Prevent Fluid Leakage Research Articles

Engineering injectable bioadhesives with sealing and anti-fouling properties for postoperative anti-adhesion

Postoperative adhesion is a common complication that follows various types of surgeries, causing patients suffering and increasing healthcare costs. Current anti-adhesion barriers fail to provide satisfactory therapeutic outcomes mainly due to their weak retention, inability to prevent fluid leakage, and potential foreign body reactions. In the present study, we fabricated a serine-modified bioadhesive (SESAgel) with improved sealing and anti-fouling properties for postoperative adhesion prevention. The resulting SESAgel exhibited good injectability and in-situ adhesion ability, forming a stable membranous anti-adhesion barrier on the wound surface. Innovatively, it possessed efficient sealing properties, effectively stopping the leakage of tissue fluid and blood, which triggers tissue adhesion formation in the early stage. On this basis, the anti-fouling property derived from the serine in this physical barrier can further prevent the accumulation of inflammatory cells and foreign body reactions, thereby minimizing tissue adhesion. Two animal models were used to demonstrate that SESAgel effectively inhibited postoperative adhesion in different surgeries. With its natural design and good biocompatibility, SESAgel is a promising anti-adhesion biomaterial for clinical translation and practice.

Effect of non-uniform circumferential spallation of seal coating on the aerodynamic performance in a transonic axial rotor: A steady numerical simulation

Seal coating is a critical component of a compressor, and its function is to minimize the blade tip clearance and prevent fluid leakage. Non-axisymmetric spallation of the seal coating can compromise its effectiveness and reduce the compressor's efficiency. In this study, a numerical simulation was performed on a transonic axial rotor to study the effect of non-axisymmetric spallation of seal coating on the aerodynamic performance. Circumferential deep grooves were used to represent the irregular peeling of the seal coating in the full-annulus grids CFD simulation. Results show that as the circumferential length of spallation of seal coating increases, the total pressure ratio and isentropic efficiency decrease, and the surge margin decreases at first but then increases. After seal coating spallation, the flow loss changes near the suction surface and the tip passage. The flow loss changes on the suction surface relate to the interaction between the leading-edge shock/passage shock and the boundary layer. At the tip passage, the tip leakage flow and secondary flow induced low-velocity region and the effect of spallation on blockage dominate the flow loss and instability. The change in surge margin is contributed to the amount of and the chordwise variation of tip leakage flow, and the surge margin drops to the minimum when the spallation length is 9 passages where a “double-twist” flow behavior of TLF occurs substantially.

Continuous Optimisation of Experimental Models - an Example from Glaucoma Research

There is a great demand for suitable models to test novel surgical and therapeutic approaches in glaucoma therapy. To address this need and to provide further alternatives to in vivo animal models, we aimed at modifying an established in vitro porcine eye perfusion model. Two weaknesses of the previously established porcine anterior segment model include media leakage during perfusion and setup disintegration due to mechanical instability. To overcome these, we slightly modified the previously used custom-made perfusion dishes and incorporated new components into the model setup. To prevent fluid leakage, we secured the anterior segments more firmly to the perfusion trays using a compression ring, steel screws, and nuts. Customised mounts were used to stabilise the perfusion dish and pressure transducer as a single unit. The mounts were made of polylactide (PLA) and printed using a 3D printer. The use of steel screws and nuts allowed tighter clamping of the anterior segments and prevented medium leakage. Our PLA custom mounts stabilised the entire assembly and facilitated handling during experiments and improved comparability between tested eyes. They also prevented accidental detachment of the pressure transducers, which resulted in more stable pressure curves. Our PLA mounts tolerated incubation temperatures of up to 37 °C and disinfection with enzymatic detergents and 70% ethanol without showing signs of deformation or degradation after four months of regular usage. Modifications introduced to an established in vitro perfusion model improved its efficacy and reproducibility. Our adjusted model is an example of how many models can be optimised through critical analysis, thereby saving resources and providing reliable results in the long run.

Skin-Attachable Ink-Dispenser-Printed Paper Fluidic Sensor Patch for Colorimetric Sweat Analysis.

