Abstract: The invention provides a mild procedure for the functionalization of cellulose and other substrates with a detection reagent such as N-(1-naphthyl)ethylenediamine and is able to achieve much higher functionalization density than previously reported. A paper-based device created using cellulose functionalized according to the invention allowed for much lower detection limits for nitrite in various kinds of water samples than have been seen using paper-based devices. In addition, grafting of N-(1-naphthyl)ethylenediamine to cellulose improved the stability of the N-(1-naphthyl)ethylenediamine in the presence of moisture and light.

Abstract: The present disclosure provides a system including an insulator-based dielectrophoresis device. The insulator-based dielectrophoresis device includes a fluid flow channel having at least one fluid inlet and at least one fluid outlet. The fluid flow channel includes at least one insulating flow structure extending from a wall to define a constriction in the fluid flow channel. The system includes a detection chamber placed in fluid communication with the fluid flow channel by an opening in the wall of the fluid flow channel, where the opening is configured downstream of the at least one insulation flow structure. The detection chamber includes an electrochemical sensor configured to constrict the flow of fluid entering the detection chamber through a pore, where the pore is sized to produce a detectable signal upon passage of an analyte through the pore. The system may process the detectable signal to output a metric indicative of the identity or physiochemical property of the analyte.

Abstract: The invention provides a mild procedure for the functionalization of cellulose and other substrates with a detection reagent such as N-(1-naphthyl)ethylenediamine and is able to achieve much higher functionalization density than previously reported. A paper-based device created using cellulose functionalized according to the invention allowed for much lower detection limits for nitrite in various kinds of water samples than have been seen using paper-based devices. In addition, grafting of N-(1-naphthyl)ethylenediamine to cellulose improved the stability of the N-(1-naphthyl)ethylenediamine in the presence of moisture and light.

Abstract: A flow cell is provided for the analysis and/or microscopy of liquid or gas samples on the nanometer to micron scale. The flow cell preferably includes a thin membrane that is transparent to electrons and/or photons, thereby enabling the penetration of electrons or photons into a liquid flowing through the cell. Trenches are provided on either side of the membrane, which advantageously minimize fluidic resistance outside of the window area of the cell and also enable a faster response time in response to changes in external fluidic pressure. This feature enables active feedback using pathlength sensitive probes to stabilize the fluid flow to thin streams from nanometer to micron scale thicknesses with nanometer precision.