Research

Spine biomechanics

Spine Biomechanics

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Elastohydrodynamics

Elastohydrodynamics and Adhesion

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Surface Bubbles

Surface Bubbles and Aerosols

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Droplets

Droplets and Capillarity

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Spine Biomechanics

The “hero shrew” (Scutisorex) has the strangest spine of any mammal: its lumbar vertebrae interlock through dense arrays of bony tubercles. We use finite-element modelling to investigate the evolutionary advantage these tubercles might confer.

The interactive animation below shows 3D micro-CT scans of three shrews: the hero shrew (Scutisorex somereni), Thor’s hero shrew (Scutisorex thori), and a shrew with an ordinary spine, the goliath shrew (Crocidura goliath).

Micro-CT scans courtesy of Stephanie Smith (Field Museum of Natural History, Chicago), from Smith & Angielczyk (2020).

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Elastohydrodynamics and Adhesion

Contactless suction cups

When a thin elastic sheet vibrates just below a ceiling, it can grip the surface in a state of seemingly contactless adhesion, an effect that can lift objects weighing from a few hundred grams up to tens of kilograms. We combine viscous lubrication theory and simulations to predict the sheet’s hovering height, deformations and load capacity, and show how the air’s compressibility and inertia weaken the adhesion.

An elastic sheet, periodically pushed and pulled at its center beneath a rigid wall, deforms and drives a viscous flow. The resulting pressure field (color) generates an effective net upward force, keeping the sheet levitating against gravity.

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Bonding of an elastic sheet

As an elastic sheet first touches a substrate, a contact front propagates, squeezing out the fluid trapped between them. We model the interplay between bending, viscous drainage, and adhesion to predict the front’s speed and shape. This is central to silicon wafer bonding, where adhesion must be controlled precisely enough to join 300 mm-diameter wafers with nanometric accuracy.

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Surface Bubbles and Aerosols

Upon bursting, surface bubbles transfer chemicals and pathogens from water to the atmosphere. We investigated the thinning dynamics of bubbles, exploring the interplay between capillary drainage, Marangoni flows, and evaporation in pure water, salt water, soapy water, and bacteria-contaminated water. We also proposed a mechanism that rationalizes their burst.

Mixing dynamics within a surface bubble at the air–water interface.

A surface bubble bursting and ejecting aerosols into the atmosphere.

We studied the fragmentation of bubbles into droplets, which, as they dry, become condensation nuclei on which clouds can form. Using simulations of turbulent flows, we investigated how turbulence affects the growth and size distribution of droplets.

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Droplets and Capillarity

Droplet impact on soft substrates

We developed a three-phase lubrication model to understand how droplets settle on solids coated with soft layers (viscous films, elastic layers). Our analysis reveals how soft coatings significantly alter droplet dynamics during gravitational settling.

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Droplets on vibrating fibers

We experimentally studied the dynamics of water droplets on tilted, vertically oscillating fibers. Droplets exhibit different modes—harmonic pumping, subharmonic pumping, rocking, and swinging—depending on the oscillation frequency and amplitude, significantly affecting their sliding speed.

A water droplet sliding on a fiber vibrating at 90 Hz exhibits a subharmonic response and sheds satellite droplets.

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Cavitation and particle dynamics

We characterized how spherical particles respond to cavitation bubbles in fluids, showing that particle velocity depends on distance from the bubble as an inverse-fourth-power law.

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