Development of low-cost micro-fabrication procedures for planar micro-thermoelectric generators based on thin-film technology for energy harvesting applications.

With the rapid proliferation of portable and wearable electronics, energy autonomy through efficient energy harvesting has become paramount. Thermoelectric generators (TEGs) stand out as promising candidates due to their silent operation, high reliability, and maintenance-free nature. This paper presents the design, fabrication, and analysis of a micro-scale TEG for powering such devices. A planar configuration was employed for its inherent miniaturization advantages. Finite element analysis using ANSYS reveals that a double-layer device under a 50 K temperature gradient generates an impressive open-circuit voltage of 1417 mV and a power output of 2.4 µW, significantly exceeding its single-layer counterpart (226 mV, 0.12 µW). Validation against the analytical model results yields errors within 2.44% and 2.03% for voltage and power, respectively. Furthermore, a single-layer prototype fabricated using paper shadow masks and sputtering deposition exhibits a voltage of 131 mV for a 50 K temperature difference, thus confirming the feasibility of the proposed design. This work establishes a foundation for developing highly efficient micro-TEGs for powering next-generation portable and wearable electronics.

Separation of microalgae from bacterial contaminants using spiral microchannel in the presence of a chemoattractant.

Cell separation using microfluidics has become an effective method to isolate biological contaminants from bodily fluids and cell cultures, such as isolating bacteria contaminants from microalgae cultures and isolating bacteria contaminants from white blood cells. In this study, bacterial cells were used as a model contaminant in microalgae culture in a passive microfluidics device, which relies on hydrodynamic forces to demonstrate the separation of microalgae from bacteria contaminants in U and W-shaped cross-section spiral microchannel fabricated by defocusing CO2 laser ablation. At a flow rate of 0.7 ml/min in the presence of glycine as bacteria chemoattractant, the spiral microfluidics devices with U and W-shaped cross-sections were able to isolate microalgae (Desmodesmus sp.) from bacteria (E. coli) with a high separation efficiency of 92% and 96% respectively. At the same flow rate, in the absence of glycine, the separation efficiency of microalgae for U- and W-shaped cross-sections was 91% and 96%, respectively. It was found that the spiral microchannel device with a W-shaped cross-section with a barrier in the center of the channel showed significantly higher separation efficiency. Spiral microchannel chips with U- or W-shaped cross-sections were easy to fabricate and exhibited high throughput. With these advantages, these devices could be widely applicable to other cell separation applications, such as separating circulating tumor cells from blood.

Design and development of a portable low-cost QCM-based system for liquid biosensing.

Quartz crystal microbalance (QCM) is a versatile sensing platform that has gained increasing attention for its use in bioapplications due to its high sensitivity, real-time measurement capabilities, and label-free detection. This article presents a portable QCM system for liquid biosensing that uses a modified Hartley oscillator to drive 14 mm-diameter commercial QCM sensors. The system is designed to be low-cost, easy to use, and highly sensitive, making it ideal for various bioapplications. A new flow cell design to deliver samples to the surface of the sensor has been designed, fabricated, and tested. For portability and miniaturization purposes, a micropump-based pumping system is used in the current system. The system has a built-in temperature controller allowing for accurate frequency measurements. In addition, the system can be used in benchtop mode. The capability of the present system to be used in liquid biosensing is demonstrated through an experimental test for sensitivity to changes in the viscosity of glycerol samples. It was found to have a sensitivity of 263.51 Hz/mPa.s using a 10 MHz QCM sensor. Future work regarding potential applications was suggested.

Fabrication of Spiral Low-Cost Microchannel with Trapezoidal Cross Section for Cell Separation Using a Grayscale Approach.

Trapezoidal cross-sectional spiral microfluidic channels showed high resolution and throughput in cell separation in bio-applications. The main challenges are the complexity and high cost of the fabrication process of trapezoidal cross-sectional channels on the micro-scale. In this work, we present the application of grayscale in microfluidic channel design to overcome the complexity of the fabrication process. We also use direct engraving with a CO2 laser beam on polymethyl methacrylate (PMMA) material to drastically reduce the microfluidic chip's cost (to <30 cents) and fabrication time (to 20 min). The capability of the present fabrication methodology for cell sorting applications is demonstrated through experimental tests for the separation of white blood cells (WBCs) from whole blood at different dilution factors. The experimental results indicated that an 800 µL/min flow rate provided the optimal separation efficiency using the fabricated chip. A 90.14% separation efficiency at 1% hematocrit diluted blood sample was reported.

