Multifunctional flexible magnetic drive gripper for target manipulation in complex constrained environments.

Soft actuators capable of remote-controlled guidance and manipulation within complex constrained spaces hold great promise in various fields, especially in medical fields such as minimally invasive surgery. However, most current magnetic drive soft actuators only have the functions of position control and guidance, and it is still challenging to achieve more flexible operations on different targets within constrained spaces. Herein, we propose a multifunctional flexible magnetic drive gripper that can be steered within complex constrained spaces and operate on targets of various shapes. On the one hand, changing the internal pressure of the magnetic gripper can achieve functions such as suction or injection of liquid and transportation of targets with smooth surfaces. On the other hand, with the help of slit structures in the constrained environment, by simply changing the position and orientation of the permanent magnet in the external environment, the magnetic gripper can be controlled to clamp and release targets of linear, flaked, and polyhedral shapes. The full flexibility and multifunctionality of the magnetic gripper suggest new possibilities for precise remote control and object transportation in constrained spaces, so it could serve as a direct contact operation tool for hazardous drugs in enclosed spaces or a surgical tool in human body cavities.

Prelimbic area to lateral hypothalamus circuit drives social aggression.

Controlling aggression is a vital skill in social species such as rodents and humans and has been associated with the medial prefrontal cortex (mPFC). In this study, we showed that during aggressive behavior, the activity of GABAergic neurons in the prelimbic area (PL) of the mPFC was significantly suppressed. Specific activation of GABAergic PL neurons significantly curbed male-to-male aggression and inhibited conditioned place preference (CPP) for aggression-paired contexts, whereas specific inhibition of GABAergic PL neurons brought about the opposite effect. Moreover, GABAergic projections from PL neurons to the lateral hypothalamus (LH) orexinergic neurons mediated aggressive behavior. Finally, directly modulated LH-orexinergic neurons influence aggressive behavior. These results suggest that GABAergic PL-orexinergic LH projection is an important control circuit for intermale aggressive behavior, both of which could be targets for curbing aggression.

Wireless and Closed-Loop Smart Dressing for Exudate Management and On-Demand Treatment of Chronic Wounds.

Chronic wounds have become a significant threat to people's physical and mental health and have increased the burden of social medical care. Intelligent wound dressing (IWD) with wound condition monitoring and closed-loop on-demand drug therapy can shorten the healing process and alleviate patient suffering. However, single-function wound dressings cannot meet the current needs of chronic wound treatment. Here, a wearable IWD consisting of wound exudate management, sensor monitoring, closed-loop therapy, and flexible circuit modules is reported, which can achieve effective synergy between wound exudate management and on-demand wound therapy. The dressing is attached to the wound site, and the wound exudate is spontaneously pumped into the microfluidic channel for storage. Meanwhile, the IWD can detect the state of the wound through the temperature and humidity sensor, and use this as feedback to control the liquid metal (LM) heater through a smartphone, thereby realizing the on-demand drug release from the hydrogel. In a mouse model of infected wounds, IWD accelerates wound healing by reducing inflammatory responses, promoting angiogenesis and collagen deposition.

Bioinspired claw-engaged and biolubricated swimming microrobots creating active retention in blood vessels.

Swimming microrobots guided in the circulation system offer considerable promise in precision medicine but currently suffer from problems such as limited adhesion to blood vessels, intensive blood flow, and immune system clearance-all reducing the targeted interaction. A swimming microrobot design with clawed geometry, a red blood cell (RBC) membrane-camouflaged surface, and magnetically actuated retention is discussed, allowing better navigation and inspired by the tardigrade's mechanical claw engagement, coupled to an RBC membrane coating, to minimize blood flow impact. Using clinical intravascular optical coherence tomography in vivo, the microrobots' activity and dynamics in a rabbit jugular vein was monitored, illustrating very effective magnetic propulsion, even against a flow of ~2.1 cm/s, comparable with rabbit blood flow characteristics. The equivalent friction coefficient with magnetically actuated retention is elevated ~24-fold, compared to magnetic microspheres, achieving active retention at 3.2 cm/s, for >36 hours, showing considerable promise across biomedical applications.

