TY - GEN
T1 - Role of occlusion in non-coulombic slip of the finger pad
AU - Dzidek, Brygida Maria
AU - Adams, Michael
AU - Zhang, Zhibing
AU - Johnson, Simon
AU - Bochereau, Séréna
AU - Hayward, Vincent
PY - 2014
Y1 - 2014
N2 - Understanding how fingers slip on surfaces is essential for elucidating the mechanisms of haptic perception. This paper describes an investigation of the relationship between occlusion and the non-Coulombic slip of the finger pad, which results in the frictional force being a power law function of the normal load, with an index n; Coulombic slip corresponds to n = 1. For smooth impermeable surfaces, occlusion of moisture excreted by the sweat glands may cause up to an order of magnitude increase in the coefficient of friction with a characteristic time of ~ 20 s. This arises because the moisture plasticises the asperities on the finger print ridges resulting in an increase in their compliance and hence an increase in the contact area. Under such steady state sliding conditions a finger pad behaves like a Hertzian contact decorated with the valleys between the finger print ridges, which only act to reduce the true but not the nominal contact area. In the limit, at long occlusion times (~ 50 s), it can be shown that the power law index tends to a value in the range 2/3 ≤ n ≤ 1. In contrast, measurements against a rough surface demonstrate that the friction is not affected by occlusion and that a finger pad exhibits Coulombic slip.
AB - Understanding how fingers slip on surfaces is essential for elucidating the mechanisms of haptic perception. This paper describes an investigation of the relationship between occlusion and the non-Coulombic slip of the finger pad, which results in the frictional force being a power law function of the normal load, with an index n; Coulombic slip corresponds to n = 1. For smooth impermeable surfaces, occlusion of moisture excreted by the sweat glands may cause up to an order of magnitude increase in the coefficient of friction with a characteristic time of ~ 20 s. This arises because the moisture plasticises the asperities on the finger print ridges resulting in an increase in their compliance and hence an increase in the contact area. Under such steady state sliding conditions a finger pad behaves like a Hertzian contact decorated with the valleys between the finger print ridges, which only act to reduce the true but not the nominal contact area. In the limit, at long occlusion times (~ 50 s), it can be shown that the power law index tends to a value in the range 2/3 ≤ n ≤ 1. In contrast, measurements against a rough surface demonstrate that the friction is not affected by occlusion and that a finger pad exhibits Coulombic slip.
KW - Coulombic slip
KW - Finger pad
KW - Friction
KW - Occlusion
KW - Skin hydration
UR - http://www.scopus.com/inward/record.url?scp=84910118817&partnerID=8YFLogxK
U2 - 10.1007/978-3-662-44193-0_15
DO - 10.1007/978-3-662-44193-0_15
M3 - Conference contribution
AN - SCOPUS:84910118817
SN - 9783662441923
VL - 8618
T3 - Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
SP - 109
EP - 116
BT - Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
PB - Springer
T2 - 9th International Conference on Haptics: Neuroscience, Devices, Modeling, and Applications, EuroHaptics 2014
Y2 - 24 June 2014 through 26 June 2014
ER -