Microbubble Removal Research Articles

Local Microbubble Removal in Polydimethylsiloxane Microchannel by Balancing Negative and Atmospheric Pressures.

Long-term experiments using organoids and tissues are crucial for drug development. Microfluidic devices have been regularly used in long-term experiments. However, microbubbles often form in these devices, and they may damage and starve cells. A method involving the application of negative pressure has been reported to remove microbubbles from microfluidic devices composed of polydimethylsiloxane; however, negative pressure affects the cells and tissues in microfluidic devices. In this study, a local microbubble removal method was developed using a microfluidic device with 0.5 mm thin polydimethylsiloxane sidewalls. The thin sidewalls counterbalanced the negative and atmospheric pressures, thereby localizing the negative pressure near the negatively pressurized chamber. Microbubbles were removed within 5 mm of the negatively pressurized chamber; however, those in an area 7 mm and more from the chamber were not removed. Using the local removal method, a long-term perfusion test was performed, and no contact was confirmed between the bubbles and the simulated tissue for 72 h.

Self-Propelled Detachment upon Coalescence of Surface Bubbles.

The removal of microbubbles from substrates is crucial for the efficiency of many catalytic and electrochemical gas evolution reactions in liquids. The current work investigates the coalescence and detachment of bubbles generated from catalytic decomposition of hydrogen peroxide. Self-propelled detachment, induced by the coalescence of two bubbles, is observed at sizes much smaller than those determined by buoyancy. Upon coalescence, the released surface energy is partly dissipated by the bubble oscillations, working against viscous drag. The remaining energy is converted to the kinetic energy of the out-of-plane jumping motion of the merged bubble. The critical ratio of the parent bubble sizes for the jumping to occur is theoretically derived from an energy balance argument and found to be in agreement with the experimental results. The present results provide both physical insight for the bubble interactions and practical strategies for applications in chemical engineering and renewable energy technologies like electrolysis.

An integrated microfluidic concentration gradient generator for mechanical stimulation and drug delivery

Mechanical stimuli, including fluid shear stress, osmotic pressure gradient, and extracellular matrix stiffness, significantly affect cellular interactions with drugs in biological structures. This paper introduces an integrated concentration gradient generator (CGG) capable of providing cell monolayers with these stimuli and demonstrates its design, fabrication, and quantification procedures. The proposed multi-layer chip consists of a CGG integrated with a membrane-based cell culture chamber (MCCC) and two bubble trappers for removal of micro-bubbles. The CGG provides cultured cells in the MCCC with four different concentrations of desirable inlet drug/chemical reagents. The MCCC is able to impose adjustable shear stresses, as well as osmotic pressure gradients on cell monolayers. The stiffness of the extracellular matrix (ECM) is also accommodating by utilizing a proper membrane in the MCCC. A numerical simulation based on the finite element method (FEM) is employed to design and optimize the integrated device, and then, the chip's performance is quantified using the experimental data. Finally, the biocompatibility of the proposed device is investigated by dynamic culturing of human lung cancer cells (A549 cell line) on the chip.

Scalable and reusable micro-bubble removal method to flatten large-area 2D materials

Bubbles generated during electro-delamination and chemical etch during large-area two-dimensional (2D) material transfer has been shown to cause rippling, and consequently, results in tears and wrinkles in the transferred film. Here, we demonstrate a scalable and reusable method to remove surface adhered micro-bubbles by using hydrophobic surfaces modified by self-assembled monolayers (SAMs). Bubble removal allows the 2D film to flatten out and prevents the formation of defects. Electrical characterization was used to verify improved transfer quality and was confirmed by increased field-effect mobility and decreased sheet resistance. Raman spectroscopy was also used to validate enhanced electrical quality following transfer. The bubble removal method can be applied to an assortment of 2D materials using diverse hydrophobic SAM variants. Our studies can be integrated into large scale applications and will lead to improved large-area 2D electronics in general.

Effects of Purge-Flow Rate on Microbubble Capture in Radial Arterial-Line Filters

The process of microbubble filtration from blood is complex and highly dependent on the forces of flow and buoyancy. To protect the patient from air emboli, arterial-line filters commonly use a micropore screen, a large volume housing with purpose-built shape, and a purge port to trap, separate, and remove circulating microbubbles. Although it has been proposed that an insufficient buoyancy force renders the purge port ineffective at removing microbubbles smaller than 500 μm, this research attempts to investigate the purge flow of an arterial-line filter to better understand the microbubble removal function in a typical radial filter design. As its primary objective, the study aims to determine the effect of purge-flow rate on bubble capture using air bolus injections from a syringe pump with 22-gauge needle and Doppler ultrasound bubble detection. The measureable bubble size generated in the test circuit ranged between 30 and 500 μm, while purge flow was varied between .1 and .5 L/min for testing. Statistical analysis of the test data was handled using a repeated measures design with significance set atp< .05 level. Outcomes demonstrated that higher purge flows yielded higher bubble counts, but the effect of purge-flow rate on bubble capture decreased as bubble size increased. Results also showed that purge flow from the test filter was capable of capturing all bubble sizes being generated over the entire flow range tested, and confirms utility of the purge port in removing microbubbles smaller than 500 μm. By analyzing bubble counts in the purge flow of a typical radial-filter design, this study demonstrates that currently available micropore filter technology is capable of removing the size range of bubbles that commonly pass through modern pump-oxygenator systems and should continue to be considered during extracorporeal circulation as a measure to improve patient safety.

