Feedback stabilized force-sensors: a gateway to the direct measurement of interaction potentials

Jarvis, Suzanne P.; Dürig, U.; Lantz, Mark A.; Yamada, H.; Tokumoto, Hiroshi

doi:10.1007/s003390051131

Cited by 14 publications

(8 citation statements)

References 13 publications

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“…The cantilever is modulated by the application of an oscillatory force to the tip . The force modulation technique is implemented by gluing a small magnetic particle to the cantilever and applying a sinusoidal magnetic field normal to the cantilever surface . The magnetic particle is magnetized such that the applied magnetic field bends the lever in the surface normal direction.…”

Section: Methodsmentioning

confidence: 99%

Damping near Solid−Liquid Interfaces Measured with Atomic Force Microscopy

1999

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An atomic force microscope (AFM) is used to investigate changes in the effective viscosity of liquids which are confined between an AFM tip and a sample surface. In both cases studied, namely octamethylcyclotetrasiloxane near graphite and water near mica, it is found using two methods that the damping increases markedly at small tip−sample separations (<20 Å), even for sharp tips. The strong change in damping with tip−sample separation allows the AFM feedback to be controlled in noncontact mode (i.e., off the surface). Hence, the increase in damping can be directly associated with changes in the material properties of the confined liquid.

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Section: Methodsmentioning

confidence: 99%

Damping near Solid−Liquid Interfaces Measured with Atomic Force Microscopy

1999

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“…7 Recent theoretical analysis of the force-feedback method shows, however, that it is very demanding to stabilize the tip position when the force gradient exceeds the cantilever spring constant. 8,9 In order to increase the stiffness of the cantilever at the undisturbed resonance frequency 0 by a factor K, the bandwidth of the controller must be at least QK times 0 . 8 For cantilevers with resonance frequencies in the 10 kHz range and Q Ͼ200, which is typical in UHV operated instruments, this means a bandwidth higher than 20 MHz for a tenfold increase of the spring constant.…”

Section: Introductionmentioning

confidence: 99%

“…8,9 In order to increase the stiffness of the cantilever at the undisturbed resonance frequency 0 by a factor K, the bandwidth of the controller must be at least QK times 0 . 8 For cantilevers with resonance frequencies in the 10 kHz range and Q Ͼ200, which is typical in UHV operated instruments, this means a bandwidth higher than 20 MHz for a tenfold increase of the spring constant. It should, however, be noted that it is a significant advantage to operate with a cantilever stiffened by force feedback at lower frequencies even if the cantilever instability still occurs when the force gradient exceeds the spring constant.…”

Section: Introductionmentioning

confidence: 99%

Electrostatic force-feedback force sensor incorporated in an ultrahigh vacuum force microscope

Yakimov

Erlandsson

2000

Review of Scientific Instruments

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A force sensor based on a fiber-optic interferometric displacement transducer incorporated in an ultrahigh vacuum atomic force microscope is described. The operation of the sensor is based on balancing the tip-sample interfacial force using an electrostatic actuator. The electrodes of the actuator are formed by the grounded W cantilever and the metallized end facet of the optical fiber used by the interferometer. Chemical reduction of Ag by a wet chemical method is used for metal coating of the fiber end. A special masking procedure is used to obtain a window hole in the metal coating at the position of the fiber core to allow for optical beam output. Using a window instead of a semitransparent metal film allows us to save the low-finesse characteristics of the interferometer which facilitates the calibration of cantilever displacement. The performance of the sensor is discussed and exemplified by experimental results from force-separation measurements on the W–Au system in ultrahigh vacuum.

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“…In addition, polarizable samples could be perturbed by the electric fields used for controlling cantilever stiffness. The second approach uses magnetic feedback to stiffen the cantilever 10 and has been utilized to measure force profiles in ultrahigh vacuum and air. 11,12 These initial studies have not, however, investigated the applicability of magnetic feedback to measure interactions between chemically well-defined surfaces in the condensed phase.…”

Section: Introductionmentioning

confidence: 99%

Probing Intermolecular Forces and Potentials with Magnetic Feedback Chemical Force Microscopy

2000

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Magnetic feedback chemical force microscopy (MF-CFM) was used to map the complete force profile between hydroxyl- and carboxyl-terminated self-assembled monolayers (SAMs) in aqueous solution. The snap-to-contact and snap-out instabilities intrinsic to force-displacement measurements made with weak spring constant cantilevers were eliminated by using a cantilever with an attached magnetic particle and a solenoid in a servo loop to balance the tip−sample interactions. The interaction between hydroxyl-terminated surfaces in deionized water was well fit by a van der Waals model to short distances. The Hamaker constant that was determined from experiment, 1.0 × 10-19 J, is similar to that expected for a gold−gold interaction and shows that the underlying gold support dominates the attractive interaction over a large range of separations. The interaction between a carboxyl-terminated tip and a sample in 0.010 M phosphate buffer at pH 7.0 was fit with a model that includes both van der Waals and electrostatic terms. The Hamaker constant, 1.2 × 10-19 J, which is similar to that obtained for hydroxyl-terminated surfaces, confirms that the gold−gold interaction dominates the attractive part of the interaction. In addition, the Debye length, 2.9 nm, surface potential, −1.5 × 102 mV, and charge regulation parameter, −0.71, obtained from analysis of the data are consistent with previous work (Vezenov et al. J. Am. Chem. Soc. 1997, 119, 2006−2015. Hu; Bard. Langmuir 1997, 13, 5114−5119). The implications of these results and applications of MF-CFM are discussed.

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Feedback stabilized force-sensors: a gateway to the direct measurement of interaction potentials

Cited by 14 publications

References 13 publications

Damping near Solid−Liquid Interfaces Measured with Atomic Force Microscopy

Damping near Solid−Liquid Interfaces Measured with Atomic Force Microscopy

Electrostatic force-feedback force sensor incorporated in an ultrahigh vacuum force microscope

Probing Intermolecular Forces and Potentials with Magnetic Feedback Chemical Force Microscopy

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