Printed electronics: New sensors for the medical field

VTT Finland

VTT Finland illustrates the potential of printed sensors in the medical field at LOPEC 2018

From March 13 to 15, 2018, LOPEC, the international exhibition and
conference for the printed electronics industry, will provide information on
state-of-the-art technologies, trends and new markets for printed
electronics. In addition to sectors such as the packaging industry, the
consumer electronics industry and the mobility sector, the healthcare
market is becoming increasingly important. In an interview, Teemu Alajoki,
senior scientist at the Technical Research Centre of Finland VTT and
speaker at the LOPEC conference, illustrates the potential of printed
sensors in the medical field.

Mr. Alajoki, you develop sensors for medical applications. What do these
sensors measure?

Sensors can be used to monitor a wide variety of physiological parameters.
Applications range from monitoring body temperature and respiratory rate to use
in electrocardiography (ECG), electroencephalography (EEG) or pulse oximetry,
a method for measuring the oxygen saturation in arterial blood.

How do you manufacture the sensors?
We print with silver inks and other mostly inorganic inks on flexible and
stretchable plastic films. We have developed multiple methods and use, for
example, reel-to-reel printing processes. Printed sensors can for example be
integrated into skin adhesives as well as bandages or band-aids.
We have not yet integrated them into textiles, but that could be the next step in
some application areas.

Why do you use printed electronics?
The biggest advantage of the printed sensors is that they are not as bulky and
voluminous as conventional sensors. They ensure much higher comfort for
patients as they wear the sensors close to their bodies. The flexibility and
conformability of printed electronics is a key factor for wearing comfort but also
for the functionality of sensors worn close to the body. In pulse oximetry, for
example, which is, among other things, used for monitoring during anesthesia,
an optical sensor is placed around the patient's fingertip. The low production
costs of printed electronics also play a decisive role, because the trend is for
medical sensors to be used just once and only for one patient. Printing
processes reduce costs significantly. However, there is still a need for further
development in this area, especially with regard to the automation of the mass
production of printed electronics components.

Sensors and other components for medical applications need to be particularly
reliable. Does printed electronics meet this requirement?

Yes, absolutely. Actually, for instance in pulse oximetry, disposable sensors
utilizing printed electronics are already commercially available. This shows that
the reliability of the printed electronics can indeed be at an adequate level for
medical sensors. The main challenge is to ensure a high level of wearing comfort
and at the same time reliable stability – despite the mechanical stress in certain
applications or in case of patient movements. Here, we have made significant
progress. Long-term reliability, in turn, plays a minor role, at least for disposable
sensors, which are only used for a short period of time.

What are the advantages of these disposable sensors?
The main reason for using disposable sensors is to prevent the transmission of
pathogens and thus obtain better infection control in healthcare facilities. In pulse
oximetry, for instance, one reason for the use of disposable sensors is because
disinfection is expensive and despite careful cleaning, there is always a residual
risk that germs will survive and spread. Multi-resistant bacteria pose an everincreasing
threat to patients in many countries. Disposable sensors can minimize
this problem.

Apart from sensors for monitoring body functions, what other medical
applications will benefit from printed electronics?

Printed electronics can be used not only for monitoring or diagnostics, but also in
therapy. In pain treatment, for example, there is a method called
electrostimulation. It is based on electrodes that sit directly on the skin and
release pain-relieving electrical impulses. Similar to the sensors we are
developing, printed electronics can improve wearing comfort and functionality.

The Technical Research Centre Finland VTT is one of LOPEC's regular
exhibitors. What will you and your colleagues present this year in Munich?

In my presentation at the LOPEC Conference, I will give an overview of our work
in the field of medical sensor technology, from the production of prototypes using
mass patterning techniques to the various test procedures with which we
characterize and test the sensors under realistic conditions. Over the past two
years, the VTT has further enhanced its reel-to-reel printing systems, so that
several steps previously carried out manually are now automated. My colleague
Tuomas Happonen will talk about this in his poster presentation. The VTT will
also demonstrate many other new developments at our booth.

To what extent does LOPEC drive the development of printed electronics for
medical purposes?

It is most important that key players from industry and science meet regularly to
build networks. As an annual event, LOPEC offers the ideal setting for this
purpose and the VTT is always represented by five to ten researchers in Munich.
I am already looking forward to many exciting conversations with members from
the printed electronics industry at LOPEC 2018. Many people think that printed
electronics is not yet ready to be used in the medical field – they will be surprised
by the advances and the many new developments that are about to be

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