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Liquid-infused slippery surfaces have replaced structural superhydrophobic surfaces in a plethora of emerging applications, hallmarked by their favorable self-healing and liquid-repelling characteristics. Their ease of fabrication on different types of materials and increasing demand in various industrial applications have triggered research interests targeted toward developing an environmental-friendly, flexible, and frugal substrate as the underlying structural and functional backbone. Although many expensive polymers such as polytetrafluoroethylene have so far been used for their fabrication, these are constrained by their compromised flexibility and non-ecofriendliness due to the use of fluorine. Here, we explore the development and deployment of a biodegradable, recyclable, flexible, and an economically viable material in the form of a paper matrix for fabricating liquid-infused slippery interfaces for prolonged usage. We show by controlled experiments that a simple silanization followed by an oil infusion protocol imparts an inherent slipperiness (low contact angle hysteresis and low tilting angle for sliding) to the droplet motion on the paper substrate and provides favorable anti-icing characteristics, albeit keeping the paper microstructures unaltered. This ensures concomitant hydrophobicity, water adhesion, and capillarity for low surface tension fluids, such as mustard oil, with an implicit role played by the paper pore size distribution toward retaining a stable layer of the infused oil. With demonstrated supreme anti-icing characteristics, these results open up new possibilities of realizing high-throughput paper-based substrates for a wide variety of applications ranging from biomedical unit operations to droplet-based digital microfluidics.

To address and extend the finite lifetime of Mg-based micromotors due to the depletion of the engine (Mg-core), we examine electric fields, along with previously studied magnetic fields, to create a triple-engine hybrid micromotor for driving these micromotors. Electric fields are a facile energy source that is not limited in its operation time and can dynamically tune the micromotor mobility by simply changing the frequency and amplitude of the field. Moreover, the same electrical fields can be used for cell trapping and transport as well as drug delivery. However, the limitations of these propulsion mechanisms are the low pH (and high conductivity) environment required for Mg dissolution, while the electrical propulsion is quenched at these conditions as it requires low conductivity mediums. In order to translate the micromotor between these two extreme medium conditions, we use magnetic rolling as means of self-propulsion along with magnetic steering. Interestingly, electrical propulsion also necessitates at least the partial consumption of the Mg, resulting in a sufficient geometrical asymmetry of the micromotor. We have successfully demonstrated the rapid propulsion switching capability of the micromotor, from chemical to electrical motions, via magnetic rolling within a microfluidic device with the concentration gradient of the simulated gastric fluid. Such triple-engine micromotor propulsion holds considerable promise for in vitro studies mimicking gastric conditions and performing various bioassay tasks.

Background: Upper abdominal surgery (like- hepatobiliary surgery, gastrectomy, esophagectomy, hepatictomy, and whipples operations that involve large surgical incisions) lead to severe postoperative pain that lead to higher doses of opoids use in post-operative period as a result incidence of unwanted side effect and respiratory complication increase hospital stay and morbidity. To reduce the use of opioids clonidine can be used as a multimodal analgesic approach. It is reported that clonidine 150mcg intravenous (I/V) produce a similar analgesic effect to morphine 5mg in patient after orthopedic surgery. Because of its dose, route, and surgical variation it is very much important to specify the dose for upper abdominal surgery. Material and methods: After considering the inclusion and exclusion criteria the patients were randomized to receive Group: A (2mcg/kg oral clonidine) and Group: B (4mcg/kg oral clonidine), one hour (60minutes) before surgery as an oral premedication. All groups were compared for preoperative analgesic, sedation and anxiety level along with changes of heart rate and mean arterial pressure prior to premedication and post-operative periods as follows VAS (visual analogue score) pain scores. Result: The post-operative pain measured on VAS showed Group A expressed highest VAS at 6thpost-operative hour Group –B showed highest VAS at 14th post-operative hour. So it is very clear to us that pethedine requirement of Group B (4mcg/kg oral clonidine) is less than Group A (2mcg/kg oral clonidine). The oral premedication with clonidine at 2 microgram per kg or 4 microgram per kg for postoperative analgesia and hemodynamic stability of elective upper abdominal surgery patients. Conclusion: As a part of multimodal analgesic approach, 4mcg/kg oral clonidine premedication is effective to perioperative pain control and keep stable the haemodynamic in upper abdominal surgery J Dhaka Medical College, Vol. 28, No.2, October, 2019, Page 131-135

