Researchers at MIT have shown that a complex class of microscopic nozzle, normally built only inside semiconductor cleanrooms, can be produced in a matter of hours using 3D printing. The devices, known as triaxial electrospray emitters, generate microscopic droplets made of three separate fluid layers, droplets that can harden into structured microparticles for uses ranging from time-release medicines to self-healing materials.
The work was led by Bryan Ivan Quintanar-Abarca of the Technological Institute of Monterrey in Mexico, with Luis Fernando Velásquez-García, a principal research scientist in MIT’s Microsystems Technology Laboratories, as senior author. Their findings were published in the journal Virtual and Physical Prototyping.
Triaxial electrospray emitters. Photo via MIT.
How the Nozzles Work
An electrospray emitter applies a high voltage to liquid as it leaves a nozzle, producing a continuous stream of extremely fine droplets. A triaxial device takes this further, using three concentric nozzles to dispense three immiscible liquids at once, layering them into a single droplet. Each droplet can then solidify into a particle with three distinct shells.
The structure lends itself to controlled-release applications. A drug-delivery particle, for example, might have an outer layer that gradually dissolves in the stomach to expose a middle layer, which in turn regulates when a medicinal core is released at a targeted point in the intestines. The same layering approach can be used to embed several chemical markers in a single biosensing particle, with one marker per layer.
Because a single emitter produces only a small output, practical manufacturing depends on packing many emitters into an array while keeping every nozzle behaving identically. Smaller emitters are also preferable, since shrinking the nozzle lowers the voltage needed to form droplets. Conventional cleanroom fabrication, however, restricts the shapes and sizes that array components can take, and the MIT group says it could find no earlier published account of a miniaturized triaxial electrospray array, underscoring how new the result is.
Printing the Impossible Part
The team’s answer was vat photopolymerization, a 3D printing method that uses light to cure ultra-thin layers of liquid resin one at a time. The precision of the technique let them print layers just 25 micrometers tall, a small fraction of the width of a human hair, fine enough to build the intricate internal geometry a triaxial emitter requires. The result is a single-piece array, slightly larger than a U.S. penny, holding 16 nozzles within roughly one square centimeter.
Inside the device, a network of coiled, helical microchannels distributes liquid evenly to every nozzle while keeping the overall footprint compact. The channels had to be formed without internal support structures, which could otherwise clog the flow paths, and all uncured resin had to be flushed out before use. The concentric nozzles themselves must be aligned precisely for the droplets to form consistently.
“We couldn’t make a device like this in a semiconductor cleanroom. This is only possible because they are 3D printed,” said Velásquez-García. He framed the broader goal in similar terms: “We want to democratize this technology so the benefits can touch many more people.”
A central advantage of the approach, the researchers say, was the speed of iteration. “We were able to aggressively optimize the design because we could iterate in a much timelier manner. This ability to exquisitely refine designs is a key advantage of 3D printing,” Velásquez-García says. He likened the array’s behavior to emitters that never realize they have neighbors, avoiding the cross-talk that would otherwise interfere between adjacent nozzles.
What the Testing Revealed
When the printed arrays were run, they produced uniform three-layered droplets at scale, the consistency that high-throughput particle manufacturing depends on. Testing across several internal architectures turned up an unexpected finding: the viscosity of the middle liquid mattered most for droplet stability, because it held the thickness of each layer in place.
A zoomed-in view of the nozzles that emit the three-layered microdroplets. Photo via MIT.
The team also found that adjusting flow rates and voltages let them tune the thickness of individual layers, a degree of control that could allow scientists to engineer drug-delivery particles that release medicine on a precise schedule.
“By making such intricate devices more practical, we can empower others to pursue entrepreneurial and scientific advances,” Velásquez-García says.
Looking ahead, the researchers intend to push the dimensions smaller still and to incorporate conductive or dielectric materials, opening the door to more sophisticated emitter arrays.
Lowering the Barrier to Microfabrication
The significance of the MIT work lies less in the emitter itself than in how it was made. The team’s strategy is to take a device that historically demanded a semiconductor cleanroom and reproduce it through a single automated print run that finishes in hours.
That ambition mirrors a broader movement among micro-scale 3D printing vendors. BMF has positioned its microArch S150 Series squarely at microfluidics, fiber optics, biomedical devices, and electronics, pairing HEPA filtration and UV-C sterilization with a heated resin vat so the system can run high-viscosity formulations in contamination-sensitive, cleanroom-adjacent settings. The pitch is much the same: deliver the precision once reserved for specialized facilities on a machine a smaller operation can own and operate.
Earlier moves point in the same direction. The microfabrication startup Horizon Microtechnologies debuted a template-based micro-additive process at Formnext 2022 aimed at producing conductive microstructures for electrodes, microfluidic devices, MEMS, and optics packaging, areas its founders argued had gone largely unserved by conventional methods.
Across these efforts runs a common thread: shifting intricate, micron-scale manufacturing away from the cleanroom and toward accessible, iterable additive workflows. For drug delivery, biosensing, and self-healing materials, the gating factor becomes design, not fabrication access. That shift is what could let the technology, as the researchers put it, reach far more people.
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Featured image shows Triaxial electrospray emitters. Photo via MIT