In situ analysis of sweat biomarkers potentially provides noninvasive lifestyle monitoring and early diagnosis. Quantitative detection of sweat rate is crucial for thermoregulation and preventing heat injuries. Here, a skin-attachable paper fluidic patch is reported for in situ colorimetric sensing of multiple sweat markers (pH, glucose, lactate, and uric acid) with concurrent sweat rate tracking. Two sets of fluidic patterns-multiplexed detection zones and a longitudinal sweat rate channel-are directly printed by an automated ink dispenser from a specially developed ceramic-based ink. The ceramic ink thermal-cures into an impervious barrier, confining sweat within the channels. The ceramic-ink-printed boundary achieves higher pattern resolution, prevents fluid leakage, attains pattern thermal stability, and resistant to organic solvents. The cellulose matrix of the detection zones is modified with nanoparticles to improve the color homogeneity and sweat sensor sensitivity. The sweat rate channel is made moisture sensitive by incorporating a metal-salt-based dye. The change in saturation/color of the detection zones and/or channels upon sweat addition can be visually detected or quantified by a smartphone camera. A cost-effective way is provided to fabricate paper fluidic sensor patches, successfully demonstrating on-body multiplexed evaluation of sweat analytes. Such skin wearables offer on-site analysis, meaningful to an increasingly health-conscious population.

Complications and prognosis of patients diagnosed with autosomal recessive polycystic kidney disease in neonatal period.

There are no clinical guidelines for performing nephrectomy in patients with autosomal recessive polycystic kidney disease (ARPKD). Few reports have described the clinical course of ARPKD diagnosed in the neonatal period in detail. Here, we report seven patients diagnosed with ARPKD and treated at our center during the neonatal period. Two died within 48h of life due to pulmonary hypoplasia. Of the remaining five patients, three had anuria and required for kidney replacement therapy (KRT) within one week after birth, whereas two with a milder phenotype survived without KRT. All three patients who received KRT underwent unilateral nephrectomy and peritoneal dialysis (PD) catheter placement. To prevent fluid leakage, PD was initiated 7-14days after catheter placement. However, peritoneal leakage occurred in two patients, resulting in peritonitis and discontinuation of PD; one who required long-term hemodialysis contracted a catheter-related bloodstream infection as well as developed subdural and epidural hematomas. Meanwhile, two patients underwent a second nephrectomy within 6weeks after birth; one developed severe persistent hypotension and neurological complications, while the other died of bacteremia that may have resulted from cholangitis diagnosed on day 67 of life. A severe clinical course, life-threatening adverse events, and severe neurological sequalae may occur in patients with ARPKD who receive KRT in neonatal period.

Enhancing Robustness of Adhesive Hydrogels through PEG-NHS Incorporation.

Tissue wounds are a significant challenge for the healthcare system, affecting millions globally. Current methods like suturing and stapling have limitations as they inadequately cover the wound, fail to prevent fluid leakage, and increase the risk of infection. Effective solutions for diverse wound conditions are still lacking. Adhesive hydrogels, on the other hand, can be a potential alternative for wound care. They offer benefits such as firm sealing without leakage, easy and rapid application, and the provision of mechanical support and flexibility. However, the in vivo durability of hydrogels is often compromised by excessive swelling and unforeseen degradation, which limits their widespread use. In this study, we addressed the durability issues of the adhesive hydrogels by incorporating acrylamide polyethylene glycol N-hydroxysuccinimide (PEG-NHS) moieties (max. 2 wt %) into hydrogels based on hydroxy ethyl acrylamide (HEAam). The results showed that the addition of PEG-NHS significantly enhanced the adhesion performance, achieving up to 2-fold improvement on various soft tissues including skin, trachea, heart, lung, liver, and kidney. We further observed that the addition of PEG-NHS into the adhesive hydrogel network improved their intrinsic mechanical properties. The tensile modulus of these hydrogels increased up to 5-fold, while the swelling ratio decreased up to 2-fold in various media. These hydrogels also exhibited improved durability under the enzymatic and oxidative biodegradation induced conditions without causing any toxicity to the cells. To evaluate its potential for clinical applications, we used PEG-NHS based hydrogels to address tracheomalacia, a condition characterized by inadequate mechanical support of the airway due to weak/malacic cartilage rings. Ex vivo study confirmed that the addition of PEG-NHS to the hydrogel network prevented approximately 90% of airway collapse compared to the case without PEG-NHS. Overall, this study offers a promising approach to enhance the durability of adhesive hydrogels by the addition of PEG-NHS, thereby improving their overall performances for various biomedical applications.

