A system for embedding invisible digital information in printed documents

A team of researchers from Universidad Carlos III de Madrid (UC3M), the Massachusetts Institute of Technology (MIT) and Adobe Research have presented Imprinto, a system for embedding invisible digital information in printed documents using infrared ink and a special camera. This technology introduces a new generation of hybrid interfaces between paper and augmented reality.

The tool, recently presented at the Conference on Human Factors in Computing Systems (CHI 2025) held in Yokohama, Japan, has been developed with the aim of enabling advanced interaction with physical documents, without altering their visual appearance. The study is published in the Proceedings of the 2025 CHI Conference on Human Factors in Computing Systems.

“Imprinto uses an infrared ink that is invisible to the human eye but detectable by means of a near-infrared camera, such as those that can be integrated into mobile devices by simply modifying the photographic sensor,” explains one of the driving forces behind the project, Raúl García Martín, from UC3M’s Department of Electronic Technology.

This technique opens the door to new methods of product traceability, document authentication, and enrichment of educational or professional content. Moreover, it can all be done without reliance on visible codes such as QR codes or adding external devices to the document.

Imprinto is part of a broader ecosystem of tools that UC3M and MIT researchers are exploring based on the possibilities of infrared technology. The authors have also developed, and are in the process of patenting, a portable camera, connectable via USB-C to any mobile device, which allows blood vessels to be observed under the skin to facilitate medical procedures. In addition, it allows biometric recognition based on the vascular patterns of the palm of the hand thanks to artificial intelligence algorithms.

“The system, called VeinGoOne, aims to analyze the images captured in real time, allowing not only 2D visualization but also 3D reconstruction of vein depth using techniques such as stereoscopy or Time-of-Flight,” says García Martín.

Another of the developments presented by the UC3M team is BrightMarker, a system that allows invisible codes to be embedded in 3D objects using fluorescent polymers. This innovation makes it possible to print objects containing hidden digital labels, useful for industrial traceability, advanced logistics or personalized interaction in augmented reality environments without altering the appearance of the object.

These advances are part of a more ambitious vision: replacing mobile phones with augmented reality glasses or contact lenses, capable of recognizing and interpreting the environment using integrated infrared cameras, according to the researchers.

“In this near future, technologies such as Imprinto, BrightMarker and VeinGoOne will allow users to interact with physical objects and documents in a digital, intuitive and personalized way,” concludes García Martín.