A research team at the University of Twente has taken one of thermal engineering’s hardest problems off the simulation bench and into the air, running pool boiling experiments on 3D-printed nickel-titanium micropillar surfaces during parabolic flights where gravity flipped between weightless, normal, and double-strength in a matter of seconds.
The work tested whether engineered “smart skins” combined with applied electric fields can replace the buoyancy that ordinarily lifts vapor bubbles off a hot surface on Earth — a mechanism that simply does not exist in orbit.
If the approach holds up, it points toward a way to cool spacecraft electronics, propellant tanks, and high-density power systems without relying on the gravity-driven physics that every terrestrial heat exchanger quietly assumes.
Why boiling breaks in space
Boiling is one of the most efficient heat transfer processes known. A bubble forms at a hot surface, grows, detaches, rises through the fluid, and carries an enormous quantity of energy with it. The cycle repeats thousands of times per second across a heated plate.
Strip out gravity and the cycle stalls. Without buoyancy, bubbles cling to the surface, merge into insulating vapor blankets, and choke off the heat path. In microgravity, the absence of buoyancy fundamentally changes how heat is transferred.
That problem has dogged spacecraft thermal engineers for decades. Research at Purdue University has spent years mapping how two-phase flow behaves under reduced gravity, with implications for everything from lunar habitats to crewed Mars vehicles.
The Twente experiment
The team, led by Davoud Jafari and working with collaborators at the University of Pisa, designed micropillar arrays from nickel-titanium — a shape-memory alloy — using additive manufacturing. The pillars act as nucleation sites where bubbles preferentially form. Crucially, the surfaces can respond to applied electric fields, which exert forces on the bubbles directly, independent of gravity.
That combination — 3D-printed functional metal, controlled boiling, and electrohydrodynamic forcing — is what the team carried aboard a parabolic flight aircraft operated by Novespace. Each parabola gave them roughly twenty seconds of microgravity, sandwiched between phases of hypergravity at nearly twice Earth gravity.
The constantly changing gravity environment provides a rigorous test of how these systems respond under dynamic conditions.
Nickel-titanium is unusual among engineering metals. It can change shape in response to temperature or stress and conducts heat well enough to matter for thermal applications. Printing it as an array of micropillars rather than machining it lets the team tune surface geometry at scales that drive boiling behavior — the size, spacing, and curvature of nucleation sites.
Additive manufacturing of high-performance nickel alloys has matured rapidly. Researchers at Japan’s National Institute for Materials Science and Osaka University have demonstrated laser printing of nickel single crystals, a technique aimed at jet engine components but directly relevant to building defect-free thermal structures.
The broader field of advanced metals and alloys has been pushed in the same direction by demand from aerospace and energy: print complex shapes in materials that survive high temperatures and aggressive cycling.
The electric field gambit
The core hypothesis the group is testing is whether an electric field can do the work that gravity does on Earth — pulling bubbles away from a hot surface fast enough to keep heat moving.
The microgravity environment is where the idea actually matters. If buoyancy contributes nothing, any departure force has to come from somewhere else. An applied field, acting on the dielectric properties of the vapor-liquid interface, is one of the few candidates that scales cleanly and can be switched on and off electronically.
The Pisa group had already shown the principle works. In an earlier ESA parabolic-flight study, pairing microstructured surfaces with an electric field pushed the critical heat flux in microgravity above the value the same researchers measured on Earth using a plain surface — evidence that a field can stand in for missing buoyancy when the surface is engineered to cooperate.
Pairing the field with a surface that itself responds to electrical input — the NiTi micropillars — adds a second layer of control. The surface can be tuned to release bubbles preferentially, and the field can sweep them away. In principle, the two together form a closed-loop cooling system with no moving parts.
The thermal management problem nobody talks about
Spacecraft thermal control rarely makes headlines, but it sets hard limits on what missions can do. Every watt of electrical power eventually becomes a watt of heat that has to be radiated to space. As satellites get denser — high-power radar, optical payloads, onboard AI inference — the heat fluxes are climbing into territory where passive radiators and single-phase pumped loops start to struggle.
Two-phase cooling, which uses boiling and condensation to move heat, can handle significantly more flux per unit area than single-phase systems. That is why NASA has run boiling and condensation experiments on the International Space Station for years through its Flow Boiling and Condensation Experiment, work covered by SpaceNews as it investigated how reduced gravity reshapes phase change. And it is why Case Western Reserve University and NASA Glenn received federal funding to expand microgravity research spanning thermal management and fluid dynamics.
Cryogenic propellant management, increasingly central to plans for in-space refueling and long-duration deep-space missions, has its own version of the same problem. Phase behavior governs whether liquid hydrogen or methane can be moved reliably between vehicles in microgravity.
What parabolic flight actually proves
Parabolic flight is an imperfect substitute for orbital microgravity. The free-fall phase lasts only seconds, the aircraft vibrates, and the transitions through hypergravity stress the equipment in ways that an orbital experiment would not see.
But those constraints are also part of the point. Performing high-precision experiments while transitioning between hypergravity and weightlessness pushes both the equipment and the team to their limits.
The Twente runs give researchers something simulations cannot: real bubble dynamics on real surfaces under real changing gravity. Computational fluid dynamics models of boiling are notoriously sensitive to assumptions about nucleation, contact angle, and bubble departure. Experimental data from flights like these is what gets fed back into the models to calibrate them.
Beyond spacecraft
The terrestrial application is less obvious but potentially larger. Power electronics — the chips that run electric vehicles, data centers, and grid-scale converters — generate heat fluxes that already exceed what conventional liquid cooling can clear in some designs. Smart surfaces that boil on demand and use electric fields rather than pumps could change the geometry of those systems.
The same logic applies to flexible and unconventional electronics, where rigid heat sinks are not an option. Thermal management is one of the bottlenecks in that field too.
What makes the Twente work worth watching is its integration. Additive manufacturing, boiling heat transfer, and electric field control have all been studied separately for decades. Putting all three together on a single surface, then flying it, is the kind of cross-disciplinary experiment that tends to produce either a dead end or a new design language for thermal systems.
The team has not yet published full results from the flight campaign. What they have shown is that the hardware survives the gravity transitions and that the measurement approach works. The harder question — whether electric fields can fully compensate for missing buoyancy at the heat fluxes spacecraft actually need — remains open.
For an engineering field that has spent half a century working around the absence of gravity rather than designing for it, even framing the question that way is a shift.
