Organic and Inorganic Contamination on Commercial AFM Cantilevers

Lo, Yuk Keung; Huefner, Neil D.; Chan, Winter S.; Dryden, P.; Hagenhoff, Birgit; Beebe, Thomas P.

doi:10.1021/la990371x

Cited by 129 publications

(100 citation statements)

References 30 publications

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“…Evidence suggests that this material is deposited by silicone oil outgassing from the "gel-pack" in which most of the probes were stored. 11 This is supported by the significant amount of movement of this contaminant over the nanotube observed during TEM imaging. We have found via TEM imaging that gel-free clamshell tip wafer enclosures deposit about an order-of-magnitude less contamination on silicon AFM probes than gel-pack enclosures.…”

mentioning

confidence: 86%

Correlating AFM Probe Morphology to Image Resolution for Single-Wall Carbon Nanotube Tips

Wade

Shapiro

et al. 2004

Nano Lett.

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Methods we compared for attaching nanotubes to silicon AFM tips include manual assembly, direct growth and pickup.Smalley's group reported the first example of the use of carbon nanotubes as AFM tips in 1996. 1 They manually attached multi-wall carbon nanotubes (MWNT) and ropes of individual SWNTs to the apex of silicon pyramidal tips using tape adhesive and a micromanipulator in an optical microscope. The main drawback to this method is that MWNT tips large enough to be seen optically did not improve the resolution much beyond standard silicon tips when imaging isolated amyloid fibrils. 2 We found it fairly efficient to manually attach MWNTs to silicon AFM cantilevers with a 1000x optical microscope. In particular, the rate of assembly was quite high when a 15 V potential was applied between the silicon probe and the nanotubes. This resulted in nearly perfect and rapid alignment of the nanotube to the silicon tip. However, there was not a clear path to doing so with the thin SWNTs required for very high-resolution imaging.Lieber ,3,4 and Quate's 5 groups later showed that individual single wall carbon nanotubes could be directly grown by chemical vapor deposition (CVD) on the silicon tips themselves by first pre-coating the tip with a metal catalyst. In the CVD synthesis of carbon nanotubes, metal catalyst nanoparticles are heated in the presence of a hydrocarbon gas or carbon monoxide; the gas molecules dissociate on the catalyst surface and carbon is adsorbed into the particle. As the carbon precipitates, a carbon nanotube is grown with a diameter similar to that of the catalyst particle.Two techniques for direct growth have been reported. One involves creating nanopores at the apex of the silicon tip by etching with hydrofluoric acid. Catalyst particles are then deposited inside the nanopores. Carbon nanotubes grown via CVD from such a tip have an appropriate geometry for AFM imaging. While this approach enables fabrication of SWNT tips, the preparation of the porous layer in the silicon is time consuming and placement of the nanotube at the optimal location near the tip apex is

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mentioning

confidence: 86%

Correlating AFM Probe Morphology to Image Resolution for Single-Wall Carbon Nanotube Tips

Wade

Shapiro

et al. 2004

Nano Lett.

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“…Glass coverslips (#1.5 type; 24 mm by 50 mm) were soaked overnight in piranha solution (1:1 volume ratio of 30% hydrogen peroxide and 70% sulfuric acid [27]) to remove any proprietary coating. These slides were then rinsed in MilliQ water (18.2 M⍀ cm), soaked in a fresh piranha solution for a second night, rinsed 10 times in MilliQ water, and finally dried with a stream of purified nitrogen gas.…”

Section: Fig 1 (A)mentioning

confidence: 99%

Simultaneous Force and Fluorescence Measurements of a Protein That Forms a Bond between a Living Bacterium and a Solid Surface

