Disorder-to-order transition induced by spontaneous cooling regulation in robotic active matter

In classical matter systems, typical phase-transition phenomena usually stem from changes in state variables, such as temperature and pressure, induced by external regulations such as heat transfer and volume adjustment. However, in active matter systems, the self-propulsion nature of active particles endows the systems with the ability to induce unique collectivestate transitions by spontaneously regulating individual properties to alter the overall states. Based on an innovative robot-swarm experimental system, we demonstrate a field-driven active matter model capable of modulating individual motion behaviors through interaction with a recoverable environmental resource field by the resource perception and consumption.In the simulated model, by gradually reducing the individual resource-conversion coefficient over time, this robotic active matter can spontaneously decrease the overall level of motion, thereby actively achieving a regulation behavior like the cooling-down control. Through simulation calculations, we discover that the spatial structures of this robotic active matter convert from disorder to order during this process, with the resulting ordered structures exhibiting a high self-adaptability on the geometry of the environmental boundaries.

Orderly hysteresis in field-driven robot swarm active matter

Boundary effect and time-reversal symmetry are hot topics in active matter. We present a biology-inspired robotenvironment-interaction active matter system with the field-drive motion and the rules of resource search, resource consumption, and resource recovery. In an environmental compression–expansion cycle, the swarm emerges a series of boundary-dependent phase transitions, and the whole evolution process is time-reversal symmetry-breaking;we call this phenomenon “orderly hysteresis”. We present the influence of the environmental recovery rate on the dynamic collective behavior of the swarm.

Skin formation in drying a film of soft matter solutions：Application of solute based Lagrangian scheme

When a film of soft matter solutions is being dried, a skin layer often forms at its surface, which is a gel-like elastic phase made of concentrated soft matter solutions. We study the dynamics of this process by using the solute based Lagrangian scheme which was proposed by us recently. In this scheme, the process of the gelation（i.e., the change from sol to gel） can be naturally incorporated in the diffusion equation. Effects of the elasticity of the skin phase, the evaporation rate of the solvents, and the initial concentration of the solutions are discussed. Moreover, the condition for the skin formation is provided.

Bio-inspired environmental adaptability of swarm active matter

How biologically active matters survive adaptively in complex and changeable environments is a common concern of scientists.Genetics,evolution and natural selection are vital factors in the process of biological evolution and are also the key to survival in harsh environments.However,it is challenging to intuitively and accurately reproduce such longterm adaptive survival processes in the laboratory.Although simulation experiments are intuitive and efficient,they lack fidelity.Therefore,we propose to use swarm robots to study the adaptive process of active matter swarms in complex and changeable environments.Based on a self-built virtual environmental platform and a robot swarm that can interact with the environment,we introduce the concept of genes into the robot system,giving each robot unique digital genes,and design robot breeding methods and rules for gene mutations.Our previous work[Proc.Natl.Acad.Sci.USA 119 e2120019119(2022)]has demonstrated the effectiveness of this system.In this work,by analyzing the relationship between the genetic traits of the population and the characteristics of environmental resources,and comparing different experimental conditions,we verified in both robot experiments and corresponding simulation experiments that agents with genetic inheritance can survive for a long time under the action of natural selection in periodically changing environments.We also confirmed that in the robot system,both breeding and mutation are essential factors.These findings can help answer the practical scientific question of how individuals and swarms can successfully adapt to complex,dynamic,and unpredictable actual environments.

Molecular dynamics simulations on the interactions between nucleic acids and a phospholipid bilayer

Recently,lipid nanoparticles(LNPs)have been extensively investigated as non-viral carriers of nucleic acid vaccines due to their high transport efficiency,safety,and straightforward production and scalability.However,the molecular mechanism underlying the interactions between nucleic acids and phospholipid bilayers within LNPs remains elusive.In this study,we employed the all-atom molecular dynamics simulation to investigate the interactions between single-stranded nucleic acids and a phospholipid bilayer.Our findings revealed that hydrophilic bases,specifically G in single-stranded RNA(ssRNA)and single-stranded DNA(ssDNA),displayed a higher propensity to form hydrogen bonds with phospholipid head groups.Notably,ssRNA exhibited stronger binding energy than ssDNA.Furthermore,divalent ions,particularly Ca2+,facilitated the binding of ssRNA to phospholipids due to their higher binding energy and lower dissociation rate from phospholipids.Overall,our study provides valuable insights into the molecular mechanisms underlying nucleic acidphospholipid interactions,with potential implications for the nucleic acids in biotherapies,particularly in the context of lipid carriers.

