Studying Liquid-Infused Surfaces with Affordable Surface Features Infiltrated with Various Lubricants from Corrosion, Biofouling, and Fluid Drag Viewpoints.

Drag force, corrosion, and biofouling have always been issues that disrupt the reliable operation of systems dealing with fluid flow. Inspired by nature, liquid- or solid-infused surfaces are brand-new surfaces that can address these problems. The present study examines nine comprehensive yet affordable samples with different surface structures, from the nanoscale to the microscale on the aluminum substrate. These surface structures, modified with stearic acid or octadecyltrichlorosilane, are infiltrated with various lubricants. The wetting test shows the magnificent slippery properties of fabricated surfaces with a contact angle hysteresis lower than 10°. The conducted polarization test reveals that the surface structures comprised of aluminum oxide or boehmite have good anti-corrosion properties. Moreover, the higher the viscosity of the lubricant, the better the anti-corrosion abilities. In the anti-bacterial tests, the surfaces possessing a liquid lubricant perform better than those containing solid ones; among them, those with lower viscosities are preferable. The frictional drag test carried out in an aquarium shows that for viscous working fluids, the layered-double hydroxide (LHD) surface containing silicone oil with a viscosity of 5 mPa s could provide a maximum drag reduction of 18%. By increasing the velocity of the surface, the drag reduction ability of LIS reduces. For more viscous lubricants and also solid ones, no appreciable drag reduction is achieved. For less viscous working fluid, however, the anodized surface filled with the same lubricant shows the best results with a maximum drag reduction of 15%. The surface based on LDH also shows good durability in the conducted stability tests.

Enhancement of Dropwise Condensation Heat Transfer through a Sprayable Superhydrophobic Coating.

Improving the shedding rate of condensed droplets has many applications in industries and daily problems, including increasing heat transfer and self-cleaning properties. One way to achieve this goal is by enhancement of the wetting properties of surfaces. In this research, the hierarchical superhydrophobic coating over aluminum has been applied using a relatively cost-effective method, spraying, which is also applicable to any metal surface used as a condenser. According to the results obtained from the experimental tests, the fabricated surface is highly superhydrophobic, with a contact angle of 158° and contact angle hysteresis of less than 5°. The results show that the presented surface increases the heat transfer coefficient by 20.6% at the subcooling temperature of 25.5 °C when the surface temperature and relative humidity are 70 °C and 98%, respectively. In addition, this coated surface showed great potential at lower surface temperatures by increasing the water condensation rate as much as 50.5% at the subcooling temperature of 12 °C, when the surface temperature and relative humidity are 11.25 °C and 70%, respectively. Therefore, it is found that for the fabricated superhydrophobic paint in the present study, the effectiveness of the dropwise condensation mode profoundly depends on surface temperatures besides subcooling temperatures. In other words, a surface with lower temperatures shows better performance for the same subcooling temperatures. In addition, various types of durability tests are carried out. The results reveal that this coating has good durability against high surface temperatures, submerged conditions for 30 days, imposing hot steam for 150 h, corrosion, and organic solvents. Hence, it is suitable for industrial applications.

Laminar drag reduction ability of liquid-infused microchannels by considering different infused lubricants.

We numerically investigate the pressure drop reduction (PDR) performance of microchannels equipped with liquid-infused surfaces, along with determining the shape of the interface between the working fluid and lubricant within the microgrooves. The effects of different parameters, such as the Reynolds number of working fluid, density and viscosity ratios between the lubricant and working fluid, the ratio of the thickness of the lubricant layer over the ridges to the depth of the groove, and the Ohnesorge number as a representative of the interfacial tension, on the PDR and interfacial meniscus within the microgrooves are comprehensively studied. The results reveal that the density ratio and Ohnesorge number do not significantly affect the PDR. On the other hand, the viscosity ratio considerably affects the PDR, and a maximum PDR of 62% compared to a smooth non-lubricated microchannel is achieved for a viscosity ratio of 0.01. Interestingly, the higher the Reynolds number of the working fluid, the higher the PDR. The meniscus shape within the microgrooves is strongly affected by the Reynolds number of the working fluid. Despite the insignificant effect of interfacial tension on the PDR, the interface shape within the microgrooves is appreciably influenced by this parameter.

Factors associated with longer length of hospital stay after primary elective ankle surgery for end-stage ankle arthritis.

BACKGROUND: Longer length of stay in the hospital after elective surgery results in increased use of health-care resources and higher costs. Improved perioperative care permits many foot and ankle surgical procedures to be performed as day surgery. This study determined perioperative factors associated with a longer length of stay after elective total ankle replacement or ankle arthrodesis. METHODS: Data were prospectively collected on patients who underwent open or arthroscopic ankle fusion or total ankle replacement for end-stage ankle arthritis at our institution from 2003 to 2010. Univariate and multivariable generalized linear regression models with gamma distribution and log link function were conducted with use of the length of the hospital stay as the dependent variable and preselected risk factors of age, sex, physical and mental functional scores, comorbid factors, American Society of Anesthesiologists grade, body mass index, type of surgery, duration of surgery, and surgery day of the week as the independent variables. RESULTS: This study included 343 patients with a median length of stay of seventy-five hours (interquartile range, fifty-two to ninety-seven hours). With use of regression analyses, the variables of age, female sex, higher American Society of Anesthesiologists grade, multiple medical comorbidities, rheumatoid arthritis, lower Short Form-36 Physical Component Summary and General Health domain scores, and open surgery were significantly associated with increased length of stay. Conversely, the variables of obesity, Short Form-36 Mental Component Summary score, surgery day of the week, and surgical duration were not associated with length of stay. Two predictive models of the length of stay were developed: one included only patient-related factors, and the other included patient and surgery-related factors. CONCLUSIONS: The patients who are identified with a higher risk of a longer length of stay may warrant better education and more focused perioperative care when designing care pathways and allocating health-care resources.

