Inspired by the complex fractal morphologies and deformations observed in animals and plants, an -dimensional soft structure composed of stretchable electronic bits has been developed. This soft structure, capable of independent and cooperative motion, can be manipulated through the programming of bits using a machine language based on instruction encoding. This method simplifies the process of changing the bit's step temperature to control its binary state. Theoretical analysis demonstrates that the fractal dimensions and deformation morphologies of the soft structure achieve stability and extremity when the total number of programming bits exceeds eighteen. Considering strip-shaped soft structures as a case study, their ultimate deformation morphologies, covering the reachable regions of all bits, can achieve complexity comparable to that of dandelion tufts and tree crowns. Moreover, the deformation process exhibits agility akin to that of an octopus. We have prepared samples that include strip-shaped soft structures, each containing multiple pairs of bits, and a hand-shaped soft structure equipped with five pairs of bits, intended for conducting deformation programming experiments. These experimental results validated the correctness of the online reprogramming method for soft structures, showing their capability to perform a range of complex deformations, such as the "OK" gesture, and highlighting potential applications in surgical contexts. This design strategy contributes to the development of soft structures, offering contributions from both theoretical and practical perspectives.

Collagen type II fibrils provide structural integrity to the articular cartilage extracellular matrix. However, the conditions that control the fibril radial size scale, distribution, and formation inside of dense networks are not well understood. We have investigated how surrounding elastic networks affect fibril formation by observing the structure and dynamics of collagen type II in model polyacrylamide gels of varying moduli. Cryogenic transmission electron microscopy (cryo-TEM) is used to image the fibril structure and is verified qualitatively with optical microscopy of fluorescently-tagged collagen within the gels. Using fluorescence correlation spectroscopy super-resolution optical fluctuation imaging (fcsSOFI), the diffusion dynamics of the collagen in low pH and neutral pH conditions are determined. Overall, the fibril bundle diameter and concentration were found to decrease as a function of gel modulus. The single fibril diameter remains constant at 30 nm within the gels; however, the diameter was found to be smaller when compared to in solution. Additionally, the mode of diffusion of the collagen triple helices changes within gel environments, decreasing the diffusion coefficient. Understanding the intricate relationship between network topology and collagen type II fibril formation is crucial in gaining deeper insights into the transport phenomena within complex acellular tissues that are necessary for the development of future therapeutic materials.

Active colloids and self-propelled particles moving through microstructured fluids can display different behavior compared to what is observed in simple fluids. As they are driven out of equilibrium in complex fluids they can experience enhanced translational and rotational diffusion as well as instabilities. In this work, we study the deterministic and the Brownian rotational dynamics of an active Janus disk propelling at a constant speed through a complex fluid. The interactions between the Janus disk and the complex fluid are modeled using a fluctuating advection-diffusion equation, which we solve using the finite element method. Motivated by experiments, we focus on the case of a complex fluid comprising molecules that are much smaller than the size of the active disk but much bigger than the solvent. Using numerical simulations, we elucidate the interplay between active motion and fluid microstructure that leads to enhanced rotational diffusion and spontaneous rotation observed in experiments employing Janus colloids in polymer solutions. By increasing the propulsion speed of the Janus disk, the simulations predict the onset of a spontaneous rotation and an increase of the rotational diffusion coefficient by orders of magnitude compared to its equilibrium value. These phenomena depend strongly on the number density of the constituents of the complex fluid and their interactions with the two sides of the Janus disk. Given the simplicity of our model, we expect that our findings will apply to a wide range of active systems propelling through complex media.

To quantify how the viscosities of silicone oil (SO) and liquid metal (LM) relate to emulsion-formation (LM-in-SO SO-in-LM), a process was developed to produce LM pastes with adjustable viscosity and minimal oxide and bubbles. Increased LM viscosity allows greater silicone oil intake and/or intake of higher-viscosity silicone oils.

: as an intelligent material, electrorheological fluids (ERFs) comprise a suspension system consisting of dielectric particles and/or their composites dispersed in an insulating liquid. In this article, MOF/g-CN composite nanoparticles were successfully synthesized and demonstrated an excellent ER effect. : first, the precursor for g-CN was synthesized using a high-temperature calcination method, followed by the synthesis of MIL-125 (MOF-Ti) on the surface of layered graphitic carbon nitride using a solvothermal approach. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were used to reveal the presence of numerous MOF particles deposited onto the surfaces of layered g-CN nanosheets. X-ray powder diffraction confirmed the growth of MOF particles on the g-CN precursor. The chemical composition and states were characterized through Fourier-transform infrared (FT-IR) spectroscopy and X-ray photoelectron (XPS) analyses. Additionally, BET analysis indicated the presence of abundant pore structures in the MOF/g-CN composite nanoparticles. : lastly, rheological and dielectric properties were investigated. The ER behavior demonstrated their excellent performance, with a 10 wt% mass fraction suspension of the MOF/g-CN-0.4 based composite material and dimethyl silicone oil exhibiting a yield stress of 300 Pa at 2 kV mm.

