Entropy drives the phase behavior of colloids ranging from dense suspensions hard spheres or rods to dilute and depletants. Entropic ordering anisotropic shapes into complex crystals, liquid even quasicrystals has been demonstrated recently in computer simulations experiments. The appears arise emergence directional entropic forces (DEFs) that align neighboring particles, but these have neither rigorously defined nor quantified generic systems. Here, we show quantitatively shape systems...

We investigate collective phenomena with rotationally driven spinners of concave shape. Each spinner experiences a constant internal torque in either clockwise or counterclockwise direction. Although the are modeled as hard, otherwise non-interacting rigid bodies, we find that their active motion induces an effective interaction favors rotation same With increasing density and activity, phase separation occurs via spinodal decomposition, well self-organization into rotating crystals. observe...

SignificanceA large subclass of biomolecular condensates are linked to RNA regulation and known as ribonucleoprotein (RNP) bodies. While extensive work has identified driving forces for condensate formation, relatively little is about that oppose assembly. Here, using a fungal RNP protein, Whi3, we show portion its intrinsically disordered, glutamine-rich region modulates phase separation by forming transient alpha helical structures promote the assembly dilute oligomers. These oligomers...

Starting with the early alchemists, a holy grail of science has been to make desired materials by modifying attributes basic building blocks. Building blocks that show promise for assembling new complex can be synthesized at nanoscale would astonish ancient alchemists in their versatility. However, this versatility means making direct connection between building-block and bulk structure is both necessary rationally engineering difficult because block altered many ways. Here we how exploit...

Significance What is the best way to pack objects into a container? This simple question, one that relevant everyday life, biology, and nanoscience, easy state but surprisingly difficult answer. Here, we use computational methods determine dense packings of set polyhedra inside sphere, for up 60 constituent packers. Our display wide variety symmetries structures, indicate presence spherical container suppresses packing effects due polyhedral shape. results have implications range biological...

Small autonomous machines like biological cells or soft robots can convert energy input into control of function and form. It is desired that this behavior emerges spontaneously be easily switched over time. For purpose we introduce an active matter system loosely inspired by biology which term colloidal cell. The cell consists a boundary fluid interior, both are built from identical rotating spinners whose activity creates convective flows. Similarly to motility, driven cytoskeletal...

Living matter, such as biological tissue, can be viewed a nonequilibrium hierarchical assembly, where at each scale self-driven components come together by consuming energy in order to form increasingly complex structures. The remarkable properties of living or "active-matter" systems, they are generally known, versatility, self-healing, and self-replicating, have prompted the following questions: (1) do we understand biology biophysics that give rise these properties? (2) achieve similar...

Packings of hard polyhedra have been studied for centuries due to their mathematical aesthetic and more recently applications in fields such as nanoscience, granular colloidal matter, biology. In all these fields, particle shape is important structure properties, especially upon crowding. Here, we explore packing a function shape. By combining simulations analytic calculations, study three 2-parameter families report an extensive systematic analysis the densest packings than 55,000 convex...

We describe experiments and simulations demonstrating the propulsion of a neutrally-buoyant swimmer that consists pair spheres attached by spring, immersed in vibrating fluid. The vibration fluid induces relative motion which, for sufficiently large amplitudes, can lead to center mass two spheres. find swimming speed obtained from both experiment simulation agree collapse onto single curve if plotted as function streaming Reynolds number, suggesting is related flows. There appears be...

Monodisperse active and active/passive systems are subsets of a larger continuum active/active mixtures. We find that an average each species' activity weighted by its amount provides quantity which tunes the dynamic steady-state behaviors

Rigid spherical particles in oscillating fluid flows form interesting structures as a result of mediated interactions. Here we show that spheres under horizontal vibration align themselves at right angles to the oscillation and sit with gap between them. The details this behavior have been investigated through experiments simulations. We carried out which pair stainless steel is shaken horizontally cell filled glycerol-water mixtures three different viscosities, various frequencies...