Background: Emergency tracheostomy is the commonest surgical intervention performed as lifesaving procedure by ENT surgeons on patients in emergency room of ENT and ICU. Several operative and postoperative complications have been reported after tracheostomy including fatal hemorrhage. Massive subcutaneous neck emphysema occurred because ventilation started at the time when the hemorrhage was not completely managed and the tracheal tube was not fully secured. Objective: This study was conducted to compare haemorrhage and surgical emphysema as complication of emergency tracheostomy among patients admitted in Department of ENT and Head-Neck Surgery in Dhaka Medical College & Hospital. Methods and Materials: This was a Cross Sectional Study conducted in the ENT and Head- Neck Surgery Department, Dhaka Medical College Hospital from July 2015 to June 2016. A total of 90 patients were included who fulfilled the selection criteria. Non probability convenient sampling was used to collect data. Statistical analysis was done by SPSS version 21. Results: Mean± SD of the study subjects was 49.84±17.4 years with most patients belonged to 40-79 years age group. 28.9% patients had habit of smoking and betel nut chewing. (48.9%) patients suffered from Ca larynx. Out of 90 tracheostomy patients, 40(44.4%) patients had had different complications including haemorrhage (13.3%), surgical emphysema (10%), haemorrhage with surgical emphysema (6.7%), tube blockage (3.3%), wound infection (3.3%) and injury to local tissue (2.2%). Haemorrhage occurs from anterior jugular vein, middle thyroid veins and thyroid gland and included peroperative haemorrhage (7.8%), immediate post- operative haemorrhage

Background: Laparoscopic cholecystectomy has emerged as a popular alternative to traditional open cholecystectomy in the management of cholelithiasis. It has several advantages .Pneumoperitoneum and trendelenburg positioning causes release of stress hormones and ultimately changes in hemodynamic parameters. Stretching of peritoneum, abdominal wall associated with postoperative pain. So maintenance of haemodynamic stability, immediate postoperative pain control continues to be a major challenge for the anaesthesiologists. Methods: Sample was selected by non-probability sampling technique in two groups distributed as- Group-L (Laparoscopic cholecystectomy, n=30) and Group-O (opencholecystectomy, n=30). Detailed history taking, physical examination and routine lab investigations were done. Approval of the study was obtained by the local Ethical Committee. Post-operative complications, postoperative pain, frequency and pattern of cardiovascular complications, frequency and pattern of respiratory complications were evaluated and compared between thegroups Result: In both groups female were predominant. In this study haemodynamic status (Heart rate, SBP, DBP, MBP) in different phases of anaesthesia, surgery and postoperative follow-up (at 4th hour, 8th hour, and 12th hour) has been observed. Conclusion: This study confirms the feasibility and safety of laparoscopic cholecystectomy is better than open technique in terms of attenuation of better haemodynamic stability, better postoperative pain control and less requirement of analgesia. J Dhaka Medical College, Vol. 28, No.2, October, 2019, Page 184-189

Background: Mild or subclinical hypothyroidism may coexist with NephroticSyndrome (NS). But persistence of this hypothyroidism is related with remission ofproteinuria. Objectives of the study is to compare thyroid function status (FT4 andTSH) in the atypical and typical NS before and 4 weeks after steroid therapy. Materials and methods: This was a hospital based comparative observational studywith prospective follow up of study subjects. It was carried out in the Department ofPediatrics and in the Department of Nephrology, Chattogram Medical CollegeHospital (CMCH) Chattogram, Bangladesh from January to December’ 2017. A total83 diagnosed admitted cases of initial attack idiopathic NS, aged 1-18 years ofeither sex divided into 2 groups were included. Typically presented NS were in groupA and atypically presented NS were in group B. FT4 and TSH were estimated in allpatients on 2 occasions before and 4 weeks after initiation of steroid therapy andcomparison was done between 2 groups. Results: FT4 level was normal before and after steroid therapy in both typically andatypically presented nephrotic syndrome. Before steroid therapy, mean TSH valuewas found significantly raised in both groups (9.28±5.17 vs 7.26±3.67 μIU/ml).Proportion of subclinical hypothyroidism was statistically similar. After treatmentwith steroid, number of subclinical hypothyroid cases reduced in both groups withreduction of TSH value (3.13±1.14 vs 5.38±2.52 μIU/ml). But significant difference inTSH value was observed in between two groups. There was persistence of subclinicalhypothyroidism after treatment with steroid among 16.6 % (14.2% grade II and2.3% grade I) children with atypically presented NS and which is statisticallysignificant (p=0.006). Conclusion: Subclinical hypothyroidism persists in atypically presented nephroticsyndrome even after treatment with steroid. Chatt Maa Shi Hosp Med Coll J; Vol.19 (1); January 2020; Page 28-32

Microfluidic systems on porous substrates, including paper-based analytical platforms, have attracted significant attention recently, primarily attributed to their diversified applications, ranging from bioanalytical devices for healthcare technologies to green energy generation and flexible electronics. In this short Review, we attempt to provide a concise overview about the fundamental premises of functionalities of these devices, starting from the understanding of flow in single one-dimensional conduit. This can be extended to more-complex systems, where an intrinsic capillary action offers the necessary provisions for continuous maintenance of heterogeneous flow over multiple spatiotemporal scales, which essentially facilitates the needs of specific applications. We discuss a few specific applications as demonstrative examples that are solely triggered by the intrinsic capillary action of the porous media. These specific examples delineate the fact that flexible architecture of the devices, in combination with the inherent capillary-driven phenomena, makes it suitable to meet the desired user-specific demands at affordable costs, rendering them immensely suitable for the low-resource-settings environment.

