This work demonstrates the manufacturing process of micro- and nanofluidic devices consisting of independent, aligned carbon pipes with potential applications as micro- and nanoscale dispensing systems, electrodes, and tools with which to study fundamental micro- and nanofluidics. A low-cost, high-throughput chemical vapor deposition (CVD) process was utilized to deposit carbon within novel silica-based templates. This simple template-based manufacturing process allows the carbon devices to be integrated into millimeter scale silica-based templates without micro- or nanoassembly, facilitating commercialization. Furthermore, the carbon-based devices were designed to readily integrate into standard laboratory equipment, promoting broad utilization. Herein, a repeatable methodology for fabricating multifunctional, carbon-based micro- and nanofluidic devices as well as establishing relationships between parameters at each stage of fabrication and the final geometry, including diameter and wall thickness of the carbon structures, of the device is presented.
We describe the development, fabrication, and characterization of a novel two‐electrode nanosensor contained within the tip of a needle‐like probe. This sensor consists of two, vertically aligned, carbon structures which function as individual electrodes. One of the carbon structures was modified by silver electrodeposition and chlorination to enable it to function as a pseudo‐reference electrode. Performance of this pseudo‐reference electrode was found to be comparable to that of commercially available Ag/AgCl reference electrodes. The unmodified carbon structure was employed as a working electrode versus the silver‐plated carbon structure to form a two‐electrode sensor capable of characterizing redox‐active analytes. The nanosensor was demonstrated to be capable of electrochemically characterizing the redox behavior of para‐aminophenol (PAP) in both bulk solutions and microenvironments. PAP was also measured in cell lysate to show that the nanosensor can detect small concentrations of analyte in heterogenous environments. As the working and reference electrodes are contained within a single nanoprobe, there was no requirement to position external electrodes within the electrochemical cell enabling analysis within very small domains. Due to the low‐cost manufacturing process, this nanoprobe has the potential to become a unique and widely accessible tool for the electrochemical characterization of microenvironments.
Micropipette-based thermocouples provide the advantage of a high tip diameter-to-length aspect ratio allowing the maintenance of a reference temperature crucial for accurate thermal sensing in microdomains. The research efforts in this field strive to achieve high thermoelectric power (voltage change per unit temperature change) while minimizing the sensing area, a pair of tasks that is by nature contradictory and thus, challenging. Herein, the design and fabrication of a carbon-based micropipette thermal sensor are described. A novel manufacturing method and set of materials are used to overcome the reduction in thermoelectric performance associated with small sensor sizes. A glass micropipette is utilized as a template in a chemical vapor deposition process to form a carbon layer in the lumen of the pipette. This carbon micropipette then serves as a scaffold on which gold and nickel are deposited, enabling the device to function as a thermocouple. This low-cost fabrication process results in a thermocouple with a sub-500 nm tip. The response of the thermocouple was characterized and demonstrated good repeatability in a temperature range of 0 to 60 °C. The unique material selection provided a thermoelectric power of 14.9 µV·K-1, a significant improvement (68%) relative to other micropipette-based thermocouples.
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