Application of Load-Sharing Concept to Mechanical Seals

Mechanical seals are mechanisms that are used to prevent fluid leakage. Since the seal surfaces are in contact with one another, hydrodynamic and contact forces are functions of surface roughness. Additionally, since the lubrication regime under specific operating conditions such as low speed or high load causes the seal to operate in the mixed lubrication regime, thus the contact of asperities plays an important role. The primary purpose of this paper is to apply the load-sharing concept to study the behavior of a mechanical seal in a mixed lubrication regime. The predicted results are compared to the published data from the literature, showing acceptable accuracy. The model presented in this paper can predict the performance of the mechanical seal system in a short execution time while providing acceptable accuracy by considering the surface roughness effect.

Microfluidics-integrated spaceflight hardware for measuring muscle strength of Caenorhabditis elegans on the International Space Station

Caenorhabditis elegans is a low-cost genetic model that has been flown to the International Space Station to investigate the influence of microgravity on changes in the expression of genes involved in muscle maintenance. These studies showed that genes that encode muscle attachment complexes have decreased expression under microgravity. However, it remains to be answered whether the decreased expression leads to concomitant changes in animal muscle strength, specifically across multiple generations. We recently reported the NemaFlex microfluidic device for the measurement of muscle strength of C. elegans (Rahman et al., Lab Chip, 2018). In this study, we redesign our original NemaFlex device and integrate it with flow control hardware for spaceflight investigations considering mixed animal culture, constraints on astronaut time, crew safety, and on-orbit operations. The technical advances we have made include (i) a microfluidic device design that allows animals of a given size to be sorted from unsynchronized cultures and housed in individual chambers, (ii) a fluid handling protocol for injecting the suspension of animals into the microfluidic device that prevents channel clogging, introduction of bubbles, and crowding of animals in the chambers, and (iii) a custom-built worm-loading apparatus interfaced with the microfluidic device that allows easy manipulation of the worm suspension and prevents fluid leakage into the surrounding environment. Collectively, these technical advances enabled the development of new microfluidics-integrated hardware for spaceflight studies in C. elegans. Finally, we report Earth-based validation studies to test this new hardware, which has led to it being flown to the International Space Station.

357 Novel Osteoconductive, Bioresorbable Bone Adhesive Provides Superior Cranial Flap Fixation Strength and Reduced CSF Leak Potential in a Cadaver Model

INTRODUCTION: Plates and screws are the gold standard for cranial flap fixation. Unfortunately, hardware may be associated with loosening and migration. Osseous union of the fixated flap to the surrounding skull is typically incomplete. Furthermore, titanium plates and screws do not provide a watertight closure of the bone and cannot mitigate CSF leakage. METHODS: 64 craniotomies were performed in 16 cadavers by a single neurosurgeon. Frontal, pterional, parietal, and parieto-occipito-temporal flaps were created in each skull. The 64 bone flaps were fixated by 16 different neurosurgeons (4 flaps/surgeon). Each flap was secured with standard cranial plates and screws, then biomechanically tested using either quasi-static compression (1mm/min) or staircase impact (up to 60J impact energy at increments of 6J) to analyze mechanical strength. Next, the plates and screws were removed and the same bone flap was secured by the same neurosurgeon using a novel bone adhesive, Tetranite®(TN). The TN-secured flaps were then biomechanically tested in similar fashion. A subset of the TN-fixated flaps was subjected to hydrostatic fluid pressure (up to 40mm Hg at steps of 5mm Hg) to determine resistance to simulated CSF leakage prior to mechanical testing. RESULTS: TN fixation was approximately 41 times stiffer and 48 times stronger than metal fixation under quasi-static loading (stiffness 4216±1544N/mm and peak force 5456±1920N for TN vs. 103 ±81N/mm and 113±89N for metal hardware: n=32). At an impact energy of 6J, cranial flaps fixated using metal hardware migrated to a peak deflection 13 times greater than TN-fixated specimens; the residual plastic deformation was 30 times greater (peak elastic deflection 2.94± 0.81mm and plastic deflection of 1.69±0.93mm for metal hardware vs. 0.24±0.07mm and 0.06±0.04mm for TN; n=31). Of 16 TN-fixated specimens tested hydrostatically, none leaked under pressures up to 35mmHg held for 5 secs, and only 2 specimens leaked at 40mmHg. CONCLUSION: TN was biomechanically superior to standard cranial hardware for flap fixation. Additionally, TN acted to prevent fluid leakage. TN holds promise for improving cranial bone flap fixation biomechanically, cosmetically, and hydrostatically.