A Self-Powered Dielectrophoretic Microparticle Manipulation Platform Based on a Triboelectric Nanogenerator.

Lab-on-a-chip systems aim to integrate laboratory operations on a miniaturized device with broad application prospects in the field of point-of-care testing. However, bulky peripheral power resources, such as high-voltage supplies, function generators, and amplifiers, hamper the commercialization of the system. In this work, a portable, self-powered microparticle manipulation platform based on triboelectrically driven dielectrophoresis (DEP) is reported. A rotary freestanding triboelectric nanogenerator (RF-TENG) and rectifier/filter circuit supply a high-voltage direct-current signal to form a non-uniform electric field within the microchannel, realizing controllable actuation of the microparticles through DEP. The operating mechanism of this platform and the control performance of the moving particles are systematically studied and analyzed. Randomly distributed particles converge in a row after passing through the serpentine channel and various particles are separated owing to the different DEP forces. Ultimately, the high-efficiency separation of live and dead yeast cells is achieved using this platform. RF-TENG as the power source for lab-on-a-chip exhibits better safety and portability than traditional high-voltage power sources. This study presents a promising solution for the commercialization of lab-on-a-chip.

RankAxis: Towards a Systematic Combination of Projection and Ranking in Multi-Attribute Data Exploration.

Projection and ranking are frequently used analysis techniques in multi-attribute data exploration. Both families of techniques help analysts with tasks such as identifying similarities between observations and determining ordered subgroups, and have shown good performances in multi-attribute data exploration. However, they often exhibit problems such as distorted projection layouts, obscure semantic interpretations, and non-intuitive effects produced by selecting a subset of (weighted) attributes. Moreover, few studies have attempted to combine projection and ranking into the same exploration space to complement each other's strengths and weaknesses. For this reason, we propose RankAxis, a visual analytics system that systematically combines projection and ranking to facilitate the mutual interpretation of these two techniques and jointly support multi-attribute data exploration. A real-world case study, expert feedback, and a user study demonstrate the efficacy of RankAxis.

Portable general microfluidic device with complex electric field regulation functions for electrokinetic experiments.

Electrokinetic sample manipulation is a key step for many kinds of microfluidic chips to achieve various functions, such as particle focusing and separation, fluid pumping and material synthesis. But these microfluidic experiments usually rely on large-scale signal generators for power supply, microscopes for imaging and other instruments for analysis, which hampers the portable process of microfluidic technology. Inspired by this situation, we herein designed a portable general microfluidic device (PGMD) with complex electric field regulation functions, which can accurately regulate static or continuous fluid samples. Through the graphical user interface (GUI) and modular design, the PGMD can generate multiple different electrical signals, and the micro-flow of fluid can be pumped through the built-in micropump, which can meet the requirements of most microfluidic experiments. Photos or videos of the microfluidic chip captured by the built-in microscope are received and displayed by a smartphone. We carried out a variety of microfluidic experiments such as induced-charge electroosmosis (ICEO), particle beam exit switching, thermal buoyancy flow and dielectrophoresis (DEP) on the PGMD. In addition, the PGMD can perform rapid microalgae concentration estimation in an outdoor environment, which can be used to guide microalgae cultivation, further demonstrating the development potential of this device in the field of microbial applications. Numerous results show that the PGMD has a high degree of integration and strong reliability, which expands the application of microfluidic electrokinetic experiments and provides technical support for the integration and portability of microfluidic experimental devices.

Liquid metal droplet motion transferred from an alkaline solution by a robot arm.

