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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2017)

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.

    Cover page: Bridging the Gap Between Technological Advancement and Manufacturability: Development of Solderable Stretchable Sensing Systems
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2015)
    New classes of ultrathin flexible and stretchable devices have changed the way modern electronics are designed to interact with their target systems. Though more and more novel technologies surface and steer the way we think about future electronics, there exists an unmet need in regards to optimizing the fabrication procedures for these devices so that large-scale industrial translation is realistic. This article presents an unconventional approach for facile microfabrication and processing of adhesive-peeled (AP) flexible sensors. By assembling AP sensors on a weakly-adhering substrate in an inverted fashion, we demonstrate a procedure with 50% reduced end-to-end processing time that achieves greater levels of fabrication yield. The methodology is used to demonstrate the fabrication of electrical and mechanical flexible and stretchable AP sensors that are peeled-off their carrier substrates by consumer adhesives. In using this approach, we outline the manner by which adhesion is maintained and buckling is reduced for gold film processing on polydimethylsiloxane substrates. In addition, we demonstrate the compatibility of our methodology with large-scale post-processing using a roll-to-roll approach.
      Cover page: Scalable Microfabrication Procedures for Adhesive-Integrated Flexible and Stretchable Electronic Sensors
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2014)
      The ability to measure subtle changes in arterial pressure using devices mounted on the skin can be valuable for monitoring vital signs in emergency care, detecting the early onset of cardiovascular disease and continuously assessing health status. Conventional technologies are well suited for use in traditional clinical settings, but cannot be easily adapted for sustained use during daily activities. Here we introduce a conformal device that avoids these limitations. Ultrathin inorganic piezoelectric and semiconductor materials on elastomer substrates enable amplified, low hysteresis measurements of pressure on the skin, with high levels of sensitivity (~0.005 Pa) and fast response times (~0.1 ms). Experimental and theoretical studies reveal enhanced piezoelectric responses in lead zirconate titanate that follow from integration on soft supports as well as engineering behaviours of the associated devices. Calibrated measurements of pressure variations of blood flow in near-surface arteries demonstrate capabilities for measuring radial artery augmentation index and pulse pressure velocity.
        Cover page: Conformable amplified lead zirconate titanate sensors with enhanced piezoelectric response for cutaneous pressure monitoring
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