Using Flexible Hybrid Electronics on a Miniaturized Non-invasive Bio-optical Sensor For Hemoglobin Detection

Flexible hybrid electronics (FHE) is an emerging technology by integrating electronic devices and circuits onto flexible or stretchable substrates and packages. Skin chromophore concentration provides rich biomarker information for non-invasive healthcare applications. From algorithm developed on DRS (Diffusion Reflectance Spectroscopy), these biomarker data can be extracted by optics measurement of skin tissue absorption, and the reduced scattering coefficient. In this study, we choose blood hemoglobin as the detection target, and developed a wearable device with miniaturization evolved from a lab benchtop equipment to a small sized LED +PD structure. To fulfill this purpose, we first surveyed LEDs at 6 different wavelengths that meet most distinguished skin tissue absorption properties to hemoglobin. To mimic configuration of fiber probe and SDS (Source Detection Separation), where original DRS algorithm derived, we apply optical simulation to design grid topology with 12 LEDs and 6 PDs. Simulation result showed this topology design can derive absorption property of tissue phantom with good correlation to measurement result. In order to realize body conformal flexible bio optical sensor, as well as addressing the necessary light barrier miniaturization and component placement pitch in small SDS design, we developed LED and PD dice DB&WB process on FPC, and choose flexible optical and opaque LSR (Liquid Silicon Rubber) material that provide good workability in small area for the dispensing process. These process and material are critical to the development of miniaturized FHE. For functionality validation, firstly we validated critical parametric on optics to confirm the performance of design, material characteristics and stability of fabrication. Secondly, we verified device on known characterized tissue phantom for absorption and scattering coefficient extraction. The last, in-vivo hemoglobin measurement performed, and showed good data correlation with commodity device.