Abstract

A new fabrication technology for stretchable electrical interconnections is presented. This technology can be used to connect various non-stretchable polyimide islands hosting conventional electronic components. The interconnections are realized by patterning a 200 nm thick sputter-deposited gold film into meandering horseshoe shapes, functioning as 'two-dimensional springs' when embedded in a silicone elastomer. Polyimide support is introduced around the meandering conductors as a means to improve the mechanical performance. Processing is done on a temporary carrier; the islands and interconnections are embedded in polydimethylsiloxane in a final stage. To this end, a release technique compatible with high temperatures up to 350• C based on the evaporation of a 400 nm thick layer of potassium chloride is developed. Test structures consisting of stretchable interconnections with a varying polyimide support width were fabricated. These were strained up to twice their original length without compromising their functionality. Also cyclic mechanical loading at various strains was performed, indicating the influence of the polyimide support width on the lifetime. At strains of 10%, a minimum lifetime of 500 000 cycles is demonstrated. The presented technology thus provides a promising route towards the fabrication of stretchable electronic circuits with enhanced reliability.

This paper presents the design and implementation of an advanced system on flexible and stretchable technology. The technology platform consists of a matrix of flexible non-stretchable functional islands linked together by a net of elastic interconnections. Several technologies have been developed and tested in the design of simplified demonstrators before studying the design of an advanced system. The target system is a wireless battery charger which supplies power and supports bidirectional data transfer during recharge. The system is intended to serve as a general purpose platform for biomedical parameter monitoring and the design is focused on the embedding in clothes.

Today electronics in "wearable systems" or "smart textiles" are mainly realised on traditional interconnection substrates, like rigid printed circuit boards or mechanically flexible substrates. The electronic modules are detachable to allow cleaning and washing of the textile. In order to achieve a higher degree of integration and user comfort, a technology for flexible and stretchable electronic circuits was developed. The electronic system is completely embedded in an elastomer material like polydimethylsiloxane (PDMS, silicone), resulting in soft and stretchable electronic modules. The technology uses standard packaged components (ICs) and meander-shaped copper tracks, so that stretchable systems with complex functionality can be achieved. This paper describes how these stretchable modules can be integrated in textiles. Also the influence of the PDMS on the stretchability of the textile has been examined. A basic electronic module with blinking light emitting diodes (LEDs) was designed and produced to illustrate the textile integration and to perform initial washing tests

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