Recently, research on particle migration in non-Newtonian viscoelastic fluids has gained considerable attention. In a viscoelastic fluid, three dimensional (3D) particle focusing can be easily ...realized in simple channels without the need for any external force fields or complex microchannel structures compared with that in a Newtonian fluid. Due to its promising properties for particle precise focusing and manipulation, this field has been developed rapidly, and research on the field has been shifted from fundamentals to applications. This review will elaborate the recent progress of particle migration in viscoelastic fluids, especially on the aspect of applications. The hydrodynamic forces on the micro/nano particles in viscoelastic fluids are discussed. Next, we elaborate the basic particle migration in viscoelasticity-dominant fluids and elasto-inertial fluids in straight channels. After that, a comprehensive review on the applications of viscoelasticity-induced particle migration (particle separation, cell deformability measurement and alignment, particle solution exchange, rheometry-on-a-chip and others) is presented; finally, we thrash out some perspectives on the future directions of particle migration in viscoelastic fluids.
In this review, we discuss the up-to-date progress of particle migration in viscoelastic fluids mainly from the aspect of applications, laying out a comprehensive perspective on their potential in future lab-on-a-chip platforms.
Conductive elastic composites have been used widely in soft electronics and soft robotics. These composites are typically a mixture of conductive fillers within elastomeric substrates. They can sense ...strain via changes in resistance resulting from separation of the fillers during elongation. Thus, most elastic composites exhibit a negative piezoconductive effect, i.e. the conductivity decreases under tensile strain. This property is undesirable for stretchable conductors since such composites may become less conductive during deformation. Here, we report a liquid metal-filled magnetorheological elastomer comprising a hybrid of fillers of liquid metal microdroplets and metallic magnetic microparticles. The composite's resistivity reaches a maximum value in the relaxed state and drops drastically under any deformation, indicating that the composite exhibits an unconventional positive piezoconductive effect. We further investigate the magnetic field-responsive thermal properties of the composite and demonstrate several proof-of-concept applications. This composite has prospective applications in sensors, stretchable conductors, and responsive thermal interfaces.
High-entropy alloys (HEAs) with unique physicochemical properties have attracted tremendous attention in many fields, yet the precise control on dimension and morphology at atomic level remains ...formidable challenges. Herein, we synthesize unique PtRuNiCoFeMo HEA subnanometer nanowires (SNWs) for alkaline hydrogen oxidation reaction (HOR). The mass and specific activities of HEA SNWs/C reach 6.75 A mg
and 8.96 mA cm
, respectively, which are 2.8/2.6, 4.1/2.4, and 19.8/18.7 times higher than those of HEA NPs/C, commercial PtRu/C and Pt/C, respectively. It can even display enhanced resistance to CO poisoning during HOR in the presence of 1000 ppm CO. Density functional theory calculations reveal that the strong interactions between different metal sites in HEA SNWs can greatly regulate the binding strength of proton and hydroxyl, and therefore enhances the HOR activity. This work not only provides a viable synthetic route for the fabrication of Pt-based HEA subnano/nano materials, but also promotes the fundamental researches on catalysis and beyond.
This paper studies the set stabilization of switched Boolean control networks, in which a feedback control design algorithm is presented by a constructive method. Necessary and sufficient conditions ...of the set stabilization of switched Boolean control networks under arbitrary switching signals are presented for the cases of the control input relying on switching signals or not, respectively. Furthermore, the corresponding switching-signal-independent and switching-signal-dependent controllers are provided for these two cases, respectively. It is shown that the condition of the switching-signal-dependent controller is less conservative than the one of the switching-signal-independent controller. Finally, examples are given to illustrate the effectiveness of the proposed results.
Abstract
CO
2
hydrogenation has attracted great attention, yet the quest for highly-efficient catalysts is driven by the current disadvantages of poor activity, low selectivity, and ambiguous ...structure-performance relationship. We demonstrate here that C
3
N
4
-supported Cu single atom catalysts with tailored coordination structures, namely, Cu–N
4
and Cu–N
3
, can serve as highly selective and active catalysts for CO
2
hydrogenation at low temperature. The modulation of the coordination structure of Cu single atom is readily realized by simply altering the treatment parameters. Further investigations reveal that Cu–N
4
favors CO
2
hydrogenation to form CH
3
OH via the formate pathway, while Cu–N
3
tends to catalyze CO
2
hydrogenation to produce CO via the reverse water-gas-shift (RWGS) pathway. Significantly, the CH
3
OH productivity and selectivity reach 4.2 mmol g
–1
h
–1
and 95.5%, respectively, for Cu–N
4
single atom catalyst. We anticipate this work will promote the fundamental researches on the structure-performance relationship of catalysts.
The controlled actuation of gallium liquid‐metal (LM) alloys has presented new and exciting opportunities for constructing mobile robots with structural flexibility. However, the locomotion of ...current LM‐based actuators often relies on inducing a gradient of interfacial tension on the LM surface within electrolytes, which limits their application outside a liquid environment. In this work, a wheeled robot using a LM droplet as the core of the driving system is developed that enables it to move outside liquid environment. The LM droplet inside the robot is actuated using a voltage to alter the robot's center of gravity, which in turn generates a rolling torque and induces continuous locomotion at a steady speed. A series of experiments is carried out to examine the robot's performance and then to develop a dynamic model using the Lagrange method to understand the locomotion. An untethered and self‐powered wheeled robot that utilizes mini‐lithium‐batteries is also demonstrated. This study is envisaged to have the potential to expand current research on LM‐based actuators to realize future complex robotic systems.
