Wearable microfluidics: fabric-based digital droplet flowmetry for perspiration analysis

Abstract

The latest development in wearable technologies has attracted much attention. In particular, collection and analysis of body fluids has been a focus. In this paper, we have reported a wearable microfluidic platform made using conventional fabric materials and laser micromachining to measure the flow rate on a patterned fabric surface, referred to as digital droplet flowmetry (DDF). The proposed wearable DDF is capable of collecting and measuring continuous perspiration with high precision (96% on average) in a real-time fashion over a defined area of skin. We have introduced a theoretical model for the proposed wearable interfacial microfluidic platform, under which various design parameters have been investigated and optimized for various conditions. The novel digitalized measurement principle of DDF provides fast responses, digital readouts, system flexibility, and continuous performance of the flow measurement. Moreover, the proposed DDF platform can be conveniently implemented on regular apparel or a wearable device, and has potential to be applied to dynamic removal, collection and monitoring of biofluids for various physiological and clinical processes.

Soft, skin-mounted microfluidic systems for measuring secretory fluidic pressures generated at the surface of the skin by eccrine sweat glands

“…These devices, with or without electronic functionality, softly seal to the skin in a manner that allows sweat glands to pump sweat into microfluidic networks where various measurements can be performed. Demonstrations include sweat rate, total sweat loss and pH, along with the concentration of glucose, lactate, chloride and creatinine 17–19 . Advanced designs allow time sequential sampling and storage of sweat for purposes of capturing temporal changes in sweat chemistry 14 .…”

A Capillary-Evaporation Micropump for Real-Time Sweat Rate Monitoring with an Electrochemical Sensor

“…Initial studies on sweat rate were performed by determining the change in body mass, which was considered as a gold standard [9]. Recently, numerous sweat rate sensors have been realized based on electrical [10,19,20], electrochemical [1,2] and optical principles [21]. Lien et al demonstrated a flow rate sensor based on the change in optical transparency of the optical fiber cantilever induced by flowing fluid.…”

Advanced Wearable Microfluidic Sensors for Healthcare Monitoring

“…In another strategy, the continuous sweat flow captured by microfluidic networks is converted into discrete droplets with equivalent volumes. Yang et al presented a real‐time wearable sweat rate sensor based on a flexible fabric for the first time (Figure b) . Due to the wicking principle of fabric, sweat is guided into the sensor.…”

“…b) Illustrations of wearable fabric‐based microfluidic sensors for sweat rate monitoring (left), and the working principle of this sensor (right). Reproduced with permission . Copyright 2017, The Royal Society of Chemistry.…”