The excellent motion performance of gallium-based liquid metals (LMs) upon the application of a modest electric field has provided a new opportunity for the development of autonomous soft robots. However, the locomotion of LMs often appears in an alkaline solution, which hampers the application under other different conditions. In this work, a novel robot arm is designed to transfer the motion of the LM from an alkaline solution in a synchronous drive mode. The liquid metal droplet (LMD) at the bottom of the robot arm is actuated using a DC voltage to provide the driving force for the system. By introducing an end effector at the center of the robot arm, the synchronous motion of the system is replicated and can be applied to different situations. The theoretical understanding of continuous electrowetting (CEW) at the LM interface is explained, and then the motion performance of the robot arm against the function of the applied voltage and driving direction is investigated. Moreover, several applications using this robot arm, such as pattern drawing, cargo transportation, and drug concentration detection, are demonstrated. The presented robot arm has the potential to observably expand the application fields of the LM.

Liquid Metal-Based Flexible and Wearable Sensor for Functional Human-Machine Interface.

Rigid sensors are a mature type of sensor, but their poor deformation and flexibility limit their application range. The appearance and development of flexible sensors provide an opportunity to solve this problem. In this paper, a resistive flexible sensor utilizes gallium-based liquid metal (eutectic gallium indium alloy, EGaIn) and poly(dimethylsiloxane) (PDMS) and is fabricated using an injecting thin-line patterning technique based on soft lithography. Combining the scalable fabrication process and unique wire-shaped liquid metal design enables sensitive multifunctional measurement under stretching and bending loads. Furthermore, the flexible sensor is combined with the glove to demonstrate the application of the wearable sensor glove in the detection of finger joint angle and gesture control, which offers the ability of integration and multifunctional sensing of all-soft wearable physical microsystems for human-machine interfaces. It shows its application potential in medical rehabilitation, intelligent control, and so on.

Three Dimensional Printing of Bioinspired Crossed-Lamellar Metamaterials with Superior Toughness for Syntactic Foam Substitution.

Biological materials such as conch shells with crossed-lamellar textures hold impressive mechanical properties due to their capability to realize effective crack control and energy dissipation through the structural synergy of interfacial modulus mismatch and lamellar orientation disparity. Integrating this mechanism with mechanical metamaterial design can not only avoid the catastrophic post-yield stress drop found in traditional architectural materials with uniform lattice structures but also effectively maintain the stress level and improve the energy absorption ability. Herein, a novel bioinspired design strategy that combines regional particularity and overall cyclicity is proposed to innovate the connotation of long-range periodicity inside the metamaterial, in which the node constraint gradient and crossed-lamellar struts corresponding to the core features of conch shells are able to guide the deformation sequence with a self-strengthening response during compression. Detailed in situ experiments and finite element analysis confirm that the rotated broad layer stacking can shorten and impede the shear bands, further transforming the deformation of bioinspired metamaterial into a progressive, hierarchical way, highlighted by the cross-layer hysteresis. Even based on a brittle polymeric resin, excellent specific energy absorption capacity [4544 kJ/kg] has been achieved in this architecture, which far exceeds the reported metal-based syntactic foams for two orders of magnitude. These results offer new opportunities for the bioinspired metamaterials to substitute the widespread syntactic foams in specific applications required for both lightweight and energy absorption.

Numerical investigation of field-effect control on hybrid electrokinetics for continuous and position-tunable nanoparticle concentration in microfluidics.

