More Like this

1. Systematic measurements of interleaflet friction in supported bilayers

   https://doi.org/10.1016/j.bpj.2022.06.023  

   Anthony, Autumn A.; Sahin, Osman; Yapici, Murat Kaya; Rogers, Daniel; Honerkamp-Smith, Aurelia R. (August 2022, Biophysical Journal)
2. Friction-induced instability and vibration in a precision motion stage with a friction isolator

   https://doi.org/10.1177/1077546321999510  

   Wang, Jiamin; Dong, Xin; Barry, Oumar R; Okwudire, Chinedum (March 2021, Journal of Vibration and Control)

   null (Ed.)

   Motion stages are widely used for precision positioning in manufacturing and metrology applications. However, they suffer from nonlinear premotion (i.e. “static”) friction, which adversely affects their speed and motion precision. In this article, a friction isolator is used as a simple and robust solution to mitigate the undesirable effects of premotion friction in precision motion stages. For the first time, a theoretical study is carried out to understand the dynamic phenomena associated with using a friction isolator on a motion stage. Theoretical analysis and numerical simulation are conducted to examine the dynamical effects of friction isolator on a proportional–integral–derivative-controlled motion stage under LuGre friction dynamics. The influence of friction isolator on the response and stability of the system is examined through theoretical and numerical analyses. Parametric analysis is also carried out to study the effects of friction isolator and friction parameters on the eigenvalue and stability characteristics. The numerical results validate the theoretical findings and demonstrate several other interesting nonlinear phenomena associated with the introduction of friction isolator. This motivates deeper nonlinear dynamical analyses of friction isolator for precision motion control. 

   more » « less
3. Creasing in microscale, soft static friction

   https://doi.org/10.1038/s41467-023-38091-7  

   Glover, Justin D.; Yang, Xingwei; Long, Rong; Pham, Jonathan T. (April 2023, Nature Communications)

   Abstract Utilizing colloidal probe, lateral force microscopy and simultaneous confocal microscopy, combined with finite element analysis, we investigate how a microparticle starts moving laterally on a soft, adhesive surface. We find that the surface can form a self-contacting crease at the leading front, which results from a buildup of compressive stress. Experimentally, creases are observed on substrates that exhibit either high or low adhesion when measured in the normal direction, motivating the use of simulations to consider the role of adhesion energy and interfacial strength. Our simulations illustrate that the interfacial strength plays a dominating role in the nucleation of a crease. After the crease forms, it progresses through the contact zone in a Schallamach wave-like fashion. Interestingly, our results suggest that this Schallamach wave-like motion is facilitated by free slip at the adhesive, self-contacting interface within the crease. 

   more » « less
4. Eccentricity evolution in gaseous dynamical friction

   https://doi.org/10.1093/mnras/stac1294  

   Szölgyén, Ákos; MacLeod, Morgan; Loeb, Abraham (May 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We analyse how drag forces modify the orbits of objects moving through extended gaseous distributions. We consider how hydrodynamic (surface area) drag forces and dynamical friction (gravitational) drag forces drive the evolution of orbital eccentricity. While hydrodynamic drag forces cause eccentric orbits to become more circular, dynamical friction drag can cause orbits to become more eccentric. We develop a semi-analytic model that accurately predicts these changes by comparing the total work and torque applied to the orbit at periapse and apoapse. We use a toy model of a radial power-law density profile, ρ ∝ r−γ, to determine that there is a critical γ = 3 power index, which separates the eccentricity evolution in dynamical friction: orbits become more eccentric for γ < 3 and circularize for γ > 3. We apply these findings to the infall of a Jupiter-like planet into the envelope of its host star. The hydrostatic envelopes of stars are defined by steep density gradients near the limb and shallower gradients in the interior. Under the influence of gaseous dynamical friction, an infalling object’s orbit will first decrease in eccentricity and then increase. The critical separation that delineates these regimes is predicted by the local density slope and is linearly dependent on polytropic index. More broadly, our findings indicate that binary systems may routinely emerge from common envelope phases with non-zero eccentricities that were excited by the dynamical friction forces that drove their orbital tightening. 

   more » « less
5. Thermobaric Activation of Fault Friction

   https://doi.org/10.1029/2024GL112959  

   Barbot, S.; Guvercin, S_E; Zhang, L.; Zhang, H.; Yang, Z. (March 2025, Geophysical Research Letters)

   Abstract The constitutive behavior of faults intervenes in virtually every aspect of the seismic phenomenon but is poorly understood, particularly regarding how effective normal stress affects the boundaries of the seismogenic zone. Here, we explore the mechanical properties of Pelona schist, Westerly granite, phyllosilicate‐rich gouge, gabbro, hornblende, lawsonite blueschist, montmorillonite, and smectite in hydrothermal conditions at various confining pressures and explain the laboratory observations with a physical model of fault friction. The thermobaric activation of healing and deformation mechanisms explains the boundaries of unstable slip as a function of slip‐rate, temperature, and effective normal stress for a given lithology. The constitutive law affords extrapolation of laboratory data in the conditions relevant to seismic cycles throughout the crust, explaining the focus of large earthquakes in collision, subduction, and continental and oceanic transform settings. 

   more » « less