Traditional surface cleaning methods often suffer from drawbacks such as chemical harshness, potential for surface damage, and high-energy consumption. This study investigates an alternative approach: acoustic-driven surface cleaning using millimeter-sized bubbles excited at low, sub-cavitation frequencies. We identify and characterize a distinct translational resonance of these bubbles, occurring at significantly lower frequencies (e.g., 50 Hz for 1.3 mm diameter bubbles) than the Minnaert resonance for a bubble of the same size. At this translational resonance, stationary bubbles exhibit amplified lateral swaying, while bubbles sliding on an inclined surface display pronounced "stop-and-go" dynamics. The theoretical model treats the bubble as a forced, damped harmonic oscillator. In this framework, surface tension supplies the restoring force, while the inertia is governed primarily by the hydrodynamic added mass of the surrounding fluid. It accurately predicts the observed resonant frequency scaling with bubble equilibrium radius (). Cleaning efficacy, assessed using protein-based artificial soil on glass slides, was significantly improved when bubbles were driven at their translational resonant frequency compared to off-resonant frequencies or nonacoustic conditions. These findings demonstrate that leveraging translational resonance enhances bubble-induced shear and agitation, offering an effective and sustainable mechanism for surface cleaning.

Locomotion and fluid pumping near surfaces are ubiquitous in nature, ranging from the slow crawling of snails to the rapid flight of bats. This study categorizes these behaviors based on the undulation number (Un) and Reynolds number ($Re$). We contrast low $Re$ undulatory propulsion ($\text{Un} \gt 1$), exemplified by freshwater snails, with high $Re$ flapping propulsion ($\text{Un} \lt 1$), seen in bats and bees. For snails, we derive lubrication models showing that pumping and swimming speeds scale with $(a/h_0)^2$, a result validated by robotic experiments which also reveal the detrimental effects of surface deformation (high capillary/Bond ratio). Conversely, for high $Re$ fliers, we examine the ground effect's role in lift enhancement. Biological data from bats (Hipposideros pratti and Rhinolophus ferrumequinum) reveal a 2.5-fold increase in lift coefficient during surface-skimming drinking flights, attributed to aerodynamic squeezing effects. Finally, we analyze honeybee fanning, demonstrating how a "jet-vortex" mechanism utilizes ground effect to transport pheromones efficiently against diffusion. These findings provide a unified framework for understanding fluid-structure interactions near boundaries in biological systems.

Interfacial deformation under electric fields is a common phenomenon in many industrial processes. Particularly, we are interested in the dynamics of sessile soap bubbles in a parallel-plate electric field which exhibits a stable deformation regime followed by conical instability. Using side-view imaging, we track the equilibrium shapes, the transition to the unstable regime, and the pre-jet apex dynamics within one experimental system. In the stable regime, the meridional profile is well described by a spheroidal fit, and the aspect ratio collapses across initial bubble sizes onto a single steady-state branch when plotted against the dimensionless field E^∗ = √(Bo_e) for data acquired within a fixed ambient session where the electric Bond number Bo_e is defined as ε_0 E_0^2 R_0/(2γ). The endpoint of this branch marks the transition to the unstable regime. Above onset of instability, the apex sharpens into a cone with half-angle 30.0^∘ ± 0.6^∘, below the classical Taylor value. To quantify the late pre-jet stage, we define the axial distance b(t) from the instantaneous apex to a fixed reference vertex determined from the terminal cone geometry and measure its evolution. The corresponding rate grows as jetting is approached, and a near-tip inertia-capillary model captures the observed logarithmic trend as an approximation. Together, these measurements establish a single-system experimental benchmark in which stable electrocapillary deformation is organized by a single steady-state branch that leads into conical instability and pre-jet dynamics.

