a, A plot of storage modulus (G′) as a function of time illustrates how the modulus of the body matrix recovers during three-phase thixotropy tests. After a probe phase, a shear stress of 100 Pa is applied for varying times during a deformation phase, resulting in temporary fluidization of the matrix material. During the recovery phase, the modulus increases over time. b, The ratio of the loss modulus to the storage modulus, G″/G′ = tan(δ), is plotted as a function time for each of the recovery phases measured in a. The onset of recovery of the yield stress of the body matrix material—and the onset of fumed silica filler percolation in a recovering matrix material—is assumed to be the moment G′ = G″ or tan(δ) = 1 (horizontal dashed line). Therefore, the ‘recovery time’ of the body matrix material (indicated by the vertical dashed lines) is approximately the time at which tan(δ) = 1 after deformation. Because the momentary deformation incurred by nozzle translation through a discrete volume of matrix material during EMB3D printing happens within a time period shorter than 1 s and with a magnitude of less than 100 Pa, the thixotropic recovery time of the body matrix material is less than 200 s—the approximate time it takes the body matrix to recover after being sheared by a 100-Pa stress for 1 s.