Compaction of calf thymus DNA (ct-DNA) by two single-head-double-tailed surfactants with variable tail lengths , Dihexadecyldimethylammonium bromide (DDAB16) and Dioctadecyldimethylammonium bromide (DDAB18), and one triple-head-double-tailed surfactant -dodecyl--(2-(dodecyldimethylammonio)ethyl)-,,,-tetramethylethane-1,2-diaminium (MQAS12) has been studied. DDAB18 is found to be the most efficient, while MQAS12 is the least efficient for cellular uptake. Hybrid materials of surfactants and silica nanoparticles have better compaction efficiency due to the cooperative binding. Silica nanoparticles (∼100 nm)-DDAB18 hybrid materials can compact ct-DNA at a much lower concentration than a conventional surfactant, addressing the cytotoxicity issues. Hybrid materials formed with smaller silica nanoparticles (∼40 nm) have also been studied. The results obtained have been used to understand whether Coulombic and/or hydrophobic interactions are responsible for DNA compaction. The hydrophobicity per unit surface area () of hybrid nanoparticles has a significant role in DNA compaction. The largely depends on the surfactants' structures and nanoparticles' sizes. Single-head-double-tailed surfactants with a comparatively smaller headgroup exhibit a large amount of adsorption on the nanoparticles' surfaces, producing a large . DDAB18 appears to be a DNA intercalative binder. Fluorescence anisotropy decay data of 4,6-diamidino-2-phenylindole (DAPI) reveal the dynamics of ct-DNA at different stages of compaction. Cell viability of mouse mammary gland adenocarcinoma cells (4T1) and human embryonic kidney (HEK) 293 cell lines and cellular uptake of the gene to 4T1 cells have been investigated. This study provides ideas for designing efficient non-viral vectors. Overall, DDAB18-coated silica nanoparticles appear to be safe and effective DNA compaction agents that can carry nucleic acids for biomedical applications.

The presence of supramolecular interactions plays a crucial role in the formation of resilient multifunctional elastomers. Nevertheless, achieving elastomers with fabulous mechanical properties remains a significant challenge due to the incomplete understanding of the underlying principles. In this study, we have presented a simple yet efficient approach for manipulating the microstructure, resulting in a significant enhancement of the mechanical properties of the elastomers. By utilizing hydrophobic and hydrophilic extended chain segments to elongate a hydrophilic oligomer, we successfully created elastomers with improved toughness and stiffness through supramolecular interactions. The elastomer with hydrophobic extended chain segments demonstrates a fracture energy (94 842 J m) and high tensile stress (16 MPa). In contrast, the elastomer with hydrophilic extended segments showed significantly lower tensile stress (0.18 MPa), even though their molecular chain structures are nearly identical. We conducted a systematic demonstration and investigation of the significant difference mentioned above and ultimately found that due to the hydrophobic-hydrophilic difference between the oligomer and extended chain segments, the hydrophobic chain segments are able to create hydrophobic association and the association can further facilitate the development of stronger and more abundant supramolecular interactions (hydrogen bonds). The resulting hydrogen bonds, combined with the hydrophobic association, effectively disperse energy and consequently improve the elastomer's capacity to withstand external forces. The hydrophilic-hydrophobic mechanism showcases the potential for creating durable supramolecular materials with promising applications in biology and electronics.

Liquid crystal elastomers (LCEs), a class of elastomers combining liquid crystals with a polymer network, have garnered significant interest for applications in the field of soft robotics. However, the fracture and fatigue characteristics of LCEs remain poorly understood. This study presents a comprehensive investigation into the fracture and fatigue characteristics of LCEs, focusing on polydomain and monodomain variants subjected to different loading directions. The fracture energy (also called toughness) and fatigue threshold of polydomain and monodomain LCEs were quantitatively measured and compared with selected elastomers. Our experimental results demonstrate that polydomain LCEs exhibit superior fracture energy and fatigue threshold compared to monodomain LCEs. Within the monodomain category, LCEs subjected to parallel loading exhibit larger fracture energy than those under vertical loading, while their fatigue thresholds remain comparable. These findings enhance our understanding of the deformation and failure characteristics of LCEs, which are crucial for their applications in various fields.