Most innovations happen at the intersections of disciplines. New products get designed through synergistic integration of multi-disciplinary concepts. For example, in today’s automobiles purely mechanical systems have been replaced by “by-wire” devices that are software controlled, lighter, more efficient, and reliable. While engineering disciplines are merging seamlessly in real world products, academic silos are mostly still intact. At University of Detroit Mercy, we have broken down some silos by launching the Robotics and Mechatronics Systems Engineering major. Mechatronic Systems Modeling is a mandatory course in this major. This course uses a technique of power flow called bond graphs to model mechatronic systems. This technique is not discipline specific and students with different disciplinary background can easily understand and master it. Recently, the use of Simscape, a MATLAB/Simulink tool for physical system modeling has also been added to this course. The use of these two tools in complex system modeling tasks helps students develop an understanding of engineering system behavior by moving beyond the narrow boundaries of individual disciplines. This paper describes the course content and structure, the modeling methods, selected student projects, some of the lessons learned, and several offshoot activities that have resulted from this course.

Developing low-weight, frugal, and sustainable power sources for resource-limited settings appears to be a challenging proposition for the advancement of next-generation sensing devices and beyond. Here, we report the use of centimeter-sized simple wet fabric pieces for electrical power generation by deploying the interplay of a spontaneously induced ionic motion across fabric nanopores due to capillary action and simultaneous water evaporation by drawing thermal energy from the ambient. Unlike other reported devices with similar functionalities, our arrangement does not necessitate any input mechanical energy or complex topographical structures to be embedded in the substrate. A single device is capable of generating a sustainable open circuit potential up to ∼700 mV, which is further scaled up to ∼12 V with small-scale multiplexing (i.e., deploying around 40 numbers of fabric channels simultaneously). The device is able to charge a commercial supercapacitor of ∼0.1 F which can power a white light-emitting diode for more than 1 h. This suffices in establishing an inherent capability of functionalizing self-powered electronic devices and also to be potentially harnessed for enhanced power generation with feasible up-scaling.

The process of localized cleaning of silver sulphide from the silver surface has been investigated in this work. An artificial black encrustation was generated on the silver surface and its laser cleaning was performed using an excimer laser (KrF based) working at a wavelength of 248 nm and pulse width 25 ns. Laser process parameters i.e. laser fluence and number of pulses were used to perform the experiment and after different optical, microstructural, elemental, microhardness and surface topography analysis of the laser ablated zone was performed. The parametric window selected for the excimer laser cleaning were laser fluence (200-400 mJ/cm2), repetition rate 4 Hz and number of pulses (60-300). It was observed that excimer laser is very effective in the cleaning of black encrustation having 6 wt. % of sulphur from the surface without any significant removal of the silver substrate. The fluence value of 260.48 mJ/cm2 was observed as above threshold value for removal of sulphide from the encrusted surface while a fluence of 384.85 mJ/cm2 and 220 pulses showed the maximum removal of sulphur encrustation (0.38 wt. % of sulphur remaining). Formation of the peripheral rim was observed to occur above 280.17 mJ/cm2 of fluence value. The topography of the ablated surface showed a removal of 5-10 um of the sulphide layer from the surface whereas the thickness of the sulphide coating was around 8-10 um. Microhardness value showed a change of microhardness of the silver surface from 75.12 HV0.5 (uncoated parent silver) to 96.07 HV0.5 (centre of the ablated zone).Finally, it was concluded that excimer laser cleaning is a novel method for localized removal of silver sulphide encrustation from silver surface., Comment: 20 pages

Axial gradients in wall elasticity may have significant implications in the deformation and flow characteristics of a narrow fluidic conduit, bearing far-reaching consequences in physiology and bio-engineering. Here, we present a theoretical and experimental framework for fluid-structure interactions in microfluidic channels with axial gradients in wall elasticity, in an effort to arrive at a potential conceptual foundation for in vitro study of mirovascular physiology. Towards this, we bring out the static deformation and steady flow characteristics of a circular microchannel made of polydimethylsiloxane (PDMS) bulk, considering imposed gradients in the substrate elasticity. In particular, we study two kinds of elasticity variations - a uniformly soft (or hard) channel with a central strip that is hard (or soft), and, increasing elasticity along the length of the channel. The former kind yields a centrally constricted (or expanded) deformed profile in response to the flow. The latter kind leads to increasingly bulged channel radius from inlet to outlet in response to flow. We also formulate an analytical model capturing the essential physics of the underlying elastohydrodynamic interactions. The theoretical predictions match favourably with the experimental observations and are also in line with reported results on stenosis in mice. The present framework, thus, holds the potential for acting as a fundamental design basis towards developing in vitro models for micro-circulation, capable of capturing exclusive artefacts of healthy and diseased conditions.

