UC Santa Cruz

Recent epidemics such as Zika and SARS-CoV-2 have demonstrated the vital need for novel sample-to-answer biosensors that enable rapid diagnoses to reduce impacts of future disease outbreaks. Additionally, it is essential that these new biosensors remain cost-effective and progress ultimately towards a complete point-of-care (POC) device, enabling access to high quality diagnostic options in developing countries where disease outbreaks are far more devastating due to lack of resources and aid. Optofluidics provides unique advantages to address this challenge. By combining the integration of photonic components with the ability to control nanoliter scales of fluids, multiple functionalities that would usually require an entire laboratory can exist in the same chip. Developing these devices establishes a pathway to point-of-care devices that can democratize infectious disease screening. By fabricating these devices on polydimethylsiloxane (PDMS), even more advantages can be exploited through rapid prototyping of novel devices. Furthermore, the advancement of organ-on-chip studies provides another avenue by which optofluidic biosensor devices can be used to investigate secreted biomarkers and inform on organ health and development. Within this thesis several PDMS-based optofluidic devices are presented. The first device demonstrated an on-chip distributed feedback laser using Rhodamine 6G dissolved in ethylene glycol that had a central lasing wavelength of 574.6 nm and a bandwidth of 1.08 nm. The threshold fluence of this laser was determined to be 52.7 µJ/cm2. A second DFB laser using 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) dissolved in dimethyl sulfoxide (DMSO) was then added to demonstrate spatially multiplexed fluorescence sensing. This second laser had a lasing wavelength of 656.5 nm, a FWHM of 1.73 nm, and threshold fluence of 307.6 µJ/cm2. A complete all-in-one lab-on-chip (LOC) system is then presented integrating the Rhodamine 6G laser with sample preparation and optical detection of Zika nucleic acids. Lastly, new directions for optofluidic biosensors are presented including educational outreach using remotely operated LOC devices to conduct fluorescence detection of Escherichia coli (E. coli) as well as optical detection of single extracellular vesicles secreted from cerebral organoids.