Numerical Modeling of Gas Migration through Cement Sheath and Microannulus.

Cement sheath is considered an important barrier throughout the life cycle of the well. The integrity of the cement sheath plays a vital role in maintaining the integrity of wells. Cement’s ability to seal the annular space or a wellbore, also known as cement sealability, is an important characteristic of the cement to maintain the well integrity. It is believed that placing cement in the annular space or wellbore can totally prevent any leakage; however, that is debatable. The reason why cement cannot completely prevent fluid leakage is that cement is considered as a porous medium, and also flaws in cement, such as microannuli, channels, and fractures, can develop within the cement sheath. Furthermore, the complexity of casing/cement and cement/formation interaction makes it very difficult to fully model the fluid migration. Hence, fluid can migrate between formations or to the surface. This article presents a numerical model for gas flow in cement sheath, including the microannulus flow. A parametric study of different variables and their effect on the leakage time is carried out, such as the microannulus gap size, cement matrix permeability, cement column length, and cement porosity. In addition, it presents leakage scenarios for different casing/liner overlap length with the existence of microannulus. The leakage scenarios revealed that the cement matrix permeability, microannulus gap size, and cement length can highly impact the leakage time; however, cement porosity has a minimal effect on the leakage time. In addition, modeling results revealed that the casing/liner overlap length should not be less than 300 ft, and the casing pressure duration should be beyond 30 min to detect any leak.

Dynamic Characteristics Analysis of a Seal-Rotor System With Rub-Impact Fault

AbstractLabyrinth seals are widely used to prevent fluid leakage in high-low pressure areas of the rotating machinery. However, the rub-impact fault easily occurs in labyrinth seals. Considering the influence of gyroscopic effect, a finite element model of seal-rubbing rotor system is established in this study based on the Muszynska seal force model, the rolling bearing force model, and the nonlinear rubbing force model. The vibration characteristics under the coupling faults of airflow excitation and rub-impact are analyzed. First, the response of the system without rub-impact fault is simulated numerically and verified by experiments. Subsequently, the dynamic characteristics of the rotor under the conditions of slight and severe rub-impact faults are analyzed. Finally, the influence of the rub-impact parameters is further studied. The results indicate that when the rub-impact fault is absent, airflow excitation occurs at a certain speed, which exhibits the characteristics of frequency locking and combination frequency. The coupling dynamic responses of airflow-induced vibration and rub-impact fault show a rich spectrum of nonlinear phenomena, which are closely related to the degree of rub impact. This study may provide a theoretical basis for the detection and diagnosis of fluid-induced rub-impact fault in labyrinth seal-rotor systems.

Validation of a bioabsorbable device that seals perforations after Tuohy needle dural puncture in an ovine model

BackgroundWe designed a device to close accidental dural puncture via the offending puncturing epidural needle directly after diagnosis of the puncture and before removing the needle. The aim of this...

