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Details of Stretchable electronics

Mechanically stretchable electronics are virtually non-existing today. In order to reach the "summum" of comfort, for electronic textiles and biomedical applications, the electronics should be flexible and stretchable to a certain extent, in order to follow all movements and deformations of the body parts onto/into which they are integrated.Mechanically stretchable electronics are virtually non-existing today. In order to reach the "summum" of comfort, for electronic textiles and biomedical applications, the electronics should be flexible and stretchable to a certain extent, in order to follow all movements and deformations of the body parts onto/into which they are integrated.

Stretchable technology 

A stretchable electronic circuit is considered as a number of rigid or flexible component islands which are connected by elastic interconnections (Figure 1). Stretchable interconnections are achieved by embedding meander shaped metal wires in an elastic base material (Figure 2). Stretchabilities of 50% and more using our technologies have been obtained and also the possibility to embed components has been demonstrated (Figure 3).

Figure 1: Elastic interconnections connecting flexible component islands

BiFigure 2: Meanders in non-stretched state and stretched up to 40%ocompatibility

Figure 3: Stretchable thermometer demonstrating possibility of embedded components

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. The BioFlex project focuses on this aspect. Certain applications for monitoring bodyfunctions are under development. 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.

Moulding technology

The electronics are embedded in stretchable materials. To create dedicated shapes of these stretchable materials, for each electronic design dedicated moulds are created. Special attention goes out to make the moulded stretchable material bubble free. In places where rigid components are placed, the areas are deliberately made a lot thicker to make it locally less stretchable. (Figure 4)

                                                         Figure 4: Dedicated mould to obtain dedicated shapes in stretchable materials 

Breathable and Washable technology

When stretchable electronics have to be worn the whole time, it is important to make them more or less breathable. These electronics will be more comfortable to wear. We try to integrate different kinds of synthetic materials, especially non-wovens, in our designs in combination with our standard stretchable materials.

As our technologies are embedded in a layer of stretchable polymers, it is possible to make the circuits watertight. (Figure 5, 6) The idea rose to make the stretchable electronics washable. And so, the SWEET-project was born. Washability is important when we want to use our technologies in health care. The electronics have to be sterilized or washed before they can be reused. Also for the textile industry, it is very important to be able to wash the clothes with integrated electronics easily.

                                               Figure 5: Stretchable LED-circuit embedded in PDMS 

Figure 6: Same stretchable LED-circuit demonstrating the possibility of water resistance

Stretchable technology demonstrators

What follows are some demonstrators made in stretchable technology. They are made in the frame of currently running projects or master thesises to obtain the degree of electronic civil engineer.

                    Figure 7: Stretchable thermometer 

Wireless link

In the frame of the BioFlex-project, a wireless link was designed in our stretchable technology. Due the inductive power transmission between the external coil and the embedded coil, a LED is burning. This application also demonstrates the possibility to make stretchable circuits water resistant. The electronic design of the wireless link and the driving circuit was done in cooperation with KULeuven ESAT-MICAS.

Figure 8: Led powered by inductive coil embedded in PDMS 

Figure 9: Same inductive coil with LED embedded in PDMS