32 The PCB Magazine • June 2014
The stretchable circuit board includes sev-
en double disks areas distributed across the
stretchable elastomer matrix to host each of
the seven discrete components (four resistors,
one capacitance, and one op-amp). Stretchable
thin gold film interconnects are patterned on
the top surface of the elastomer membrane to
complete the circuit. The components are po-
sitioned above the rigid areas and electrically
connected with the stretchable wiring using
silver paste.
When the circuit is stretched, the resistance
of the meander is increased, decreasing the
flashing rate of the LED. Graph 4c shows the
flashing rate of the LED, which linearly decreas-
es with the applied tensile strain. The stretch-
able resistance increases by about a factor of
four when stretched to 20% strain leading to
a frequency decrease from 1.55 to 1.15, corre-
sponding to the theoretical variation of f.
Conclusion
This paper provides a solution to a very
common problem faced in fabricating stretch-
able circuits. When non-stretchable regions are
created in a stretchable media, for example,
PDMS, high-strain regions are created while
stretching. For practical circuits, electrical wir-
ing between components must run across the
stretchable and non-stretchable regions, where
large tensile strain may occur and lead to poor
reliability of the electrical circuit and early elec-
tromechanical failure. The "double disk" design
proposed in this paper provides a simple, yet
efficient strategy to integrate disparate electri-
cal components on a stretchable substrate. The
proposed stretchable circuit boards will allow
for straightforward manufacturing of stretch-
able electronics.
Acknowledgements
This work was supported by the UK Engi-
neering and Physical Sciences Research Coun-
cil—EPSRC, the Bertarelli Foundation, and a Eu-
ropean Research Council Starting Grant, ERC,
No. 259419. Q.Liu and Z.Suo acknowledge the
support of the National Science Foundation
Materials Research Science and Engineering
Center.
PCB
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HyBRID STRETCHABLE CIRCUITS oN SILICoNE SUBSTRATE continues
