3D Printing and Magnetic Actuation: Breaking the Size Limit of Endoscopes

Drivable endoscopes manufactured by traditional methods, which integrate optical components, actuators and mechanical structures, are limited in their miniaturization capability, with an overall outer diameter typically exceeding 1 mm. This poses challenges for their access to the finest blood vessels and narrow lumens in the human body.

In 2025, a study published in Communications Engineering, a sister journal of Nature, has achieved a groundbreaking advance. Today we will interpret this research report.

This collaborative study by the University of Stuttgart in Germany and other institutions proposed and verified a highly compact, magnetically drivable 3D-printed endoscopic microsystem. Its core lies in the combination of two-photon polymerization 3D printing technology and magnetic actuation, which enables the one-step integrated fabrication of a complete microsystem with optical, mechanical and microfluidic structures directly on the end face of an imaging fiber bundle.

The working mode of this new technology may be hard to comprehend, and the key point first lies in the phrase "one-step integrated fabrication". Traditional methods involve manufacturing micro-components such as microlenses, microsprings and micromagnets separately, then assembling them under a microscope like performing micro-sculpture surgery – a process that is extremely difficult and error-prone. In contrast, this new technology realizes "one-time printing, integral forming": all components are printed as an interconnected whole, inherently a single unit, thus completely eliminating the nightmarish micro-assembly steps.

Eliminating the tedious micro-assembly process, complex and precise micro-optical systems are fabricated in one step via 3D printing.

Electromagnetic microcoils are integrated into the system, and the magnetic field controlled by electric current drives the polymer-bonded magnets embedded in the microstructure, thereby achieving precise movement of optical components.

The overall diameter of all demonstrated systems has been successfully controlled below 900 micrometers (0.9 mm), with the most compact rotary actuation system measuring only about 660 micrometers in diameter, realizing a remarkable miniaturization of drivable endoscopic devices.

The research team demonstrated three magnetically actuatable microsystems with distinct functions, endowing endoscopes with the capabilities of zooming, high definition imaging, and panoramic viewing respectively.

Principle: A microlens is supported by three helical springs and embedded in an axially magnetized polymer magnet. When energized, the magnetic field generated by the electromagnetic coil pushes the magnet and the lens to move along the optical axis.

Function: The forward and backward movement of the lens changes the focal length to achieve zoom (a zoom ratio of approximately 1.3 times was obtained in experiments), and it can also be used for refocusing at different object distances without moving the entire endoscope.

Dimensions: The microsystem itself has a diameter of 500 micrometers and is integrated on a 500-micrometer optical fiber, with a total diameter of about 810 micrometers.

Principle: A specially designed flexible hinge (e.g., four parallel leaf springs) allows the microlens to perform precise lateral translation under the action of a magnetic field.

Function: Lateral movement causes a slight shift in the imaging optical path, thus acquiring multiple slightly offset images of the same object. By fusing these images through algorithms, the inherent "honeycomb-like" pixelation problem of imaging fiber bundles can be effectively overcome, significantly improving image resolution. Experiments have proven that the reconstructed images can clearly distinguish fringes that were originally indistinguishable.

Dimensions: The overall diameter is also approximately 810 micrometers.

Principle: A microprism with an eccentric polymer magnet is mounted via two torsion bars. An axial magnetic field drives the magnet, causing the prism to rotate around its axis (a rotation angle of approximately -6.9° to +9.0° was measured in experiments).

Function: The rotation of the prism changes the direction of the optical path, thereby translating and expanding the observed field of view. This enables clinicians to view lateral areas without moving the endoscope itself, enhancing situational awareness in narrow spaces.

Dimensions: Printed on a 350-micrometer optical fiber, the overall system has a diameter of only about 660 micrometers, making it the most compact of the three.

This study marks an important step forward in the miniaturization of drivable endoscopes. By combining cutting-edge micro/nano 3D printing technology with an ingenious magnetic actuation design, it paves a brand-new technical path for future ultra-precise minimally invasive surgery and diagnosis in extremely narrow spaces such as cardiac blood vessels, the nervous system and pediatric applications. When the "eye" of an endoscope can not only "see", but also "zoom", "pan around" and see more clearly, the boundaries of minimally invasive medicine will be broadened once again.

Citation Source:

Rothermel, F., Toulouse, A., Thiele, S. et al. Magnetically actuatable 3D-printed endoscopic microsystems. Commun Eng 4, 69 (2025). https://doi.org/10.1038/s44172-025-00403-8