Conventional optics in the radio frequency ͑rf͒ through far-infrared ͑FIR͒ regime cannot resolve microscopic features since resolution in the far field is limited by wavelength. With the advent of near-field microscopy, rf and FIR microscopy have gained more attention because of their many applications including material characterization and integrated circuit testing. We provide a brief historical review of how near-field microscopy has developed, including a review of visible and infrared near-field microscopy in the context of our main theme, the principles and applications of near-field microscopy using millimeter to micrometer electromagnetic waves. We discuss and compare aspects of the remarkably wide range of different near-field techniques, which range from scattering type to aperture to waveguide structures.

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Dip Pen Nanolithography (DPN TM) is an important technique for nanotechnology and a fundamental new tool for studying the consequences of miniaturization. In this scanning probe technique a sharp tip is coated with a functional molecule (the 'ink') then brought into contact with a surface where it deposits ink via a water meniscus. The DPN process is a direct-write pattern transfer technique with nanometer resolution and is inherently general with respect to usable inks and substrates, including biomolecules such as proteins and oligonucleotides. We present functional extensions of the basic DPN process by showing multiple active probes along with the ability to load different inks onto probe tips. We present the fabrication process and characterization of thermomechanically actuated probes that use the bimorph effect to induce deflection of individual cantilevers as well as the integration of these probes with control electronics and an interface module. As an additional improvement to DPN functionality, we developed the capability to write with different inks on the probe array, permitting the fabrication of multicomponent nanodevices in one writing session. For this purpose, we fabricate passive microfluidic devices and present the microfluidic behavior and ink loading performance of these components.