Membrane tension evolution and mechanical regulation of melittin-induced membrane poration

Membrane tension plays a crucial role in various fundamental cellular processes,with one notable example being the T cell-mediated elimination of tumor cells through perforin-induced membrane perforation by amplifying cellular force.However,the mechanisms governing the regulation of biomolecular activities at the cell interface by membrane tension remain elusive.In this study,we investigated the correlation between membrane tension and poration activity of melittin,a prototypical pore-forming peptide,using dynamic giant unilamellar vesicle leakage assays combined with flickering tension analysis,molecular dynamics simulations,and live cell assays.The results demonstrate that an increase in membrane tension enhances the activity of melittin,particularly near its critical pore-forming concentration.Moreover,peptide actions such as binding,insertion,and aggregation in the membrane further influence the evolution of membrane tension.Live cell experiments reveal that artificially enhancing membrane tension effectively enhances melittin’s ability to induce pore formation and disrupt membranes,resulting in up to a ten-fold increase in A549 cell mortality when exposed to a concentration of 2.0-μg·mL^(-1)melittin.Our findings elucidate the relationship between membrane tension and the mechanism of action as well as pore-forming efficiency of melittin,while providing a practical mechanical approach for regulating functional activity of molecules at the cell-membrane interface.

Estimation of cancer cell migration in biomimetic random/oriented collagen fiber microenvironments

Increasing data indicate that cancer cell migration is regulated by extracellular matrixes and their surrounding biochemical microenvironment,playing a crucial role in pathological processes such as tumor invasion and metastasis.However,conventional two-dimensional cell culture and animal models have limitations in studying the influence of tumor microenvironment on cancer cell migration.Fortunately,the further development of microfluidic technology has provided solutions for the study of such questions.We utilize microfluidic chip to build a random collagen fiber microenvironment(RFM)model and an oriented collagen fiber microenvironment(OFM)model that resemble early stage and late stage breast cancer microenvironments,respectively.By combining cell culture,biochemical concentration gradient construction,and microscopic imaging techniques,we investigate the impact of different collagen fiber biochemical microenvironments on the migration of breast cancer MDA-MB-231-RFP cells.The results show that MDA-MB-231-RFP cells migrate further in the OFM model compared to the RFM model,with significant differences observed.Furthermore,we establish concentration gradients of the anticancer drug paclitaxel in both the RFM and OFM models and find that paclitaxel significantly inhibits the migration of MDA-MB-231-RFP cells in the RFM model,with stronger inhibition on the high concentration side compared to the low concentration side.However,the inhibitory effect of paclitaxel on the migration of MDA-MB-231-RFP cells in the OFM model is weak.These findings suggest that the oriented collagen fiber microenvironment resembling the late-stage tumor microenvironment is more favorable for cancer cell migration and that the effectiveness of anticancer drugs is diminished.The RFM and OFM models constructed in this study not only provide a platform for studying the mechanism of cancer development,but also serve as a tool for the initial measurement of drug screening.

Confinement-induced nanocrystal alignment of conjugated polymer by the soft-stamped nanoimprint lithography

Soft-stamped nanoimprint lithography（NIL） is considered as one of the most effective processes of nanoscale patterning because of its low cost and high throughput. In this work, this method is used to emboss the poly（9, 9-dioctylfluorene）film. By reducing the linewidth of the nanogratings on the stamp, the orientations of nanocrystals are confined along the grating vector in the nanoimprint process, where the confinement linewidth is comparable to the geometrical size of the nanocrystal. When the linewidth is about 400 nm, the poly（9, 9-dioctylfluorene）（PFO） nanocrystals could be orderly arranged in the nanogratings, so that both pattern transfer and well-aligned nanocrystal arrangement could be achieved in a single step by the soft-stamped NIL. The relevant mechanism of the nanocrystalline alignment in these nanogratings is fully discussed. The modulation of nanocrystal alignment is of benefit to the charge mobilities and other performances of PFO-based devices for the future applications.

