No abstract

Hydrogels that are capable of wet adhesion and self-healing can enable major advances in a variety of biomedical applications such as tissue regeneration, wound dressings, wearable/implantable devices, and drug delivery. We hereby developed an innovative but simple strategy to achieve adhesive, self-healing, and highly stretchable double-network hydrogels, which were composed of a primary covalent polyethylene glycol diacrylate (PEGDA) network in combination with a noncovalent network of highly diffusive, giant PEG chains. The adhesion to substrates including tissue matrices was instant and repeatable due to the diffusive PEG chains that can spontaneously penetrate and entangle with the substrate network. Combining the intrinsic biocompatibility of PEG and rational design for tuning the hydrogel network properties, we exemplarily demonstrated that this hydrogel can be used as a three-dimensional matrix for cell culture or as a tissue adhesive for wound healing. The in vivo study showed that the hydrogel is capable of effectively triggering skin wound healing with a significantly lower immune response in comparison to commercial tissue adhesives currently used in clinics. Therefore, our study provides new and critical insights into the design strategy to achieve adhesion and rehealability by taking advantages of the entanglement effect from double-network hydrogels and opens up a new avenue for the application of entanglement-driven hydrogels in regenerative medicine.

No abstract

A lab-scale two-stage reactor has been constructed for studying the release and destruction of tars in the twostage gasifier. First, the pyrolysis characteristics of three fuel samples are investigated only using the single stage reactor. The results show that the maximum value of tar yield is: rice straw 25%, corn straw 22%, and fir sawdust 31% of the initial fuel. Then, the experimental program is extended to investigate the effect of operating conditions in the second stage of the reactor on tar removal. The effects of temperature, residence time, char particle size, char type, fuel type, and diluted air feeding to throat on tar emission has been studied. The results show that the tar decreased with increasing temperature and residence time and with decreasing char particle size. The char type has little effect on tar reduction. Tar emission with limited diluted air feeding is obviously less than that with empty second stage due to the more reactive radicals produced in oxidative conditions. The straw tars appear to have a different suite of compounds than the other two samples of derived material and presumably have different cracking pathways. The tars collected from first stage and second stage have been characterized by gas chromatography/mass spectrometry (GC/MS) and gel permeation chromatography (GPC). The results indicate that tar after pyrolysis contains a large amount of oxygenated constituents. With the increasing of reaction severity (from the empty heated second stage to heated second stage with char bed), the tar compounds reacted further (polymerized) to form larger molecular mass material. It is clear that the material characterized by GC/MS represents a very small part of the total tar. The results have shown that the tar emission from two-stage gasifier can reduce to low levels using optimized operating conditions, but complete tar removal is difficult to realize due to manipulation of operating parameters and fuel type.