The spatial distribution of microplastics in large bodies of water like Lake Ontario depends on the lake's hidden flow patterns. By analyzing a time series of offshore circulation and employing backward Finite-Time Lyapunov Exponent (FTLE) fields along with Lagrangian particle tracking, we find correlations between the Earth's rotation, basin-wide internal waves, and the localized fate of microplastic pollution. Our findings reveal two distinct regimes in pollution transport: a high-speed transport "Southern Conveyor Belt" that acts as a regional transport of plastics, and a low-speed or diffusive spread "Toronto Trap" that serves as a local accumulator of urban waste. Furthermore, Mean Square Displacement (MSD) analysis shows three distinct kinematic transport regimes governing this dispersal: an early-time diffusive regime, an intermediate super-ballistic regime driven by rapid spatial acceleration and shear dispersion into Lagrangian Coherent Structures (LCS), and a late-time ballistic regime reflecting steady advection. This quantitative analysis confirms that particles released from southern sources travel significantly farther distances overall, reinforcing the contrast between the high-transport southern coastal jet and the low-transport northwestern retention zones.

Abstract Hygroscopic surfaces act as local vapor sinks that reshape the condensation field around them, but whether distributed biological structures do the same has not been investigated. We have established that hyphae of fungal colonies functionally behave as vapor sinks, creating a dry region of width δ around themselves when placed on a cooled substrate. In addition, the radial distribution of droplet sizes steepens during condensation, and the rate at which droplets evaporate locally after chamber drying increases. In order to quantify this behavior, we employed a combination of time-resolved imaging and survival analysis to determine how long individual droplets persist on the surface surrounding the colony. These data were used to derive three quantitative measures of the vapor-sink effect. Each measure was found to be directly proportional to the vapor-sink strength of the substrate, as calibrated against NaCl–agar hydrogels of known water activity (LOOCV RMSE = 0.031 for recovered a w ). These findings were consistent across three fungal genera (35 experiments), and all species fell along calibration lines defined by the hydrogel standards. This result is consistent with a diffusion-limited vapor-depletion framework. The measured genus-level δ ratios agreed to within 6% of predictions from structural absorbing capacity, and field measurements on Gymnosporangium -infected apple leaves were consistent with the same signatures under natural conditions. These results establish a non-contact method for inferring the material properties of thin hygroscopic biological surfaces from their condensation patterns.

We study a rain-powered energy-harvesting device inspired by the natural impact of raindrops on leaves. In nature, a raindrop striking a leaf at high speed causes it to deform and vibrate. Inspired by this dynamic response, our device uses an elastic beam coupled to a piezoelectric material to convert mechanical vibrations from droplet impacts into electrical energy. We conduct experiments to analyze how beam length, droplet impact location, and residual droplet mass affect energy conversion. Our results, supported by a theoretical model, show strong agreement when the beam length exceeds 5 cm. Beyond this length, the energy conversion becomes independent of further increases, suggesting that 5 cm is optimal for maximizing output. To validate practical applicability, we also test the device under real rain conditions, demonstrating consistent performance. Understanding the interplay between raindrop dynamics and energy conversion can guide the design of efficient, scalable rain-powered energy-harvesting systems for environmental applications.

This paper evaluates a cantilever system as a simple method for measuring the mechanical rigidity (bending rigidity EI or Young's modulus E) of plants. Using soybeans as a test sample – whose E values have rarely been reported – we conducted static and dynamic experimental measurements alongside numerical modal analysis. Results showed good agreement in EI values between the static and dynamic tests when branches and leaves were removed, provided the stem responded uniformly. However, the added mass of attached foliage causes complex dynamic interactions, which we analyze through both experimental and numerical approaches. Ultimately, our findings suggest that cantilever force-deflection measurements provide a practical, on-site approach, contributing to the development of an affordable and reliable standard for estimating plant mechanical properties.

