolution of memristor-based devices, from their initial use in creating artificial synapses and neural networks to their application in developing advanced AI systems and brain-like chips. It offers a broad perspective of the key device primitives enabling their special applications from the view of materials, nanostructure, and mechanism models. We highlight these demonstrations of memristor-based nanoelectronic devices that have potential for use in the field of brain-like AI, point out the existing challenges of memristor-based nanodevices toward brain-like chips, and propose the guiding principle and promising outlook for future device promotion and system optimization in the biomedical AI field.

Piezoelectric Drop-on-Demand Inkjet Printing with Ultra-High Droplet Velocity.

Improving droplet velocity as much as possible is considered as the key to improving both printing speed and printing distance of the piezoelectric drop-on-demand inkjet printing technology. There are 3 tough and contradictory issues that need to be addressed simultaneously, namely, the actuation pressure of the piezoelectric printhead, satellite droplets, and the air resistance, which seems almost impossible to achieve with classical methods. Herein, a novel solution is introduced. By modulating the positive crosstalk effect inside and outside the printhead, self-tuning can be achieved, including self-reinforcing of the actuation pressure, self-restraining of satellite droplets, and self-weakening of the air resistance, thereby greatly improving droplet velocity. Based on these mechanisms, waveform design methods for different inks and printheads are investigated. The results demonstrate that monodisperse droplet jetting with a maximum velocity of 27.53 m/s can be achieved, reaching 3 to 5 times that of the classical method (5 to 8 m/s). Correspondingly, the printing speed and distance can be simultaneously increased by almost 10 times, demonstrating an ability of direct printing on irregular surface. Meanwhile, the compatibility of ink materials is expanded, as the Ohnesorge number and the viscosity of printable inks for the printhead used are increased from 0.36-0.72 to 0.03-1.18 and from 10-12 cp to 1-40.3 cp, respectively, even breaking the traditional limitations of the piezoelectric printing technology (Ohnesorge number of 0.1 to 1; viscosity of 1 to 25 cp). All the above provide a new perspective for improving droplet velocity and may even offer a game-changing choice for expanding the boundaries of the piezoelectric drop-on-demand inkjet printing technology.

Electrically active smart adhesive for a perching-and-takeoff robot.

Perching-and-takeoff robot can effectively economize onboard power and achieve long endurance. However, dynamic perching on moving targets for a perching-and-takeoff robot is still challenging due to less autonomy to dynamically land, tremendous impact during landing, and weak contact adaptability to perching surfaces. Here, a self-sensing, impact-resistant, and contact-adaptable perching-and-takeoff robot based on all-in-one electrically active smart adhesives is proposed to reversibly perch on moving/static dry/wet surfaces and economize onboard energy. Thereinto, attachment structures with discrete pillars have contact adaptability on different dry/wet surfaces, stable adhesion, and anti-rebound; sandwich-like artificial muscles lower weight, enhance damping, simplify control, and achieve fast adhesion switching (on-off ratio approaching ∞ in several seconds); and the flexible pressure (0.204% per kilopascal)-and-deformation (force resolution, <2.5 millinewton) sensor enables the robot's autonomy. Thus, the perching-and-takeoff robot equipped with electrically active smart adhesives exhibits tremendous advantages of soft materials over their rigid counterparts and promising application prospect of dynamic perching on moving targets.

Discretely-supported transfer nanoimprint anti-reflection nanostructures on complex uneven surface of Fresnel lenses.

Nanopatterning complex uneven surface of numerous functional devices to improve their performance is significantly appealing; however, it is extremely challenging. This study proposes a discretely-supported transfer nanoimprint technique to fabricate nanostructures on complex device surfaces containing multi-spatial frequencies. First, a discretely-supported nanoimprint template was designed based on the built energy criterion. A contact fidelity of over 99% was achieved between the designed template and the targeted complex uneven substrate surface. Next, the prefilled nanostructures on the template were transferred to the target surface after contact. By precisely controlling the amount of micro-droplet jetting on the template on-demand, the accumulation of the polymer in the micro-valley sites on the complex substrate was avoided, thus maintaining the morphology and generating function of the devices. Finally, high-quality Fresnel lenses with broadband wide-directional antireflection and excellent imaging performance were developed by imprinting subwavelength-tapered nanostructures on the relief surface.

Smart Manipulation of Complex Optical Elements via Contact-adaptive Dry Adhesives.

The implementation of complex, high-precision optical devices or systems, which have vital applications in the aerospace, medical, and military fields, requires the ability to reliably manipulate and assemble optical elements. However, this is a challenging task as these optical elements require contamination-free and damage-free manipulation and come in a variety of sizes and shapes. Here, a smart, contact-adaptive adhesive based on magnetic actuation is developed to address this challenge. Specifically, the surface bio-inspired adhesives made of fluororubber facilitate contamination-free and damage-free adhesion. The stiffness modulation of packaged magnetorheological grease based on the magnetorheological effect endows the smart adhesive with a high conformability to the optical elements in the soft state, a high grip force in the stiff state, and the ability to quickly release the optical elements in the recovered soft state. The smart adhesive provides a versatile solution for reliably and quickly manipulating and assembling multiscale optical elements with planar or complex 3D shapes without causing surface contamination or damage. These extraordinary capabilities are demonstrated by the manipulation and assembly of various optical elements, such as convex/concave/ball lenses and extremely complex-shaped light guide plates. The proposed smart adhesive is a promising candidate for conventional optical element manipulation technologies.

