TY - JOUR
T1 - Stick-Slip Friction Reveals Hydrogel Lubrication Mechanisms
AU - Shoaib, Tooba
AU - Heintz, Joerg
AU - Lopez-Berganza, Josue A.
AU - Muro-Barrios, Raymundo
AU - Egner, Simon A.
AU - Espinosa-Marzal, Rosa M.
N1 - Support to T.S. by the Fulbright Program, U.S. Department of State is acknowledged. We also thank financial support by the National Science Foundation under Grant No. CMMI-1435920. We would like to acknowledge Mr. Andreas Hofheinz for his contribution in the analysis of the multimodal distributions of force drops during slip, and thank Prof. Helen Nguyen for providing access to DLS. We also acknowledge the facilities provided by Materials Research Laboratory (MRL) at UIUC.
PY - 2018/1/23
Y1 - 2018/1/23
N2 - The lubrication behavior of the hydrated biopolymers that constitute tissues in organisms differs from that outlined by the classical Stribeck curve, and studying hydrogel lubrication is a key pathway to understand the complexity of biolubrication. Here, we have investigated the frictional characteristics of polyacrylamide (PAAm) hydrogels with various acrylamide concentrations, exhibiting Young's moduli (E) that range from 1 to 40 kPa, as a function of applied normal load and sliding velocities by colloid probe lateral force microscopy. The speed-dependence of the friction force shows an initial decrease in friction with increasing velocity, while, above a transition velocity V∗, friction increases with speed. This study reveals two different boundary lubrication mechanisms characterized by distinct scaling laws. An unprecedented and comprehensive study of the lateral force loops reveals intermittent friction or stick-slip above and below V∗, with characteristics that depend on the hydrogel network, applied load, and sliding velocity. Our work thus provides insight into the closely tied parameters governing hydrogel lubrication mechanisms, and stick-slip friction.
AB - The lubrication behavior of the hydrated biopolymers that constitute tissues in organisms differs from that outlined by the classical Stribeck curve, and studying hydrogel lubrication is a key pathway to understand the complexity of biolubrication. Here, we have investigated the frictional characteristics of polyacrylamide (PAAm) hydrogels with various acrylamide concentrations, exhibiting Young's moduli (E) that range from 1 to 40 kPa, as a function of applied normal load and sliding velocities by colloid probe lateral force microscopy. The speed-dependence of the friction force shows an initial decrease in friction with increasing velocity, while, above a transition velocity V∗, friction increases with speed. This study reveals two different boundary lubrication mechanisms characterized by distinct scaling laws. An unprecedented and comprehensive study of the lateral force loops reveals intermittent friction or stick-slip above and below V∗, with characteristics that depend on the hydrogel network, applied load, and sliding velocity. Our work thus provides insight into the closely tied parameters governing hydrogel lubrication mechanisms, and stick-slip friction.
UR - https://www.scopus.com/pages/publications/85041031631
UR - https://www.scopus.com/pages/publications/85041031631#tab=citedBy
U2 - 10.1021/acs.langmuir.7b02834
DO - 10.1021/acs.langmuir.7b02834
M3 - Article
C2 - 28961012
AN - SCOPUS:85041031631
SN - 0743-7463
VL - 34
SP - 756
EP - 765
JO - Langmuir
JF - Langmuir
IS - 3
ER -