Dynamics of Purcell-type microswimmers with active-elastic joints.

Purcell's planar three-link microswimmer is a classic model of swimming in low-Reynolds-number fluid, inspired by motion of flagellated microorganisms. Many works analyzed this model, assuming that the two joint angles are directly prescribed in phase-shifted periodic inputs. In this work, we study a more realistic scenario by considering an extension of this model which accounts for joints' elasticity and mechanical actuation of periodic torques so that the joint angles are dynamically evolving.

Multistable Metafluid based Energy Harvesting and Storage.

The thermodynamic properties of fluids play a crucial role in many engineering applications, particularly in the context of energy. Fluids with multistable thermodynamic properties may offer new paths for harvesting and storing energy via transitions between equilibria states. Such artificial multistable fluids can be created using the approach employed in metamaterials, which controls macro-properties through micro-structure composition.

A metafluid with multistable density and internal energy states.

Investigating and tailoring the thermodynamic properties of different fluids is crucial to many fields. For example, the efficiency, operation range, and environmental safety of applications in energy and refrigeration cycles are highly affected by the properties of the respective available fluids. Here, we suggest combining gas, liquid and multistable elastic capsules to create an artificial fluid with a multitude of stable states.

Coupling between wetting dynamics, Marangoni vortices, and localized hot cells in drops of volatile binary solutions.

Hypothesis: A sessile drop comprising a mixture of volatile solvents supports spatial variations in interfacial energy, which gives rise to solutal Marangoni flow, alongside evaporative loss of drop mass. Both the Marangoni flow and evaporation bring about a dance of concurrent and inter-connected phenomena: internal Marangoni vortices, localized hot cells, and complex wetting dynamics.

Experiment: We employ Particle Image Velocimetry and Infra-Red Microscopy to visualize Marangoni vortices, temperature variations, and the wetting dynamics of drops of toluene and ethanol mixtures.

The Electrical Double Layer Force between Spherical Particles Which Are Partially Submerged in Water.

We study the EDL force between two colloidal particles that are adsorbed to the surface of an electrolyte solution. The attachment of colloidal particles to a free surface of an electrolyte solution, which may interface with another liquid or vapor phase, is a well-known phenomenon that is employed in many scientific and industrial applications, the most well-known of which is the Pickering emulsion. In addition to capillary stresses, the particles will experience an electrical double layer (EDL) force when they are close to each other.

Transitions between different motion regimes of the three-phase contact line during the pattern deposition of polymer from a volatile solution.

Hypothesis: The interplay between different transport mechanisms during polymer deposition from a volatile solution determines the motion regime of the three-phase contact line, e.g. monotonous slip, stick-slip, and oscillatory wetting-dewetting regimes of motion, which define the morphology of the deposit.

Analysis of the oscillatory wetting-dewetting motion of a volatile drop during the deposition of polymer on a solid substrate.

A recent experimental work revealed an oscillatory wetting-dewetting motion of the three phase contact line during the deposition of polymer from a volatile solution. Here we employ a theoretical model to explain the wetting-dewetting motion of the contact line by incorporating opposing evaporation and Marangoni induced flows in the deposition process. We take into account the contribution of polymer concentration to the surface tension of the volatile drop and show that by changing the different parameters of the system we are able to traverse the dynamics of the three phase contact line from a simple dewetting regime to the wetting-dewetting regime, observed in experiment.

Connecting Monotonic and Oscillatory Motions of the Meniscus of a Volatile Polymer Solution to the Transport of Polymer Coils and Deposit Morphology.

We study the deposition mechanisms of polymer from a confined  meniscus of volatile liquid. In particular, we investigate the physical processes that are responsible for qualitative changes in the pattern deposition of polymer and the underlying interplay of the state of pattern deposition, motion of the meniscus, and the transport of polymer within the meniscus. As a model system we evaporate a solution of poly(methyl methacrylate) (PMMA) in toluene.

Signatures of van der Waals and Electrostatic Forces in the Deposition of Nanoparticle Assemblies.

We evaporate aqueous suspensions in a microchamber to explore the connection between the morphology of the nanoparticle deposits at nanometer resolutions and at micrometer and hundreds of micrometers resolutions. Repulsive or weakly attractive electrical double-layer and van der Waals surface forces render the deposition of detached particles and small aggregates at nanometer resolutions. However, strongly attractive surface forces render the dense deposition of large aggregates.

Simulations of the dynamic deposition of colloidal particles from a volatile sessile drop.

Hypothesis: The deposition of particles from a volatile liquid drop atop a substrate is primarily governed by the advection and diffusion of the particles in the liquid. Colloidal particles may further coagulate and adsorb to the substrate during the deposition process. The external geometry and the internal composition of the particulate deposit are then determined by an interplay between these four mechanisms.

The deposition of colloidal particles from a sessile drop of a volatile suspension subject to particle adsorption and coagulation.

Electrical double layer and van der Waals (DLVO) forces are known to determine the morphology of the deposit of colloidal particles following the evaporation of the carrier liquid. It is assumed that the adsorption of particles to the solid substrate and their coagulation in the liquid are the mechanisms connecting DLVO forces to the morphology of the deposit. We use theory to test this assertion.

Influence of a Propagating Megahertz Surface Acoustic Wave on the Pattern Deposition of Solute Mass off an Evaporating Solution.

We study the influence of a megahertz Rayleigh surface acoustic wave (SAW), propagating in a solid substrate, on the pattern deposition of a solute mass off an evaporating solution. An experimental procedure, where a film of a solution undergoes a controlled evaporation in a chamber, shows that the SAW alters the state of the pattern deposition. Increasing the power of the SAW supports an increase in the density of the deposited patterns.

A model for pattern deposition from an evaporating solution subject to contact angle hysteresis and finite solubility.

We propose a model for the pattern deposition of the solute from an evaporating drop of a dilute solution on a horizontal substrate. In the model we take into account the three-phase contact angle hysteresis and the deposition of the solute whenever its concentration exceeds the solubility limit. The evaporating drop is governed by a film equation.