Abstract
The separation of liquid mixtures is demonstrated using the vibrating tip of an Atomic Force Microscope (AFM). Fluid is collected onto the tip from a liquid surface while under tapping mode operation. This suppresses bulk capillary flow and enhances partitioning based on molecular affinity to the tip. AFM tapping mode separation was tested on liquid films consisting of binary and complex mixtures. The separated components were analyzed using tip enhanced infrared spectroscopy and direct analysis in real time mass spectrometry. The results demonstrate nanometer scale chemical separation for ultratrace analysis and nanofluidic applications.
Highlights
Atomic Force Microscopy (AFM) is an established imaging tool for nanotechnology
A new nanofluidic AFM function is presented, AFM tapping mode separation (AFM-TMS) that mediates molecular separation of molecules on to the AFM tip that is vibrating on a liquid surface
The detection of the separated components on the AFM tip used a sensitive mass spectrometry method consisting of a Direct Analysis in Real Time (DART) ion source interfaced to a high mass accuracy time of flight mass spectrometer system (DART-AccuTOF, Jeol, Peabody Ma)
Summary
Atomic Force Microscopy (AFM) is an established imaging tool for nanotechnology. The central component is a tip mounted on a microfabricated cantilever that is raster scanned over a surface. A new nanofluidic AFM function is presented, AFM tapping mode separation (AFM-TMS) that mediates molecular separation of molecules on to the AFM tip that is vibrating on a liquid surface. The inhibition capillary flow by tapping mode AFM was observed in previous work where it enabled imaging of liquid surfaces.7 In
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