Shear thinning behavior of monolayer liquid lubricant films measured by fiber wobbling method

Hamamoto, Yuya; Itoh, Shintaro; Fukuzawa, Kenji; Zhang, H

doi:10.1088/1742-6596/258/1/012010

Cited by 4 publications

(7 citation statements)

References 9 publications

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“…The dashed line in Fig. 5 is the fitted curve of Cross's equation: a phenomenological equation that explains shear thinning expressed as follows [11]: (4) Here, and are the constant. and represent damping coefficient and shear rate, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, viscous friction must be evaluated at high sliding speeds that are equivalent to those at the HDI. However, sliding speeds are typically less than 1 mm/s in conventional measuring methods including surface force apparatus [1]- [3] and the fiber wobbling method (FWM) [4]- [6]. Pin-on-disk type friction measurements can reach faster sliding speeds of over 1 mm/s [7], [8], but it is usually difficult to determine the shearing gap, which is the most important design parameter of the HDI.…”

Section: Introductionmentioning

confidence: 99%

“…The FWM is a highly sensitive shear force measuring method developed in our previous study that uses a spherical-ended optical fiber as the shearing probe and enables us to measure dynamic viscoelastic properties of nanometer-thick lubricant films under shearing motion [4], [9]. The shearing speeds in the previous study were less than 1 mm/s.…”

Section: Introductionmentioning

confidence: 99%

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High-Speed Friction Measurements for a Molecularly Thin Lubricant Film Using a Fiber Wobbling Method

et al. 2012

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Flying height between magnetic heads and magnetic disks must be minimized to realize high-recording-density hard disk drives. To lubricate the head-disk interface, the magnetic disks are coated with a molecularly thin lubricant film. Optimal design of the lubricant film is essential to ensure durability and reliability of hard disk drives. The mechanical properties of such a thin film are quite different from those in the bulk state. In our previous study, we developed highly sensitive shear force measuring method, which we called the fiber wobbling method (FWM), and revealed that the viscosity decreases with increasing sliding speed, known as shear thinning. However, the sliding speeds were much slower than those at the head disk interface. In this study, we utilized resonant oscillation of the probe and realized the high-speed friction measurements using FWM. Sliding speed achieved was 0.12 m/s, which is more than 100 times faster than that of conventional study. Our experimental results showed that the effect of shear thinning still remains at a sliding speed of 0.12 m/s and that the viscous friction forces are greatly decreased.Index Terms-Head disk interface, lubricant film, magnetic data storage, tribology.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High-Speed Friction Measurements for a Molecularly Thin Lubricant Film Using a Fiber Wobbling Method

et al. 2012

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“…The FWM measurements were applied to thin lubricant films coated on magnetic disks as in the actual HDI [26,28]. From the measured mechanical responses, we firstly discuss the deformation of the lubricant film caused by the approaching and separating probe tip, which imitates the touchdown and takeoff behavior in the HDI.…”

Section: Viscoelastic Measurement With the Thin-film Systemmentioning

confidence: 99%

“…For a quantitative comparison, the damping coefficient c f and elastic coefficient k f of the samples can be obtained as follows [28]: tip first touches the lubricant film surface in the approaching process. The takeoff gap h f was defined by the gap width for which the probe tip and lubricant film came apart in the separating process.…”

Section: Calculation Of the Viscoelasticitymentioning

confidence: 99%

Nanorheometry of Molecularly Thin Liquid Lubricant Films Coated on Magnetic Disks

Itoh

Hamamoto

Ishii

et al. 2012

Advances in Tribology

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Molecularly thin lubricant films are used for the lubrication of head disk interfaces in hard disk drives. The film thickness is reduced to 1-2 nm to minimize the magnetic spacing, and optimal, precise design is required to obtain sufficient lubrication. However, until now, there was no generally applicable method for investigating such thin films. Therefore, we developed a highly sensitive shear force measuring method and have applied it to the viscoelastic measurement of lubricant films coated on magnetic disk surfaces. In this paper, we review the method and summarize the useful findings we have demonstrated so far.

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Contributions of Mobile and Bonded Molecules to Dynamic Friction of Nanometer-Thick Perfluoropolyether Films Coated on Magnetic Disk Surfaces

et al. 2013

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Shear thinning behavior of monolayer liquid lubricant films measured by fiber wobbling method

Cited by 4 publications

References 9 publications

High-Speed Friction Measurements for a Molecularly Thin Lubricant Film Using a Fiber Wobbling Method

High-Speed Friction Measurements for a Molecularly Thin Lubricant Film Using a Fiber Wobbling Method

Nanorheometry of Molecularly Thin Liquid Lubricant Films Coated on Magnetic Disks

Contributions of Mobile and Bonded Molecules to Dynamic Friction of Nanometer-Thick Perfluoropolyether Films Coated on Magnetic Disk Surfaces

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