A Case of Failed Macular Hole Closure Associated with an Entrapped Microbubble in the Hole

Purpose: To report a case of failed sealing of full-thickness macular hole associated with an entrapped microbubble in the hole after vitrectomy, peeling of the internal limiting membrane and C3F8 (14%) gas injection. Case summary: A 69-year-old female visited our clinic for decreased visual acuity in her right eye. The best corrected visual acuity (BCVA) was 20/200 in the right eye. The fundoscopy and spectral domain optical coherence tomography (SD-OCT) showed a full-thickness macular hole. She had a history of spine surgery and, thus was unable to maintain a prone position after surgery. The patient underwent pars plana vitrectomy, peeling of the internal limiting membrane and C3F8 (14%) gas injection in a sitting position postoperatively. Three weeks postoperatively, fundoscopy showed an entrapped microbubble within the macular hole, which was not sealed as observed on SD-OCT. We thought the entrapped microbubble within the macular hole prevented closure of the hole and removed it during the repeated surgery. At 2 weeks after the microbubble removal, fundoscopy and SD-OCT in the right eye showed the closure of the macular hole and the BCVA was improved to 20/40. Conclusions: We experienced a failed sealing of full-thickness macular hole due to an entrapped microbubble within the hole after macular hole surgery and observed the closure of the macular hole after removal of the microbubble. Based on our results, early microbubble removal operation should be considered in the treatment of an entrapped microbubble within the hole. J Korean Ophthalmol Soc 2016;57(5):853-856

Effectiveness of microbubble removal in an airtrap with a free surface interface

An end stage renal disease patient will undergo haemodialysis (HD) three or four times a week for four to five hours per session. Because of the chronic nature of the treatment, any minor imperfection in the extracorporeal system may become significant over time. Clinical studies have raised concerns relating to small microbubbles entering HD patients. These bubbles lead to further pathophysiological complications with the size of the bubble being a major factor. Microbubbles of different sizes can be generated throughout the extra-corporeal HD circuit. It is important to understand the possibility of these bubbles passing through the air trap or successfully being removed which indicates the performance of the air trap, the only mechanics of removing air bubbles. Chronic exposure to various sizes of microbubbles was analysed in detail for haemodialysis patients. However, smaller microbubbles are shown to be able to pass our modelled air trap. While studies have reported the presence of bubbles before and after the air trap, because these bubbles are only counted and not tracked, the performance of the air trap for removing different bubble sizes is not understood. Here, the performance of the air trap in filtering bubbles and the possibility of different bubble sizes passing through the air trap with the presence of the free surface interface have been evaluated. The modelled air trap is shown to be ineffective for filtering small micro bubbles.

Effect of surfactant addition on removal of microbubbles using ultrasound

It is difficult to control the bubble in a liquid by the external operation, because the behavior of the bubble is controlled in buoyancy and flow of liquid. On the other hand, microbubbles, whose diameter is several decades μm, stably disperse in static liquid because of their small buoyancy and electrical repulsion. When an ultrasound, whose frequency was 2.4MHz, was irradiated, the milky white microbubbles suspended solution became rapidly clear. In this study, the effects of surfactant addition on the removal of microbubbles from a liquid in an ultrasonic field were investigated. The efficiency of removal of microbubbles decreased with surfactant addition. Surfactant type influenced the size of agglomerated microbubbles, and the efficiency of removal of microbubbles changed. The surface of microbubble was modified by surfactant adsorption, and the steric inhibition influenced the removal of microbubbles.

Highly efficient CO 2 bubble removal on carbon nanotube supported nanocatalysts for direct methanol fuel cell

In this paper, we investigate the CO 2 microbubble removal on carbon nanotube (CNT)-supported Pt catalysts in direct methanol fuel cells (DMFCs). The experiments involve the incorporation of near-catalyst-layer bubble visualization and simultaneous electrochemical measurements in a DMFC anodic half cell system, in which CH 3OH electro-oxidation generate carbon dioxide (CO 2) microbubbles. We observe rapid removal of smaller CO 2 bubble sizes and less bubble accumulation on a Pt-coated CNT/CC (Pt/CNT/CC, CC means carbon cloth) electrode. The improved half cell performances of the high CO 2 microbubble removal efficiency on the CNT-modified electrode (Pt/CNT/CC) were 34% and 32% higher than on Pt/CC and Pt/CP electrodes, respectively.

Micro Bubble Removal Depending on Glass Cleanness

One serious problem for immersion lithography is micro bubble adhesion which is responsible for various exposure failures. In immersion lithography, it seems reasonable to suppose that organic contamination of lens surface brings about micro bubble adhesion onto them. Therefore, this study is intended as an analysis of adhesion and removal of micro bubbles on quartz surfaces by the contact angle method. We discuss the adhesion and removal behavior of micro bubble on the point of the balance model of surface energy. In the consequence, the micro bubbles are more likely to adhere to the organic contaminate on the quartz substrate. Keeping cleanness of a lens surface is necessary in order to prevent the micro bubble adhesion.

