Integrating multifunctionality such as adhesiveness, stretchability, and self-healing ability on a single hydrogel has been a challenge and is a highly desired development for various applications including electronic skin, wound dressings, and wearable devices. In this study, a novel hydrogel was synthesized by incorporating polydopamine-coated talc (PDA-talc) nanoflakes into a polyacrylamide (PAM) hydrogel inspired by the natural mussel adhesive mechanism. Dopamine molecules were intercalated into talc and oxidized, which enhanced the dispersion of talc and preserved catechol groups in the hydrogel. The resulting dopamine-talc-PAM (DTPAM) hydrogel showed a remarkable stretchability, with over 1000% extension and a recovery rate over 99%. It also displayed strong adhesiveness to various substrates, including human skin, and the adhesion strength surpassed that of commercial double-sided tape and glue sticks, even as the hydrogel dehydrated over time. Moreover, the DTPAM hydrogel could rapidly self-heal and regain its mechanical properties without needing any external stimuli. It showed excellent biocompatibility and improved cell affinity to human fibroblasts compared to the PAM hydrogel. When used as a strain sensor, the DTPAM hydrogel showed high sensitivity, with a gauge factor of 0.693 at 1000% strain, and was capable of monitoring various human motions such as the bending of a finger, knee, or elbow and taking a deep breath. Therefore, this hydrogel displays favorable attributes and is highly suitable for use in human-friendly biological devices.
Cardiovascular
diseases plague human health because of the lack
of transplantable small-diameter blood vessel (SDBV) grafts. Although
expanded polytetrafluoroethylene (ePTFE) has the potential to be used
as a biocompatible material for SDBV grafts, long-term patency is
still the biggest challenge. As discussed in this paper, by virtue
of a novel material formulation and a new and benign alcohol/water
lubricating agent, biofunctionalized ePTFE blood vessel grafts aimed
at providing long-term patency were fabricated. Compared to the most
prevalent modification of PTFE, namely surface treatment, this method
realized bulk treatment, which could guarantee homogeneous and long-lasting
performance throughout PTFE products. These blood vessel grafts included
embedded functional biomolecules, such as arginylglycylaspartic acid,
heparin, and selenocystamine, using water as a solvent in paste extrusion
and in the expansion of ePTFE. Fourier-transform infrared spectroscopy,
X-ray photoelectron spectroscopy, and scanning electron microscope
results confirmed the existence of these targeting biomolecules in
the as-fabricated ePTFE blood vessel grafts. Meanwhile, the greatly
improved biological functions of the grafts were demonstrated via live and dead assays, cell morphology, CD31 staining,
nitric oxide (NO) release, and anticoagulation tests. This novel and
benign material formulation and fabrication method provides an opportunity
to produce multibiofunctional ePTFE blood vessel grafts in a single
step, thus yielding a potent product with significant commercial and
clinical potential.
Oil spills in the
ocean greatly threaten local environments, marine
creatures, and coastal economies. An automatic water/oil separation
material system was proposed in this study, and a tubular geometry
was chosen to demonstrate the water/oil separation efficiency and
effectiveness. The water/oil separation tubes were made of expanded
polytetrafluoroethylene (ePTFE) and graphite composites. The permeation
pressures of water and oil through the tube walls were tuned by adjusting
the ePTFE microstructure, which, in turn, depended on the degree of
expansion and the graphite content. Fourier-transform infrared spectroscopy
was performed to confirm the compositions of the ePTFE/graphite composites,
and a scanning electron microscope was used to examine the microstructure
and morphology of the expanded PTFE/graphite composite tubes. When
a proper pressure was applied, which was higher than the oil’s
permeation pressure (3.0 kPa) but lower than the water’s permeation
pressure (57 kPa), the oil leaked out of the tube walls while the
water went through the ePTFE/graphite tubes. As such, the water/oil
mixture could be separated and collected in different containers or
an outer tube. Due to this automatic separation, the whole process
could be done continuously and conveniently, thus exhibiting great
potential in the practical applications of oil spill and water separation/remediation.
Polytetrafluoroethylene (PTFE) and expanded PTFE (ePTFE) are ideal for various applications. Because PTFE does not flow, even when heated above its melting point, PTFE components are fabricated using a process called paste extrusion. This process entails blending PTFE powder particles with a lubricant to form PTFE paste, which is subsequently preformed, extruded, expanded (in the case of ePTFE), and sintered. In this study, ethanol was proposed as an alternative green lubricant for PTFE processing. Not only is ethanol benign and biofriendly, it provides excellent wettability and processing benefits. Using ethanol as a lubricant, the shear viscosity of PTFE paste and its flow behavior during paste extrusion were investigated. Frequency sweeps using a parallel‐plate rheometer were performed on PTFE paste samples and various grits of sandpaper were used to reduce wall slip of PTFE paste. A viscosity model was generated and a multiphysics software was used to simulate PTFE paste extrusion. The simulated extrusion pressure was compared to experimental data of actual paste extrusion. Flow visualization experiments using colored PTFE layers were conducted to reveal the flow profile of the PTFE paste. The morphology of the expanded ePTFE tubes was examined using scanning electron microscopy and the effect of expansion ratio on ePTFE morphology was quantified.
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