Nanoparticle adhesion at liquid interfaces plays an important role in drug delivery, dust removal, the adsorption of aerosols, and controlled self-assembly. However, quantitative measurements of capillary interactions at the nanoscale are challenging, with most existing results at the micrometre to millimetre scale. Here, we combine atomic force microscopy (AFM) and computational simulations to investigate the adhesion and removal of nanoparticles from liquid interfaces as a function of the particles' geometry and wettability. Experimentally, AFM tips with controlled conical geometries are used to mimic the nano-asperities on natural nanoparticles interacting with silicone oil, a model liquid for many engineering applications including liquid-infused surfaces. Computationally, continuum modelling with the Surface Evolver software allows us to visualise the interface configuration and predict the expected force profile from energy minimisation. Quantitative agreement between the experimental measurements and the computational simulations validates the use of continuum thermodynamics concepts down to the nanoscale. We demonstrate that the adhesion of the nanoparticles is primarily controlled by surface tension, with minimum line tension contribution. The particle geometry is the main factor affecting the length of the capillary bridge before rupture. Both the particle geometry and liquid contact angle determine the shape of the adhesion force profile upon removal of the particle from the interface. We further extend our simulations to explore more complex geometries, rationalising the results from experiments with imperfect AFM tips. Our results could help towards the design of smart interfaces, for example, able to attract or repel specific particles based on their shape and chemistry.

Quasicrystals are unique materials characterized by long-range order without periodicity. They are observed in systems such as metallic alloys, soft matter, and particle simulations. Unlike periodic crystals, which are invariant under real-space symmetry operations, quasicrystals possess symmetry that requires description by a space group in reciprocal space. In this study, we report the self-assembly of a six-fold chiral quasicrystal using molecular dynamics simulations of a two-dimensional particle system. The particles interact the Lennard-Jones-Gauss pair potential and are subjected to a periodic substrate potential. We confirm the presence of chiral symmetry through diffraction patterns and order parameters, revealing unique local motifs in both real and reciprocal space. The quasicrystal's properties, including the tiling structure and symmetry and the extent of diffuse scattering, are strongly influenced by substrate potential depth and temperature. Our results provide insights into the mechanisms of chiral quasicrystal formation and the role and potential of external fields in tailoring quasicrystal structures.

In this study, we develop a comprehensive two-phase model to analyze the dynamics of bacterial swarming on porous substrates. The two distinct phases under consideration are the cell and aqueous phases. We use the thin-film approximation, as the characteristic height of the swarm is significantly lower than its characteristic radius. Our model incorporates surfactant generation by microorganisms, drag forces between the cell and aqueous phases, osmotic influx, and Marangoni stresses. The disjoining pressure is included to account for substrate wettability, and a precursor film is used to address the contact line singularity. Several morphologies of bacterial swarms, such as arrested, circular, modulated, branching, droplet, fingering, and dendrite, have been observed experimentally. The model developed is capable of predicting all these shapes for realistic parameter values. An increase in the wettability of the substrate leads to faster expansion, while increased surface tension helps redistribute biomass radially. The role of biomass growth and surfactant production rate, surfactant diffusivity, and osmotic influx on the morphology of bacterial swarms are explained.

The molecular mobility of thin films of poly(bisphenol A carbonate) (PBAC) was systematically investigated using broadband dielectric spectroscopy, employing two distinct electrode configurations. First, films were prepared in a capped geometry between aluminum electrodes employing a crossed electrode capacitor (CEC) configuration, down to film thicknesses of 40 nm. The Vogel temperature, derived from the temperature dependence of relaxation rates of the α-relaxation, increases with decreasing film thickness characterized by an onset thickness. The onset thickness depends on the annealing conditions, with less intense annealing yielding a lower onset thickness. Additionally, a broadening of the β-relaxation peak was observed with decreasing thickness, attributed to the interaction of phenyl groups with thermally evaporated aluminum, resulting in a shift of certain relaxation modes to higher temperatures relative to the bulk material. A novel phenomenon, termed the slow Arrhenius process (SAP), was also identified in proximity to the α-relaxation temperature. For films with thicknesses below 40 nm, nanostructured electrodes (NSE) were utilized, incorporating nanostructured silica spacers to establish a free surface with air. This free surface causes an enhancement in the molecular mobility for the 40 nm sample, preserving the β-relaxation as a distinct peak. The α-relaxation was detectable in the dielectric loss down to 18 nm, shifting to higher temperatures as film thickness is decreased. Notably, the onset thickness for the increase in Vogel temperature was lower in the NSE configuration compared to the CEC setup, attributed to the presence of the polymer-air interface.