A Developed Jerk Sensor for Seismic Vibration Measurements: Modeling, Simulation and Experimental Verification.

Acceleration-based sensors are widely used in indicating the severity of damage caused to structural buildings during dynamic events. The force rate of change is of interest when investigating the effect of seismic waves on structural elements, and hence the calculation of the jerk is necessary. For most sensors, the technique used for measuring the jerk (m/s3) is based on differentiating the time-acceleration signal. However, this technique is prone to errors especially in small amplitude and low frequency signals, and is deemed not suitable when online feedback is required. Here, we show that direct measurement of the jerk can be achieved using a metal cantilever and a gyroscope. In addition, we focus on the development of the jerk sensor for seismic vibrations. The adopted methodology optimized the dimensions of an austenitic stainless steel cantilever and enhanced the performance in terms of sensitivity and the jerk measurable range. We found, after several analytical and FE analyses, that an L-35 cantilever model with dimensions 35 × 20 × 0.5 (mm3) and a natural frequency of 139 (Hz) has a remarkable performance for seismic measurements. Our theoretical and experimental results show that the L-35 jerk sensor has a constant sensitivity value of 0.05 ((deg/s)/(G/s)) with ±2% error in the seismic frequency bandwidth of 0.1~40 (Hz) and for amplitudes in between 0.1 and 2 (G). Furthermore, the theoretical and experimental calibration curves show linear trends with a high correlation factor of 0.99 and 0.98, respectively. These findings demonstrate the enhanced sensitivity of the jerk sensor, which surpasses previously reported sensitivities in the literature.

Association of Modified Sequential Organ Failure Assessment (MSOFA) Score and C-reactive protein (CRP) With the Outcome of Patients under Mechanical Ventilation.

Different scoring systems has been discovered in medical practice, more specifically for ICU treatment, are designed to objectively quantify physiologic derangements and comorbid conditions for estimating mortality, length of stay and ICU resource use. This observational and descriptive study was carried out in the ICU, BSMMU, Dhaka, during March 2014 to May 2016, to determine the association of MSOFA score, CRP level with the outcome of patients on mechanical ventilation as well as compare the MSOFA and CRP combined with MSOFA alone. For this purpose, a total of 60 critically ill patients admitted in the above hospital were included in this study. Patients with an ICU stay of less than 48 hours, readmissions not considered, known case of neuromuscular disease, connective tissue disorder, renal disease and pregnancy and Patients refused to give written consent were excluded from the study. Patients who had MSOFA ≥7, their mean duration of ICU stay were 10.9±6.7 days and mean duration of mechanical ventilation 7.63±5.2 days. Patients who had CRP >11mg/L, their mean duration of ICU stay was 10.8±7.2 days and mean duration of mechanical ventilation was 7.35±5.1 days. Patients who had MSOFA score ≥7 and CRP ≥11mg/L with mean duration of ICU stay was 10.82±7.2 days and mean duration of mechanical ventilation was 7.12±5.2 days. 69.2% patients were CRP status positive (≥11) in death group and 33.3% had alive group. 92.3% patients were Positive (CRP ≥7 or MSOFA ≥11) in death group and 14.3% had alive group. MSOFA identified true positive 32 cases for death, false positive 5 cases, false negative 7 cases and true negative 16 cases confirmed by patient's outcome. CRP level identified true positive 27 cases for death, false positive 7 cases, false negative 12 cases and true negative 14 cases confirmed by patients outcome. Combined (CRP ≥11mg/L and MSOFA score ≥7) identified true positive 33 cases for death, false positive 1 case, false negative 6 cases and true negative 20 cases confirmed by patient's outcome. We concluded that there is a positive correlation (r=0.323; p=0.014) between CRP status with MSOFA score, positive correlation (r=0.402; p=0.002) between MSOFA score with MSOFA score and CRP combined and a positive correlation (r=0.999; p=0.001) between CRP level with MSOFA score and CRP combined.

