Paper-based device provides low-power, long-term method for analyzing
sweat

Date:
June 9, 2020
Source:
American Institute of Physics
Summary:
Researchers have constructed a paper-based device as a model
of wearables that can collect, transport and analyze sweat in
next-generation wearable technology. Using a process known as
capillary action, akin to water transport in plants, the device
uses evaporation to wick fluid that mimics the features of human
sweat to a sensor for up to 10 days or longer.



FULL STORY ========================================================================== Human sweat contains several biomolecules the research community is
exploring for noninvasive medical testing. Analyzing sweat for research, however, is often expensive, and devices typically are reliable for only
a limited amount of time.


========================================================================== Researchers at North Carolina State University have constructed a
paper-based device as a model of wearables that can collect, transport
and analyze sweat in next-generation wearable technology. Using a process
known as capillary action, akin to water transport in plants, the device
uses evaporation to wick fluid that mimics the features of human sweat
to a sensor for up to 10 days or longer. They discuss their work in the
journal Biomicrofluidics, from AIP Publishing.

The work was a collaboration between Orlin Velev and Michael Dickey,
advising the research of graduate students Timothy Shay and Tamoghna
Saha, as part of the NSF Center for Advanced Self-Powered Systems of
Integrated Sensors and Technologies. The goal is to use the properties
of paper to point a way forward for more affordable, longer-term devices.

One central problem for any device in analyzing sweat is that sweat
contains salt, which, upon evaporation, will become deposited on a device
and interfere with fluid flow. The team's device densely packs deposited
salt crystals, allowing for longer use and a way to study the timing of
when chemicals present in the sweat.

"We expected that the flow of the model sweat will be suppressed by
the deposition of a salt layer inside the drying pad," Velev said. "By following the flow of model sweat, we found, quite surprisingly, that
such a simple paper construct can achieve continuous sweat pumping and
disposal for very long periods." Paper microfluidic devices could also
be used as wearable patches to assess the course of certain diseases or
how well patients adhere to drug regimens.

"The biological markers or drug metabolites that seep in the patient's
sweat over a long period will be captured on the paper pad and preserved
in a time- stamped manner to be analyzed later, similar to tree rings preserving the record of tree development," Dickey said.

Driven by the liquid wicking through paper, the device doesn't require
external power. Its low cost also poses uses for inexpensive medical
testing in under- resourced patient populations who struggle to have
access to such testing. Such skin patch assays could remove the need to
take blood samples.

The team has started a series of human trials to explore how the
technology provides longer term biomarker analysis, and they look
to resume the trials when pandemic safety measures make it feasible
to proceed.


========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Timothy Shay, Tamoghna Saha, Michael D. Dickey, Orlin D. Velev.

Principles of long-term fluids handling in paper-based wearables
with capillary-evaporative transport. Biomicrofluidics, 2020; 14
(3): 034112 DOI: 10.1063/5.0010417 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200609111102.htm

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