A novel tribometer for the measurement of friction in MEMS

Ku, I.S.Y.; Reddyhoff, Tom; Choo, J. H.; Holmes, Andrew S.; Spikes, H. A.

doi:10.1016/j.triboint.2009.12.029

Cited by 18 publications

(10 citation statements)

References 8 publications

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“…The microtribometer used in this work to test high-sliding contacts under real MEMS conditions is similar to that described by Ku et al [10]. A schematic of the apparatus is shown in Fig.…”

Section: Test Rigmentioning

confidence: 99%

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Friction Modifier Behaviour in Lubricated MEMS Devices

Reddyhoff

Holmes

et al. 2010

Tribol Lett

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Low viscosity fluids could provide reliable lubrication for certain microelectromechanical system's (MEMS) applications where high-sliding speeds and/or high sliding distances occur. However, while the use of low viscosity fluids leads to reduced hydrodynamic friction, high boundary friction can be a significant issue at low entrainment speeds. This article describes a series of tests of low viscosity fluids, blended with a friction modifier additive so as to provide a combination of both low hydrodynamic and low boundary friction at MEMS scales. The low viscosity fluids tested were hexadecane, low viscosity silicone oil, toluene and water. With the exception of water, the addition of the organic friction modifier octadecylamine to all these lubricating fluids produced a significant reduction in boundary friction. For a MEMS contact lubricated with silicone oil for instance, boundary friction was reduced from 0.5 to close to 0.05. The presence of the amine dissolved in the toluene had the effect of reducing boundary friction from 0.75 to 0.55; this was further reduced to 0.25 after the specimens had been immersed in the toluene-additive blend for 48 h. A watersoluble additive, diethylamine, was added to de-ionized water, at 0.1% by weight concentration. Although an initial reduction in boundary friction was observed (0.45-0.25), under these conditions the rapid onset of severe wear negated these effects. It is suggested that corrosion of silicon by water, followed by abrasion, is the cause of this accelerated wear.

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“…The microtribometer used in this work to test high-sliding contacts under real MEMS conditions is similar to that described by Ku et al [10]. A schematic of the apparatus is shown in Fig.…”

Section: Test Rigmentioning

confidence: 99%

“…Recently the authors have shown, using a custom-built tribometer [10], that acceptably low friction can be achieved in MEMS sliding contacts lubricated by liquids provided the lubricants are of sufficiently low viscosity. It has also been demonstrated that drag forces can be very low for sliding contacts submerged in low viscosity liquids.…”

Section: Introductionmentioning

confidence: 99%

Friction Modifier Behaviour in Lubricated MEMS Devices

Reddyhoff

Holmes

et al. 2010

Tribol Lett

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“…The experimental work was carried out with a micro-tribometer developed by Ku et al [27]. The set up comprises two 2 mm diameter silicon specimens, one stationary, with a surface pattern similar to that of a step bearing (see figure 1), whilst the other is a polished rotating surface (with an Ra roughness of 0.65 -0.75 nm).…”

Section: Experimental Approachmentioning

confidence: 99%

“…The oscillatory solvation is rarely noted at the micro-scale, especially at slow sliding speeds. Therefore, based on the modified Eyring thermal activation approach, the current study attempts to investigate the solvation phenomenon under slow sliding speeds using a micro-tribometer developed by Ku et al [27].…”

Section: Introductionmentioning

confidence: 99%

Frictional characteristics of molecular length ultra-thin boundary adsorbed films

Chong

Reddyhoff

et al. 2015

Meccanica

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The paper presents measurements of friction of any ultra-thin film entrained into the contact of a pair of very smooth specimen subjected to entrainment in a converging micro-wedge of a special-purpose micro-tribometer. An ultra-thin film is expected to form at the boundary solids through adsorption of boundary active molecules. Fluids with linear and branched molecules are used in the investigation. It is found that the frictional characteristics of these films can be adequately described through use of Eyring thermal activation energy and a potential energy barrier to sustain conjunctional sliding motion. The combined experimental measurement and the simple activation energy approach shows that the thin molecular adsorbed films act like hydroLangmuir-Blodgett layers, the formation and frictional characteristics of which are affected by the competing mechanisms of adsorption, forced molecular re-ordering and discrete-fashion drainage through the contact by the solvation effect. This process is a complex function of the contact sliding velocity as well as a defined Eyring activation density (packing density of the molecules within the conjunction). It is shown that the contribution of solvation to friction is in the form of energy expended to eject layers of lubricant out of the contact, which unlike the case of micro-scale hydrodynamic films, is not a function of the sliding velocity.

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“…MEMS friction and wear have been emphasized because surface forces outweigh the effects of inertia due to the large ratio of surface area to volume. Ku and Guo [ 18 , 19 ] developed a tribometer to measure friction in high sliding MEMS devices lubricated with liquids. Surface-micromachined nanotractor devices were also used to investigate the tribological behavior of linear sliding MEMS devices [ 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

Measuring Micro-Friction Torque in MEMS Gas Bearings

Fang

Liu

2016

Sensors

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An in situ measurement of micro-friction torque in MEMS gas bearings, which has been a challenging research topic for years, is realized by a system designed in this paper. In the system, a high accuracy micro-force sensor and an electronically-driven table are designed, fabricated and utilized. With appropriate installation of the sensor and bearings on the table, the engine rotor can be driven to rotate with the sensor using a silicon lever beam. One end of the beam is fixed to the shaft of the gas bearing, while the other end is free and in contact with the sensor probe tip. When the sensor begins to rotate with the table, the beam is pushed by the sensor probe to rotate in the same direction. For the beam, the friction torque from the gas bearing is balanced by the torque induced by pushing force from the sensor probe. Thus, the friction torque can be calculated as a product of the pushing force measured by the sensor and the lever arm, which is defined as the distance from the sensor probe tip to the centerline of the bearing. Experimental results demonstrate the feasibility of this system, with a sensitivity of 1.285 mV/μN·m in a range of 0 to 11.76 μN·m when the lever arm is 20 mm long. The measuring range can be modified by varying the length of the lever arm. Thus, this system has wide potential applications in measuring the micro-friction torque of gas bearings in rotating MEMS machines.

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A novel tribometer for the measurement of friction in MEMS

Cited by 18 publications

References 8 publications

Friction Modifier Behaviour in Lubricated MEMS Devices

Friction Modifier Behaviour in Lubricated MEMS Devices

Frictional characteristics of molecular length ultra-thin boundary adsorbed films

Measuring Micro-Friction Torque in MEMS Gas Bearings

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