Effect of Low Hydroxyapatite Loading Fraction on the Mechanical and Tribological Characteristics of Poly(Methyl Methacrylate) Nanocomposites for Dentures.

Denture base materials need appropriate mechanical and tribological characteristics to endure different stresses inside the mouth. This study investigates the properties of poly(methyl methacrylate) (PMMA) reinforced with different low loading fractions (0, 0.2, 0.4, 0.6, and 0.8 wt.%) of hydroxyapatite (HA) nanoparticles. HA nanoparticles with different loading fractions are homogenously dispersed in the PMMA matrix through mechanical mixing. The resulting density, Compressive Young's modulus, compressive yield strength, ductility, fracture toughness, and hardness were evaluated experimentally; the friction coefficient and wear were estimated by rubbing the PMMA/HA nanocomposites against stainless steel and PMMA counterparts. A finite element model was built to determine the wear layer thickness and the stress distribution along the nanocomposite surfaces during the friction process. In addition, the wear mechanisms were elucidated via scanning electron microscopy. The results indicate that increasing the concentration of HA nanoparticles increases the stiffness, compressive yield strength, toughness, ductility, and hardness of the PMMA nanocomposite. Moreover, tribological tests show that increasing the nanoparticle weight fraction considerably decreases the friction coefficient and wear loss.

Determination of damping coefficient of soft tissues using piezoelectric transducer.

Measuring viscoelastic properties of soft tissues becomes a new biomarker in the medical diagnosis field. It can help in early diagnosis and related fields, such as minimally-invasive-surgery (MIS) applications and cell mechanics. The current work presents a tactile sensor for measuring the damping coefficient of the soft tissues. The proposed sensor can be miniaturized easily and used in MIS applications. Besides the proposed sensor, a mathematical model, based on Jacobsen's approach, is built to calculate the damping coefficient of the specimens and the surrounding. These damping sources significantly influence the proposed sensor, such as air damping and hysteretic damping. The sensor system principally depends on a piezoelectric transducer, which is cheap, commonly available, and easily integrated into MEMS. To conceptually prove the sensor feasibility, silicon rubber samples with different stiffnesses have been fabricated and tested by the new sensor. The obtained results prove the newly proposed sensor's capability to differentiate the damping coefficients for soft materials effectively.

Translating complexity and heterogeneity of pancreatic tumor: 3D in vitro to in vivo models.

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive type of cancer with an overall survival rate of less than 7-8%, emphasizing the need for novel effective therapeutics against PDAC. However only a fraction of therapeutics which seemed promising in the laboratory environment will eventually reach the clinic. One of the main reasons behind this low success rate is the complex tumor microenvironment (TME) of PDAC, a highly fibrotic and dense stroma surrounding tumor cells, which supports tumor progression as well as increases the resistance against the treatment. In particular, the growing understanding of the PDAC TME points out a different challenge in the development of efficient therapeutics - a lack of biologically relevant in vitro and in vivo models that resemble the complexity and heterogeneity of PDAC observed in patients. The purpose and scope of this review is to provide an overview of the recent developments in different in vitro and in vivo models, which aim to recapitulate the complexity of PDAC in a laboratory environment, as well to describe how 3D in vitro models can be integrated into drug development pipelines that are already including sophisticated in vivo models. Hereby a special focus will be given on the complexity of in vivo models and the challenges in vitro models face to reach the same levels of complexity in a controllable manner. First, a brief introduction of novel developments in two dimensional (2D) models and ex vivo models is provided. Next, recent developments in three dimensional (3D) in vitro models are described ranging from spheroids, organoids, scaffold models, bioprinted models to organ-on-chip models including a discussion on advantages and limitations for each model. Furthermore, we will provide a detailed overview on the current PDAC in vivo models including chemically-induced models, syngeneic and xenogeneic models, highlighting hetero- and orthotopic, patient-derived tissues (PDX) models, and genetically engineered mouse models. Finally, we will provide a discussion on overall limitations of both, in vitro and in vivo models, and discuss necessary steps to overcome these limitations to reach an efficient drug development pipeline, as well as discuss possibilities to include novel in silico models in the process.

