Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
Lab Chip. 2019 Nov 21;19(22):3899-3908. doi: 10.1039/c9lc00842j. Epub 2019 Oct 23.
Dilatometric strain sensors (DSS) that work based on detection of volume change in microfluidic channels; i) are highly sensitive to biaxial strain, ii) can be fabricated using only soft and transparent materials, and iii) are easy to integrate with smart-phones. These features are especially attractive for contact lens based intraocular pressure (IOP) sensing applications. The inherent flow stabilization of the microfluidic systems is an additional advantage suitable for filtering out rapid fluctuations. Here, we have demonstrated that the low-pass filtering in microfluidic sensors improves the signal-to-noise-ratio for ophthalmic applications. We have fabricated devices with a time constant in the range of 1-200 seconds. We have demonstrated that the device architecture and working liquid viscosity (10-866 cSt) are the two independent factors that determine the sensor time constant. We have developed an equivalent circuit model for the DSS that accurately represents the experimental results thus can be used as a computational model for design and development of microfluidic sensors. For a sensor with the time constant of 4 s, we report that microfluidic signal filtering in IOP monitoring applications can suppress the rapid fluctuations (i.e., the noise due to ocular pulsation, blinking etc.) by 9 dB without the need for electronic components.
基于微流道体积变化检测的膨胀式应变传感器（DSS）：i）对双轴应变非常敏感，ii）可仅使用柔软透明的材料制造，iii）易于与智能手机集成。这些特点特别适合基于隐形眼镜的眼压（IOP）传感应用。微流系统的固有流量稳定是另一个适合滤除快速波动的优点。在这里，我们已经证明了微流体传感器中的低通滤波可以提高眼科应用的信噪比。我们已经制造出时间常数在 1-200 秒范围内的器件。我们已经证明，器件结构和工作液体粘度（10-866 cSt）是决定传感器时间常数的两个独立因素。我们已经为 DSS 开发了等效电路模型，该模型准确地表示了实验结果，因此可以用作微流传感器设计和开发的计算模型。对于时间常数为 4 s 的传感器，我们报告说，在 IOP 监测应用中，微流体信号滤波可以在不使用电子元件的情况下将快速波动（即由于眼球搏动、眨眼等引起的噪声）抑制 9 dB。