Micropatterned Fluororubber-Based Dry Adhesive for Pan-Semiconductor Production Line with Complicated Operating Conditions.

The efficient and safe manipulation of precision materials (such as thin and fragile wafers and glass substrates for flat panel displays) under complicated operating conditions with vacuum, high temperature, and low preload stress is an essential task for pan-semiconductor production lines. However, current manipulation approaches such as suction-based gripping (invalid under vacuum conditions) and mechanical clamping (stress concentration at the contact interfaces) are challenged to satisfy such complex requirements. Herein, fluororubber (FKM) is employed as an adhesive material to overcome such challenges due to its outstanding thermostability, availability under vacuum environments, and high adhesion at low contacting preloads. However, the adhesion of the FKM film decreases significantly with increasing temperature (decrease by 84.83% at 245 °C). Consequently, a micropatterned FKM-based dry adhesive (MFA) fabricated by laser etching is developed. The experimental results reveal that MFAs are efficient in restraining adhesion attenuation at high temperatures (minimum 15% decrease at 245 °C). The numerical analysis and in situ observations reveal the mechanism of the MFAs in restraining adhesion attenuation. The contamination-free and high adhesion at low contacting preload of MFAs can be of great interest in pan-semiconductor production lines that require complicated operating conditions on temperature, vacuum, and interface stress.

Bioinspired Dry Adhesives for Highly Adaptable and Stable Manipulating Irregular Objects under Vibration.

For dry adhesive-based operation, highly adaptable and stable manipulation is important but also challenging, especially for irregular objects with complex surface (such as abrupt profile and acute projection) under vibration-inducing environments. Here, a multi-scale adhesive structure, with mechanically isolated energy-absorbing backing, based on the synergistic action of microscale contact end (seta), mesoscale supporting layer (lamella), and macroscopic backing (muscle tissues) of gecko's sole, is proposed. Top layer of mushroom-like micro tips provides dry adhesion via mimicking gecko's seta, and bottom layer of physical cuts and porous feature achieves the interfacial mechanical decoupling and crack inhibition via mimicking the non-continuous distributing of lamella and compliance of muscle. The proposed dry adhesive exhibits excellent adaptable adhesion to various objects with curved or irregular surfaces, even for that with abrupt contours, as well as an amazing stable anti-vibration ability, opening a new avenue for the development of dry adhesive-based device or system.

Electrowetting-assisted printing of 3D-architectured microelectrodes inside flexible piezoelectric films for sensitive, robust responses to bending deformation.

The voltage outputs of flexible piezoelectric films after bending deformation have always been limited by two factors, including the incompatible polarization direction with bending strain and the interfacial fatigue failure between the piezoelectric films and the electrode layers, largely hindering the applications in wearable electronics. Herein, we demonstrate a new piezoelectric film design, where 3D-architectured microelectrodes are fabricated inside a piezoelectric film by electrowetting-assisted printing of conductive nano-ink into the pre-formed meshed microchannels in the piezoelectric film. The 3D architectures increase the piezoelectric output of a typical P(VDF-TrFE) film by more than 7 fold compared with the conventional planar design at the same bending radius, and, more importantly, decrease the output attenuation down to only 5.3% after 10 000 bending cycles, less than one third of that for the conventional design. The dependence of piezoelectric outputs on feature sizes of 3D microelectrodes was investigated numerically and experimentally, providing a route for optimizing the 3D architecture design. Different composite piezoelectric films with internal 3D-architectured microelectrodes were fabricated, exhibiting improved piezoelectric outputs under bending deformations, demonstrating that our printing methods could have broad applications in various fields. The fabricated piezoelectric films, worn on human fingers, are used for remotely controlling the robot hand gestures by human-machine interaction; furthermore, the fabricated piezoelectric patches are used to successfully sense the pressure distribution by integrating with spacer arrays to convert the pressing movement into bending deformation, demonstrating the enormous potential of our piezoelectric films in practical applications.

Microcrack Arrays in Dense Graphene Films for Fast-Ion-Diffusion Supercapacitors.

Laminated graphene film has great potential in compact high-power capacitive energy storage owing to the high bulk density and opened architecture. However, the high-power capability is usually limited by tortuous cross-layer ion diffusion. Herein, microcrack arrays are fabricated in graphene films as fast ion diffusion channels, converting tortuous diffusion into straightforward diffusion while maintaining a high bulk density of 0.92 g cm-3 . Films with optimized microcrack arrays exhibit sixfold improved ion diffusion coefficient and high volumetric capacitance of 221 F cm-3 (240 F g-1 ), representing a critical breakthrough in optimizing ion diffusion toward compact energy storage. This microcrack design is also efficient for signal filtering. Microcracked graphene-based supercapacitor with 30 µg cm-2  mass loading exhibits characteristic frequency up to 200 Hz with voltage window up to 4 V, showing high promise for compact, high-capacitance alternating current (AC) filtering. Moreover, a renewable energy system is conducted using microcrack-arrayed graphene supercapacitors as filter-capacitor and energy buffer, filtering and storing the 50 Hz AC electricity from a wind generator into the constant direct current, stably powering 74 LEDs, demonstrating enormous potential in practical applications. More importantly, this microcracking approach is roll-to-roll producible, which is cost-effective and highly promising for large-scale manufacture.