PROJECT SUMMARY/ABSTRACT Problem statement: The investigation and manipulation of complex biological systems require lab-on-a-chip (LOC) systems that can perform spatially resolved, localized sensing (e.g., detection of biomarkers) and actuation (e.g., micropatterning, and electrical stimulation) on a single entity (e.g., within the surface of a soft tissue). Faradaic electrochemistry involving reduction/oxidation (redox) reactions is commonly used as the driving force for these operation modalities and processes. However, array-type electrodes prepared by conventional lithography-based technologies have limitations in their flexibility as the dimensions, designs, and locations are tailored to specific tasks, making it difficult to adjust the regions of measurement/manipulation of dynamic cellular processes as required. Additionally, redesigning these electrodes requires time-consuming, expensive, and highly sophisticated fabrication and read-out procedures. Furthermore, the predetermined geometry may limit the achievable density of effective working sites due to the use of conductive pads/interconnects within the electrode arrays. As a result, there is a need to explore novel LOC systems with improved resolution, flexibility, and adaptability to shift the paradigm of spatially resolved biosensing and actuation applications. Hypothesis: This project aims to develop a photoelectrochemistry-enabled multi-utility lab-on-a-chip (LOC) system, known as the "optoelectronic micro-gadget" (OMG), for sensing and actuation by utilizing cross- disciplinary expertise in electrical engineering, optoelectronics, and analytical chemistry. The OMG system will be based on a monolithic, flexible silicon thin film (thickness < 10 μm) and a reconfigurable focused laser beam for spatially resolved photoexcitation. The working principle is that, when the semiconductor thin-film contacts a redox solution, a space-charge region develops at the interface due to the Fermi energy level mismatch. A photoexcitation will result in the generation of electron-hole pairs that are delivered to the semiconductor- electrolyte interface, causing charge transfer and triggering redox reactions that can be used for amperometric sensing and actuation in the localized spot. The hypothesis is that the flexible OMG system can achieve accurate light-induced sensing and actuation within a single entity of curvilinear surfaces at a cellular or sub-cellular dimension scale, and thus can serve as a powerful tool for biomedical investigation supporting multiple operation modalities such as biosensing, micropatterning, pH regulation and electrical stimulation. The study will include the following aims: Aim 1: Develop flexible photoelectrodes supporting light-induced redox reactions. Aim 2: Integrate the photoelectrodes with an optical system and test the feasibility of conducting spatially resolved, localized photoelectrochemistry. Aim 3: Evaluate performance/multifunctionality of “OMG” for applications in neuroscience & other fields.

PROJECT NARRATIVE This project aims to develop a photoelectrochemistry-enabled multi-utility LOC system for sensing and actuation, namely the “optoelectronic micro-gadget” (OMG). The study will pioneer a design, simulation, implementation, and validation of a mechanically flexible photoelectrode paired with an intensity-modulated illumination source to generate photocurrents for probing and manipulating the local environment in the biosystem at a cellular or sub-cellular dimension scale. The proposed research is relevant to public health because the envisioned system could enable bi-directional engineering technologies in biomedical investigation with minimized resources, improved efficiency, customizable operational modalities, and enhanced opportunities.