Electrocatalytic properties improvement on carbon-nanotubes coated reaction surface for micro-DMFC

In this paper, the enhancement of electrocatalytic performance of carbon nanotubes (CNTs) grown on silicon substrate was demonstrated as compared with the conventional reaction surfaces including bare silicon wafer, carbon cloth and carbon paper, and all were with a thin Pt film (10 nm) coating. The peak current density was doubled by the Pt film/CNTs electrode comparing to Pt film/carbon cloth and about six times comparing to silicon wafer because of the large reaction surface area and excellent CO 2 microbubble removal capability by the CNTs nanostructure. The results indicated that the electrocatalytic performance of catalyst was significantly improved for the peak current density on better linear relationship to methanol concentration and square root of sweeping-rate, better exponential relationship to temperature and higher peak current density on different substrate tiling angles, which greatly attribute to the rapid microbubbles removal on nanostructured hydrophilic CNTs surface. These conclusions can be taken as references to designing micro-DMFC in the future.

Dynamic bubble trap can replace an arterial filter during cardiopulmonary bypass surgery

The arterial filter (AF) and the dynamic bubble trap (DBT) reduce the number of air microbubbles passing through these devices. The aim of the study was to confirm that the DBT diminishes microbubbles in the arterial line similar to, or better than, the AF, and can replace it. In a clinical study, we evaluated 60 patients undergoing cardiopulmonary bypass surgery, divided into two groups (30 patients each). In the first group, we used an open extracorporeal system, and in the second group, a closed system. For 15 patients in each group, the AF was incorporated, the other 15 patients received the DBT. The microbubbles were counted before and after the AF or DBT, using two-channel-ultrasonic Doppler devices. The exposure of patients to small bubbles (< 45 microm) is significantly higher in the AF than in the DBT group. The DBT reduces large bubbles (> 45 microm) better than the AF, with a rate exceeding 16%. The use of the DBT instead of the AF yields higher air microbubble removal efficacy, allowing replacement of the AF, assuming the AF is used for air removal purpose only.

Condensation mechanism of microbubbles depending on DFR pattern design

The condensation mechanism of the microbubble is analyzed thermodynamically. Particularly, the microbubble condensation is controlled by the dry film resist (DFR) pattern design. As the bubble condensation analysis, deionized water (DI water) is dropped on a DFR pattern array. The microbubble condensed at the different position in various shape patterns. The experimental results obtained are analyzed based on the free energy balance model thermodynamically. The factor of microbubble removal from the DFR pattern is discussed for the suitable micro pattern fabrication.

Significant reduction of air microbubbles with the dynamic bubble trap during cardiopulmonary bypass.

Air microbubbles mostly occur unnoticed during cardiopulmonary bypass and are predominantly responsible for serious postoperative psychoneurological dysfunction. A dynamic bubble trap (DBT), which removes air microbubbles from the arterial blood, was tested in a clinical study. The aim was to evaluate the efficiency of microbubble removal under clinical conditions. As blood passes through the DBT, which is placed in the arterial line between the arterial filter and arterial cannula, it is converted into a rotating stream. The bubbles are directed to the centre of the blood flow and are collected in the distal end of the DBT, from where they are returned to the cardiotomy reservoir. Doppler ultrasonography was used to detect the microbubbles before and after the DBT, and also the number of high-intensity transient signals (HITS) in the right and left middle cerebral artery during extracorporeal circulation. A significant reduction of microbubbles in the arterial line (3,990 before DBT, 537 after, p < 0.001) and HITS in the brain (51 in the DBT group, 77 in the placebo group, p = 0.04) was measured.

Performance characteristics of a new arterial line filter

A new 40 micron polyester screen arterial line filter with integral automatic blood gas separator has been designed with the potential for improved removal characteristics for gas microbubbles and massive air. A simple in vitro evaluation has been carried out comparing the new filter (Pall EC+) against a standard widely-used reference arterial line filter (Pall EC 3840). The filters have been compared in terms of their haemodynamic performance, specifically pressure drop at incremental flow rates and haemolysis characteristics measuring generated plasma free haemoglobin. In addition, the relative abilities of the test and reference filters to remove gaseous microbubbles, and also to vent massive air introduced into the test circuits have been assessed using an ultrasound based microbubble detection system. The results of the studies indicate that the test and reference filters are identical in terms of haemodynamics, with maximal pressure drops of 30 mmHg at 4-5 litres mean flow rate. Neither filter is associated with significant haemolysis in bovine blood test circuits flowing at 4 I/min for 60 minutes. However, the EC+ filter has significantly superior performance over the reference EC 3840 filter in both microbubble removal and in removal of nitrogen gas introduced directly into the test circuit at up to 5 litres gas/min ( p &lt; 0.01). The new EC+ filter appears to offer safety in terms of haemodynamics and haemolysis, while providing maximal protection against massive arterial gas embolism.