A collection of spherical particles subjected to horizontal oscillatory fluid flow is known form chains perpendicular the direction oscillation. We have developed computer simulations model such a system and validated them against experiments carried out in small fluid-filled cell. In both experiment simulation we find that go through same stages evolution from dispersed initial configuration an ordered chain structure. then use our investigate detail interactions responsible for formation...

We propose a reciprocal, self-propelled model swimmer at intermediate Reynolds numbers ($Re$). Our consists of two unequal spheres that oscillate in antiphase generating nonlinear steady streaming (SS) flows. show computationally the SS flows enable to propel itself, and also switch direction as $Re$ increases. quantify transition swimming by collapsing our data on critical directions corresponds reversal Based findings, we can be an important physical mechanism for motility $Re$.

We computationally study the thermodynamic assembly of more than 40 000 hard, convex polyhedra belonging to three families shapes associated with triangle groups 323, 423, and 523. Our results provide a guide self-assembling host related colloidal crystals through systematic design, careful tweaking particle shape.

We simulate crystallisation of hard spheres with short-ranged attractive potentials as a model self-assembling system. Using measurements correlation and response functions, we develop method whereby the interaction parameters between particles are automatically tuned during assembly process, in order to obtain high-quality crystals avoid kinetic traps. The use is independent details potential structure final crystal—we propose that it can be applied wide range systems.

We investigate the self-assembly (crystallisation) of particles with hard cores and isotropic, square-well interactions, using a Monte Carlo scheme to simulate overdamped Langevin dynamics. measure correlation response functions during early stages assembly, we analyse results fluctuation-dissipation theorems, aiming predict which systems will self-assemble successfully get stuck in disordered states. The early-time measurements are made before significant crystallisation has taken place,...

In Stokes flow, Purcell's scallop theorem forbids objects with time-reversible (reciprocal) swimming strokes from moving. the presence of inertia, this restriction is eased and reciprocally deforming bodies can swim. A number recent works have investigated dimer models that swim at intermediate Reynolds numbers ${\textit Re} \approx 1$ –1000. These show interesting results (e.g. switches direction as a function inertia) but vary seem to be case specific. Here, we introduce general model...

We study quasi two-dimensional, monodisperse systems of active Brownian particles (ABPs) for a range activities, stiffnesses, and densities.

We computationally study the kinematics of a simple model reciprocal swimmer (asymmetric dumbbell) as function Reynolds number (Re) and investigate how onset gradual increase inertia impacts swimming behavior: reversal in swim direction, flow directions, stroke. divide stroke into expansion compression two spheres relate them to power recovery strokes. find that switch direction also corresponds obtain expressions for mean velocity by collapsing net displacement during under law...

The movement of plankton is often dictated by local flow patterns, particularly during storms and in environments with strong flows. Reefs, macrophyte beds, other immersed structures can provide shelter against washout drastically alter the distributions as these redirect slow flows through them. Advection–diffusion agent-based models are used to describe within marine fresh water across multiple scales. Experimental validation such complex challenging because difference both time spatial...

How do mesoscale swimmers interact with one another when there is finite inertia? Do they repel, attract, how arrange? We numerically study simple model at intermediate Reynolds numbers and find that form specific stable pairs depending on system parameters (e.g. number). By looking the flow fields, we relate assemblies nonlinear hydrodynamic interactions, namely steady streaming flows discuss implications for collective behavior beyond pairs.

We computationally study suspensions of slow and fast active Brownian particles that have undergone motility induced phase separation are at steady state. Such mixtures, varying non-zero activity, remain largely unexplored even though they relevant for a plethora systems applications ranging from cellular biophysics to drone swarms. Our mixtures modulated by their activity ratios ($\mathrm{Pe}^\mathrm{R}$), which we find encode information giving rise three regimes, each display unique...

Abstract This is a Work in Progress paper that describes our development of first-year engineering class at University North Carolina Chapel Hill. We are comprehensive university with an department. While we require students to take introductory classes, also want attract from across campus these courses, creating culture "engineering for everyone". has several advantages, as it provides different majors some exposure engineering, and the academic diversity classroom enhances activities...