1 Department of Electrical Engineering, The University of Texas at Dallas, Richardson, TX, USA.
2 EnLiSense LLC, Allen, TX, USA.
SLAS Technol. 2018 Dec;23(6):529-539. doi: 10.1177/2472630318759257. Epub 2018 Feb 15.
A four-channel electrochemical impedance spectroscopy (EIS) analyzer module has been demonstrated on flexible chemi-impedance sensors fabricated with gold electrodes for wearable applications. The module can perform time division multiplexed (TDM) impedance measurements on four sensors at 1 kHz. In this work, we characterize the system for the detection of cortisol in an ultralow volume (1-3 µL) of perspired human sweat, sensor performance, and effects during continuous cortisol dosing and with pH and temperature variations expected on the surface of the skin that would be representative of use conditions as seen by a wearable device. Detection of cortisol was shown for concentrations of 1 pg/mL to 200 ng/mL in both synthetic and perspired human sweat, and output response reported as a change in impedance with varying cortisol concentrations. Continuous dose testing was performed to demonstrate the stability of the sensors over prolonged periods of operation for cortisol concentrations within the physiologically relevant range of 10-200 ng/mL reported in human sweat. Temperature and pH effects testing was performed for pH range 4-8 and in a temperature chamber for the clinical range reported on the surface of human skin: 25-40 °C. The cortisol sensor demonstrated stability of operation with 7.58% variability under these conditions.
已在用于可穿戴应用的金电极制成的柔性化学阻抗传感器上展示了具有四个通道的电化学阻抗谱 (EIS) 分析仪模块。该模块可以以 1 kHz 的频率对四个传感器进行时分复用 (TDM) 阻抗测量。在这项工作中，我们对系统进行了表征，用于检测超低体积（1-3 μL）人汗液中的皮质醇，包括传感器性能以及在连续皮质醇给药期间的影响，以及皮肤表面预期的 pH 和温度变化，这些变化代表了可穿戴设备所见的使用条件。在合成汗液和人汗液中，均显示出 1 pg/mL 至 200 ng/mL 浓度范围内的皮质醇检测，输出响应报告为随皮质醇浓度变化的阻抗变化。连续剂量测试表明，在生理相关范围内（10-200 ng/mL），传感器在人汗液中报告的皮质醇浓度下长时间运行的稳定性。进行了 pH 值和温度影响测试，pH 值范围为 4-8，并在人体皮肤表面报告的临床范围内的温度室中进行测试：25-40°C。在这些条件下，皮质醇传感器的运行稳定性为 7.58%。