CO2 Laser Fabrication of PMMA Microfluidic Double T-Junction Device with Modified Inlet-Angle for Cost-Effective PCR Application.

The formation of uniform droplets and the control of their size, shape and monodispersity are of utmost importance in droplet-based microfluidic systems. The size of the droplets is precisely tuned by the channel geometry, the surface interfacial tension, the shear force and fluid velocity. In addition, the fabrication technique and selection of materials are essential to reduce the fabrication cost and time. In this paper, for reducing the fabrication cost Polymethyl methacrylate (PMMA) sheet is used with direct write laser technique by VERSA CO2 laser VLS3.5. This laser writing technique gives minimum channel width of about 160   µ m , which limit miniaturizing the droplet. To overcome this, modification on double T-junction (DTJ) channel geometry has been done by modifying the channel inlets angles. First, a two-dimensional (2D) simulation has been done to study the effect of the new channel geometry modification on droplet size, droplets distribution inside the channel, and its throughput. The fabricated modified DTJ gives the minimum droplet diameter of 39 ± 2   µ m , while DTJ channel produced droplet diameter of 48 ± 4   µ m at the same conditions. Moreover, the modified double T-junction (MDTJ) decreases the variation in droplets diameter at the same flow rates by 4.5 - 13 % than DTJ. This low variation in the droplet diameter is suitable for repeatability of the DNA detection results. The MDTJ also enhanced the droplet generation frequency by 8 - 25 % more than the DTJ channel. The uniformity of droplet distribution inside the channel was enhanced by 3 - 20 % compared to the DTJ channel geometry. This fabrication technique eliminates the need for a photomask and cleanroom environment in addition shortening the cost and time. It takes only 20   min for fabrication. The minimum generated droplet diameter is within 40   µ m with more than 1000 droplets per second (at 10   mL / h . oil flow rate). The device is a high-throughput and low-cost micro-droplet formation aimed to be as a front-end to a dynamic droplet digital PCR (ddPCR) platform for use in resource-limited environment.

Design Procedure and Experimental Verification of a Broadband Quad-Stable 2-DOF Vibration Energy Harvester.

Vibration-based energy harvesters brought the idea of self-powered sensors to reality in the past few years. Many strategies to improve the performance of linear vibration energy harvesters that collect energy over a limited bandwidth have been proposed. In this paper, a bi-stable two degrees of freedom (2-DOF) cut-out vibration energy harvester employing a pair of permanent magnets is designed through a proposed design methodology. Based on this methodology, the nonlinear harvesters can be optimally designed such that the bandwidth can be widened for a targeted output voltage. The proper selection of the harvester parameters as well as the gap distances between the tip and the fixed magnets are the bases of this methodology. The mathematical modeling of the proposed harvester and the formula for the potential energy between the tip and the fixed magnets are presented. Additionally, to enhance the performance of the bi-stable energy harvester (BEH), a quad-stable energy harvester (QEH) was configured by adding more fixed magnets. Experiments were performed to validate the numerical simulations and the results showed that, the simulation and experimental results are consistent. The results indicate that, the QEH covers a wider bandwidth than the BEH and based on a figure of merit the QEH shows the best performance among many harvesters presented in the literature.

Effect of topical mometasone furoate on adenoidal lymphoid tissue: a light microscopic study.

