A new nonlinear compliant mechanism for harvesting energy from ocean waves

Traditonal linear oscillators, such as cantilevers or pendulums, are only sensitive to specific resonant frequencies. They have then very narrow frequency bandwidths when harvesting energy from ocean waves. In order to enhance the dynamic performance of the wave energy converters (WECs), used to expand the autonomy of Lagrangian Drifters, a statically balanced compliant mechanism (SBCM) is investingated. It is based on finite element analysis (FEA) simulaitons. The design of the SBCM is introduced and its static force-displacement curve is obtained in FEA. The dynamic response of the SBCM to harmonic base excitiaons at low frequencies and low accelerations is investigated based on time-domian FEA simulations. The close agreement between simulations, numerial and analytical results verifies that the SBCM is sensitive to ultra-low frequencies with weak accelerations in a wide frequency range. The applicability of the SBCM in WECs is demonstrated by adding PVDF films in the FEA model. In the time-domian simulation, the SBCM-based WEC is excited by the drifter motion pattern obtained from Orcaflex and corresponding to two typical ocean waves (i.e. synthesized Airy and Jonswap models). Relative displacement between the base and mass and the electric outputs are obtained. According to this work, the SBCM provides a structural solution for WECs with enhanced energy harvesting performance.Postprint (published version

Ultra-low and wide bandwidth vibrational energy harvesting using a statically balanced compliant mechanism

The development of Internet of Things (IoT) in recent times has met with the challenges of powering numerous sensors in a wireless sensor network with traditional batteries, owing to their limited lifetime, environmental pollution, high maintenance cost, etc. Vibrational energy harvesting is an ideal and green powering solution due to the ubiquitous environmental vibrations and their sufficient power density (~0.3 μW/mm3). A systematic review on state-of-the-art structural methodologies of vibrational energy harvesters from the aspect of compliant mechanisms (CMs) is first carried out, focusing on the energy conversion mechanism by piezoelectric effect in particular. The frequency gap between the majority of energy harvesting devices (with narrow bandwidth in the high frequency range) and the accessible vibrational sources (at 1-10 Hz levels) is observed and is still to be filled. In this thesis, a structural solution of vibrational energy harvesters using a statically balanced compliant mechanism (SBCM) is proposed, theoretically characterised, and experimentally demonstrated to address this need. This SBCM is designed based on the concept of stiffness compensation between a linear positive-stiffness component (two double parallelograms in parallel) and a nonlinear negative-stiffness component (two sets of post-buckled fixed-guided compliant beams in parallel). A design guideline of the SBCM starting from using a rapid-design stiffness compensation equation is provided for a reasonable approximation of results. The whole-range nonlinear force-displacement relationship of the SBCM is obtained through nonlinear finite element analysis (FEA) simulations and a 5th order polynomial fit is chosen taking only odd terms into account. Subsequently, a dynamic analytical model of the displacement response of the SBCM to harmonic base excitations has been derived based on the averaging method. The accuracy of this analytical model is confirmed by numerical analysis and FEA simulations. Next, an SBCM prototype was fabricated and its applicability to piezoelectric vibrational energy harvesters (PVEHs) was demonstrated by integrating piezoelectric transducers, made of PVDF films, with compliant beams of the SBCM to generate electric outputs in response to bending of the beams. Static balancing was successfully tuned in the static experiments. Displacement responses and electric outputs were obtained from the preliminary SBCM-based PVEH in the ultra-low and wide frequency range with weak accelerations in the dynamic experiments. Two application cases of the SBCM in macro and micro scales in vibrational energy harvesting were investigated using FEA simulations. The integration of the SBCM into an oceanic drifter for harvesting vibrational energy from ocean waves was first explored. The SBCM is then miniaturized in the MEMS scale and its dynamic displacement under harmonic base excitation was then demonstrated. In conclusion, a novel SBCM structure is designed based on the stiffness compensation principle. It is verified analytically, numerically and experimentally that this SBCM structure responds to regular and irregular vibrations over ultra-low wide bandwidth frequencies (theoretically starting above 0 Hz) and low accelerations regardless of the dimensions and scales. It provides an effective structural solution to the ultra-low wide bandwidth vibrational energy harvesters. Future work of this research includes optimization of the SBCM structure and electric circuits, application of the SBCM-based PVEHs in real vibrational conditions, miniaturization of the SBCM in the MEMS scale, and integration of the SBCM with other nonlinear oscillators