A novel wheeled robot using a liquid metal (LM) as the core of the driving module is developed. The LM droplet within the robot is actuated using a voltage to alter the robot's center of gravity for generating a rolling torque; this induces continuous locomotion of the robot at a steady speed outside the liquid environment in both self‐driven and untethered manners.
Functional nanoparticles comprised of liquid metals, such as eutectic gallium indium (EGaIn) and Galinstan, present exciting opportunities in the fields of flexible electronics, sensors, catalysts, ...and drug delivery systems. Methods used currently for producing liquid metal nanoparticles have significant disadvantages as they rely on both bulky and expensive high‐power sonication probe systems, and also generally require the use of small molecules bearing thiol groups to stabilize the nanoparticles. Herein, an innovative microfluidics‐enabled platform is described as an inexpensive, easily accessible method for the on‐chip mass production of EGaIn nanoparticles with tunable size distributions in an aqueous medium. A novel nanoparticle‐stabilization approach is reported using brushed polyethylene glycol chains with trithiocarbonate end‐groups negating the requirements for thiol additives while imparting a “stealth” surface layer. Furthermore, a surface modification of the nanoparticles is demonstrated using galvanic replacement and conjugation with antibodies. It is envisioned that the demonstrated microfluidic technique can be used as an economic and versatile platform for the rapid production of liquid metal‐based nanoparticles for a range of biomedical applications.
An innovative microfluidics‐enabled platform as an inexpensive, easily accessible method for the on‐chip mass production of eutectic gallium indium nanoparticles with tunable size distributions is developed. A novel nanoparticle stabilization approach in an aqueous medium using brushed polyethylene glycol chains with trithiocarbonate end‐groups is also investigated. Furthermore, a surface modification of the nanoparticles is demonstrated using galvanic replacement and conjugation with antibodies.
In this paper, we study the distributed synchronization and pinning distributed synchronization of stochastic coupled neural networks via randomly occurring control. Two Bernoulli stochastic ...variables are used to describe the occurrences of distributed adaptive control and updating law according to certain probabilities. Both distributed adaptive control and updating law for each vertex in a network depend on state information on each vertex's neighborhood. By constructing appropriate Lyapunov functions and employing stochastic analysis techniques, we prove that the distributed synchronization and the distributed pinning synchronization of stochastic complex networks can be achieved in mean square. Additionally, randomly occurring distributed control is compared with periodically intermittent control. It is revealed that, although randomly occurring control is an intermediate method among the three types of control in terms of control costs and convergence rates, it has fewer restrictions to implement and can be more easily applied in practice than periodically intermittent control.
Artificial muscles possess a vast potential in accelerating the development of robotics, exoskeletons, and prosthetics. Although a variety of emerging actuator technologies are reported, they suffer ...from several issues, such as high driving voltages, large hysteresis, and water intolerance. Here, a liquid metal artificial muscle (LMAM) is demonstrated, based on the electrochemically tunable interfacial tension of liquid metal to mimic the contraction and extension of muscles. The LMAM can work in different solutions with a wide range of pH (0–14), generating actuation strains of up to 87% at a maximum extension speed of 15 mm s−1. More importantly, the LMAM only needs a very low driving voltage of 0.5 V. The actuating components of the LMAM are completely built from liquids, which avoids mechanical fatigue and provides actuator linkages without mechanical constraints to movement. The LMAM is used for developing several proof‐of‐concept applications, including controlled displays, cargo deliveries, and reconfigurable optical reflectors. The simplicity, versatility, and efficiency of the LMAM are further demonstrated by using it to actuate the caudal fin of an untethered bionic robotic fish. The presented LMAM has the potential to extend the performance space of soft actuators for applications from engineering fields to biomedical applications.
A liquid metal artificial muscle (LMAM) based on the electrochemically tunable interfacial tension of EGaIn liquid metal is demonstrated to mimic the contraction and extension of muscles. The actuating components of the LMAM are completely built from liquids, which avoids mechanical fatigue and provides actuator linkages without mechanical constraints to movement. Various proof‐of‐concept applications are demonstrated using the LMAM.
In this paper, the consensus problem is studied for a class of multi-agent systems with sampled data and packet losses, where random and deterministic packet losses are considered, respectively. For ...random packet losses, a Bernoulli-distributed white sequence is used to describe packet dropouts among agents in a stochastic way. For deterministic packet losses, a switched system with stable and unstable subsystems is employed to model packet dropouts in a deterministic way. The purpose of this paper is to derive consensus criteria, such that linear multi-agent systems with sampled-data and packet losses can reach consensus. By means of the Lyapunov function approach and the decomposition method, the design problem of a distributed controller is solved in terms of convex optimization. The interplay among the allowable bound of the sampling interval, the probability of random packet losses, and the rate of deterministic packet losses are explicitly derived to characterize consensus conditions. The obtained criteria are closely related to the maximum eigenvalue of the Laplacian matrix versus the second minimum eigenvalue of the Laplacian matrix, which reveals the intrinsic effect of communication topologies on consensus performance. Finally, simulations are given to show the effectiveness of the proposed results.
PDF