We introduce herein an effective way for continuous delivery and position-switchable trapping of nanoparticles via field-effect control on hybrid electrokinetics (HEK). Flow field-effect transistor exploiting HEK delicately combines horizontal linear electroosmosis and transversal nonlinear electroosmosis of a shiftable flow stagnation line (FSL) on gate terminals under DC-biased AC forcing. The microfluidic nanoparticle concentrator proposed herein makes use of a simple device geometry, in which an individual or a series of planar metal strips serving as gate electrode (GE) are subjected to a hybrid gate voltage signal and arranged in parallel between a pair of 3D driving electrodes. On the application of a DC-biased AC electric field across channel length direction, all the GE are electrochemically polarized, and the action of imposed hybrid electric field on the multiple-frequency bipolar counterions within the composite-induced double layer generates two counter-rotating induced-charge electroosmotic (ICEO) micro-vortices on top of each GE. Symmetry breaking in ICEO flow profile occurs once the gate voltage deviates from natural floating potential of corresponding GE. The gate voltage offset not only results in an additional pump motion of working fluid for enhanced electroosmotic transport but also directly changes the location of FSL where nanoparticles are preferentially collected by field-effect HEK. Our results of field-effect control on HEK are supposed to guide an elaborate design of flexible electrokinetic frameworks embedding coplanar metal strips for a high degree of freedom analyte manipulation in modern micro-total-analytical systems.

Expandable carboxymethyl chitosan/cellulose nanofiber composite sponge for traumatic hemostasis.

Uncontrolled hemorrhage poses a severe life-threatening situation. However, traditional hemostats still have various limitations. It is urgent to develop a material with excellent biocompatibility and hemostatic ability. Evidence has shown that carboxymethyl chitosan (CMCS) has hemostatic properties and good compatibility. Herein, we develop an expandable hemostatic sponge by modifying CMCS with cellulose nanofibrils (CNFs) through the CO-NH cross-linking method. We verified its potential as a hemostatic agent both in vivo and in vitro. The results demonstrated that the prepared carboxymethyl chitosan/cellulose nanofiber composite (CNF-CMCS) sponges could absorb blood, quickly expand to exert pressure in the wound, and exhibit an excellent coagulation ability. The CNF-CMCS sponges significantly decreased the bleeding time and blood loss in several hemorrhage models and possessed a significant advantage in treating the deep penetrating injury hemorrhage. Therefore, the sponges provide a unique application prospect and potential as a penetrating trauma hemostatic agent.

Numerical characterization of inter-core coalescence by AC dielectrophoresis in double-emulsion droplets.

The utilization of an alternating current electric field provides a good means to achieve controlled coalescence between paired inner cores encapsulated in water-in-oil-in-water double-emulsion (DE) droplets. Although previous studies have experimentally determined the conditions under which inter-core electrokinetic fusion occurs, the transient interfacial dielectrophoretic (DEP) dynamics key to understand the underlying fluid mechanics is still unclear from a physical point of view. By coupling DEP motion of two-phase flow to phase-field formulation, bulk-coupled numerical simulations are conducted to characterize the spatial-temporal evolution of the surface charge wave and the resulting nonlinear electrical force induced at both the core/shell and medium/shell oil/water interfaces. The effect of interfacial charge relaxation and droplet geometry on inter-core attractive dipolar interaction is investigated within a wide parametric space, and four distinct device operation modes, including normal inter-core fusion, shell elongation, partial core leakage, and complete core release, are well distinguished from one another by flow regime argumentation. Our results herein reveal for the first time the hitherto unknown transient electrohydrodynamic fluid motion of DE droplet driven by Maxwell-Wagner structural polarization. The dynamic simulation method proposed in present study points out an effective outlet to predict the nonlinear electrokinetic behavior of multicore DE droplets for realizing a more controlled triggering of microscale reactions for a wide range of applications in drug discovery, skin care, and food industry.

A tripodal wheeled mobile robot driven by a liquid metal motor.

As a novel driving concept, the liquid metal motor (LMM) has been regarded as a promising actuator due to its unique traits, such as infinitely variable speed, lack of transmission chain, convenient maintenance, and silence. However, at present, driving devices based on this material are still in the preliminary and rudimentary stage, and representative application examples are scarce. Therefore, an 8-shaped tripodal wheeled mobile robot (WMR) completely driven by a LMM is designed in this study to further prove the practicability of this material. Through combining the Marangoni surface flow on a liquid metal droplet (LMD) caused by an electrochemical reaction and the eccentric torque generated by the change in droplet shape and position, the two independently driven wheels of the mobile robot are actuated at differential moving speeds. Additionally, a matching control module, a cell phone application, and a battery have been developed and added for wireless control of three types of driving functions (moving forward, steering, and stopping). It is expected that this work could further advance the development and application of LMMs and bring new ideas to the design of WMRs.

