Scanning Dielectrophoretic Tweezers for Particle Manipulation and Sensing
Summary Invention This invention is capable of positioning and sensing particles with intense localized electric fields. In one implementation of the invention, closely spaced electrodes on a tip generate a local radio frequency (RF) electric field at the end of the tip. In one aspect, the tip can be positioned by a manipulator or by a scanning probe microscope (SPM). In another aspect, the dielectrophoretic (DEP) force produced by the FR field is used to trap microscopic objects and particles. Once trapped, the microscopic objects or particles can be positioned or otherwise manipulated by moving the tip via the SPM or other manipulator. Monitoring the conductance between the electrodes provides a means for sensing the presence of a particle trapped at the end of the tip. To achieve effective DEP trapping forces, conventional microfabrication methods may be used to deposit two electrodes in a variety of manners onto a sharp elongated object (an SPM tip, an AFM tip, a sharpened glass tip). Matching the electrode spacing to the size of the particle, particles with diameters from hundreds of microns to tens of nanometers can be trapped. The trapping force further may be tuned by adjusting the amplitude and frequency of the voltage applied to the two electrodes. The localized nature of the RF field and DEP force facilitates single-particle manipulation. In operation, the tip is scanned close to the target particle. By applying a voltage across the electrodes, the â€œtweezersâ€ tip can â€œpick upâ€ the particle. Using a scanning or manipulating element to drive the tip motion, the particle can be moved to another desired location. The tweezers can subsequently release the particle by turning the electrode voltage off.
Applications DEP tweezers apparatus may be employed in a variety of applications to facilitate manipulation, detection, imaging, and characterization of small particles or biological samples. Some examples of such applications include, but are not limited to, in vitro fertilization, moving and positioning individual biological cells for research or tissue assembly, microinjecting or transfecting individual cells, controlled manipulation of objects with nanometer-scale dimensions, and building useful devices from nanoscale components by precisely placing the components in desired locations.
Westervelt, Robert M.
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