The self-assembly behaviors of rod-coil asymmetric diblock molecular brushes (ADMBs) bearing responsive side chains in a selective solvent are investigated dissipative particle dynamics simulations. By systematically varying the polymerization degree, copolymer concentration, and side chain length, several morphological phase diagrams were constructed. ADMB assemblies exhibited a rich variety of morphologies, including cylindrical micelles, spherical micelles, nanowires, polyhedral micelles, ellipsoid micelles, and large compound micelles. The structures of the representative nanowires were analyzed in detail. A kinetics study revealed that the one-dimensional growth of nanowires follows the step-growth polymerization mechanism. Besides, by calculating the local order parameter of the rigid chains, we found that increasing the lengths of A and C side chains can promote the ordered arrangement of the rigid chains. Moreover, the rod-to-coil conformation transitions were simulated to explore the stimuli-responsive behaviors of ADMBs with responsive rigid side chains. The simulation results indicated that the volume of the assemblies expanded without the support of the rigid chains. The present work not only provides a comprehensive understanding of the self-assembly behaviors of ADMBs but also provides meaningful theoretical support for the development of novel molecular brush materials.

We develop an approximate, analytical model for the velocity of defects in active nematics by combining recent results for the velocity of topological defects in nematic liquid crystals with the flow field generated from individual defects in active nematics. Importantly, our model takes into account the long-range interactions between defects that result from the flows they produce as well as the orientational coupling between defects inherent in nematics. Our work complements previous studies of active nematic defect motion by introducing a linear approximation that allows us to treat defect interactions as two-body interactions and incorporates the hydrodynamic screening length as a tuning parameter. We show that the model can analytically predict bound states between two +1/2 winding number defects, effective attraction between two -1/2 defects, and the scaling of a critical unbinding length between ±1/2 defects with activity. The model also gives predictions for the trajectories of defects, such as the scattering of +1/2 defects by -1/2 defects at a critical impact parameter that depends on activity. In the presence of circular confinement, the model predicts a braiding motion for three +1/2 defects that was recently seen in experiments, as well as stable and ergodic trajectories for four or more defects.

Gene therapies, drug delivery systems, vaccines, and many other therapeutics, although seeing breakthroughs over the past few decades, still suffer from poor stability, biocompatibility, and targeting. Coacervation, a liquid-liquid phase separation phenomenon, is a pivotal technique increasingly employed to enhance the effectiveness of therapeutics. Through coacervation strategies, many current challenges in therapeutic formulations can be addressed due to the tunable nature of this technique. However, much remains to be explored to enhance these strategies further and scale them from the benchtop to industrial applications. In this review, we highlight the underlying mechanisms of coacervation, elucidating how factors such as pH, ionic strength, temperature, chirality, and charge patterning influence the formation of coacervates and the encapsulation of active ingredients. We then present a perspective on current strategies harnessing these systems, specifically for nucleic acid-based therapeutics. These include peptide-, protein-, and polymer-based approaches, nanocarriers, and hybrid methods, each offering unique advantages and challenges. Nucleic acid-based therapeutics are crucial for designing rapid responses to diseases, particularly in pandemics. While these exciting systems offer many advantages, they also present limitations and challenges which are explored in this work. Exploring coacervation in the biomedical frontier opens new avenues for innovative nucleic acid-based treatments, marking a significant stride towards advanced therapeutic solutions.

In this study, we utilized the origami technique to integrate various types of spacers into the double-stranded crossover and examined their flexibilities using single-molecule fluorescence resonance energy transfer (smFRET). We discovered that for the traditional Holliday Junction connection with zero-base spacers, the inter-structural angle measures 58.7 degrees, which aligns well with previous crystallographic research. When introducing non-complementary double-stranded spacers as a free leash, we observed that longer spacers resulted in a more relaxed connection. In contrast, when using complementary segments, the two origami structures rotated as the number of base pairs increased, reflecting the structural characteristics of the B-duplex. Our findings indicate that a stable intramolecular duplex requires a minimum of 5 base pairs. Overall, our results highlight the potential for re-engineering crossovers and designing materials that can change volume with shrink-swell capabilities, as well as applications in torque sensing using short DNA duplexes.

