10 research outputs found
Electroosmotic Soft Actuators
No full textThis dissertation details the research involved in creating the first paper-based soft actuator driven by electroosmosis. To accomplish this, research breakthroughs were made in the fields of electrokinetic pumping and device manufacturing using soft materials.
Electroosmosis is an electrically induced microfluidic flow phenomenon. When an electric field is applied to the fluid, across the microchannels, electroosmotic flow occurs in the direction of the applied electric field. In this work, liquid was electroosmotically displaced within a flexible microfluidic device to actuate an elastomeric membrane.
The goal of this work was to create a fully sealed fluidic actuator. It was therefore necessary to encapsulate the pumping fluid within the device, and to maximize pressure it was necessary to eliminate compliance caused by trapped gases. Electrolytic gas formation is well known to disrupt pumping in DC electroosmotic systems that use water as the pumping liquid. In this work, electrolysis was eliminated by replacing water with propylene carbonate (PC): PC was determined to be electrochemically stable up to at least 10 kV, in the absence of moisture or salt contaminants. Bubble-free electroosmotic pumping with PC was achieved within sealed miniature actuators, which could be continuously operated for at least one hour.
Benchtop fabrication techniques were developed to build encapsulated fluidic actuators composed entirely of soft, flexible materials. Stretchable electrochemically stable electrodes were made using a conductive paint made by mixing carbon nanoparticles into a silicone base. High-density microchannel networks were incorporated by using paper and other flexible porous materials, instead of conventional planar replica-molded microchannels. The device was filled with pumping fluid without the use of external tubing, and then encapsulated by casting a film of elastomer over the filled reservoir to form the actuating membrane. The resulting actuators were flexible and stretchable, demonstrating significant membrane deformations (hundreds of micrometers) within seconds of applying the electric field and ability to lift large loads (tens of grams). These polymeric electroosmotic actuators are unique among electroactive polymer actuators because they are able to simultaneously generate high force as well as large stroke. It is envisioned that this research will pave the way for the creation of artificial muscles and smart shape-changing materials that can be actuated by electroosmosis
Fabrication of a Miniature Paper-Based Electroosmotic Actuator
No full textA voltage-controlled hydraulic actuator is presented that employs electroosmotic fluid flow (EOF) in paper microchannels within an elastomeric structure. The microfluidic device was fabricated using a new benchtop lamination process. Flexible embedded electrodes were formed from a conductive carbon-silicone composite. The pores in the layer of paper placed between the electrodes served as the microchannels for EOF, and the pumping fluid was propylene carbonate. A sealed fluid-filled chamber was formed by film-casting silicone to lay an actuating membrane over the pumping liquid. Hydraulic force generated by EOF caused the membrane to bulge by hundreds of micrometers within fractions of a second. Potential applications of these actuators include soft robots and biomedical devices
A design of experiment study to investigate the effects of hardener concentration, stirring time, and air bubbles on the tensile strength of epoxy resin
No full textClick on the DOI to access the publisher's version of this article.Epoxy is one of the widely used polymeric resin systems in composite industries, which is a two-part resin system that requires the mixing of a hardening agent to trigger the polymerization process. The mixing ratio and pot-life are usually specified and provided by the manufacturer; however, the stirring time and the details of the mixing process were left to the fabricator to configure, based on some visual observations, which may vary from person to person. Although the mixing ratio is fixed by the resin manufacturer, errors may occur during the weighing and transfer of resin parts. The hardener concentration and stirring time are two of the most important factors that can affect the resin properties. In addition, air bubbles can be formed during the stirring process, which is inevitable. Design of experiment (DOE) is one of the widely used tools to design, control, and study the effects of multiple factors. In this research, DOE with a factorial design of 2 (2) was used to study the effects of hardener concentration, stirring time, and air bubbles on the tensile strength of epoxy resin. Test specimens were fabricated, cut, and tested as per ASTM D638 standard (i.e., common test performed in the industry for plastics) in a randomized order and then the results were statistically analyzed using Design-Expert software. The test results showed that all three factors significantly affect the tensile strength of the epoxy, and they should be carefully optimized and used for the fabrication of composite materials with optimal properties.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by John A. See Innovation Awards 2017 and 2019 at Wichita State University
Impact of Clinically Relevant Elliptical Deformations on the Damage Patterns of Sagging and Stretched Leaflets in a Bioprosthetic Heart Valve
No full textRemote sensing and GIS