Wire rod linear actuator seals inspired by earthworm: tube seal

This Letter presents a flexible wire-driven linear actuator using a bio-inspired sealing method that allows to replace a rigid rod by a flexible one and reduce the size of a robot link containing pneumatic or hydraulic linear actuators. Conventional pneumatic or hydraulic linear actuator sealing hinders the use of flexible wires as actuator rods. In contrast, the proposed tube sealing resembles a long balloon wrapping around the wire and stretching or contracting with the wire rod motion. Therefore, the wire is separated from the chamber and prevents fluid leakage through the flexible wire rod. This sealing method is inspired by earthworm which has slippery skin and stretching or contracting motion. The authors fabricated a prototype wire rod pneumatic linear actuator using the proposed tube seal and conducted leakage tests. In addition, the authors evaluated linearity between the input pressure and output force to determine the linear actuator performance.

A wedge penetration model to estimate leak through elastomer–metal interface

Elastomeric seals are devices that are widely used to prevent fluid leakage through the interface of a variety of mating industrial components. Gas leak through these seals involves gas flow through the interface of the seal and its corresponding mating component. This flow is understood to initiate due to separation of the surfaces at the sealing interface due to gas pressure. Modelling this separation can aid in optimizing seal designs and in estimating seal failure. In this paper, we develop a simple wedge penetration-based model to describe the separation. The frame work of the model is generic so that it can represent gradual as well as complete seal failures. We illustrate the applicability of this model for elastomer–metal interfaces which involve gradual separation. Nitrogen gas leak rate experimental data for stainless steel with three different elastomers are described using the model. We further discuss the processes and challenges involved in employing this model to estimate leak rate of gas through elastomeric seals of different geometries.

Tracheoesophageal Voice Prosthesis Use and Maintenance in Laryngectomees.

Tracheoesophageal speech is the most common voicing method used by laryngectomees. This method requires the installation of tracheoesophageal prosthesis (TEP), which requires continuous maintenance to achieve optimal speaking abilities and prevent fluid leakage from the esophagus to the trachea. The present manuscript describes the available types of TEPs, the procedures used to maintain them, the causes for their failure due to fluid leakage, and the methods used for their prevention. Knowledge and understanding of these issues can assist the otolaryngologist in caring for laryngectomees who use tracheoesophageal speech.

An endotracheal tube providing "pressurized sealing" prevents fluid leakage in mechanically ventilated critically ill patients: a pilot study.

Microaspiration of bacteriologically contaminated oropharyngeal secretions alongside the cuff of an endotracheal tube (ETT) is a key mechanism for development of ventilator-associated pneumonia. We have constructed a prototype double-cuffed ETT equipped with a supplemental port in-between the cuffs through which continuous positive airway pressure (CPAP) is delivered. Pressure in the intercuff space propels secretions upwards and produces 100% tracheal sealing in an in vitro model. We conducted a 24 h study to investigate the sealing effect of this ETT in 12 critically ill mechanically ventilated patients. Methylene blue, instilled through a bronchoscope on top of the proximal cuff, was used as leakage tracer. Fiberoptic visualisation of the trachea was performed 1 h and 24 h thereafter. Leakage was confirmed if blue dye was detected on the tracheal mucosa beyond the tip of the ETT. In no patient, dye passed by the cuffs during the study period. Presence of the ETT did not interfere with ventilator settings, patient mobilization, physiotherapy, and technical acts. Overall, pressures in the intercuff space remained between 10 and 15 cmH2O. Excessive pressure swings were swiftly corrected by the CPAP system. A double-cuffed ETT, offering “pressurized sealing” of the trachea, safely and effectively prevented leakage during 24 h mechanical ventilation.

Stress Analysis and Performance Evaluation of Flange Spool Subjected to Pressure

In the present scenario, the prevention of failure of a component is having a vital role in piping industry. Failure of a single component can cease the entire functionality of the system. So the prevention of failure is significant to satisfy the customer needs not only aesthetic but also functionality, reliability and utility of the system. With the advancement of new technologies, finding out the failures and giving a pertinent solution is possible. Value engineered component is an added advantage to the industry in all aspects. A flange spool is a basic type of dismantling joint that connect long pipes with flanges at the ends so that they can be bolted to another pipe with matching flange. The flange joint involves interaction between bolts, flange and gasket and it is the most essential part of Pressure vessel, Condenser, Heat exchanger and Storage tank. This flange joint aims at preventing fluid leakage and maintaining the structural integrity of the joint. The objective of this paper is to design and analyze a flange spool which is used to carry and transport processed fluid and gas. This work deals with the replacement of molybdenum steel material flange spool with a silicon-manganese flange spool. The modeling was done using CATIA software as per API standards. The flange spool is modeled and simulated using ANSYS 15 Software. The design optimization also showed significant potential improvement in the performance of flange spool. In the present work finite element analysis procedure is used in ANSYS simulation to predict the levels of stress and deformation of flange spool under subjected loads.

