Biocompatible mechanically flexible electronics are virtually non-existing today and although devices can be embedded into fabric they cannot stretch the same way as textile does.
Consumers today are increasingly taking responsibility for their health and physical condition: they want to manage their own health and feel good, by monitoring a variety of functions of the human body (ECG, heart rate, heart rate variability, blood oxygen saturation, temperature, etc) and activity related data (speed and acceleration obtained from body sensors) while doing sports, or throughout the day, or during recovery from illness.
Researchers are developing biocompatible, stretchable, waterproof electronic circuit technology that can be integrated in stretchable applications like bandages or medical implants. The stretchability poses particular challenges with regard to the desirable stretchability of the final product and the need to achieve continuous operation through the complete range of strain.
Direct skin contact allows for full measurement capabilities, but wearing comfort requires that the monitor will not only be flexible, but also of stretchable and soft-touch nature in order to follow all movements and deformations of the body parts onto/into which they are integrated.
For implants the stretchable electronics have to be biocompatible. The metal wires and electronic components must be shielded from the biological environment of the body. An embryonic technology for stretchable electronic circuits for medical (implantable) applications is currently under development through the "BioFlex" project which hopes to seriously shift the frontiers of what is acceptable today. If the electronics behave like the tissues itself, one can really speak of biocompatible or bio-identical devices.
A stretchable electronic circuit is considered as a number of rigid or flexible component islands which are connected by elastic interconnections. Stretchable interconnections are achieved by embedding meander shaped plated metal wires in an elastic base material. Stretchabilities of 50% and more using this technology have been obtained and also the possibility to embed components has been demonstrated by the researchers. Research on biocompatibility is being done in cooperation with the Department of Biomedical Science and the Department of Physical Engineering at the University of Ghent and is due to complete in February 2009.
A lot of work is still to be done to further develop this technology and adapt it for embedding in textile. To reach this goal a 3-year work-plan was set up in March 2007 through the SWEET (Stretchable and Washable Electronics for Embedding in Textiles) project, which aims to develop a technology platform for stretchable and washable electronic circuits and for embedding technologies of these circuits in textiles.
The technology is also being developed through the Stella Project which consists of a consortium of 11 partners from industry from 4 European countries. 7 million Euros is being funded by the European Commission and completion is expected January 2010.
Stretchable Thermometer from the Stella Project
References: www.stella-project.de, tfcg.elis.ugent.be
Source top image: tfcg.elis.ugent.be
For more on stretchable, conformal, rollable and foldable electronics read Introduction to Printed Electronics or attend Printed Electronics Asia 2007 and Printed Electronics USA 2007.