Stretchable, Wireless Sensors and Functional Substrates for Epidermal Characterization of Sweat

Abstract

This paper introduces materials and architectures for ultrathin, stretchable wireless sensors that mount on functional elastomeric substrates for epidermal analysis of biofluids. Measurement of the volume and chemical properties of sweat via dielectric detection and colorimetry demonstrates some capabilities. Here, inductively coupled sensors consisting of LC resonators with capacitive electrodes show systematic responses to sweat collected in microporous substrates. Interrogation occurs through external coils placed in physical proximity to the devices. The substrates allow spontaneous sweat collection through capillary forces, without the need for complex microfluidic handling systems. Furthermore, colorimetric measurement modes are possible in the same system by introducing indicator compounds into the depths of the substrates, for sensing specific components (OH(-) , H(+) , Cu(+) , and Fe(2+) ) in the sweat. The complete devices offer Young's moduli that are similar to skin, thus allowing highly effective and reliable skin integration without external fixtures. Experimental results demonstrate volumetric measurement of sweat with an accuracy of 0.06 μL/mm(2) with good stability and low drift. Colorimetric responses to pH and concentrations of various ions provide capabilities relevant to analysis of sweat. Similar materials and device designs can be used in monitoring other body fluids.

Autonomous sweat extraction and analysis applied to cystic fibrosis and glucose monitoring using a fully integrated wearable platform

“…Despite significant progress made in printed and flexible biosensors in the field, a majority of wearable devices focus on monitoring of physical activity or selected electrophysiological parameters, providing only limited information regarding physiological changes of complex homeostatic responses (4)(5)(6)(7)(8)(9)(10). Wearable chemical sensors offer great opportunities for collecting physiological information at the molecular level (3,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Recently research advances have resulted in a variety of wearable sweat sensors that can be used for real-time analysis of sweat biomarkers including electrolytes, metabolites, and heavy metals (11)(12)(13)(14)(15)(16)(17)(18)(19)(20).…”

Flexible a‐IGZO Phototransistor for Instantaneous and Cumulative UV‐Exposure Monitoring for Skin Health

“…Data on instantaneous and cumulative UV exposures provide important information for dermatology, skin and general healthcare and eventually help to prevent damages to the dermis, epidermis [5] or eyes [6] . Wearable and, more recently, epidermal or skin-like devices, such as UV-dosimeter temporary tattoos [7] or highly stretchable photodetectors [8] have shown great potential to achieve accurate and unobtrusive sensing of important bio-signals and represent a promising technology for health monitoring [9,10] .Among the palette of materials, wide bandgap semiconductors, such as ZnO and its composites (Indium-Gallium-Zinc-Oxide (IGZO), Indium-Zinc-Oxide (IZO), Zinc-Tin-Oxide (ZTO), etc.) can be used for UV-photodetection [11] .…”

Deformable printed circuit boards that enable metamorphic electronics

“…This arrangement is different from others produced in earlier reports. [6][7][8][9][10][11][24][25][26] In our case, the metal tracks and components are not 'floating' on top of the rubber support. Instead, at least three faces are surrounded by EcoFlex to increase the level of fixation.…”

“…This research has led to several interesting publications. [3][4][5][6][7][8][9][10][11][12][13]19,[21][22][23][24][25][26] From a technical point of view, a classification into two fabrication strategies can be made. The first strategy uses a rubber support toward the beginning of the processing sequence.…”

“…These materials enable new types of applications, such as smart clothing, 1,2 conformable photovoltaics, [3][4][5] optoelectronics, [6][7][8][9][10][11] digital cameras, 12,13 artificial electronic skins, [14][15][16] stretchable batteries, [17][18][19][20] robotics, 21 and mechanically soft and conformable health-monitoring devices, [22][23][24][25][26] to give a few recent examples.…”