Combination Of Negative Pressure Research Articles

A Tough Reversible Biomimetic Transparent Adhesive Tape with Pressure-Sensitive and Wet-Cleaning Properties.

Dry adhesives that combine strong adhesion, high transparency, and reusability are needed to support developments in emerging fields such as medical electrodes and the bonding of electronic optical devices. However, achieving all of these features in a single material remains challenging. Herein, we propose a pressure-responsive polyurethane (PU) adhesive inspired by the octopus sucker. This adhesive not only showcases reversible adhesion to both solid materials and biological tissues but also exhibits robust stability and high transparency (>90%). As the adhesive strength of the PU adhesive corresponds to the application force, adhesion could be adjusted by the preloading force and/or pressure. The adhesive exhibits high static adhesion (∼120 kPa) and 180° peeling force (∼500 N/m), which is far stronger than those of most existing artificial dry adhesives. Moreover, the adhesion strength is effectively maintained even after 100 bonding-peeling cycles. Because the adhesive tape relies on the combination of negative pressure and intermolecular forces, it overcomes the underlying problems caused by glue residue like that left by traditional glue tapes after removal. In addition, the PU adhesive also shows wet-cleaning performance; the contaminated tape can recover 90-95% of the lost adhesion strength after being cleaned with water. The results show that an adhesive with a microstructure designed to increase the contribution of negative pressure can combine high reversible adhesion and long fatigue life.

Predictive Numerical Analysis to Optimize Ventilation Performance in a Hydropower Surge Chamber for H2S Removal

The role of a hydropower plant surge chamber as a pressure buffer to compensate excessive pressure fluctuations as a result of load demand variations contributes to the degassing phenomenon of hydrogen sulfide (H2S). Recent data collected from the surge chamber of a hydropower plant reveals that the H2S extraction designs are not effective in controlling the H2S concentration levels especially during surge events. To manage a safe working environment in the presence of H2S requires a systematic evaluation and prediction of the influence of critical flow control conditions in relation to suction optimization and exhaust ducting location. A numerical study was carried out to analyze the flow dynamics and the subsequent response of H2S concentrations to cases involving the following flow mixing and suction scenarios: C1 - absence of suction fans, C2 - absence of fresh air supply, C3 - enhanced suction capability, C4 - reduction in the amount of fresh air supply and C5 - presence of additional ducting. The CFD model was able to provide a reliable assessment of the case scenarios as justified by the validation carried out with in-situ measurements (within 10 % of the actual measured data). The cases where the H2S presence was found to be acceptable with concentrations less than 5 ppm at the upper region of the surge chamber, are C3, C4 and C5. A major finding from the flow studies in the surge chamber is that a combination of negative pressure at the suction locations and the absence of the forced fresh air resulted in significant amount of air drawn in from the outdoors. It was also found that the existing forced fresh air inlet locations are inappropriate as they generate vortex flows which displaces the H2S adjacent to the water level upwards and would later fill the entire chamber. All in all, the validated CFD model of the hydropower plant surge chamber was helpful in providing an understanding of the flow conditions in relation to the management of H2S concentrations.

Combinatorial therapy using negative pressure and varying lithium dosage for accelerated wound healing

In this work, we investigated the effects of negative pressure, applied using a pump designed for Negative Pressure Wound Therapy (NPWT), on the process of wound healing in vitro via initiation of the Wnt signaling pathway. Results indicate that negative pressure enhanced Wnt signaling and migration into a simulated wound in vitro in NIH-3T3 murine fibroblast cells. Increasing doses of lithium (upto 15mM) increased basal Wnt signaling and enhanced cell migration into the simulated wound site. A combination of negative pressure and increased doses of lithium synergistically increased Wnt signaling and demonstrated further enhanced cell migration into simulated wound sites, with maximal filling of the simulated wound observed at lithium concentrations of at least 10mM.