High-efficiency 3D cell spheroid formation via the inertial focusing effect in rotating droplets

The three-dimensional(3D)spheroid culture has been widely used as an important tool in biological research.Although several techniques have been established to prepare cell spheroids,fast and controllable production remains one of the major challenges.In this study,a simple but efficient method utilizing the inertial focusing effect in rotating hanging droplets is demonstrated for the rapid and controllable production of cell spheroids.

Local Rotational Jamming and Multi-Stage Hyperuniformities in an Active Spinner System

An active system consisting of many self-spinning dimers is simulated, and a distinct local rotational jamming transition is observed as the density increases. In the low density regime, the system stays in an absorbing state,in which each dimer rotates independently subject to the applied torque;while in the high density regime,a fraction of the dimers become rotationally jammed into local clusters, and the system exhibits microphaseseparation like two-phase morphologies. For high enough densities, the system becomes completely jammed in both rotational and translational degrees of freedom. Such a simple system is found to exhibit rich and multiscale disordered hyperuniformities among the above phases: the absorbing state shows a critical hyperuniformity of the strongest class and subcritically preserves the vanishing density fluctuation scaling up to some length scale;the locally jammed state shows a two-phase hyperuniformity conversely beyond some length scale with respect to the phase cluster sizes;the totally jammed state appears to be a monomer crystal, but intrinsically loses large-scale hyperuniformity. These results are inspiring for designing novel phase-separation and disordered hyperuniform systems through dynamical organization.

Parallel DNA G-Quadruplex Induced and Stabilized by Curaxin CBL0137

G-quadruplex(G4)is one of the higher-order DNA structures in guanine-rich sequences which are widely distributed across the genome.Due to their presence in oncogenic promoters and telomeres,G4 DNA structures become the novel targets in anticancer drug designs.Curaxin CBL0137,as an important candidate anticancer drug,can effectively inhibit the growth of multiple cancers.Although there is evidence that anticancer activity of curaxin is associated with its ability to bind DNA and to change the DNA topology,its therapeutic target and the underlying anti-cancer mechanism are still unclear.Here we show,for the first time,that curaxin CBL0137 induces G4 folding from anti-parallel to parallel structures,by single-molecule fluorescence resonance energy transfer technique.More importantly,we find that curaxin CBL0137 promotes G4 folding as well as stabilizes the folded G4 structures with long loops,giving a novel insight into effects of curaxin CBL0137 on DNA structures.Our work provides new ideas for the therapeutic mechanism of curaxin CBL0137 and for designs of new G4-targeting anticancer drugs.

Tunable Memory and Activity of Quincke Particles in Micellar Fluid

Memory can remarkably modify the collective behavior of active particles. We show that, in a micellar fluid, Quincke particles driven by a square-wave electric field exhibit a frequency-dependent memory. Upon increasing the frequency, a memory of directions emerges, whereas the activity of particles decreases. As the activity is dominated by interaction, Quincke particles aggregate and form dense clusters, in which the memory of the direction is further enhanced due to the stronger electric interactions. The density-dependent memory and activity result in dynamic heterogeneity in flocking and offer a new opportunity for research of collective motions.

Preface to the special topic on active matter

Active matter refers to systems composed of individual units that consume locally stored energy to generate mechanical motion.Examples of active matter include biological entities such as schools of fish,flocks of birds,bacterial colonies,and synthetic systems such as self-propelled colloidal particles and engineered nanobots.The study of active matter seeks to provide understanding for complex behaviors and emergent phenomena arising from interactions of these energy-consuming units,with implications for fields ranging from physics and biology to materials science and robotics.

An Ultra‑Durable Windmill‑Like Hybrid Nanogenerator for Steady and Efficient Harvesting of Low‑Speed Wind Energy

Wind energy is one of the most promising and renewable energy sources;however,owing to the limitations of device structures,collecting low-speed wind energy by triboelectric nanogenerators(TENGs)is still a huge challenge.To solve this problem,an ultra-durable and highly efficient windmill-like hybrid nanogenerator(W-HNG)is developed.Herein,the W-HNG composes coupled TENG and electromagnetic generator(EMG)and adopts a rotational contact-separation mode.This unique design efficiently avoids the wear of friction materials and ensures a prolonged service life.Moreover,the generator group is separated from the wind-driven part,which successfully prevents rotation resistance induced by the friction between rotor and stator in the conventional structures,and realizes low-speed wind energy harvesting.Additionally,the output characteristics of TENG can be complementary to the different performance advantages of EMG to achieve a satisfactory power production.The device is successfully driven when the wind speed is 1.8 m s−1,and the output power of TENG and EMG can achieve 0.95 and 3.7 mW,respectively.After power management,the W-HNG has been successfully applied as a power source for electronic devices.This work provides a simple,reliable,and durable device for improved performance toward large-scale low-speed breeze energy harvesting.

