When most people think about resin 3D printing, they picture miniatures, collectibles, or highly detailed prototypes.
But what happens when the parts get so small that their features are measured in microns instead of millimeters?
That is where micro 3D printing starts to change more than the manufacturing process. It can change the size of a surgical tool, how invasive a procedure needs to be, and how quickly a patient may recover afterward.
In the second part of our conversation with Carl Leonard, an application development material specialist at Boston Micro Fabrication, we explore how microscopic resin 3D printing is being used to develop medical devices that would be extremely difficult—or sometimes impossible—to manufacture using traditional methods.
Why Smaller Medical Tools Matter
Medical tools often need to operate in extremely limited spaces. If a surgeon can perform a procedure through a two-millimeter opening instead of a 10-millimeter opening, that difference can mean a smaller incision, a smaller scar, a less invasive procedure, and a shorter recovery period.
That sounds simple enough: Just make the tool smaller.
But shrinking a device is rarely that easy.
A small surgical tool may still need to hold a camera, provide lighting, move fluids, and operate tiny mechanical components. Every feature has to fit into a smaller space without sacrificing the function of the device.
This is one area where micro 3D printing can give engineers new options.
From Thumb-Sized Endoscopes to Devices the Size of a Grain of Rice
Endoscopes have changed dramatically over time. Earlier commercial devices were much larger and less flexible than the tools available today. According to Carl, some of the devices being developed now can be approximately the size of a grain of rice while still containing a camera and other functional components.
That level of miniaturization creates manufacturing challenges.
An endoscope shell may need internal holes, channels, curves, and openings smaller than 100 microns—and sometimes smaller than 50 microns. Once those features begin twisting or curving inside the part, traditional machining and molding methods can run into practical limits.
Micro 3D printing makes it possible to build those complex internal features as part of the object instead of trying to drill, cut, or assemble them afterward.
Print the Difficult Feature First
One of the most interesting parts of the conversation was Carl’s approach to prototyping.
Imagine that an engineer is designing an endoscope with a spiraled internal channel measuring only 20 microns in diameter. Instead of immediately printing the entire device, Carl may isolate that one section in CAD and print it by itself.
Why?
Because that channel is the uncertain part of the design.
If the rest of the device contains features that the team already knows how to manufacture, printing the complete model would use more time and material without answering the most important question. A small test section lets the team determine whether the channel prints correctly, whether it remains open, and whether the geometry needs to change.
That creates a much faster feedback loop:
1. Identify the most challenging feature.
2. Isolate it in the CAD model.
3. Print only that section.
4. Inspect the result.
5. Adjust the design and repeat if necessary.
This is additive manufacturing doing what it does best: shortening the distance between an idea and a physical test.
An Hour Can Still Be Fast
At Boston Micro Fabrication’s highest resolutions, Carl estimates that printing one millimeter of height can take around an hour.
That may sound slow until you consider the scale and complexity involved.
These are not ordinary millimeter-scale features. A printer may be producing channels and details measured in tens of microns. More importantly, if no conventional process can manufacture the same geometry, the meaningful comparison is not whether the print is fast by desktop 3D printing standards. The comparison is whether the part can be produced at all.
When micro 3D printing is the only practical way to create a design, an hour per millimeter can be remarkably fast.
Resolution Is Only Half the Story
A machine capable of printing a two-micron feature does not automatically mean every material can produce a usable two-micron part.
The printer creates the geometry, but the material has to preserve it.
At this scale, a tiny wall, pin, channel, or mechanical feature may print successfully and still fail if the resin is too brittle, too flexible, or unable to hold its shape. That means the printer and the material have to work together.
This is an important distinction for anyone used to ordinary resin printing. Resolution numbers can tell you what a machine is theoretically capable of reproducing, but they do not tell you whether the finished component will survive cleaning, handling, assembly, or actual use.
The real question is not simply, “Can the printer create this feature?”
It is, “Can this printer and this material create a functional part?”
One Device May Need More Than One Material
Medical devices often have components with completely different jobs.
The tip of an endoscope may need to be rigid enough to securely hold a camera, a light, and fluid channels. The probe attached to it may need to remain flexible so it can move safely through the body.
Those requirements point toward different materials.
The components do not necessarily have to be printed together, but engineers still need to consider how the rigid and flexible sections will work as one device. Material selection becomes part of the design process instead of a decision made after the geometry is finished.
That is also why there is no single “best” resin for every medical application. The correct material depends on what the part needs to do, how small its features are, and what mechanical properties it must have.
Designing for the Manufacturing Process
An engineer may arrive with a CAD model originally created for CNC machining or micro-injection molding and ask to have it 3D printed. The model might be printable, but that does not mean it takes full advantage of the process.
Every manufacturing method has its own design rules.
A part intended for injection molding may include geometry shaped around tooling requirements. A CNC-machined part must account for how a cutting tool reaches each feature. Micro 3D printing removes some of those restrictions, but it introduces new considerations involving orientation, supports, material behavior, channel clearance, and post-processing.
The best results come when engineers think about the manufacturing process from the beginning.
Boston Micro Fabrication often works directly with research and development teams to help them understand those considerations. That collaboration gives designers the information they need to adjust a model before spending time printing a complete device.
Where Micro 3D Printing Fits
Traditional resin 3D printers can produce impressive detail, but they eventually reach a lower practical limit. At the opposite end of the spectrum, technologies such as two-photon lithography can create features at one micron and below.
Micro 3D printing occupies an important space between those technologies. It gives engineers the ability to create functional parts with extremely small features while maintaining a practical build size for medical devices, electronics, microfluidics, and other applications.
That space opens the door to designs that engineers may not have considered manufacturable before.
Small Parts, Big Possibilities
Micro 3D printing is not simply ordinary resin printing at a smaller scale. As the dimensions shrink, every part of the process becomes more demanding: the CAD model, the printer, the material, the orientation, and the post-processing.
But the payoff can be enormous.
Smaller tools can help make procedures less invasive. Complex internal channels can combine more functions inside a single component. Targeted test prints can help engineering teams evaluate difficult features without manufacturing an entire device.
And in medical applications, a feature measured in microns can ultimately make a very human difference.
Sometimes the smallest innovation makes the biggest difference.