High-speed experiments in DMSO/water mixtures test how trace Tween 80 and sodium dodecyl sulphate affect bubble bursting near the conditions that minimise the first jet droplet. Surfactant increases that droplet's radius and lowers its speed even when the initial surface tension changes little. For Tween 80 at c/ccmc = 0.0233, the measured radius rises by a factor of 2.8 and the paper reports an approximately twentyfold increase in volume. The authors interpret the observations through surfactant accumulation, local surface-tension gradients and Marangoni stress, which widens the jet and delay

THE SCIENCE OF A BURSTING BUBBLE

The smallest droplet has a hidden ingredient.

A bubble can look almost perfectly clean—and still launch a much larger drop. This study follows how a tiny amount of surfactant transforms the final millisecond of a bubble’s life.

Rodríguez-Aparicio et al. · Journal of Fluid Mechanics · 2026

larger first-drop radius

more liquid in the first drop

lower initial surface tension

Measured with trace Tween 80: c/ccmc = 0.0233, near the minimum-drop regime.

01 / THE BURST LAB

Follow the surface. Change the drop.

Add a trace of surfactant, then slow down the burst. Watch where the molecules gather—and what happens next.

A nearly unchanged initial surface tension hides the trace surfactant.

Illustrative transition between measured endpoints; shapes, timing and intermediate doses are schematic. The clean endpoint has Rd/Rb = 0.023. The trace endpoint gives 2.8× that radius.

A surface rushes inward

Once the cap breaks, capillary waves travel down the cavity. The collapse focuses liquid at the bottom.

Molecules crowd together

Surfactant rides the moving interface. Its local concentration rises near the cavity bottom, even when its initial concentration is tiny.

The jet changes course

Surface-tension gradients create Marangoni stress. The jet becomes wider, its surface motion slows, and the first drop detaches later—allowing more liquid into it.

02 / THROUGH THE HIGH-SPEED CAMERA

The bottom gets narrower. The drop gets bigger.

The surprise starts before the jet. These original frames resolve the cavity’s final approach to reversal at 420,000 frames per second.

Original images: Rodríguez-Aparicio et al. (2026), supplementary Figure S3, CC BY 4.0. Frames extracted, cropped and enlarged. Times are (t − tr)/t₀, aligned to each experiment’s own reversal; the pair does not share the same absolute time.

03 / THE MEASURED PAYOFF

A little chemistry. A larger first drop.

The original photographs show the first-emitted drop at increasing Tween 80 concentration. Even the largest dose shown barely changes the initial surface tension.

Original images: Rodríguez-Aparicio et al. (2026), Figure 10, CC BY 4.0. Photographs extracted from the figure and enlarged; original arrows and scale annotation omitted. Concentration labels recreated.

The average is not the whole story.

Measuring the initial surface tension alone misses the local dynamics. During a burst, a sparse layer becomes a crowded patch—and differences along the interface change how liquid moves.

04 / BEYOND A SINGLE BUBBLE

From a tiny jet to the atmosphere.

Sea spray begins with bubbles. Their drops carry salts, chemicals and biological material from water into air.

This study offers a mechanism for why even faint surface contamination can make the smallest jet drops larger. That may help explain the size of sea-spray particles and the material they transport.

The experiments use a controlled DMSO–water mixture; the ocean connection is an implication of the mechanism.

05 / MAKING THE EXPERIMENT POSSIBLE

From a printed tip to an airborne drop.

Two-photon lithography made the bubble-source needle tips. The study’s central question is fluid mechanics; precise microfabrication makes that question experimentally accessible.

10–40 µm needle openings

IP-S resin tips, printed on a Nanoscribe Photonic Professional GT2 in dip-in laser lithography mode.

One controlled bubble at a time

Nitrogen enters through the tips into a 40 mm cubic glass tank. Bubble radii range from 180 to 650 µm.

Catch the last microseconds

High-speed imaging reaches 420,000 fps to resolve the reversal and the birth of the jet.

Fabrication and imaging: paper §2.1. The GT2 uses two-photon polymerization; instrument technology.

The regime studied

The researchers focus on the smallest first-emitted droplets, near a Laplace number La ≈ 1100 and a Bond number Bo ≈ 0.01. A 50/50 wt DMSO–water mixture provides experimentally accessible bubbles while reproducing the relevant viscous–capillary regime.

A moving monolayer

Before bursting, the surfactant monolayer is treated as equilibrated. Over the roughly 1 ms burst, it is effectively insoluble: convection redistributes molecules along the interface, with negligible exchange with the bulk.

Reading the virtual experiment

The lab is a conceptual animation, not a numerical flow simulation. The dose slider interpolates between clean and measured trace endpoints. Its shapes and timing show the sequence of mechanisms rather than measured trajectories or an empirical dose–response fit.

Connecting to seawater

The laboratory mixture and seawater differ in surfactant adsorption, the equation of state and Bond number. The paper identifies a physical mechanism with relevance to sea spray, rather than measuring sea spray directly. The effect was also measured with the weaker surfactant sodium dodecyl sulphate (SDS), supporting the relevance of faint contamination.

THE SOURCE PAPER

Sergio Rodríguez-Aparicio · Alberto Cebrián-García · Emilio J. Vega · José María Montanero · María Guadalupe Cabezas

Journal of Fluid Mechanics 1032 , A49 (2026) · DOI: 10.1017/jfm.2026.11412