Aerosol filters composed of electrostatically charged bipolar fibers are referred to as electret filters. A novel computational model is developed in this work to study the impact of droplet deposition on aerosol capture efficiency of electret fibers. The electret fibers were assumed to have a dipole orientation that was either parallel or perpendicular to the airflow direction. The simulations were conducted using the ANSYS CFD code after it was enhanced with a series of in-house subroutines. Our simulations revealed that droplet deposition on electret fibers decreases their ability to capture airborne particles. More specifically, the simulations were devised to isolate droplet's physical and electrical properties (, surface tension, electrical conductivity…) and quantify their impact on fiber capture efficiency. It was found, in particular, that droplet's electrical conductivity and permittivity have the most adverse impact on the performance of an electret fiber. This is perhaps because higher droplet conductivity results in severe fiber charge neutralization, and higher droplet permittivity leads to a stronger fiber charge shielding. In contrast, fiber wettability was found to have a negligible impact on fiber efficiency. The work presented in this paper offers valuable insights into the complex nature of electret filters used in different industrial and environmental applications.

The interfacial behavior of micro-/nanogels is governed to a large extent by the hydrophobicity of their polymeric network. Prevailing studies to examine this influence mostly rely on external stimuli like temperature or pH to modulate the particle hydrophobicity. Here, a sudden transition between hydrophilic and hydrophobic state prevents systematic and gradual modulation of hydrophobicity. This limits detailed correlations between interfacial behavior and network hydrophobicity. To address this challenge, we introduce a nanogel platform that allows accurate tuning of hydrophobicity on a molecular level. For this, post-functionalization of active ester-based particles, we prepare poly(-(2-hydroxypropyl)methacrylamide) (PHPMA) nanogels as a hydrophilic benchmark and introduce gradually varied amounts of hydrophobic propyl or dodecyl moieties to increase the nanogel hydrophobicity. We study the deformation and arrangement of these particles at an air/water interface and correlate the results with quantitative measures for nanogel hydrophobicity. We observe that increasing hydrophobicity of nanogels, either by increasing the hydrophobic moiety ratio or the alkyl chain length, leads to decreased particle deformability and aggregation of an interfacially-adsorbed monolayer. Contrary to what may be intuitively assumed, these changes are not gradual, but rather occur suddenly above a threshold in hydrophobicity. Our study further shows that the effect of hydrophobicity affects the nanogel properties differently in bulk and when adsorbed at liquid interfaces. Thus, this study establishes the transition of interfacial behavior between soft gel-like particles to a solid spherical morphology triggered by the increase in hydrophobicity.

The surface tension of partially wetting droplets deforms soft substrates. These deformations are usually localized to a narrow region near the contact line, forming a so-called 'elastocapillary ridge.' When a droplet slides along a substrate, the movement of the elastocapillary ridge dissipates energy in the substrate and slows the droplet down. Previous studies have analyzed isotropically spreading droplets and found that the advancing contact line 'surfs' the elastocapillary ridge, with a velocity determined by a local balance of capillary forces and bulk rheology. Here, we experimentally explore the dynamics of a droplet sliding across soft substrates. At low velocities, the contact line is nearly circular, and dissipation increases logarithmically with speed. At higher droplet velocities, the contact line adopts a bullet-like shape, and the drag force levels off. At the same time, droplets shed a pair of 'elastocapillary rails' that fade away slowly behind them. These results suggest that sliding along the parallel edges of a bullet-shaped droplet dissipates less energy than surfing the wetting ridges at the front and back.

We numerically study the dynamics of topological defects in 2D polar active matter coupled to a conserved density field, which shows anomalous kinetics and defect distribution. The initial many-defect state relaxes by pair-annihilation of defects, which behave like Ostwald ripening on short timescales. However, defect coarsening is arrested at long timescales, and the relaxation kinetics becomes anomalously slow compared to the equilibrium state. Specifically, the number of defects in the active system approaches a steady state, following a power-law dependence in the rate of change of the inverse density. In contrast, in thermal equilibrium, the decay is exponential. Finally, we show that the anomalous coarsening of defects leads to unique patterns in the coupled density field, which is consistent with patterns observed in experiments on the actin cytoskeleton. These patterns can act as cell signaling platforms and may have important biological consequences.

Upon decreasing the temperature, agarose solution exhibited gelation and phase separation, forming a cloudy gel consisting of agarose-rich and agarose-poor phases. Both phenomena contribute to the formation of a heterogeneous gel structure, but the primary influence of both processes on this heterogeneity remains unclear. In this study, we defined the specific gelation and phase separation temperatures of an agarose solution and examined the resulting gel structures with and without phase separation. Microscopic observation and colloid diffusion analysis revealed that phase separation leads to inhomogeneities several micrometers in size. Furthermore, we found that the distributions of colloidal diffusion coefficients and particle displacements strongly reflected the heterogeneity primarily induced by phase separation and gelation. Our findings contribute to the physicochemical understanding of the heterogeneous structures of various (bio) polymer gels associated with the phase separation of polymers.