Stretchable, wireless sensors and functional substrates for epidermal characterization of sweat.
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.
University of Illinois at Urbana-Champaign, Frederick Seitz Materials Research Laboratory, 104 S. Goodwin Ave, Urbana, IL, 61801, USA.
Xian
X
Huang
Yuhao
Y
Liu
Kaile
K
Chen
Woo-Jung
WJ
Shin
Ching-Jui
CJ
Lu
Gil-Woo
GW
Kong
Dwipayan
D
Patnaik
Sang-Heon
SH
Lee
Jonathan Fajardo
JF
Cortes
John A
JA
Rogers
D015374:Biosensing Techniques / Q000295:instrumentation; D003124:Colorimetry / Q000295:instrumentation*; D003217:Conductometry / Q000295:instrumentation*; D055119:Elastic Modulus; D004566:Electrodes; D004817:Epidermis / Q000378:metabolism*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013542:Sweat / Q000737:chemistry*; D059015:Wireless Technology / Q000295:instrumentation*
epidermal electronics; flexible electronics; stretchable electronics; sweat sensor; wireless sensor