A doctor's visit, blood draw or laboratory test provides a snapshot of a person's health at a particular moment. But the body is constantly changing: the way a person puts weight on their feet can change after a hip injury, sweat composition varies with physical exertion, and changes in a wound can indicate problems with healing.

The researchers are working on ways to turn health monitoring from a cumbersome process into a continuous stream of data collected by inexpensive sensors that patients barely notice in everyday life.

One of the team's first steps was a pulse sensor unveiled in 2016 that could be applied to the wrist like a temporary tattoo. The researchers envisaged similar devices analysing sweat and transmitting the results to a mobile phone.

Although the chemical sensors functioned only in laboratory conditions at the time, they represented the possibility of medical monitoring extending beyond the clinic.

Developing such solutions proved to be a complex process. The sensors are printed using special pastes that serve as electronic ink. They contain materials such as graphene particles, which provide the electrical properties needed in the resulting layer.

The paste must pass through the fine apertures of the printer's screen and then remain precisely in the designated spot on a flexible film or other material. The nanomaterials in the ink need to arrange themselves to conduct electricity while simultaneously allowing contact with the substance being analysed.

It is also essential to ensure that each of the thousands of printed sensors performs consistently. The research team therefore spent several years optimising paste composition and density, applying successive layers and controlling print quality.

One of the results of this work is the EUKINES project, which involved developing a thin shoe insole containing eight printed zones that measure foot pressure.

The system's electronics generate a real-time map of the load on the feet. It can show a physiotherapist whether a patient recovering from surgery is favouring one leg and, in the future, could provide patients with guidance on improving their gait.

The prototype was first tested on 25 adult volunteers. They walked on a treadmill for approximately one minute at a speed of 2 km/h, and the readings were compared with those from the commercial Medilogic system.

EUKINES produced a stable signal and yielded similar average foot-load values. There were no adverse events or malfunctions that interrupted the trial, although the insole occasionally creased, causing slight discomfort.

A full clinical study was subsequently conducted involving 200 patients who had undergone hip replacement surgery at an orthopaedic department affiliated with the Faculty of Medicine of Cardinal Stefan Wyszyński University in Warsaw.

Participants were randomly assigned to groups using the EUKINES system, either with or without feedback, or to groups using a certified comparative system or undergoing rehabilitation without the device.

Over six weeks, the researchers assessed factors including weight-bearing on the operated leg, gait symmetry, pain levels and hip function. The study concluded in November 2025.

The EUKINES project also led to the development of electronic tattoos capable of measuring physical activity through human sweat. The device contains printed pH and lactate sensors and enables real-time analysis of physiological processes occurring in the body during activities such as running or intense exercise.

The project, funded by the Polish National Centre for Research and Development and valued at nearly PLN 10 million, brought together the Warsaw University of Technology, Cardinal Stefan Wyszyński University in Warsaw and two companies: NovelInks, a manufacturer of materials for printed electronics and a specialist in scaling printing technologies, and Talkin’ Things, a manufacturer of electronic communication modules and RFID/NFC tags.

Patent applications have been filed for both the pH sensor and the insole.

The same Warsaw University of Technology research team has also developed printed electronics for medical applications in other areas.

In 2022, they launched the SmartHEAL project, involving a wound dressing equipped with a pH sensor designed to assess a wound's condition without removing the dressing. The solution would be particularly beneficial for patients suffering from chronic wounds, such as diabetic foot ulcers.

The project won the international James Dyson Award.

The team's work has also moved beneath the skull. Scientists print dual-purpose electrodes onto a thin, flexible film. They can record the faint electrical signals generated by neurons, allowing researchers to monitor how the brain responds to stimuli; sounds were used in the experiment.

The electrodes can also deliver a low-level current to the cerebral cortex, increasing or decreasing activity in a specific region. The solution therefore enables both brain stimulation and monitoring of the brain's response.

In the future, devices based on this technology could aid in studying the nervous system and developing therapies to regulate the function of specific brain areas.

One of the team's most recent achievements has taken printed sensors beyond the human body — into rivers.

As part of the ASIR project, carried out under the Polish National Centre for Research and Development's Hydrostrateg programme, an autonomous WaterSense monitoring station for continuous water-quality assessment is being developed.

Its core is a patented module featuring a reel of hundreds of low-cost, disposable sensors that measure parameters such as pH, chlorides, nitrates, ammonium ions and dissolved oxygen levels.

When a sensor loses its measurement capability, the system automatically replaces it with another sensor, allowing the station to operate unattended year-round, even in winter.

The collected data are fed into a system equipped with artificial intelligence modules that detect anomalies and forecast water parameters 72 hours in advance.

The technology has already been deployed on the water. An expanding network of autonomous, floating monitoring stations on Polish rivers and lakes is providing strategic data to companies and institutions.

The project, valued at over PLN 22 million, brings together the Warsaw University of Technology as the lead partner, the Institute of Meteorology and Water Management - National Research Institute, and the companies MAGLY and NABUCODE.

After more than a decade of development, the team's printed-sensor technology now spans medical monitoring, rehabilitation, wound assessment, brain research and environmental monitoring, with the latest systems moving from laboratory development into real-world applications.

Krzysztof Petelczyc (PAP)

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