Experimental characterisation of leak through elastomer-metal interface

Elastomeric seals are devices that are widely used to prevent fluid leakage through the interface of mating parts. In this paper, we study the leak characteristics of a representative elastomeric s...

An ex vivo comparison of cuffed endotracheal tubes and self-sealing baffled endotracheal tubes

AIMSTo compare cuffed silicone endotracheal tubes with self-sealing baffled silicone endotracheal tubes in an ex vivo canine tracheal model, to determine whether the tubes differed in their maintenance of a seal and their effectiveness in removing fluid from the tracheal lumen, and whether the self-sealing endotracheal tubes would release pressure when a closed anaesthetic circuit reached ≥30 cm H2O.METHODSTwelve cadaver tracheae were randomly selected to be intubated with either cuffed or self-sealing baffled endotracheal tubes. To test tracheal seal efficacy, the tracheae were positioned vertically, 5 mL of water was instilled proximal to the tube cuff or baffles and they were monitored for leakage at 0, 15, 30, 45, and 60 minutes, recording the total volume leaked. To test fluid removal at extubation, the tracheae were intubated, then 5.6 g of 60% barium sulphate suspension was instilled proximal to the seal and left undisturbed for 5 minutes. The tubes were then extubated, with the cuffed endotracheal tubes being partially deflated before extubation, and the amount of barium recovered was weighed. These procedures were repeated on the same tracheae using the other endotracheal tubes. To test whether self-sealing baffled endotracheal tubes would release pressure at ≥30 cm H2O, the tracheae were intubated, connected to an anaesthetic machine and pressurised to 30 cm H2O for 5 minutes and then 50 cm H2O for 5 minutes. Release of pressure was defined as a decrease in pressure within the closed anaesthetic circuit.RESULTSMore cuffed (7/12) than baffled (0/12) endotracheal tubes leaked water after 60 minutes (p=0.016). The mean amount of barium removed by the self-sealing baffled endotracheal tubes (4.9 (95% CI=3.8–4.4) g) was greater than that removed by the partially deflated cuffed endotracheal tubes (0.4 (95% CI=0.14–0.66) g) (p<0.001). None of the self-sealing baffled endotracheal tubes released pressure at ≥30 cm H2O in a closed anaesthetic circuit.CONCLUSIONS AND CLINICAL RELEVANCESelf-sealing baffled endotracheal tubes were more effective than cuffed endotracheal tubes at both preventing fluid leakage at the tracheal seal and removing fluid from the lumen of the trachea in cadaver tracheae. However they did not release pressure when the closed-circuit system was at ≥30 cm H2O in a canine cadaver model. The self-sealing baffled endotracheal tubes may be a suitable substitute for cuffed endotracheal tubes.

Application of segmented rubber rings to increase the sealing efficiency in hydroforming

The tube hydroforming process uses a pressurized fluid as the forming medium, and the sealing efficiency of the internal fluid has an important influence on the hydroformability. This study investigates the applicability of segmented rubber rings to prevent pressure leakage in hydroforming. When the target shape is non-axisymmetric, the possibility of pressure leakage is increased due to the biased stress distribution on the punch. A sealing system is proposed, which is composed of segmented rubber rings, a cylindrical sleeve, and a punch with an end fillet. When the rubber rings are compressed, the reaction force acting on the rings contributes to the prevention of pressure leakage. The circumference of the tube end becomes more tightly sealed by the axial pressure between the punch and sleeve. A deformation analysis was conducted using a compression test, which revealed that the combined use of a steel ring with a rubber ring was more efficient in preventing fluid leakage. The enhanced sealing effect of the proposed system with rubber and steel rings was confirmed by comparing the experimental results with a conventional hydroforming process.