No full textPresented at the fifth international conference on irrigation and drainage, Irrigation and drainage for food, energy and the environment on November 3-6, 2009 in Salt Lake City, Utah.Managing water resources in western US has been a challenge for decision makers. In the last few decades, the rapid growth rates of population along with the alarming rates of global warming have added to the complexity of this issue. In this study, remote sensing techniques have been applied to evaluate the performance of agricultural irrigation, the largest consumptive user of water. The study area, "Palo Verde irrigation District" which is located in Riverside and Imperial counties, California, is an old irrigation district with a fairly heterogeneous cropping pattern. Landsat Thematic Mapper satellite images were used to estimate the actual ET using the SEBAL energy balance model. These estimates were integrated to obtain crop water demand for different periods throughout the growing season. The amount of diverted water was also estimated for the same periods, using flow measurements within the Palo Verde irrigation district. The results were analyzed within the ArcGIS environment in conjunction with water conveyance and field boundary layers to evaluate different performance indicators such as relative water supply, overall consumed ratio, depleted fraction, crop water deficit, and relative evapotranspiration. The results of these indicators can help irrigation managers to get a general idea of how the system performs and to identify possible ways of improving it
Initial UK Experience of Focal Pulsed Field Ablation
No full text\ua9 2025 The Author(s). Pacing and Clinical Electrophysiology published by Wiley Periodicals LLC. Background: Pulsed field ablation (PFA) offers potential safety and efficacy advantages for catheter ablation. Delivering this energy source using pre-existing contact force sensing catheters and mapping systems is attractive due to familiarity and accessibility. Methods: Retrospective data collection from four centers for cases performed using focal PFA delivered through conventional contact force sensing catheters. Results: One hundred and twelve cases were included in the study. 80% of the cases were atrial tachycardia/atrial fibrillation ablations and over two thirds of these redo ablation cases; most of these patients (79%) had ablation delivered beyond the pulmonary veins. Twenty-nine cavotricuspid isthmus (CTI) and 29 mitral valve isthmus (MVI) ablations were performed. There was no relationship between center case number and procedure or fluoroscopy time for atrial cases suggesting no evident learning curve with this technology. One stroke occurred acutely, one patient had ST elevation during CTI ablation without sequelae and one had tamponade. Acute success was excellent with all ablations successful, apart from failure to block one MVI. Short-term success rates (median follow-up 5[3] months) were 74% for atrial ablations and 63% for ventricular ablations (45% for ventricular tachycardia, 100% for ventricular ectopic). Conclusions: This multicenter cohort suggests the versatility of this focal PFA platform. The use of conventional mapping and ablation equipment abrogates any learning curve. The short-term success rates are encouraging for ventricular ectopic and atrial ablation, but the waveform may need optimizing for ventricular tachycardia ablation. Randomized trials are needed to investigate further the success and complication rates with this technology
Prostate cancer in firefighting and police work: a systematic review and meta-analysis of epidemiologic studies
No full textInternational audienceOBJECTIVES:We conducted a systematic review and meta-analysis to evaluate potential associations between firefighting and police occupations, and prostate cancer incidence and mortality.METHODS:Original epidemiological studies published from 1980 to 2017 were identified through PubMed and Web of Science. Studies were included if they contained specific job titles for ever/never firefighting and police work and associated prostate cancer risk estimates with 95% confidence intervals (CI). Study quality was assessed using a 20-point checklist. Prostate cancer meta-risk estimates (mRE) and corresponding 95% CIs were calculated for firefighting and police work separately and by various study characteristics using random effects models. Between-study heterogeneity was evaluated using the I2 score. Publication bias was assessed using Begg's and Egger's tests.RESULTS:A total of 26 firefighter and 12 police studies were included in the meta-analysis, with quality assessment scores ranging from 7 to 19 points. For firefighter studies, the prostate cancer incidence mRE was 1.17 (95% CI = 1.08-1.28, I2 = 72%) and the mortality mRE was 1.12 (95% CI = 0.92-1.36, I2 = 50%). The mRE for police incidence studies was 1.14 (95% CI = 1.02-1.28; I2 = 33%); for mortality studies, the mRE was 1.08 (95% CI = 0.80-1.45; I2 = 0%). By study design, mREs for both firefighter and police studies were similar to estimates of incidence and mortality.CONCLUSION:Small excess risks of prostate cancer were observed from firefighter studies with moderate to substantial heterogeneity and a relatively small number of police studies, respectively. There is a need for further studies to examine police occupations and to assess unique and shared exposures in firefighting and police work
Expression of fatty acid and triacylglycerol synthesis genes in interspecific hybrids of oil palm
No full text© 2020, The Author(s). Evaluation of transcriptome data in combination with QTL information has been applied in many crops to study the expression of genes responsible for specific phenotypes. In oil palm, the mesocarp oil extracted from E. oleifera × E. guineensis interspecific hybrids is known to have lower palmitic acid (C16:0) content compared to pure African palms. The present study demonstrates the effectiveness of transcriptome data in revealing the expression profiles of genes in the fatty acid (FA) and triacylglycerol (TAG) biosynthesis processes in interspecific hybrids. The transcriptome assembly yielded 43,920 putative genes of which a large proportion were homologous to known genes in the public databases. Most of the genes encoding key enzymes involved in the FA and TAG synthesis pathways were identified. Of these, 27, including two candidate genes located within the QTL associated with C16:0 content, showed differential expression between developmental stages, populations and/or palms with contrasting C16:0 content. Further evaluation using quantitative real-time PCR revealed that differentially expressed patterns are generally consistent with those observed in the transcriptome data. Our results also suggest that different isoforms are likely to be responsible for some of the variation observed in FA composition of interspecific hybrids