A visual portable microfluidic experimental device with multiple electric field regulation functions.

High portability and miniaturization are two of the most important objectives pursued by microfluidic methods. However, there remain many challenges for the design of portable and visual microfluidic devices (e.g., electrokinetic experiments) due to the use of a microscope and power supply. To this end, we report a visual portable microfluidic experimental device (PMED) with multiple electric field regulation functions, which can realize the electric field regulation functions of various basic microfluidic experiments through modular design. The internal reaction process of the microfluidic chip is displayed by a smartphone, and the experimental results are analyzed using a mobile phone application (APP). Taking the induced-charge electroosmosis (ICEO) particle focusing phenomenon as an example, we carried out detailed experiments on PMED and obtained conclusions consistent with numerical simulations. In addition to ICEO experiments, other functions such as alternating electroosmosis (ACEO), thermal buoyancy convection, and dielectrophoresis (DEP) can be realized by replacing module-specific covers. The device expands the application of microfluidic experiments and provides a certain reference for the further integration and portability of subsequent microfluidic experiment devices.

Fluid pumping by liquid metal droplet utilizing ac electric field.

We report a unique phenomenon in which liquid metal droplets (LMDs) under a pure ac electric field pump fluid. Unlike the directional pumping that occurs upon reversing the electric field polarity under a dc signal, this phenomenon allows the direction of fluid motion to be switched by simply shifting the position of the LMD within the cylindrical chamber. The physical mechanism behind this phenomenon has been termed Marangoni flow, caused by nonlinear electrocapillary stress. Under the influence of a localized, asymmetric ac electric field, the polarizable surface of the position-offset LMD produces a net time-averaged interfacial tension gradient that scales with twice the field strength, and thus pumps fluid unidirectionally. However, the traditional linear RC circuit polarization model of the LMD/electrolyte interface fails to capture the correct pump-flow direction when the thickness of the LMD oxide skin is non-negligible compared to the Debye length. Therefore, we developed a physical description by treating the oxide layer as a distributed capacitance with variable thickness and connected with the electric double layer. The flow profile is visualized via microparticle imaging velocimetry, and excellent consistency is found with simulation results obtained from the proposed nonlinear model. Furthermore, we investigate the effects of relevant parameters on fluid pumping and discuss a special phenomenon that does not exist in dc control systems. To our knowledge, no previous work addresses LMDs in this manner and uses a zero-mean ac electric field to achieve stable, adjustable directional pumping of a low-conductivity solution.

Controllable Fabrication of Molecularly Imprinted Microspheres with Nanoporous and Multilayered Structure for Dialysate Regeneration.

Adsorption of urea from dialysate is essential for wearable artificial kidneys (WRK). Molecularly imprinted microspheres with nanoporous and multilayered structures are prepared based on liquid-liquid phase separation (LLPS), which can selectively adsorb urea. In addition, we combine the microspheres with a designed polydimethylsiloxane (PDMS) chip to propose an efficient urea adsorption platform. In this work, we propose a formulation of LLPS including Tripropylene glycol diacrylate (TPGDA), ethanol, and acrylic acid (30% v/v), to prepare urea molecularly imprinted microspheres in a simple and highly controllable method. These microspheres have urea molecular imprinting sites on the surface and inside, allowing selective adsorption of urea and preservation of other essential constituents. Previous static studies on urea adsorption have not considered the combination between urea adsorbent and WRK. Therefore, we design the platform embedded with urea molecular imprinted microspheres, which can disturb the fluid motion and improve the efficiency of urea adsorption. These advantages enable the urea absorption platform to be highly promising for dialysate regeneration in WRK.