Magnetic Array Assisted Triboelectric Nanogenerator Sensor for Real‑Time Gesture Interaction

In human-machine interaction,robotic hands are useful in many scenarios.To operate robotic hands via gestures instead of handles will greatly improve the convenience and intuition of human-machine interaction.Here,we present a magnetic array assisted sliding triboelectric sensor for achieving a real-time gesture interaction between a human hand and robotic hand.With a finger’s traction movement of flexion or extension,the sensor can induce positive/negative pulse signals.Through counting the pulses in unit time,the degree,speed,and direction of finger motion can be judged in realtime.The magnetic array plays an important role in generating the quantifiable pulses.The designed two parts of magnetic array can transform sliding motion into contact-separation and constrain the sliding pathway,respectively,thus improve the durability,low speed signal amplitude,and stability of the system.This direct quantization approach and optimization of wearable gesture sensor provide a new strategy for achieving a natural,intuitive,and real-time human-robotic interaction.

Fabricating a reactive surface on the fibroin film by a room-temperature plasma jet array for biomolecule immobilization

A simple dielectric barrier discharge（DBD） jet array was designed with a liquid electrode and helium gas.The characteristics of the jet array discharge and the preliminary polymerization with acrylic acid（AA） monomer were presented.The plasma reactor can produce a cold jet array with a gas temperature lower than 315 K,using an applied discharge power between 6 W and 30 W（V dis × I dis）.A silk fibroin film（SFF） was modified using the jet array and AA monomer,and the treated SFF samples were characterized by atomic force microscopy（AFM）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FTIR）,and contact angle（CA）.The deposition rate of the poly acrylic acid（PAA） was able to reach 300 nm/min,and the surface roughness and energy increased with the AA flow rate.The FTIR results indicate that the modified SFF had more carboxyl groups（-COOH） than the original SFF.This latter characteristic allowed the modified SFF to immobilize more quantities of antimicrobial peptide（AP,LL-37） which inhibited the Escherichia coli（E.Coli） effectively.

Onsager principle as a tool for approximation

Onsager principle is the variational principle proposed by Onsager in his celebrated paper on the reciprocal relation.The principle has been shown to be useful in deriving many evolution equations in soft matter physics.Here the principle is shown to be useful in solving such equations approximately.Two examples are discussed：the diffusion dynamics and gel dynamics.Both examples show that the present method is novel and gives new results which capture the essential dynamics in the system.

Detection of Electronic Coherence via Two-Dimensional Electronic Spectroscopy in Condensed Phase

Two dimensional Fourier transforrn electronic spectroscopy （2DES） in the visible region enables direct observation of complex dynamics of molecules including quantum coherence in the condensed phase. This review aims to provide a bridge between the principles and intuitive physical description of 2DES for tutorial purpose. Special emphasis is laid upon how 2DES circumvents the restrictions from both uncertainty principle and the wave-packet collapse during the coherent detection, leading to the successful detection of the coherence in terms of energy difference between the eigenstates showing as the quantum beats; then upon the possible mixing among the pure electronic transition, single-rnode and multi-mode coupled vibronic transition leading to the observed beating phenomena. Finally, recent ad- vances in experimentally distinguishing between the electronic coherence and the vibrational coherence are briefly discussed.

Experimental and numerical study on energy dissipation in freely cooling granular gases under microgravity

Energy dissipation is one of the most important properties of granular gas, which makes Its behavior dltterent trom that of molecular gas. In this work we report our investigations on the freely-cooling evolution of granular gas under microgravity in a drop tower experiment, and also conduct the molecular dynamics （MD） simulation for comparison. While our experimental and simulation results support Haff＇s law that the kinetic energy dissipates with time t as E（t） （1 ＋ t/v） 2, we modify ~＂ by taking into account the friction dissipation during collisions, and study the effects of number density and particle size on the collision frequency. From the standard deviation of the measured velocity distributions we also verify the energy dissipation law, which is in agreement with Haff＇s kinetic energy dissipation.