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Increased sensor sensitivity is important for enabling detection of low concentrations of target analyte. Being able to quickly and accurately detect low concentrations of proteins at point-of-care allows for results to be analyzed more easily and effectively. Vertically-aligned carbon nanotubes (VACNTs) were patterned into interdigitated electrodes (IDEs) and then functionalized with the representative protein streptavidin that was functionalized on the VACNT surfaces by covalent bonding (with EDC/NHS). Further detection was observed by binding biotin to the streptavidin. Fluorescence microscopy enabled the optimization of protein loading on VACNTs. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrodes and monitor the associated changes with the addition of streptavidin and biotin. A unique change in impedance is observed, which allows for monitoring the quantity of target analyte bound to the VACNT electrode surface with an observed 14x increase in resistance.

Condensation heat transfer is significant in many applications such as desalination, energy conversion, atmospheric water harvesting, electronics cooling, and other high heat flux applications. However, condensate on the surface adds a thermal resistance that limits condensation rates. The rate of condensation heat transfer is inversely proportional to the diameter of the condensate drops. In industrial condensing systems, the resistance is minimized by removing the condensate via gravity or a vapor shear, but the minimum size of droplet removal is typically on the order of the capillary length of the condensate, about 2.7 mm for water.

Increased sensitivity of electrochemical sensors is important for detection of low analyte concentrations. A unique flow-through sensor is demonstrated by depositing nanostructured platinum catalyst onto high aspect ratio, porous membranes of vertically-aligned carbon nanotubes (CNTs). Convective mass transfer enhancement was shown to improve the platinum-nanowire-coated CNT (PN-CNT) sensor performance in amperometric sensing of hydrogen peroxide (H2O2). Over 90% of the H2O2 was oxidized as it passed through the PN-CNT sensor, even for low concentrations in the range of 50 nM to 500 μM. This effective utilization of the analyte in detection demonstrates the utility of exploiting convection in electrochemical sensing. At a 100 μL s-1 flow rate, a sensitivity of 24,300 μA mM-1 cm-2 was achieved based on the frontal projected area, with a 0.03 μM limit of detection and a linear sensing range of 0.03-500 μM. Glucose oxidase was also functionalized unto the surfaces of PN-CNT sensors by polymer entrapment to enable detection of low glucose concentrations.

Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate.

Micropumping has emerged as a critical research area for many electronics and biological applications. A significant driving force underlying this research has been the integration of pumping mechanisms in micro total analysis systems and other multi-functional analysis techniques. Uses in electronics packaging and micromixing and microdosing systems have also capitalized on novel pumping concepts. The present work builds upon a number of existing reviews of micropumping strategies by focusing on the large body of micropump advances reported in the very recent literature. Critical selection criteria are included for pumps and valves to aid in determining the pumping mechanism that is most appropriate for a given application. Important limitations or incompatibilities are also addressed. Quantitative comparisons are provided in graphical tabular forms.

An enhanced electrohydrodynamic micropump for use in small-scale liquid pumping applications is developed. The micropump can be incorporated into an integrated circuit chip to provide active cooling or used as a fluid delivery agent in microdevices. Liquid flow is achieved by combining two actuation mechanisms: electrohydrodynamics (EHD) and the action of a vibrating diaphragm. Heat generated by active devices creates a thermal gradient in the fluid allowing induction of ions to be driven by EHD. The vibrating diaphragm enhances the EHD efficiency, allowing more pumping power to be transferred to the fluid. Boundary condition effects, as a result of scaling, are considered through numerical modeling. Flow rate enhancement with the addition of a vibrating diaphragm is also presented.