Mean BMI of overweight and obese patients does not decrease after successful ankle reconstruction.

BACKGROUND: End-stage arthritis may be associated with increased body mass index (BMI). Overweight patients with ankle arthritis often request surgery in the hope that this will allow them to initiate a weight loss program. METHODS: One hundred and forty-five overweight (BMI = 25.1 to 29.9 kg/m2) or obese (BMI > 30 kg/m2) patients who had successful ankle replacement or ankle fusion, as defined by the absence of revision ankle surgery and a postoperative improvement in the Ankle Osteoarthritis Scale (AOS) score, were identified in a retrospective cohort ankle database. Their BMIs at six months and one, two, and five years postoperatively were compared with their preoperative BMI as the primary outcome measure. Linear regression analysis was used to correlate the outcome scores against BMI with time. RESULTS: No significant change in the mean BMI, compared with the preoperative BMI, was found at six months or one, two, or five years postoperatively, despite significant improvement in the AOS and Short Form-36 (SF-36) Physical Component Summary scores at all time points. The factor that most strongly correlated with postoperative BMI was preoperative BMI. CONCLUSIONS: Pain and disability are significantly reduced in overweight and obese patients after successful ankle replacement or fusion. Despite this, the mean BMI remains unchanged after the surgery, indicating that weight loss does not commonly occur following successful ankle reconstruction in this patient population. Obesity is likely attributable to factors other than limited mobility caused by ankle arthritis.

Delay in operative stabilization of spine fractures in multitrauma patients without neurologic injuries: effects on outcomes.

BACKGROUND: Optimal timing for surgical stabilization of the fractured spine is controversial. Early stabilization facilitates mobilization and theoretically reduces associated complications. METHODS: We identified consecutive patients without neurologic injury requiring stabilization surgery for a spinal fracture at an academic tertiary-care hospital over a 12-year period. Incidences of postoperative complications were prospectively evaluated. We analyzed results based on the time elapsed before the final surgical stabilization procedure. Multivariate analyses were performed to explore the effects of potential confounders. RESULTS: A total of 83 patients (60 men, 23 women; mean age 39.4 yr) met the eligibility criteria and were enrolled. The mean Injury Severity Score (ISS) was 27.1 (range 12.0-57.0); 35% of patients had a cervical fracture and 65% had a thoraco-lumbar fracture. No statistically significant associations were uncovered between time to surgical stabilization and age, ISS or comorbidities. Comparing patients stabilized after 24 hours with those stabilized within 24 hours, there was an almost 8-fold greater risk of a complication related to prolonged recumbency (p = 0.007). We observed similar effects for other types of complications. Delays of more than 72 hours had a negative effect on complication rates; these effects remained significant after multivariate adjustments for age, comorbidity and ISS. CONCLUSION: This study demonstrates a strong relation between timing of surgical stabilization of spinal fractures in multitrauma patients without neurologic injuries and complications. Further studies with larger samples may allow for better adjustment of potentially confounding factors and identify subgroups in which this effect is most pronounced.

The evaluation of patellar height: a simple method.

BACKGROUND: Patellar height is evaluated with ratios that have been derived from measurements made on lateral radiographs of the knee. The importance of using a ratio is that magnification, physical size, and flexion angle are eliminated as factors that affect the values. The Insall-Salvati index was the first ratio to be described. It remains the most popular, possibly because normal values are easy to remember. As all of the currently accepted methods are cumbersome to use because they require two measurements as well as a calculation, a single angular measurement was devised (the plateau-patella angle) to offer a simpler alternative. The purpose of this study was to introduce the new method and to assess its validity by comparing it with three classic, commonly used ratios. METHODS: In two groups of patients, after exclusions, 269 lateral radiographs of the knee were evaluated. All measurements required for the Insall-Salvati, the Blackburne-Peel, and the Caton-Deschamps indices plus the plateau-patella angle were recorded, along with basic demographics. For validation, the new method was compared with the established methods, and interobserver and intraobserver reliability were computed. RESULTS: There was excellent correlation between the proposed angle and the three selected indices, especially with the Blackburne-Peel index. Interobserver and intraobserver reliability was high and compared favorably with that reported in the literature for the three classic ratios. The calculated ratios were in line with those described in the literature. The mean plateau-patella angle was 25°. Ninety percent of the measurements fell between 20° and 30°, and one standard deviation above and below was 21° to 29°. CONCLUSIONS: The plateau-patella angle, a new method of evaluating patellar height, can be measured rapidly with use of either a goniometer or digital software. Its range is easy to remember, it is reliably reproduced, and it correlates well with traditional methods. It is thus a valid and easy alternative method for the evaluation of patellar height.