Consumers 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.

Stretchable substrate with LEDs, still functioning after being crumpled (TU Berlin)

Physically such monitors consist of three technology elements:

• Unobtrusive sensors -small, wireless, virtually invisible, low weight- that measure relevant (body) parameters.
• Algorithms that interpret these measurements.
• Connectivity, preferably wireless to transfer the data to a body network for further processing.

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 the STELLA project the development of such stretchable and soft-touch substrates, including assembly with electronic devices on these substrates is proposed.

Processes will be developed to produce a stretchable conductive pattern that can be composed of printed wiring, discrete wiring, or a combination thereof formed in a predetermined arrangement on a stretchable common base substrate. The soft-touch will be achieved by using base materials with a different chemistry than what is used today for flex substrates.

Assembly methods for component mounting and interconnection, based on existing platform techniques, will have to be adapted.

Innovations from the STELLA project include:

• New stretchable substrates with stretchable conductor patterns
• Assembly technology on stretchable substrates, based on lead-free reflow soldering
• Integration methods for electronics in stretchable products

The new technology will be proven through a number of demonstrators for the end-users in the project. The STELLA project's duration is from 01.February 2006 till 31. January 2010. Eleven partners from industry and research located in 4 European countries cover the knowledge required for development and exploitation.

The project budget amounts to 13.157.000 € and is funded by the European Commission with 7 Mil. €.