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Open Access Publications from the University of California

Bridging the Gap Between Technological Advancement and Manufacturability: Development of Solderable Stretchable Sensing Systems

  • Author(s): Kim, Yun Soung
  • Advisor(s): Coleman, Todd P.
  • et al.

In the past decade, development of stretchable, thin-lm electronics have

garnered attention from healthcare industries to general public, since such platform

would enable a direct integration with skin, providing the means of intimate

and unobtrusive health monitoring. However, such transition of the technology to

consumers has been hampered by challenges associated with high-cost, inability

to scale, and low device reliability. To address this, we see an increase in researcheort in adopting the use of rigid, yet small, commercial-off-the-shelf chip components.

The value gained by employing the full sophistication of modern integrated

circuits (ICs) is disproportionate to the slight loss in overall stretchability.

This dissertation aims to provide a unique methodology that weds the bene

ts of both thin-lm and surface mount technologies. However, the focus is

not only on developing the new sophisticated systems but also on scalability of

the manufacturing process. First, we introduce a method to produce a stretchable,

thin-lm interconnection platform exhibiting an excellent solderability with

industry-standard SAC (Sn96.5/Ag3.0/Cu0.5) solder alloy. This platform, which

we call Solderable and Stretchable Sensing System (S4), was further veried for

its feasibility to be scalably manufactured through the demonstrative production

of S4 respiration sensing devices. Finally, we demonstrated the direct integration

of fully assembled S4 devices with a large area adhesive lm, proving the methods

compatibility with a roll-to-roll process.

Next we explored S4s capacity as a platform for wireless communication devices

involving high frequency radio signals, such as those involved with Bluetooth

protocols. We introduced the engineering challenges found in designing thin-lm

conductive traces for reliably accommodating radio frequency RX/TX. As a solution

to these challenges, S4s utilized novel stretchable antennas boasting similar

thin-lm conductive properties, obviating chip antennas and further demonstrating

their versatility as an electronic platform. Finally, we employed S4 devices capable

of physiological monitoring, signal amplication, analog-to-digital conversion, andwireless communication via Bluetooth Low Energy protocols using the integrated

stretchable antennas.

We demonstrated S4s capacity for adopting various surface mount chip

packages, scalable manufacturing and packaging, support for high frequency digital

signals, and transmitting/receiving wireless radio signals. We believe the compatibility

of the manufacturing methods with existing tools and materials, as well

as S4s versatile and modular characteristics successfully tie together the values of

stretchable electronics and advanced IC technologies.

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