NER: Acoustic Radiation Pressure Driven Atomic Force Microscope for Fast Imaging and Parallel Sensing of Biological and Chemical Processes at the Nanoscale

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0210415DegertekinThe capability of operating in liquid environments has been one of the key reasons for the atomic force microscope's (AFM) indisputable role in the recent advances in nanoscience and nanotechnology. This capability has not only enabled imaging biological samples and observation of biological and chemical processes at the nanoscale, but also led to the development of many microcantilever-based devices in the area of biosensing and proteomics.The liquid environment presents significant challenges to the operation of the AFM, especially in dynamic imaging modes such as tapping mode, and fast imaging applications. As compared to air, the liquids provide a more efficient coupling medium for mechanical perturbations. Hence regular piezoelectric actuation of the AFM cantilever results in spurious resonant signals due to the liquid filled cavity surrounding the sample and the actuator structure. Several novel actuators, based on magnetic, electrostatic, and thin-film piezoelectric techniques have been developed to solve this problem, but these methods severely limit the type of cantilevers and liquids that can be used for experiments. Furthermore, these methods are not suitable for actuation of individual cantilevers in an array, an important capability required for biosensing applications.This exploratory research proposal aims to remove these important obstacles in the implementation of a versatile AFM for applications in liquids using a novel microcantilever actuation technique. The technique uses the acoustic radiation force generated by collimated high frequency (100-400MHz) acoustic waves directed to the AFM cantilever to actuate the cantilever in the DC-MHz frequency range. Promising initial results using the technique have been recently obtained and presented in the proposal. Based on these results, the following objectives are proposed:-Design and microfabrication of individual and arrays of acoustic radiation pressure (ARP) actuators: The actuators will be fabricated on silicon substrates using a thin Zinc Oxide film to generate acoustic waves around 250MHz and silicon micromachining techniques will be used to fabricate acoustic Fresnel lenses to direct the acoustic beams to AFM cantilevers.-Integration of the actuator to a widely available commercial AFM system: A fluid-cell including an ARP actuator will be manufactured and used on a commercial AFM system with appropriate electronics.-Evaluation of the capabilities and limitations of the integrated actuator: The performance of the ARP actuator for fast imaging, as well as array operation will be tested and compared with conventional methods.-Study of possible adverse effects of the ARP actuator: Interaction of high frequency acoustic waves with biological processes will be explored on several important samples and the actuator design will be improved accordingly. Successful implementation of this project will impact numerous areas of nanoscience and engineering, because it will help researchers in the testing and implementation of innovative ideas and in probing a wider variety of biological and chemical processes at the nanoscale.