Stiffness control in dual color tomographic volumetric 3D printing.

Tomographic volumetric printing (TVP) physically reverses tomography to offer fast and auxiliary-free 3D printing. Here we show that wavelength-sensitive photoresins can be cured using visible ([Formula: see text] nm) and UV ([Formula: see text] nm) sources simultaneously in a TVP setup to generate internal mechanical property gradients with high precision. We develop solutions of mixed acrylate and epoxy monomers and utilize the orthogonal chemistry between free radical and cationic polymerization to realize fully 3D stiffness control. The radial resolution of stiffness control is 300 µm or better and an average modulus gradient of 5 MPa/µm is achieved. We further show that the reactive transport of radical inhibitors defines a workpiece's shape and limits the achievable stiffness contrast to a range from 127 MPa to 201 MPa according to standard tensile tests after post-processing. Our result presents a strategy for controlling the stiffness of material spatially in light-based volumetric additive manufacturing.

Trefoil factor peptide 3 is positively correlated with the viscoelastic properties of the cervical mucus plug.

INTRODUCTION: The viscoelastic properties of the cervical mucus plug are considered essential for the occlusion of the cervical canal and thereby for protection against ascending infections during pregnancy. Factors controlling this property are virtually unknown. This study explores a possible role of trefoil factor peptides 1, 2 and 3 (TFF1-3); peptides believed to influence mucus viscosity. MATERIAL AND METHODS: The study is based on spontaneously shed cervical mucus plugs from 14 women in active labor. The viscoelastic properties; the elastic modulus (G') and the viscous modulus (G") were determined by an oscillatory rheometer. The concentrations of TFF1-3 were measured by an in-house enzyme-linked immunosorbent assay. Associations were analyzed by random-effects generalized least-squares regression analyses. RESULTS: Median (range) concentrations of TFF1, TFF2 and TFF3 were 3.1 (1.2-8.6), 1.1 (<0.006-3.7) and 1000 (170-5300) nmol/g cervical mucus plug, respectively. The TFF3 concentration was associated with G' (regression coefficient 11.7 Pa/Log nm; 95% CI 3.0-20.4, p = 0.009) and G" (regression coefficient 3.2 Pa/Log nm; 95% CI 1.5-5.0, p < 0.001). CONCLUSION: We suggest that TFF3 plays a role in the viscoelastic properties of the cervical mucus plug.

The viscoelastic properties of the cervical mucus plug.

OBJECTIVE: To characterize the viscoelastic properties of cervical mucus plugs(CMPs) shed during labor at term. DESIGN: Experimental research. SETTING: Department of Obstetrics and Gynecology, Aarhus University Hospital, Denmark. POPULATION/SAMPLE: Spontaneously shed CMPs from 18 healthy women in active labor. METHODS: Viscoelastic properties of CMPs were investigated with a dynamic oscillatory rheometer using frequency and stress sweep experiments within the linear viscoelastic region. MAIN OUTCOME MEASURES: The rheological variables obtained were as follows: elastic modulus (G'), viscous modulus (G″) and tan delta (G″/G'). Random-effects regression was used for statistical analysis. RESULTS: All CMPs showed solid-like viscoelastic behavior.This was substantiated by the elastic modulus which was three to four times greater than the viscous modulus and by tan delta, which was <1 at all frequencies.Mean tan delta at 0.01 Hz was 0.38 (95% CI 0.34-0.43) and 0.27(95% CI 0.23-0.32) at 1 Hz. The elastic modulus could be described by the relation G'(ω) = K(ω)(A) [mean R2 0.95 (95% CI 0.93-0.98)]. Despite relatively large variation in the rheological properties within CMPs, rheological variables obtained from frequency sweeps differed significantly among CMPs (p < 0.05). CONCLUSION: The CMPs are solid-like viscoelastic structures. These rheological characteristics are probably essential for the CMP's ability to form and sustain a plug in the cervical canal during pregnancy, thereby reducing the risk of ascending infections. The technique described here might be used for evaluation of an association between CMP viscoelasticity and preterm delivery.