A new research group at the University of Stuttgart is working on a study that involves 3D printing tissue directly inside the human body.
Led by Dr. Andrea Toulouse from the Institute of Applied Optics, the project has received €1.8 million in funding from the Carl-Zeiss-Stiftung (CZS) through its CZS Nexus program. This funding has allowed Dr. Toulouse to establish a junior research group focused on micro-optics and fiber-based 3D printing.
Named “3D Endoscopic Microfabrication” (3DEndoFab), the group began its work on October 1, 2025. It brings together two doctoral researchers from engineering and one from biotechnology, forming an interdisciplinary team that bridges optical technology and the life sciences.
The research marks a step toward combining optical engineering with regenerative medicine, an area that could reshape how surgeons and clinicians approach tissue repair. If successful, the project could lead to techniques that eliminate the need for invasive implantation procedures and enable on-site regeneration inside the body.
“Leading my own independent junior research group allows me to advance endoscopic 3D printing with both responsibility and freedom,” said Dr. Toulouse.
Miniaturizing 3D printing for the human body
Current 3D printing techniques can already create living materials such as cartilage, muscle, or lung tissue using light-based processes. Yet these methods depend on large laboratory printers, which means the printed tissue must be implanted after production. The 3DEndoFab team wants to overcome this limitation by developing tools small enough to print directly where the tissue is needed inside the body.
At the heart of their work is the challenge of miniaturization. The team aims to design a light-based 3D printing system capable of operating through an optical fiber, using biocompatible materials rather than the non-degradable photoresists typically used in microfabrication.
One key objective is to create a microscopic optical element, roughly the size of a grain of salt, that can sit on the tip of a fiber and precisely control light to build complex, tissue-like structures with micrometer accuracy.
Beyond tissue engineering, the researchers hope their approach could offer new tools for biological studies, for example to observe how cells grow and organize themselves on finely structured surfaces.
The project builds on earlier results from the EndoPrint3D project, in which Dr. Toulouse worked with Professors Alois Herkommer, Michael Heymann, and Harald Giessen to demonstrate that 3D printing through an optical fiber is possible using ultrashort femtosecond laser pulses.
Building on that foundation, 3DEndoFab will explore which optical printing methods are best suited for biomedical use and how such systems can be made minimally invasive and dependable.
Dr. Toulouse’s group will work closely with Professor Heymann at the Institute for Biomaterials and Biomolecular Systems to address the biological aspects of the research. It will also take part in the Bionic Intelligence Tübingen Stuttgart (BITS) network within Cyber Valley and contribute to the University of Stuttgart’s Biomedical Systems and Robotics for Health initiative.
Having merged optics, engineering, and biology, 3DEndoFab aims to open the door to a future where damaged tissue could be repaired or regenerated directly within the body, using light to build life at the smallest scales.
3D printing moves inside living systems
What began as a way to build tissue outside the body is now entering the realm of living systems, as researchers find ways to print structures inside both cells and organs.
Researchers from the J. Stefan Institute and the University of Ljubljana achieved a scientific first by 3D printing functional microstructures inside living cells directly using a technique called two-photon polymerization. In their experiments, a tiny droplet of photoresist was injected into HeLa cells, and a femtosecond 780 nm laser was used to solidify the material with submicron precision, creating structures such as microlasers, optical barcodes, and even a 10 µm model of an elephant.
Published in arXiv, the process preserved cell integrity, with more than half of the cells remaining viable and some even dividing normally. This approach demonstrated that complex microdevices can be fabricated within living cells without disrupting their natural functions, opening new possibilities for studying and engineering biological systems from the inside.
In the US, California Institute of Technology (Caltech) researchers developed Deep Tissue In Vivo Sound Printing (DISP), a technique that uses focused ultrasound to 3D print polymers inside living tissues. The method relied on temperature-sensitive liposomes that released crosslinking agents when heated by ultrasound, causing polymer solidification precisely at targeted sites.
Gas vesicles from bacteria acted as ultrasound contrast agents to monitor printing in real time. Using this approach, the team printed drug-loaded hydrogels containing doxorubicin near bladder tumors in mice, achieving higher tumor cell death than standard drug injections and demonstrating potential for noninvasive, targeted in-body fabrication.
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Featured image shows Andrea Toulouse and her team are researching high-resolution 3D printing using light-based processes. The vision: To develop tiny 3D printers that will one day be able to build biological tissue directly inside the body. Here, laser light is coupled into an optical fiber, whose glowing tip is intended to become a mini 3D printer. Photo via University of Stuttgart / Uli Regenscheit.
