Sweat monitoring beneath garments using passive, wireless resonant sensors interfaced with laser-ablated microfluidics

Carr, Adam R.; Patel, Yash; Neff, Charles R; Charkhabi, Sadaf; Kallmyer, Nathaniel E.; Angus, Hector F.; Reuel, Nigel F.

doi:10.1038/s41746-020-0270-2

Cited by 26 publications

(26 citation statements)

References 56 publications

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“…The sweat loss level obtained by measuring sweat volumes (SSV and inSSV) is the main characteristic of most microfluidics‐based and absorbent‐material‐based SLMDs that utilize the capillarity of microchannels and wicking materials to collect and quantify sweat from the skin surface. [ 65 , 66 ] An appropriate volume that will be filled with collected sweat gradually is also required to prevent premature saturation while wearing and using the device. The specific sweat collection volume of the devices needs to be determined and designed according to the inlet size and usage scenario, similar to measurement of the sweat rate.…”

Section: Sweat Loss: Sensible and Insensible Sweatmentioning

confidence: 99%

Wearable Sweat Loss Measuring Devices: From the Role of Sweat Loss to Advanced Mechanisms and Designs

et al. 2021

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Wearable sweat sensors have received significant research interest and have become popular as sweat contains considerable health information about physiological and psychological states. However, measured biomarker concentrations vary with sweat rates, which has a significant effect on the accuracy and reliability of sweat biosensors. Wearable sweat loss measuring devices (SLMDs) have recently been proposed to overcome the limitations of biomarker tracking and reduce inter-and intraindividual variability. In addition, they offer substantial potential for monitoring human body homeostasis, because sweat loss plays an indispensable role in thermoregulation and skin hydration. Previous studies have not carried out a comprehensive and systematic review of the principles, importance, and development of wearable SLMDs. This paper reviews wearable SLMDs with a new health perspective from the role of sweat loss to advanced mechanisms and designs. Two types of sweat and their measurement significance for practical applications are highlighted. Then, a comprehensive review of advances in different wearable SLMDs based on hygrometers, absorbent materials, and microfluidics is presented by describing their respective device architectures, present situations, and future directions. Finally, concluding remarks on opportunities for future application fields and challenges for future sweat sensing are presented.

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Section: Sweat Loss: Sensible and Insensible Sweatmentioning

confidence: 99%

Wearable Sweat Loss Measuring Devices: From the Role of Sweat Loss to Advanced Mechanisms and Designs

et al. 2021

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“…As such, using a single signal generator we successively target the resonance frequency of the MEMS resonators. Frequency modulation of the resonance modes stemming from exposure to respiratory flow necessitates that the excitation signal frequency closely follows the resonance frequencies [16]. For this reason, a dynamic frequency locking mechanism is incorporated into the signal acquisition/generation software.…”

Section: Systems Components and Methodsmentioning

confidence: 99%

A Battery-Less Wireless Respiratory Sensor Using Micro-Machined Thin-Film Piezoelectric Resonators

et al. 2021

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In this work, we present a battery-less wireless Micro-Electro-Mechanical (MEMS)-based respiration sensor capable of measuring the respiration profile of a human subject from up to 2 m distance from the transceiver unit for a mean excitation power of 80 µW and a measured SNR of 124.8 dB at 0.5 m measurement distance. The sensor with a footprint of ~10 cm2 is designed to be inexpensive, maximize user mobility, and cater to applications where disposability is desirable to minimize the sanitation burden. The sensing system is composed of a custom UHF RFID antenna, a low-loss piezoelectric MEMS resonator with two modes within the frequency range of interest, and a base transceiver unit. The difference in temperature and moisture content of inhaled and exhaled air modulates the resonance frequency of the MEMS resonator which in turn is used to monitor respiration. To detect changes in the resonance frequency of the MEMS devices, the sensor is excited by a pulsed sinusoidal signal received through an external antenna directly coupled to the device. The signal reflected from the device through the antenna is then analyzed via Fast Fourier Transform (FFT) to extract and monitor the resonance frequency of the resonator. By tracking the resonance frequency over time, the respiration profile of a patient is tracked. A compensation method for the removal of motion-induced artifacts and drift is proposed and implemented using the difference in the resonance frequency of two resonance modes of the same resonator.

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“…Another commonly used geometry in wireless sensors is the spiral resonator (SR) geometry. Spiral resonators have found applications in many fields, such as wearables [13,14], biomedical [13,15], strain [14], eddy current [16], and displacement [17][18][19] sensing.…”

Section: Introductionmentioning

confidence: 99%

Design Guidelines for Sensors Based on Spiral Resonators

Elgeziry

Costa

Genovesi

2022

Sensors

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Wireless microwave sensors provide a practical alternative where traditional contact-based measurement techniques are not possible to implement or suffer from performance deterioration. Resonating elements are commonly used in these sensors as the sensing concept relies on the resonance properties of the employed structure. This work presents some simple guidelines for designing displacement sensors based on spiral resonator (SR) tags. The working principle of this sensor is based on the variation of the coupling strength between the SR tag and a probing microstrip loop with the distance between them. The performance of the sensor depends on the main design parameters, such as tag dimensions, filling factor, number of turns, and the size of probing loop. The guidelines provided herein can be used for the initial phase of the design process by helping to select a preliminary set of parameters according to the desired application requirements. The provided conclusions are supported using electromagnetic simulations and analytical expressions. Finally, a corrected equivalent circuit model that takes into account the phenomenon of the resonant frequency shift at small distances is provided. The findings are compared against experimental measurements to verify their validity.

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Sweat monitoring beneath garments using passive, wireless resonant sensors interfaced with laser-ablated microfluidics

Cited by 26 publications

References 56 publications

Wearable Sweat Loss Measuring Devices: From the Role of Sweat Loss to Advanced Mechanisms and Designs

Wearable Sweat Loss Measuring Devices: From the Role of Sweat Loss to Advanced Mechanisms and Designs

A Battery-Less Wireless Respiratory Sensor Using Micro-Machined Thin-Film Piezoelectric Resonators

Design Guidelines for Sensors Based on Spiral Resonators

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