symbol	description	units
ag	equivalent contact radius of the finger pad	m
ar	semi-contact width of fingerprint ridge	m
k	power-law load coefficient for contact area	m2 N−m
kf	load-dependent coefficient of friction	m2 N−n
kg	power-law load coefficient for finger pad gross contact area	m2 N−mg
	load coefficient for finger pad gross contact area	m2 N−2/3
kr	power-law load coefficient for fingerprint ridge contact area
	load coefficient for fingerprint ridge contact area	m2 N−5/6
	semi-axis to palmar face of finger pad ellipsoid	m
	semi-axis to distal face of finger pad ellipsoid	m
	semi-axis to ulnar/radial faces of finger pad ellipsoid	m
m	power-law load index for contact area
mg	power-law load index for finger pad gross contact area
mr	power-law load index for fingerprint ridge contact area
n	power-law load index for frictional force
p	mean contact pressure = W/A	Pa
pg(r)	finger pad pressure radial distribution	Pa
q	number of fingerprint ridges in an annulus of width δr
r	radial coordinate from contact centre	m
s	fingerprint ridge spacing factor
u	palmar axis angular coordinate of point on finger pad ellipsoid	rad
v	radial axis angular coordinate of point on finger pad ellipsoid	rad
w	fingerprint ridge load per unit length	Nm−1
x	palmar coordinate of point on finger pad ellipsoid	m
y	distal coordinate of point on finger pad ellipsoid	m
z	ulnar/radial coordinate of point on finger pad ellipsoid	m
A	contact area	m2
Ag	finger pad gross contact area	m2
Ar	fingerprint ridge contact area	m2
	contact area of a fingerprint ridge at radius r in region δθ	m2
C	constraint coefficient for secant modulus
Eg	secant modulus of the finger pad	Pa
	reduced secant modulus of the finger pad	Pa
E0 g	Young's modulus of the finger pad	Pa
	reduced Young's modulus of the finger pad	Pa
Er	elastic modulus of the fingerprint ridge	Pa
	reduced elastic modulus of the fingerprint ridge	Pa
F	friction force	N
H0 g	mean curvature of the finger pad ellipsoid	m−1
Rg	effective radius of the finger pad	m
R0 g	mean radius of curvature of the finger pad ellipsoid	m
Rr	radius of cylindrically capped fingerprint ridge	m
W	normal force	N
α	pressure coefficient of interfacial shear strength
β	load coefficient for secant modulus	N−1
ɛ	compressive Hertzian strain
η	strain index for secant modulus
θ	angular coordinate about contact centre	rad
μ	coefficient of friction = F/W
νg	Poisson's ratio of the finger pad
νr	Poisson's ratio of the fingerprint ridge
ξ	compressive displacement	m
τ	interfacial shear strength	Pa
τ0	intrinsic interfacial shear strength (at p = 0)	Pa