Like a crêpe resting on a plate, a thin elastic sheet can fold smoothly under its own weight, forming reversible shapes without creases or imposed hinges. Such soft folds arise from a balance between elastic bending and gravity, yet their stability, packing limits, and dynamics remain poorly understood. Here we show that these behaviors are governed by a single physical length scale, the elasto-gravity length ℓ_eg. Using experiments and heavy-elastica theory, we demonstrate that ℓ_eg sets the characteristic fold geometry, determines when a fold becomes unstable and unfolds, and limits how many reversible folds can be stacked in rectangular and circular sheets. In particular, when lengths are rescaled by ℓ_eg, fold shapes and stability thresholds collapse across materials and thicknesses. We further show that unfolding follows a universal speed scaling v ∼√(g ℓ_eg), revealing a gravity-controlled time scale for the release of stored bending energy. Together, these results establish a unified physical framework for reversible folding, compact storage, and gravity-assisted deployment of thin elastic sheets.

The effective transport of heat and mass is crucial to both industrial applications and physiological processes. Recent research has evaluated the benefit of using flexible reeds for triggering the vortex induced vibration to enhance mixing, as opposed to traditional techniques like rigid blender or static meshes. Inspired by the soft, porous, and moving fish gill lamellae, we proposed a new concept of thermal dispenser that prescribes active pitching motion to the leading edge of an otherwise passively flapping perforated panel. Experimental measurements revealed drastic differences between the steady leaky flow wake behind a statically deflected perforated panel and the periodic shedding wakes with complex vortex structure transitions behind an actuated perforated panel with or without chord-wise flexibility. A semi-empirical simulation of the thermal convection and diffusion takes the experimentally obtained velocity as input and yields the temperature results. Vortex dynamics, Lagrangian coherent structures, and thermal mixing behaviors were analyzed and compared to elucidate the effects of kinematics, perforation, and flexibility on the wake mode transitions, lateral entrainment mixing, and overall heating. Our work provides a foundational understanding of the fluid-structure interactions of perforated bendable panels under active control which has not been described before in the intermediate Reynolds number range. It provides insights for developing an innovative bio-inspired heat or mass dispenser potentially suitable for subtle and small scale applications.

Blisters, delaminated regions that form in multilayered structures under compressive stresses, are observed across a wide range of length scales, from two-dimensional materials to protective coatings and laminated composites. Far from being passive defects, such interfacial features have emerged as functional motifs for three-dimensional architectures and reconfigurable surfaces. Here we reveal an unusual peel response of a blistered thin film on a soft substrate. When peeled from one end, the advancing peel front triggers reattachment at the blister edge once a critical separation is reached, initiating spontaneous rolling of the film on the substrate. This peel-to-roll transition produces a sharp drop in the measured adhesion force, which then remains constant throughout the rolling phase. Using experiments, scaling analysis, and molecular dynamics simulations, we resolve the contact morphology at the transition and identify the contact length at which rolling initiates. We show that this length arises from interactions between the two contact edges and is independent of the work of adhesion. Once rolling begins, a dynamically imposed dwell time - defined by the rolling length and peel speed - translates contact history into spatial variations in adhesion force, thereby governing the magnitude of the force drop. Together, these results point to a new pathway for generating spatially tunable, heterogeneous adhesion from otherwise homogeneous interfaces.

Understanding gravity-driven preferential flow in uniform porous materials is important as it can facilitate the movement of pollutants, pathogens and pesticides to groundwater. Previous studies have suggested that the dynamic contact angle could be used to model unstable gravity-driven flow in coarse sand. This study examines this theory in a broader context involving a range of porous media with different static contact angles. A high-resolution, high-speed camera recorded the movement of water in pores at the wetting front. Water velocity and associated dynamic contact angles were calculated using image analysis. The results show that the movement of the wetting front was non-Darcian as the advancement of the front occurred intermittently through the smallest pore in 0.01 s at velocities of 0.06 m/s, one pore at a time. The high velocity increased the (dynamic) contact angle. The increase followed the Baver-Hoffman equation for all media with the different static contact angles. It confirms that the matric potential across the wetting front was discontinuous for unstable gravity-driven flow.