BACKGROUND: Adenoid hypertrophy is a common cause of upper airway obstruction, and adenoidectomy is one of the most frequently performed operations in children. Topical nasal steroids can act directly on nasopharyngeal lymphoid tissue to decrease its reactive inflammatory changes and potentially reduce its size. OBJECTIVE: To study the light microscopic changes in adenoidal lymphoid tissue after one month of topical steroid use. METHODS: Twenty-six children with adenoid hypertrophy grade 3 scheduled for adenoidectomy were randomly divided into two equal groups: one group received mometasone furoate aqueous nasal spray (Nasonex) 100 mcg/day for four weeks, and a control group received nasal normal saline 0.9 per cent for four weeks. The removed adenoids were examined histopathologically. RESULTS: Adenoidal tissue from the mometasone group had less reactive germinal centres and less spongiosis compared to the control group. The latter showed proliferating, reactive, variable sized and shaped lymphoid follicles, with congested blood vessels in the interfollicular areas. CONCLUSION: The use of intranasal mometasone furoate aqueous nasal spray (Nasonex) for one month reduced adenoidal tissue reactive cellular changes and its vascularity. This is, however, a pilot study; a longer treatment period is needed to assess the effect of treatment on adenoidal size.

Endoscopic push-through technique compared to microscopic underlay myringoplasty in anterior tympanic membrane perforations.

BACKGROUND: Microscopic myringoplasty is the most frequently performed procedure for repairing tympanic membrane perforations. The endoscopic transcanal approach bypasses the narrow ear canal segment and provides a wider view. METHODS: An open-label randomised clinical trial was conducted on 56 patients with small anterior tympanic membrane perforations. Perforations were repaired with an endoscopic push-through technique (n = 28) or a microscopic underlay technique (n = 28). Follow up was conducted using endoscopic examination and pure tone audiometry three months' post-operatively. RESULTS: Graft success rate was 92.9 per cent in the endoscopic group versus 85.7 per cent in the microscopic group. The corresponding pre-operative mean air-bone gaps were 17.4 dB and 18.5 dB, improving to 6.1 dB and 9.3 dB post-operatively (p > 0.05). Mean air-bone gap closure was 11.4 dB in the endoscopic group and 9.2 dB in the microscopic group (p > 0.05). Mean operative time and estimated blood loss were 37.0 minutes and 29 ml in the endoscopic group, versus 107 minutes and 153 ml in the microscopic group (both p < 0.05). CONCLUSION: The endoscopic push-through technique for anterior tympanic membrane perforations is as effective as microscopic underlay myringoplasty; furthermore, it is less invasive and takes less operative time.

Evaluation of Maternal Health Service Indicators in Urban Slum of Bangladesh.

BACKGROUND: A continuous influx of poor people to urban slums poses a challenge to Bangladesh's health system as it has failed to tackle maternal morbidity and mortality. BRAC is the largest non-governmental organisation in Bangladesh. BRAC has been working to reduce maternal, neonatal and under-five children morbidity and mortality of slum dwellers in cities. BRAC has been doing this work for a decade through a programme called MANOSHI. This programme provides door-to-door services to its beneficiaries through community health workers (CHWs) and normal delivery service through its delivery and maternity centres. BRAC started the 'MANOSHI' programme in Narayanganj City Corporation during 2011 to address maternal, neonatal and child health problems facing slum dwellers. We investigated the existing maternal health-service indicators in the slums of Narayanganj City Corporation and compared the findings with a non-intervention area. METHODS: This cross-sectional study was conducted during 2012, in 47 slums of Narayanganj City Corporation as intervention and 10 slums of Narsingdi Sadar Municipality as comparison area. A total of 1206 married women, aged 15-49 years, with a pregnancy outcome in the previous year were included for interview. Data on socio-demographic characteristics, reproductive and maternal health-care practices like use of contraceptive methods, antenatal care (ANC), delivery care, postnatal care (PNC) were collected through a structured questionnaire. The chi-square test, Student t test, Mann Whitney U-test, factor analysis and log-binominal test were performed by using STATA statistical software for analysing data. RESULTS: The activities of BRAC CHWs significantly improved four or more ANC (47% vs. 21%; p<0.000) and PNC (48% vs. 39%; p<0.01) coverage in the intervention slums compared to comparison slums. Still, about half of the deliveries in both areas were attended at home by unskilled birth attendants, of which a very few received PNC within 48 hours after delivery. The poorest and illiterate women received fewer maternal health services from medically trained providers (MTPs). The poorest had a lower likelihood of receiving services from MTPs during delivery complications. CONCLUSION: The MANOSHI programme service coverage for delivery care and PNC-checkup for women who prefer home delivery needs to be improved. For sustainable improvement of maternal health outcomes in urban slums, the programme needs to facilitate access to services for poor and illiterate women.

