An Artificial Sweating System for Sweat Sensor Testing Applications

Abstract

This research proposes a completely automated, computer-controlled fluid mixing and dispensing system, which is suitable for testing sweat sensing devices, as an alternative to requiring human trials during the development phase of a sweat sensor device. An arm mold was designed and implemented with dragon skin and pores to simulate sweating action. The relay controlled mixing tanks allow for the different concentration of fluid solutions at various rates of fluid dispensing through pores. The onboard single board computer controls a dozen electronic relays and it switches and presents an easy to use graphical user interface to allow end users to conduct the experiments with ease and not require further programming. With the recent advances in sweat sensors, this platform offers a unique way of testing sensing devices during development, allowing for researchers to focus on their design parameters one at a time before actual validation through human trials are conducted. The current device can provide sweat rates from 1 µL/min to 500 µL/min. Furthermore, concentrations of 10 mM up to 200 mM of salt concentrations were able to be repeatedly produced. In an ANOVA test with salt concentrations varying from 40–60 mM, a p-value of 0.365 shows that the concentration does not have any effect on the flow rate. Similarly, a p-value of 0.329 and 0.167 for different relative humidity and temperature shows that the system does not present a statistical difference. Lastly, when the interactions among all the factors were considered, a p-value of 0.416 clearly presents that the system performance is insensitive to different factors, thus validating the system reliability.

Recent Impact of Microfluidics on Skin Models for Perspiration Simulation

“…Recent proposals of perspiration models are not reduced solely to laser-machined membranes. With a methodology similar to thermal manikins, Brueck et al [ 49 ] designed an arm mold with casted silicone, which was coupled with a complex electronic system capable to control the desired sweat rate dispensed by a peristaltic pump (from 1 to 500 µL/min) and the salt concentration of the emerging sweat (from 10 to 200 mM) ( Figure 4 a). Details on the fabrication of the sweat pores are not given in the publication, probably opting for a system of pipes and holes similar to the one used in thermal manikins.…”

“…Koh et al [ 47 ] also used their perspiration model to confirm the viability of their microfluidic device for sweat sampling in aspects such as possible sweat leakage or the quantitative correlation of sweat collected. Similarly, the arm mold that Brueck et al [ 49 ] developed was used as a with their sweat rate wearable that was previously published [ 55 ], as shown in Figure 4 a, or the hydrogel interface used in Garcia-Cordero et al [ 52 ].…”

“… Alternative approaches for perspiration models. ( a ) Image of the sweating arm prototype developed by Brueck et al [ 49 ] showing the arm mold and the fluid tanks for sweat solution (left). In vitro test with a wearable device that monitors sweat rate (right).…”

“…In vitro test with a wearable device that monitors sweat rate (right). Adapted with permission from [ 49 ]. Copyright 2019, MDPI.…”

Sweat as a Source of Next-Generation Digital Biomarkers

“…An HTMC PM23300 Windows phone served as the monitoring terminal. Nevertheless, there are increasing numbers of upcoming sensors along with novel approaches to automatically and artificially test those devices [21] and to fabricate cost-effective sensors on a large scale [22]. These are all significant requirements that pave the way for a successful clinical implementation of wearable sweat sensors.…”