Wearable Breath Sensors with Chip Integrated Mid-Infrared Slow Light Enhanced Absorbance Spectroscopy on Conformal Flexible Substrates

欧米茄光学和德克萨斯大学奥斯汀分校提出可穿戴式呼吸酒精监测 在柔性基底上具有可穿戴的集成芯片的红外（IR）光学传感器。智能传感 通过将柔性衬底上的器件与个人服装集成来实现。集成 通过柔性印刷电路板上的蓝牙，系统将能够实现真实的时间，连续， 远程监控，以及针对高危驾驶员和药物滥用者的个性化警告通知器。 芯片集成的气体吸收传感包括量子级联激光器（QCL） 和量子级联检测器（QCD）晶片，其结合到硅基硅中的硅无源波导， 蓝宝石（SoS）晶片。被引导的光的增强的光吸收通过使用 实验证明了SoS中的中红外多孔缝隙光子晶体波导（HPCW）， 以前用于检测化学战模拟物磷酸三乙酯。原则 增强的吸收依赖于PCW结构特有的慢光现象， 在低折射率窄槽中增强的光场强度，这些光场强度联合收割机组合以增加有效的 导波穿过被感测气体的路径长度。相比于常规 QCL和QCD依赖于庞大的电子驱动电路和台式偏置设备， 该建议将实验证明的基于印刷电路板的驱动元件 到柔性Kapton衬底上。分布式 芯片上的反馈（DFB）QCL发射多个离散波长，中心波长=3.4µm 和=4.2µm将分别监测呼吸中的乙醇和二氧化碳（CO2）。每个 QCD，对应于QCL，测量中间体转导后的光强度 HPCW。来自QCD的积分信号产生吸收光谱。变化 吸收光谱定性和定量地识别气体， 蓝牙到手机或远程设备。我们的可穿戴平台可以轻松检测乙醇 吸收截面2×10- 19 cm 2/分子，通过吸光度特征具有特异性 低至十亿分之20的检测限，低于呼吸中100 ppb对应的 0.02%血液酒精浓度（BAC）。 所提出的传感平台及其与智能服装的潜在集成， 智能珠宝和配件，将使应用超越呼吸酒精监测， 监测癌症和传染病，民用和工业空气质量监测， 机载平台，以及军事、执法和消防应用。我们的系统是 易于扩展到其它波长，这将使得能够监测其它气体和蒸汽。

Omega Optics and the University of Texas, Austin, propose wearable breath alcohol monitoring with a wearable chip-integrated infrared (IR) optical sensor on flexible substrate. Smart sensing is achieved by integrating the devices on flexible substrates with personal clothing. Integrated with Bluetooth on the flexible printed circuit board, the system will enable real time, continuous, remote monitoring, as also personalized warning notifiers for at-risk drivers and drug abusers. The chip-integrated absorption sensing of gases comprises a quantum cascade laser (QCL) and quantum cascade detector (QCD) wafer bonded to silicon passive waveguides in silicon-on- sapphire (SoS) wafer. Enhanced optical absorbance by the guided light is achieved by using an experimentally demonstrated mid-IR holey slotted photonic crystal waveguide (HPCW) in SoS, previously used for detection of chemical warfare simulant triethylphosphate. The principle of enhanced absorption relies on the phenomenon of slow light unique to PCW structures and enhanced optical field intensities in low index narrow slots that combine to increase the effective path length traversed by the guided wave through the sensed gas. In contrast to conventional QCLs and QCDs that rely on bulky electronic drive circuits and benchtop biasing equipment, this proposal transfers experimentally demonstrated printed circuit board based drive elements to a flexible Kapton substrate via demonstrated ink-jet printing techniques. Distributed feedbacks (DFB) QCLs on chip emitting multiple discrete wavelengths centered on =3.4µm and =4.2µm will monitor both ethanol and carbon dioxide (CO2) in breath respectively. Each QCD, corresponding to a QCL, measures light intensity after transduction by the intermediate HPCW. The integrated signal from QCDs generates the absorption spectrum. Change in absorption spectrum identifies the gas qualitatively and quantitatively, notifying wirelessly via Bluetooth to cell phones or remote devices. Our wearable platform can easily detect ethanol with absorption cross-section 2×10-19cm2/molecule, with specificity via absorbance signatures down to 20 parts per billion detection limits, lower than the 100ppb in breath corresponding to 0.02% blood alcohol concentration (BAC) level. The proposed sensing platform together with its potential integration with smart clothing and smart jewelry and accessories, will enable applications beyond breath alcohol monitoring to the monitoring of cancers and infectious diseases, in civilian and industrial air quality monitoring on airborne platforms, and in military, law-enforcement and fire-fighting applications. Our system is readily scalable to other wavelengths that will enable monitoring of other gases and vapors.