Table 1.

Biomechanical properties and characteristic layers thicknesses of the zona pellucida isolated from mature and fertilized oocytes. Poisson ratio is set equal to 0.5 to simulate material incompressibility. Values listed in the table were obtained by taking the F–δ curves averaged over AFM measurements carried out on each sample as the target. The standard deviation of material parameters determined from the different optimization runs carried out for each sample and each constitutive model is much smaller than the statistical dispersion of AFM experimental data.

	d1 (nm)	elastic parameters (kPa)	Young's modulus E (kPa)	d2 (nm)	elastic parameters (kPa)	Young's modulus E (kPa)	r2
mature ZP
neo-Hookean	from 0 to 100	C10 : 2.42 → 2.49	14.52 → 14.94	from 100 to 199	C10 : 2.49 → 3.91	14.94 → 23.46	0.921
Mooney–Rivlin		C10 : 2.03 → 2.08	12.97 → 13.28		C10 : 2.08 → 3.29	13.28 → 21.01	0.927
		C01 : 0.131 → 0.134			C01 : 0.134 → 0.211
Arruda–Boyce		μ :2.43 → 2.49	7.29 → 7.47		μ :2.49 → 3.91	7.47 → 11.73	0.970
		λL = 1.61			λL = 1.61
fertilized ZP: outer layer
neo-Hookean	from 0 to 96	C10 : 2.34 → 23.23	14.04 → 139.38	from 96 to 198	C10 : 23.23 → 54.84	139.38 → 329.04	0.922
Mooney–Rivlin		C10 : 2.34 → 23.23	14.19 → 140.88		C10 : 23.23 → 54.73	140.88 → 331.85	0.927
		C01 : 0.025 → 0.25			C01 : 0.25 → 0.579
Arruda–Boyce		μ :2.42 → 24.2	7.26 → 72.6		μ :24.2 → 56.6	72.6 → 169.8	0.997
		λL = 1.61			λL = 1.61
fertilized ZP: inner layer
Arruda–Boyce	from 0 to 97	μ : 2.41 → 38	7.23 → 114	from 97 to 198	μ : 38 → 200	114 → 600	0.993
		λL = 1.56			λL = 1.56