Fabrication of syntactic foam fillers via integrated on/off-chip microfluidic methods for optimized geopolymer composites.

To meet the evolving requirements of material designability, sustainability, and eco-friendliness, the development of syntactic foams puts great emphasis on filler optimization and matrix selection. Here, we present a novel microfluidic expansion coupled with the thermal contraction method to improve the fabrication of syntactic foam fillers (SFFs), highlighted by the independently regulated parameters in contrast to the hydrodynamic regulation approach. The eccentricity of droplets can be reduced via osmotic swelling under a hypotonic circumstance and further preserved through real-time UV polymerization. The eccentricity of shrunken SFFs after heat treatment is found to inherit the regulated configurations of droplets and this homogeneity difference of shell thickness can result in the mechanical performance deviation. Then, we choose greener material, geopolymer, as the binder matrix and prepare geopolymer syntactic foams (GSFs) by mold casting. The inclusion of SFFs has increased the atomic volume ratio of Si : Al in the matrix, thereby forming a strong interfacial bonding. The compressive yield strength of GSFs is inversely proportional to the volume fraction of SFFs, and the specimens after thermal exposure can still maintain their shape integrity and exhibit similar mechanical performance even with the formation of cracks. Moreover, the fire-resistant performance of GSFs has been visually validated by the combustion comparison experiment, characterized as flame retardancy, smoke-free, and basically intact morphology, which should give insights into the design and fabrication of functional composites.

Desktop-level small automatic guided vehicle driven by a liquid metal droplet.

Gallium-based liquid metals (LMs) are a new type of intelligent material, and their ability to move under the action of an electric field provides new opportunities for the design of small flexible vehicles. However, due to the extremely high fluidity of LMs and the poor automatic control ability of LM vehicles, it's still a huge challenge to control the movement of LMs flexibly and accurately. Therefore, in this paper, a small traction vehicle is designed by putting the flexible LM in rigid armor to make the movement more controllable. Moreover, a desktop-level small automatic guided vehicle (sAGV) system is built by using an external control circuit to follow a predetermined trajectory. Firstly, the basic characteristics of the vehicles driven by a LM droplet are simulated and analyzed. Then the effects of different factors on the movement velocity of the vehicles are measured by experiment. Finally, as a preliminary application test, the sAGV system is used to control the vehicles following a specific trajectory and realize the targeted transportation of cargos. The sAGV system designed in this paper can realize the automatic and precise control of the movement of the small vehicle. The current findings will inspire the further construction of complex small operating systems and the realization of accurate control.

DC electric field-driven heartbeat phenomenon of gallium-based liquid metal on a floating electrode.

The heart beating phenomenon of room temperature liquid metal (LM) mercury has attracted much attention in the past years, but its research and application are limited because of the low vapor pressure and high toxicity. Here, a fundamental scientific finding is reported that the non-toxic eutectic gallium indium (EGaIn) alloy droplets beat periodically at a certain frequency based on a floating electrode under the stimulation of the direct current (DC) field. The essential characteristics of heart beating are the displacement and the projected area change of the LM droplet. The mechanism of this phenomenon is the self-regulation of interfacial tension caused by chemical oxidation, chemical corrosion, and continuous electrowetting. In this article, a series of experiments are also carried out to examine the effects of different factors on the heartbeat, such as voltage, the volume of the droplet, the droplet immersion depth, the electrolyte solution concentration, the distance of electrodes, and the type of floating electrode. Finally, the heartbeat state and application boundary of the LM droplet under different conditions are summarized by imitating the human life process. The periodic changes of the LM droplet under an external DC electric field provide a new method to simulate the beating of the heart artificially, and can be applied to the research of organ chip fluid pumping in the future.