et al. 2005

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All microbial biofilms are initiated through direct physical contact between a bacterium and a solid surface, a step that is controlled by inter-and intramolecular forces. Atomic force microscopy and confocal laser scanning microscopy were used simultaneously to observe the formation of a bond between a fluorescent chimeric protein on the surface of a living Escherichia coli bacterium and a solid substrate in situ. The chimera was composed of a portion of outer membrane protein A (OmpA) fused to the cyan-fluorescent protein AmCyan. Sucrose gradient centrifugation and fluorescent confocal slices through bacteria demonstrated that the chimeric protein was targeted and anchored to the external cell surface. The wormlike chain theory predicted that this protein should exhibit a nonlinear force-extension "signature" consistent with the sequential unraveling of the AmCyan and OmpA domains. Experimentally measured force-extension curves revealed a unique pair of "sawtooth" features that were present when a bond formed between a silicon nitride surface (atomic force microscopy tip) and E. coli cells expressing the OmpA-AmCyan protein. The observed sawtooth pair closely matched the wormlike chain model prediction for the mechanical unfolding of the AmCyan and OmpA substructures in series. These sawteeth disappeared from the measured force-extension curves when cells were treated with proteinase K. Furthermore, these unique sawteeth were absent for a mutant stain of E. coli incapable of expressing the AmCyan protein on its outer surface. Together, these data show that specific proteins exhibit unique force signatures characteristic of the bond that is formed between a living bacterium and another surface.A nearly universal trait of bacteria is their ability to attach to solid surfaces. Attached cells often form a biofilm, which is defined as a structured community of bacteria enclosed in a self-produced polymeric matrix adherent to an inert or living surface (6). Abundant evidence suggests that proteins on the outer wall of a bacterium play a critical role in initiating contact with another surface. Surface-induced expression of genes coding for various adhesins (e.g., flagella, pili, and fimbriae) have been characterized in the literature (28,39,45,48,51,54). Many of these studies rely on the mutation of genes of interest followed by a comparative analysis of the number of cells (wild type versus mutant) that are attached to a solid substrate. While these types of studies provide detailed characterizations of the proteins involved in mediating contact with another surface, the inherent surface-sensing mechanism remains hidden. The actual mechanism that allows a bacterium to sense or perceive another surface is the physical force(s) that exists in the nanometer-scale interface between a cell and that other surface. This type of elementary force, which includes van der Waals, electrostatic, solvation, and steric interactions (21,22,26), controls the way in which a protein on a bacterium's cell wall physically touches anoth...

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“…If the cantilever/tip requires extensive cleaning (e.g., after prolonged storage in gel box), add a 30 min soaking in acetone (> 99.5% purity) before step 1 (see also the section addressing contamination). The storage of tips in gel boxes is, in our experience, one of the primary source of contamination that can occur very rapidly 59 . 3.…”

Section: Preparation Of Cantilever and Tipmentioning

confidence: 99%

“…If stored in a gel box, the cantilever may pick up traces of gel polymers or silicon oil 59 that can appear, in extreme cases, as darker spots, on the back of the cantilever (as in Figure 5A). Photothermal oscillation of the cantilever can induce similar spots, but they are due to degradation/overheating of the cantilever coating by the driving laser.…”

Section: Bad Cantilever/tipmentioning

confidence: 99%

Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

Miller

Trewby

Payam

et al. 2016

JoVE

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Atomic force microscopy (AFM) has become a well-established technique for nanoscale imaging of samples in air and in liquid. Recent studies have shown that when operated in amplitude-modulation (tapping) mode, atomic or molecular-level resolution images can be achieved over a wide range of soft and hard samples in liquid. In these situations, small oscillation amplitudes (SAM-AFM) enhance the resolution by exploiting the solvated liquid at the surface of the sample. Although the technique has been successfully applied across fields as diverse as materials science, biology and biophysics and surface chemistry, obtaining high-resolution images in liquid can still remain challenging for novice users. This is partly due to the large number of variables to control and optimize such as the choice of cantilever, the sample preparation, and the correct manipulation of the imaging parameters. Here, we present a protocol for achieving high-resolution images of hard and soft samples in fluid using SAM-AFM on a commercial instrument. Our goal is to provide a step-by-step practical guide to achieving high-resolution images, including the cleaning and preparation of the apparatus and the sample, the choice of cantilever and optimization of the imaging parameters. For each step, we explain the scientific rationale behind our choices to facilitate the adaptation of the methodology to every user's specific system.

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Organic and Inorganic Contamination on Commercial AFM Cantilevers

Cited by 129 publications

References 30 publications

Correlating AFM Probe Morphology to Image Resolution for Single-Wall Carbon Nanotube Tips

Correlating AFM Probe Morphology to Image Resolution for Single-Wall Carbon Nanotube Tips

Simultaneous Force and Fluorescence Measurements of a Protein That Forms a Bond between a Living Bacterium and a Solid Surface

Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

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