Exposure to particulate matter has various health consequences, and high-efficiency particulate air (HEPA) filters and facial masks are used to remove such pollutants. However, these have issues of producing microplastics, being environmentally unfriendly, and sometimes expensive. This study aims to discover the potential of recycling natural fibrous materials as an environmentally friendly and cost-effective alternative to plastic-based filters. Various fibers - carbonized rice husks (CRH), rice husks (RH), sugarcane bagasse (sugarcane), and coconut fibers - are characterized by their filtration performance, tensile strength, wettability, and morphology. The quality factors were 12.4 X10-3, 8.48 X10-3, 7.53 X10-3, 5.21 X10-3, 6.46 X10-3, and 1.15 X10-3 for HEPA, facial mask, CRH, RH, sugarcane, and coconut fiber filters, respectively. The tensile strengths (MPa) were 69.3 X10-2, 82.6 X10-2, 32.7 X10-2, 25.5 X10-2, 102 X10-2, and 87.2 X10-2 of HEPA, dental mask, CRH, RH, sugarcane, and coconut fiber filters, respectively. HEPA filters performed best, though their materials were made from non-biodegradable materials. CRH and dental masks were second best, with both maintaining a similar level of performance. Overall, CRH demonstrated the highest potential as an air filtration media of the natural fibrous materials. (sic)(sic)(sic)(sic)(sic)(PM)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(HEPA)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)--(sic)(sic)(sic)(sic)(CRH),(sic)(sic)(RH),(sic)(sic)(sic)((sic)(sic))(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic),CRH,RH,(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)12.4 x 10-3,8.48 x 10-3(sic)7.53 x 10-3. HEPA,(sic)(sic),CRH,RH,(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(MPa)(sic)(sic)(sic)69.3 x 10-2,82.6 x 10-2(sic),32.7 x 10-2(sic),25.5 x 10-2,102 x 10-2(sic)(sic)87.2 x 10-2(sic)(sic). HEPA(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). CRH(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic), CRH(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

IntroductionImproving the efficacy of nasal sprays by enhancing targeted drug delivery to intra-airway tissue sites prone to infection onset is hypothesized to be achievable through an optimization of key device and formulation parameters, such as the sprayed droplet sizes, the spray cone angle, and the formulation density. This study focuses on the nasopharynx, a primary locus of early viral entry, as the optimal target for intranasal drug delivery.MethodsTwo full-scale three-dimensional anatomical upper airway geometries reconstructed from high-resolution computed tomography scans were used to numerically evaluate a cone injection approach, with inert particles mimicking the motion of sprayed droplets within an underlying inhaled airflow field of 15 L/min, commensurate with relaxed breathing conditions. Therein we have considered monodisperse sprayed particles sized between 10–50 μm, six material densities ranging from 1.0–1.5 g/mL for the constituent formulation, and twelve plume angles spanning 15 ° – 70 ° subtended by the spray jet at the nozzle position. Large Eddy Simulation-based modeling of the inhaled airflow physics within the anatomical domains was coupled with a Lagrangian particle-tracking framework to derive the drug deposition trend at the nasopharynx.ResultsThe resulting three-dimensional deposition contour map, obtained by interpolating the outcomes for the discrete test parameters, revealed that the mean nasopharyngeal deposition rate peaked for particle sizes d∈ [25, 45] μm and plume angles θ≲ 30 °, with the deposition rates averaged over the test airway geometries and formulation densities. That mean deposition rate at the nasopharynx was approximately 11.4% within the specified {d,θ} parametric bounds. In addition, the formulation density of 1.0 g/mL yielded the highest mean deposition rate, over the comprehensive tested range of sprayed particle sizes and plume angles. A subset of the simulated nasopharyngeal deposition trends was experimentally validated through representative physical spray tests conducted in a 3D-printed replica of one of the test geometries.DiscussionThe overall findings, while implicitly tied to the two test subjects (i.e., for spray administration through four representative nasal pathways), do collectively demonstrate that rational optimization of the intranasal sprays for targeted nasopharyngeal deposition is attainable with actionable design modifications on the sprayed droplet sizes and device plume angles.