Correlation of obstructive sleep apnoea and laryngopharyngeal reflux: phmetry study.

OBJECTIVE: To study the correlation of obstructive sleep apnoea (OSA) and laryngopharyngeal reflux (LPR). DESIGN: A descriptive study. SETTING: Suez Canal University Hospital, Ismailia, Egypt. PATIENTS: 62 patients with polysomnography confirmed OSA. INTERVENTION: Patients were evaluated with ambulatory 24-h double channel pH monitoring. RESULTS: Mean reflux symptom index in the study group was 9 ± 5.5, and it was > 13 in all patients with severe OSA. Signs of LPR reflux were present in 34 (55%) patients. Abnormal reflux was detected in the distal oesophagus in 41 patients (66%) and in the proximal oesophagus in 21 patients (34%). Patients with severe OSA had significantly higher nocturnal LPR reflux episodes compared to patients with mild disease (P < .05). Number of reflux episodes and total duration of reflux during sleep are significantly correlated to degree of OSA (P < .05). No difference was found in relation to age or sex. Daytime reflux was not related to the degree of obstructive sleep apnoea (P > .05). CONCLUSION: LPR is common in patients with OSA. Patients with severe OSA have significantly higher nocturnal LPR. This should be considered when treating this group of patients.

Amelioration of some immunological disorders caused by the faeces of the dominant true house dust mites in El-Minia Governorate, Egypt.

BACKGROUND: House dust mites (HDMs) faeces are the main factor involved in respiratory disorder. The true HDMs, Dermatophagoides pteronyssinus and D. farinae, detected in the samples collected from the house dust are the most important causes of allergic disorders such as asthma. OBJECTIVE: The aim of this investigation was to study the curcuma and karkade amelioration of the allergenic immunological disorder, especially some cytokines, IgE and ROS, caused by the faeces of the dominant true HDM, D. pteronyssinus and D. farinae in valley and desert houses in EL-Minia Governorate, respectively. METHODS: HDM cultures, faeces isolation, plant extraction and ELISA techniques were used. Male albino rats were classified into control, inhaled, and treated groups. RESULTS: The present immunological study on the dominant allergenic true HDMs, D. pteronyssinus and D. farinae, revealed that significantly higher serum levels of TNF-α, IL-1ß, IL-4, IL-13 and IgE were found in rats treated with both D. pteronyssinus and D. farinae faeces than the other groups. In addition, statistical analysis of ROS data showed significant difference between the curcuma- and karkade-treated groups and either the control or the faeces-treated groups (P<0.05). CONCLUSIONS: Some immunological disturbances caused by repeated exposure to the faeces of two dominant allergenic true HDM species (D. pteronyssinus and D. farinae) in the valley and desert houses could be ameliorated by curcuma and karkade.

Outcome evaluation of clarithromycin, metronidazole and lansoprazole regimens in Helicobacter pylori positive or negative children with resistant otitis media with effusion.

OBJECTIVE: To compare the efficacy of two treatment regimens among Helicobacter pylori stool antigen positive children suffering from resistant otitis media with effusion. METHODS: The study comprised 258 children with bilateral otitis media with effusion; 134 were positive for H pylori stool antigen, and were equally and randomly allocated to the control group or study group. The control group received standard otitis media with effusion therapy (amoxicillin and clavulanate), while the study group received standard H pylori triple therapy (clarithromycin, metronidazole and lansoprazole). RESULTS: In the control group, there was a marked clinical response to treatment in 33 of the 67 children (49.3 per cent). In the study group, there was a marked response in a significantly higher number of children (46 out of 67, 68.7 per cent). The 124 H pylori stool antigen negative children not included in the 2 aforementioned groups received amoxicillin and clavulanate, and a marked response in symptoms was evident in 98 of these children (79 per cent). CONCLUSION: H pylori infection may lead to resistance to traditional otitis media with effusion treatment in some cases. H pylori eradication is associated with a high cure rate.