Electrostatically Tunable Adhesion in a High Speed Sliding Interface

Abstract

Contact hysteresis between sliding interfaces is a widely observed phenomenon from macro-to nano-scale sliding interfaces. Most of such studies are done using an atomic force microscope (AFM) where the sliding speed is a few µm/s. Here, we present a unique study on stiction between the head-disk interface of commercially available hard disk drives, wherein vertical clearance between the head and the disk is of the same order as in various AFM based fundamental studies, but with a sliding speed that is nearly six orders of magnitude higher. We demonstrate that although the electrostatic force (DC or AC voltage) is an attractive force, the AC voltage induced out-of-plane oscillation of the head with respect to disk is able to suppress completely the contact hysteresis.The ability to reduce stiction in sliding surfaces is extremely important for a variety of applications ranging from very-high-density data storage (> 1 Tb/inch 2 ) [1-3] to nanoscale manufacturing in micro or nano mechanical systems (M/NEMS) [4][5][6]. Our research focuses on data storage in hard disk drives, in which the recording heads fly at sub-nanometer spacing from the disk and move at relative sliding speeds of 5-40 m/s. Maintaining good tribological properties such as low wear and stiction of such a high speed sliding interface at low clearance is critical for the long term reliability of hard disk drives [7]. Any contact between the head and the disk leads to friction and wear of the head overcoat layer, adversely impacting the disk drive performance [8][9][10][11].A unique way of reducing the friction during contact is through externally imposed oscillations of small amplitude and energy. Previous experimental and theoretical work to reduce the friction at a sliding interface explored the use of external excitation with either surface acoustic waves or electrostatic forces to modulate the out-of-plane or in-plane motion [12][13][14][15]. The out-of-plane vibrations reduce the friction by momentarily separating the interfering surfaces such that the friction is zero during this time. Consequently, the time averaged friction is reduced below the value that occurs in the absence of oscillation. In this letter, we describe an experimental study of contact events at the head-disk interface, focusing on hysteresis in contact cycle. We show that although the electrostatic force (DC or AC voltage) at the interface is an attractive force, the AC voltage induced oscillation can significantly reduce the contact hysteresis. We provide a fully quantitative analysis of the hysteresis in such a high sliding speed system which shows that the AC voltage induced oscillation has a dominant influence on suppressing the contact hysteresis.

Controlling Friction With External Electric or Magnetic Fields: 25 Examples

“…Example 12: Electrostatically Tunable Adhesion Via Oscillation Induced Reductions in Contact Hysteresis at a Head-Disk Interface (Rajauria et al, 2018) Rajauria et al have recently studied the impact of vibrations induced by an external field on a high speed sliding interface, namely a recording head-disk contact moving in close proximitry at high speeds on the order of 5-40 m/s. Contact hysteresis between sliding interfaces is a common phenomenon that has a major impact on the tribological performance of a head-disk system.…”

“…The goal is not to present a comprehensive list of all publications in this rapidly growing area, but rather to demonstrate the variety and versatility of approaches reported on in the literature. Examples are divided into 4 sections: (I) Field induced changes to bulk lubricants (Boulware et al, 2010a,b;Démery and Dean, 2010;De Vicente et al, 2011;Tusch et al, 2014;Ashtiani et al, 2015;Kabeel et al, 2015;Rodriguez-López et al, 2015;Vlachová et al, 2015;Zhao et al, 2017;Pardue et al, 2018; Acharya et al, 2019) (II) Field induced changes to solid contacts (Gabureac et al, 2004;Highland and Krim, 2006;Park et al, 2006Park et al, , 2007Socoliuc et al, 2006;Qi et al, 2008;Pierno et al, 2010;Kisiel et al, 2011;Krim et al, 2011;Altfeder and Krim, 2012;Benassi et al, 2014;Mao et al, 2017;Popov et al, 2017;Benad et al, 2018;Popov and Li, 2018;Rajauria et al, 2018;Wolloch et al, 2018); (III) Field induced changes to surface boundary layers (Zhu et al, 1994;Coffey and Krim, 2005;Ismail et al, 2009;Drummond, 2012;Wolter et al, 2012;Wei et al, 2013;de Wijn et al, 2014de Wijn et al, , 2016Kreer, 2016;Zeng et al, 2017;…”

QCM Study of Tribotronic Control in Ionic Liquids and Nanoparticle Suspensions

“…A multitude of ionic liquid pair combinations are moreover possible, and new combinations are readily manufactured for specific applications if their properties could be predicted in advance [10]. Methods such as electrochemical surface force apparatus (EC-SFA) [24], atomic force microscopy (AFM) [25][26][27], head-disk contacts [28], and other traditional macroscale tribometers have successfully demonstrated tribotronic control of ionic liquids in both pure forms and as additives to base fluids [15,29]. Progress in the field would be accelerated by studies that expand the materials combinations available and probe the details of the friction at the solid-liquid interface.…”

Precise nanoscale temperature mapping in operational microelectronic devices by use of a phase change material

“…The head of the hard disk drive provides a unique platform for such studies as it has several embedded heat sources, which differ in heated area by three orders of magnitude [33,34]. At the microscale, it has a micro-heater, which is used to adjust the clearance between the head and the rotating disk [35]. The micro-heater is embedded a few micrometers from the surface, and it produces a microscale temperature contour.…”