Cutting onions often leads to tear-inducing aerosol release, yet the underlying mechanics remain poorly understood. In this work, via high-speed characterizations, we show that droplet formation occurs via a two-stage process: an initial high-speed outburst followed by slower ligament fragmentation. By systematically varying blade sharpness and speed, we find that faster or blunter blades significantly increase both the number and energy of ejected droplets. Strain mapping reveals that the onion's tough epidermis acts as a barrier to fracture, enabling the underlying mesophyll to undergo significant compression before rupture. Developing a simplified bilayer model, we experimentally and theoretically capture the mechanism behind, with numerical calculations of the onion critical fracture forces matching independent Instron results. The work highlights the importance of blade sharpening routines to limiting ejected droplets infected with pathogens in the kitchen, which pack additional outburst energy due to vegetables' outer strong casings.

When a slice of beet is placed on a plate with a thin layer of beet juice, one can observe a clear fringe around the beet, where the color is more translucent than the rest of the juice. The hypotheses in literature were inconsistent and limited, which motivated us to revisit this phenomenon. Using a motorized confocal displacement sensor, we measured the temporal evolution of the liquid surface profile across the fringe. Our findings suggest that a suction flow, induced by the capillary rise of the contact line, causes a dimple - a small concave depression - to form on the liquid surface. While surface tension and gravity tends to smooth out the dimple, viscous drag acts against them if the liquid film is sufficiently thin. Our scaling analysis correctly estimates the dependence of dimple lifetime on liquid properties and film thickness. We also capture the dimple formation dynamics by numerically solving the lubrication equation with the Young-Laplace equation. This work provides a new interpretation for a common phenomenon.

Currently, mankind is fiercely struggling with cancer. Recently, we have been winning the battle against cancer through precision medicine and accompanying diagnostic methods, and we are raising many hopes with blockbuster drugs. It would be even better if we could read the cancer nucleotide sequence, identify them in advance, and suggest treatments simultaneously. However, this may be an impossible dream because it takes a lot of time and effort to diagnose and ensure all the long gene sequences of cancer at once. Thus, victory will be even closer if a rapid and accurate diagnosis of the cancer-specific gene biomarkers that will soon be imprinted can be made. With the advent of nanotechnology, a new short cancer diagnostic toolkit has been proposed to achieve the goal. This review presents a small diagnostic device that detects certain cancers' genetic fragments (simply 'Gizmo'). The development of numerous diagnostic methods has focused on (1) directly detecting pre-selectively targeted genes using novel diagnostic systems, and (2) indirectly detecting substantial improvements in diagnostic sensitivity only through detection signal amplification without existing gene amplification steps. Our fight against cancer is not a dream, but the result of success, and it is assumed that victory will accelerate as soon as possible.

Active matter systems, due to their spontaneous self-propulsion ability, hold potential for future applications in healthcare and environmental sustainability. Marangoni swimmers, a type of synthetic active matter, are a common model system for understanding the underlying physics. Existing studies of the interactions of active matter with passive particles have mostly focused on the modification of the behavior of the passive particles. In contrast, we analyse here experimentally the impact on the self-propulsion of camphor-infused agarose disks (active) of their interactions with floating hollow glass microspheres (passive) within an annular channel. Two distinct regimes are observed: a steady regime with unidirectional motion of the swimmer at low packing fractions (ϕini ≲ 0.45) and an oscillatory regime with to-and-fro motion at higher packing fractions (ϕini ≳ 0.45). In the former, the swimmer pushes nearly the entire particle raft together with it, like towing a cargo, causing a decrease in swimmer speed with increasing packing fraction due to the additional drag from the particle raft. A simplified force-balance model is finally proposed that captures the experimental trend in swimmer speed reasonably well.