3D-Printed Heatsink Trims Cooling Mass in APL Tests

A 3D-printed heatsink is the garage-and-lab thermal story this week, not a new desktop metal SKU: Johns Hopkins APL printed single-piece SPEAR sinks, filled them with phase-change material, and ran them next to aluminum. APL’s September 2, 2026 release says the design can cut size and weight by more than 50% at the same thermal capacity. For a tight radio or ESC bay, that is a sealed cavity that melts on purpose — not a FibreSeeker that prints aluminum fins.

What's Happening

SPEAR stands for Smart Phase-change Enhanced Re-entry. Engineers at APL in Laurel, Maryland combined a phase-change material (PCM) with additive manufacturing so the sink is one printed piece instead of a stack of machined parts. A PCM stores heat while it changes from solid to liquid. Senior mechanical engineer Greg Merboth used the ice-in-a-drink analogy: the melt holds temperature down while the phase change is underway. Mechanical engineer Yoni Ferneau said that is useful where electronics dump a lot of heat for a short time — hypersonics, space systems, radio-frequency gear, transmitters, interceptors, and other transient or low-duty-cycle loads. It is not a pitch for a server that runs at 100% all afternoon.

The team started with a baseline aluminum sink and made two SPEAR parts for a side-by-side test. One matched the aluminum volume, to show how much extra thermal storage fits in the same space. The other matched the aluminum thermal capacity, to show how much size and weight they could shed. They filled and sealed the printed sinks and reported no leaks. They then built a demo box that heats several sinks at once and plots temperatures live. Danielle Hilliard, who oversees design, engineering, and fabrication at APL, framed SPEAR as a shared thermal problem turned into a capability the lab can retarget. All of those performance lines — the 50% cut, the dry seals, the “expected” SWaP benefit — are the laboratory’s. This is not a flight-qualified coupon and not a part number you can order.

Why a 3D-Printed Heatsink Matters for Compact Electronics

A garage drone build and a hypersonic bay are different programs. They share one packing problem: the board gets hot in a burst, and you do not have room for a brick of fins. A phase-change cavity buys time. It does not invent a new way to dump heat to air once the wax is liquid. If your transmitter keys for thirty seconds, a PCM sink can be the difference between a thermal trip and a clean pass. If the same radio keys for an hour, you still need convection, a fan, or a bigger metal path.

Keep the process map honest. APL used additive manufacturing to make a single-piece sink it could fill. That is almost certainly a metal or high-conductivity print, compared against aluminum. A desktop FFF shell filled with craft wax is a leak experiment, not SPEAR. Continuous fiber on a thermoplastic printer can hold the radio, the fan, or the sink itself. It is a poor heat spreader. Do not treat a carbon-fiber tray as the thermal path, and do not treat “more than 50%” as a number you will hit with PLA ribs.

How a 3D-Printed Heatsink Compares to Shop Options

Cooling job	Typical hardware	What fails first
Steady high load	Aluminum or copper fins + airflow	Not enough area; fan dies
Short burst, tight bay	PCM cavity (APL SPEAR class)	Wax fully melted; then it is just a block
Garage FFF “sink”	Hollow PLA/PETG + poured wax	Seam leak; plastic is an insulator
Printed metal lattice + wax	AM aluminum filled with paraffin	Peer-reviewed path; still a seal problem
Composite radio tray	Continuous-fiber or PETG bracket	Holds the board; does not cool it

What the Research Says

Wei, Cui, Sun, and colleagues melt-blended paraffin in a polymer, added modified boron nitride, and used fused jet deposition to print phase-change heat sinks for electronics. In their practical sink test, the printed composite dropped the cooled surface by more than 50 °C versus the untreated case. That is a polymer-matrix PCM you can shape on a printer, not APL’s metal-class comparison, and the 50 °C figure is their cooling delta, not APL’s mass cut. It does show why labs keep trying to print the cavity instead of machining a puzzle of plates (Wei et al., 2025).

Righetti, Savio, Meneghello, Doretti, and Mancin printed three aluminum periodic lattices (10, 20, and 40 mm cells, 95% porosity), filled them with about 50 g of paraffin that melts near 55 °C, and heated at 10, 20, and 30 W. The metal ligaments sped both melting and solidification compared with a wax-only volume, because plain PCM conducts heat poorly. APL’s “print it as one piece, then fill” move sits on that same physics: the printed metal is the conductivity; the wax is the storage (Righetti et al., 2020).

Frequently Asked Questions

What is a 3D-printed heatsink with phase-change material?

It is a printed cavity filled with a material that melts and stores heat, so temperature rises more slowly on a short load. Johns Hopkins APL printed single-piece SPEAR sinks, filled and sealed them, and compared them with aluminum. That is a lab prototype, not a catalog part, for heat bursts rather than a motor that runs all day.

Can I print a phase-change heatsink on a desktop FFF printer?

You can print a polymer shell or coarse lattice and pour wax, but that is not APL’s metal-class comparison and not a FibreSeeker job. Peer-reviewed FFF work has used nylon mixed with encapsulated wax for building-scale storage. Treat a garage print as a leak experiment. Do not put paraffin next to a flight battery without a sealed, tested design.

Is a continuous fiber bracket a substitute for a metal heatsink?

No. Continuous fiber is for the clamp, duct, or radio tray that has to hold a load path. Heat still needs a conductive path — aluminum, copper, or a designed PCM cavity. A carbon-fiber jig can locate a sink. It does not replace the sink, and it should not be your plan for dumping a transmitter’s waste heat.

Fibricate's Place in This Story

A printed metal PCM cavity and a desktop thermoplastic tow answer different packing questions. Companies like Fibricate, whose FibreSeeker 3 continuous carbon fiber 3D printer lays polymer with a tow from feedstock such as the continuous carbon fiber spool, are not printing SPEAR sinks and are not a substitute for aluminum. Use the desktop machine when the radio tray, fan shroud, or clamp needs a designed fiber path in a tight bay. Leave the heat path to metal, copper, or a sealed PCM part someone has actually leak-tested. Do not treat a carbon-fiber bracket as a heatsink, and do not treat APL’s 50% mass cut as a FibreSeeker spec.

What to Watch Next

Watch the duty cycle, not the Pelican-case photo. The useful public signals are melt temperature versus the board’s trip point, how many heat pulses a fill survives before the seal weeps, and whether APL publishes the metal process and the PCM chemistry. Over the next year, expect more compact radios and compute modules to show up with printed cavities instead of fin stacks — and more garage builds that pour wax into PLA and then clean it off the bench. The split that will still matter in 2027 is bursts you can store in a melt versus heat you still have to dump to air after the wax is liquid.

References & Further Reading

1. Wei, F., Cui, G. P., Sun, K. Y., et al. (2025). 3D printing phase-change-based heat sinks for cooling electronic devices. Progress in Additive Manufacturing.
2. Righetti, G., Savio, G., Meneghello, R., Doretti, L., & Mancin, S. (2020). Experimental study of phase change material (PCM) embedded in 3D periodic structures realized via additive manufacturing. International Journal of Thermal Sciences.
3. Johns Hopkins APL Researchers Developing New Heatsink Using Additive Manufacturing. Newswise / Johns Hopkins Applied Physics Laboratory. Retrieved September 3, 2026.