Salvianolic-Acid-B-Loaded HA Self-Healing Hydrogel Promotes Diabetic Wound Healing through Promotion of Anti-Inflammation and Angiogenesis

Inflammatory dysfunction and angiogenesis inhibition are two main factors leading to the delayed healing of diabetic wounds. Hydrogels with anti-inflammatory and angiogenesis-promoting effects have been considered as promising wound care materials. Herein, a salvianolic acid B (SAB)-loaded hyaluronic acid (HA) self-healing hydrogel (HA/SAB) with anti-inflammatory and pro-angiogenesis capacities for diabetic wound healing is reported. The HA hydrogel was prepared via the covalent cross-linking of aldehyde groups in oxidized HA (OHA) and hydrazide groups in adipic dihydrazide (ADH)-modified HA (HA-ADH) with the formation of reversible acylhydrazone bonds. The obtained HA hydrogel exhibited multiple favorable properties such as porous structures, excellent self-healing properties, a sustainable release capacity of SAB, as well as excellent cytocompatibility. In addition, the effects of the SAB-loaded HA self-healing hydrogel were investigated via a full-thickness skin defect model using diabetic rats. The HA/SAB hydrogel showed enhanced skin regeneration effects with accelerated wound closure, shorter remaining dermal space length, thicker granulation tissue formation, and more collagen deposition. Furthermore, reduced inflammatory response and enhanced vascularization were found with HA/SAB2.5 hydrogel-treated wounds, indicating that the hydrogel promotes diabetic wound healing through the promotion of anti-inflammation and angiogenesis. Our results suggest that the fabricated SAB-loaded HA self-healing hydrogel is promising as a wound dressing for the treatment of diabetic wounds

Polydatin prevent lung epithelial cell from Carbapenem-resistant Klebsiella pneumoniae injury by inhibiting biofilm formation and oxidative stress

Abstract Carbapenem-resistant Klebsiella pneumoniae (CRKP) causes severe inflammation in various infectious diseases, such as bloodstream infections, respiratory and urinary tract infections, which leads to high mortality. Polydatin (PD), an active ingredient of Yinhuapinggan granule, has attracted worldwide attention for its powerful antioxidant, anti-inflammatory, antitumor, and antibacterial capacity. However, very little is known about the effect of PD on CRKP. In this research, we evaluated the inhibitory effects of PD on both the bacterial level and the bacterial-cell co-culture level on anti-biofilm and efflux pumps and the other was the inhibitory effect on apoptosis, reactive oxygen species (ROS), mitochondrial membrane potential (MMP) after CRKP induction. Additionally, we validated the mechanism of action by qRT-PCR and western blot in human lung epithelial cells. Firstly, PD was observed to have an inhibitory effect on the biofilm of CRKP and the efflux pump AcrAB-TolC. Mechanically, CRKP not only inhibited the activation of Nuclear Factor erythroid 2-Related Factor 2 (Nrf-2) but also increased the level of ROS in cells. These results showed that PD could inhibit ROS and activate Nrf-2 production. Together, our research demonstrated that PD inhibited bacterial biofilm formation and efflux pump AcrAB—TolC expression and inhibited CRKP-induced cell damage by regulating ROS and Nrf-2-regulated antioxidant pathways

A novel method revealing animal evolutionary relationships based on milk Mid-infrared

AbstractMid-infrared spectra (MIRS) can effectively reflect the chemical bonds in milk, which has been widely used in dairy herd improvement. However, the relationship between MIRS and animal evolution remains largely unclear. This study firstly found great differences in MIRS and the components of milk by analyzing MIRS information of 12 different mammal species. A five-level discriminant model of evolutionary level based on MIRS was established with a test set kappa coefficient >0.97. In addition, a regression model of genetic distance was also established to estimate the genetic distance of different animal species with a correlation coefficient of R >0.94. These results showed that this method could be used for accurate mammalian evolutionary relationship assessment. We further clarified the potential relationship between MIRS and genes, such as PPP3CA and SCD that could change MIRS by regulating specific milk components. In conclusion, we expand the application of MIRS in animal species identification and evolution research and provide new perspectives for the research on the formation mechanism of different animal milk special components