Stretchability-The Metric for Stretchable Electrical Interconnects.

Bart Plovie,Jan Vanfleteren,Frederick Bossuyt

doi:10.3390/mi9080382

Abstract

Stretchable circuit technology, as the name implies, allows an electronic circuit to adapt to its surroundings by elongating when an external force is applied. Based on this, early authors proposed a straightforward metric: stretchability—the percentage length increase the circuit can survive while remaining functional. However, when comparing technologies, this metric is often unreliable as it is heavily design dependent. This paper aims to demonstrate this shortcoming and proposes a series of alternate methods to evaluate the performance of a stretchable interconnect. These methods consider circuit volume, material usage, and the reliability of the technology. This analysis is then expanded to the direct current (DC) resistance measurement performed on these stretchable interconnects. A simple dead reckoning approach is demonstrated to estimate the magnitude of these measurement errors on the final measurement.

Highlights

Stretchable circuit technology is a recent development, having seen the light of day over the span of the last two decades
This paper aims to demonstrate this shortcoming and proposes a series of alternate methods to evaluate the performance of a stretchable interconnect
A slight drop in resistance from 537.5 Ω to 536.37 Ω was observed during the experiment, contrary to what might be expected from a meander under significant strain

Summary

Introduction

Stretchable circuit technology is a recent development, having seen the light of day over the span of the last two decades. Before the development of stretchable circuit technology, this was usually solved using long spring-loaded cables, stored in an enclosure that fed and retracted the cable as was necessary to cover the distance [3] This cable-based approach has the advantage of being incredibly reliable if implemented correctly; it works from direct current (DC) all the way up to the gigahertz range and offers the capability to handle large currents. An alternative method, which remains popular and still makes a frequent appearance, is the use of coiled flexible circuit boards to cover these transitions [4] Both methods are surprisingly common in consumer-applications (e.g., devices with retractable power cords and hard drive reading heads)

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