A rapid method for fabrication of micro-channel on glass substrates is introduced and investigated in this paper. Wire-cut electro discharge machining (WEDM) and ultrasonic machining (USM) were used as manufacturing processes for machining the micro-tools and micro-channels, respectively. The copper micro-tool was machined using WEDM and the optimal design of the tool was achieved using Taguchi design of experiment. After overall evaluation criteria (OEC) analysis, the optimum conditions were achieved as Ton as 25 μs, Toff as 6 μs, Ip as 1 A, and Wf as 75 mm/s. Further, it was used for fabrication of micro-tools with different profiles such as square, circular, and zigzag. The fabricated micro-tools were used to machine serpentine micro-channels on glass using USM at various power ratings such as 40, 50, and 60%. After machining, net overcut of the micro-channels were found as 74.65, 75.86, and 81.75 μm for square, circular, and zigzag profiles, respectively.

This paper represents a numerical and experimental investigation of fluids mixing in straight and serpentine micro-channels. These microchannels are fabricated with the help of soft lithography technique. The width of straight and serpentine micro-channels after fabrication is obtained around 335 and 282 µm respectively. Numerical simulations of fluids mixing in micro-channels are performed by solving momentum, continuity and mass diffusion equations. Mixing performance has been evaluated in three average inlet velocities such as 0.001, 0.007 and 0.0167 m/s. The numerical results show that in serpentine micro-channel, an effective mixing has been achieved in almost all the flow conditions whereas in straight channel that is achieved for 0.001 m/s velocity only. Water and water-KMnO4 solution are used as working fluids in this study. The experimental results show that the mixing efficiency of around 95.5, 70.20, and 48.54% has been achieved for straight channel at inlet velocities 0.001, 0.007 and 0.0167 m/s respectively. However, in serpentine micro-channel, the mixing efficiency has been achieved around 97.12, 95.10, and 65.21% at inlet velocities 0.007, 0.0167 and 0.03 m/s respectively. Moreover, the experimental results are compared with the numerical results where it has been observed that the results are quite identical to each other.

This study demonstrates controlled maneuvering of polystyrene particles in a simple microfluidic device by exploiting the underlying electrokinetic phenomena, primarily dielectrophoresis (DEP). The device mainly uses negative DEP force to trap micrometer-sized particles near the positive electrode in a low-conductivity suspension, but also exploits positive DEP force if the conductivity increases. This device furthermore shows flexibility in selective yet localized trapping with low electric field requirements, laying a foundation for flexible preconcentrators in low-cost bioanalytical detection systems for $e.g.$ medical diagnostics.

Enhancing the sensitivity of colorimetric detection in paper-devices is a quintessential step in achieving frugal diagnosis. Here, we demonstrate an effective way of improving the detection sensitivity of paper-based devices, as mediated by electro-kinetic mechanisms. By directly employing blood plasma, we investigate the electro-kinetic clustering of glucose, a neutral molecule in paper devices. Under the influence of uniform electric field, dispersed glucose gets accumulated in the paper strips. Due to the combination of electroosmotic flow and electrophoretic migration, we achieve two-fold increase in the colour intensity for both normal and diabetic samples. This approach is robust and possesses better sensitivity than conventional colorimetric assays and can be easily extended to other body fluid based diagnosis. These results may turn out to be of profound importance in improving the quality of pathological diagnosis in low-cost paper-based point-of-care devices deployed in resourcelimited settings

Diffusion of colored dye on water saturated paper substrates has been traditionally exploited with great skill by renowned water color artists. The same physics finds more recent practical applications in paper based diagnostic devices deploying chemicals that react with a bodily fluid yielding colorimetric signals for disease detection. During spontaneous imbibition through the tortuous pathways of a porous electrolyte saturated paper matrix, a dye molecule undergoes diffusion in a complex network of pores. The advancing front forms a strongly correlated interface that propagates diffusively but with an enhanced effective diffusivity. We measure this effective diffusivity and show that it is several orders of magnitude greater than the free solution diffusivity and has a significant dependence on the solution pH and salt concentration in the background electrolyte. We attribute this to electrically mediated interfacial interactions between the ionic species in the liquid dye and spontaneous surface charges developed at porous interfaces, and introduce a simple theory to explain this phenomenon., 14