Focused ion beam modification of atomic force microscopy tips for near-field scanning optical microscopy

Krogmeier, Jeffrey R.; Dunn, Robert C.

doi:10.1063/1.1430028

Cited by 16 publications

(19 citation statements)

References 7 publications

(8 reference statements)

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confidence: 99%

“…These tips incorporate the well-known properties of fiber optic NSOM probes and are much less rigorous to fabricate than the previous hybrid design. 9 While still requiring access to FIB technology, the micromachining requirements are greatly relaxed since fabrication of the aperture itself is not required. Moreover, since these tips are designed around conventional fiber optic NSOM probes, they take advantage of the past work done in fabricating and understanding the optical properties of these tips.…”

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“…These have largely involved either changing the feedback mechanism utilized to hold the tip close to the sample or modifying the probes themselves to lower the spring constant and thus the forces generated in force feedback. 2,5,9 For the latter, an obvious route of exploration is to incorporate a near-field light source onto conventional atomic force microscopy ͑AFM͒ cantilevers.9-11 AFM is widely used in biological applications on unfixed tissues under physiological conditions.Commercially available silicon nitride AFM cantilevers come in a variety of geometries that offer a range of cantilever spring constants and tip parameters. Using these tips, AFM techniques have been widely utilized for studies of sample surfaces, including living cells, while operating with the AFM tip either directly in contact with the sample surface or through a tapping, or intermittent, contact mode of force mapping.…”

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confidence: 99%

“…For the experiments described here, the 514 nm line from an argon ion source ͑Liconix, 5000 series͒ is focused onto the backside of the AFM cantilever and serves as both the excitation source through the NSOM tip and to generate the force feedback signal, as previously reported. 9 The sample is mounted on x-y closed-loop piezo stage ͑Mad City Labs, Inc.͒ and used to raster scan the sample beneath the probe. Fluorescence is collected beneath the sample with a high numerical aperture objective lens ͑Zeiss, Fluar 100X, 1.3 NA͒, appropriately filtered, and imaged onto an avalanche photodiode ͑EG&G, SPCM-200͒.…”

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“…9 The FIB was used to cut a small hole into the end of an AFM tip, into which a high index glass sphere ͑ϭ1.9͒ was glued. The glass sphere was then milled into a pyramid shape with the FIB and the sides were coated with aluminum to confine the light inside the taper region.…”

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Hybrid near-field scanning optical microscopy tips for live cell measurements

Kapkiai

Moore-Nichols

Carnell

et al. 2004

Applied Physics Letters

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We report a near-field scanning optical microscopy ͑NSOM͒ probe that enables high-resolution imaging of living cells under physiological buffered conditions. The hybrid design combines a conventional fiber optic near-field probe with a standard atomic force microscopy cantilever. Imaging of fluorescent latex spheres suspended in an acetate matrix demonstrates the subdiffraction limited fluorescence and topography capabilities of the tips. The reduced spring constant of the hybrid tip is also shown to be amenable to measurements on living cells. Near-field scanning optical microscopy ͑NSOM͒ is a scanning probe technique that utilizes specially fabricated probes to deliver light down to the nanometric dimension.1,2 NSOM provides opportunities to simultaneously measure both optical and topographic features of samples with subdiffraction limited spatial resolution. These capabilities have been utilized to probe thin films, solid-state devices, and due to the unique electromagnetic fields emerging from the nearfield aperture, single molecule orientations.2 The potential impact of NSOM is arguably the greatest in the biological sciences, where there is a well-developed history of using fluorescence probes to tag specific proteins or structures. This field seems particularly well suited to take advantage of the single molecule fluorescence sensitivity, high spatial resolution, and simultaneous force information that NSOM offers. However, current applications of NSOM to biological samples are largely limited to isolated protein samples, model membranes, or chemically fixed biological cells. 2-5The extension to viable, unfixed biological tissues has previously proven problematic.The difficulty in conducting NSOM measurements on viable biological tissues arises from the forces generated in maintaining the NSOM tip close to the specimen. Highresolution NSOM measurements require that the tip be held within nanometers of the sample while scanning. This necessitates the implementation of a feedback system for sensing the sample surface and maintaining the tip-sample gap. [6][7][8] Traditionally, a force feedback approach is implemented in which the tip is either dithered laterally or vertically to the sample surface, depending on probe geometry. The dampening in the amplitude of the oscillating NSOM tip as the tip interacts with the sample surface is monitored and used to hold the tip-sample gap constant during scanning. While straightforward and highly successful for most applications, the large forces generated using conventional fiber optic NSOM probes often damage fragile biological samples such as living cells.A number of approaches have been reported in attempts to circumvent the large forces generated under normal NSOM feedback operation and thus open applications in the biological sciences. These have largely involved either changing the feedback mechanism utilized to hold the tip close to the sample or modifying the probes themselves to lower the spring constant and thus the forces generated in force feedback. 2,5,9 ...

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Hybrid near-field scanning optical microscopy tips for live cell measurements

Kapkiai

Moore-Nichols

Carnell

et al. 2004

Applied Physics Letters

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Scanning Micro‐ and Nanoprobes for Electrochemical Imaging

Kranz¹,

Kueng²,

Mizaikoff³

2004

Advanced Micro and Nanosystems

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Near-Field Scanning Optical Microscopy: A New Tool for Exploring Structure and Function in Biology

Dickenson

Mooren

Erickson

et al. 2014

Surface Analysis and Techniques in Biology

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Optical microscopy in the biological sciences has proven invaluable for understanding structure and dynamics in these complicated systems. It is a noninvasive tool that is amenable with fragile samples and is easily implemented under physiological conditions. It also benefits from a wide array of contrast mechanisms that can be exploited to gain detailed insight into sample properties. One limitation, however, concerns spatial resolution, which is limited to approximately half the excitation wavelength by the diffraction of light. Overcoming this limitation has motivated the development of near-field scanning optical microscopy (NSOM) or scanning near-field optical microscopy (SNOM). NSOM uses specially fabricated probes to deliver light down to the nanometric dimension, enabling optical microscopy with a spatial resolution of tens of nanometers. For the biological sciences, NSOM can simultaneously map sample fluorescence and topography with high spatial resolution and single-molecule detection limits. This makes NSOM a powerful new tool for understanding biological structure at the nanometric dimension.

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Focused ion beam modification of atomic force microscopy tips for near-field scanning optical microscopy

Cited by 16 publications

References 7 publications

Hybrid near-field scanning optical microscopy tips for live cell measurements

Hybrid near-field scanning optical microscopy tips for live cell measurements

Scanning Micro‐ and Nanoprobes for Electrochemical Imaging

Near-Field Scanning Optical Microscopy: A New Tool for Exploring Structure and Function in Biology

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