Proximal Sound Printing: Ultrasound 3D Prints Microstructures Directly Onto Silicone

The Problem With Printing On Silicone

Silicone is the go-to material for soft robotics, microfluidics, lab-on-a-chip devices, and biomedical sensors. It's flexible, biocompatible, and chemically stable. But structuring silicone at the microscale has always been painful.

Conventional 3D printing methods rely on light or heat — neither of which plays nicely with silicone's chemistry. Photopolymer resins aren't silicone. Heat-curing methods are slow and imprecise. The result: microscale manufacturing on silicone often means complex molding processes or expensive cleanroom equipment.

Enter Proximal Sound Printing

Researchers at Concordia University have developed Proximal Sound Printing (PSP) — a new class of additive manufacturing that uses focused ultrasound to cure polymers directly on soft substrates like silicone.

The technique, published in Microsystems & Nanoengineering, positions an ultrasound transducer very close to the substrate surface (hence "proximal") and triggers localized polymerization through cavitation — tiny bubbles formed and collapsed by sound waves.

The Breakthrough Numbers

Compared to existing sound-based 3D printing methods, PSP delivers:

• 10x better resolution — Features down to tens of microns
• 4x lower power consumption — Gentler on sensitive substrates
• 1600x lower acoustic streaming velocity — More controlled, repeatable curing

Most importantly, PSP can print directly onto PDMS (polydimethylsiloxane) — the standard silicone elastomer used in microfluidics and soft lithography — without changing its formulation.

How It Works

The process works by positioning a focused ultrasound transducer just above the liquid polymer reservoir. When activated, the sound waves create cavitation bubbles in the polymer. These bubbles collapse, generating localized heat and pressure that triggers polymerization exactly where you want it.

By moving the transducer (or the substrate), you draw 3D structures. The proximity of the transducer to the work area is the key innovation — it dramatically improves resolution and repeatability compared to previous ultrasound printing techniques.

What You Can Make

The Concordia team demonstrated:

• Multi-material structures — Different polymers printed in a single build
• Microfluidic channels — Direct printing of fluidic networks on silicone
• Soft sensors — Conductive traces embedded in elastomer substrates
• Lab-on-chip devices — Complete microsystems printed in place

Why This Matters

Microfluidics and soft sensors have been stuck in a manufacturing bottleneck. Designing these devices is relatively easy with modern CAD tools. But fabricating them at scale, with the precision needed for commercial applications, has meant expensive cleanroom processes or injection molding.

PSP offers a path to rapid prototyping of microscale soft devices on standard silicone substrates. For researchers and small companies, that's a significant reduction in the barrier to entry.

Current Limitations

This is a research technology, not a commercial product yet. The Concordia team has demonstrated the principle and published the science, but you can't buy a PSP printer today.

However, the technique uses relatively standard components — ultrasound transducers, motion systems, polymer reservoirs. A determined engineering team could replicate the setup without exotic equipment.

The Bigger Picture

PSP joins a growing family of alternative 3D printing technologies that move beyond light-curing. Sound-based, magnetic, and electrostatic printing methods are opening new material possibilities that photopolymers can't touch.

For makers working in soft robotics, biomedical devices, or microfluidics, this is worth watching. The ability to print microscale structures directly onto silicone — without molds, without cleanrooms — would change how these devices go from concept to reality.

The Bottom Line

Proximal Sound Printing represents a genuine advance in microscale additive manufacturing. By using ultrasound to cure polymers on silicone with unprecedented precision, it opens new possibilities for soft devices that were previously stuck in the research lab.

Watch this space. When PSP hits commercial availability, it could democratize microfluidic and soft sensor fabrication in the same way desktop FDM democratized mechanical prototyping.