Papers by Sanam Pudasaini
Towards the development of paper analytical devices for testing alkaline phosphatase, starch, and urea in milk
International Dairy Journal
Sensors and Actuators B: Chemical, 2020
Precise, automatic and reliable position control of micro-objects such as single particles, biolo... more Precise, automatic and reliable position control of micro-objects such as single particles, biological cells or bio-organisms is critical for applications in biotechnology and tissue engineering. However, conventional acoustofluidic techniques generally lack reliability and automation capability thus are often incapable of building an efficient and automated system where the biological cells need to be precisely manipulated in three dimensions (3D). To overcome these limitations, we developed an acoustofluidic closed-loop control system which is combined with computer vision techniques and standing surface acoustic waves (SSAWs) to implement selective, automatic and precise position control of an object, such as a single cell or microparticle in a microfluidic chamber. Position of the object is in situ extracted from living images that are captured from a video camera. By utilizing the closed-loop control strategy, the object is precisely moved to the desired location in 3D patterns or along designed trajectories by manipulating the phase angle and power signal of the SSAWs. Controlling of breast cancer cells has been conducted to verify the principle and biocompatibility of the control system. This system could be employed to build an automatic system for cell analysis, cell isolation, self-assembling of materials into complex microstructures, or lab-on-chip and organ-on-chip applications.
ELECTROPHORESIS, 2019
We report a microfluidic paper based analytical device implementing ion concentration polarizatio... more We report a microfluidic paper based analytical device implementing ion concentration polarization (ICP) for rapid pre-concentration of Escherichia coli (E. coli) in water. The fabricated device consists of a paper channel with a Nafion membrane and in-built micro wire electrodes to supply electric voltage to induce the ICP effect. E. coli cells were stained with SYTO 9 and fluorescence was used as a sensing method. The device achieved high concentration factor up to 2 10 5 within minutes. The effect of total ion concentration, on ICP and fluorescence intensity was studied. The reported device and method are suitable and effective for detection of E. coli during ballast water quality monitoring, coastal water quality monitoring where high salinity water is present.
ObjectivesAntimicrobial resistance (AMR) is a global public health threat. Surveillance of AMR re... more ObjectivesAntimicrobial resistance (AMR) is a global public health threat. Surveillance of AMR requires affordable, rapid, and user-friendly diagnostic method. Our aim was to develop a low-cost thermocycler to perform polymerase chain reaction (PCR).MethodsWe developed a smartphone-operated PCR thermal cycler using locally available recycled materials. The thermal cycler was used for the amplification for three bacterial genes - bla-TEM and bla-CTXM and 16s rRNA in human urine samples. The performance of custom-built thermal cycler was compared with the commercial one.ResultsThe thermal cycler was portable (<1kg weight), required 12 V power supply, 25 µL of solution, and cost only USD50.0. Temperature and time conditions were instructed using a custom-built smartphone application. The ramping rate of was 0.23°C for heating and 0.43°C for cooling, set temperatures were within ± 0.5 °C of target showing a good thermal stability. The antibiotic sensitivity test of human urine sample...
ACS Omega
Paper analytical devices (PADs) are a class of low-cost, portable, and easy-touse platform for se... more Paper analytical devices (PADs) are a class of low-cost, portable, and easy-touse platform for several analytical tests in clinical diagnostics, environmental pollution monitoring, and food and drug safety screening. These devices are primarily made from cellulosic paper. Considering the importance of eco-friendly and local or distributed manufacturing of devices realized during the COVID-19 pandemic, we systematically studied the potential of handmade Nepali paper to be used in fabricating PADs in this work. We characterized five different handmade papers made from locally available plant fibers using an eco-friendly method and used them to fabricate PADs for determining the drug quality. The thickness, grammage, and apparent density of the paper samples ranged from 198.6 to 314.8 μm, 49.1 to 117.8 g/m 2 , and 0.23 to 0.43 g/cm 3 , respectively. The moisture content, water filtration, and wicking speed ranged from 5.8 to 7.1%, 35.7 to 156.7, and 0.062 to 0.124 mms −1 , respectively. Furthermore, the water contact angle and porosity ranged from 76.6 to 112.1°and 79 to 83%, respectively. The best paper sample (P5) was chosen to fabricate PADs for the determination of metformin, an antidiabetic drug. The metformin assay on PADs followed a linear range from 0.0625 to 0.5 mg/mL. The assay had a limit of detection and limit of quantitation of 0.05 and 0.18 mg/mL, respectively. The average amount of metformin concentration in samples collected from local pharmacies (n = 20) was 465.6 ± 15.1 mg/tablet. When compared with the spectrophotometric method, PAD assay correctly predicted the concentration of 90% samples. The PAD assay on handmade paper may provide a low-cost and easy-to-use system for screening the quality of drugs and other point-of-need applications.
Recent trends on the detection of intestinal parasites
Parasitic infection by protozoans and helminths remains one of the major public health problems i... more Parasitic infection by protozoans and helminths remains one of the major public health problems in developing countries due to unavailability of safe drinking water and poor sanitary conditions. There are several methods for the detection of helminths and intestinal protozoa. The choice of a method depends on various factors such as the nature of a matrix, affordability, and appropriateness. In addition, the lack of a globally recognized method for detecting intestinal parasites in real samples poses a challenge for the comparative evaluation of parasites in different sample matrices and different locations. In this paper, we thoroughly reviewed commonly used methods and emerging techniques for the detection and quantification of intestinal parasites in various sample matrix. We focused primarily on papers published in last one decade and most tested parasites such as <em>Ascaris lumbricoides</em>, <em>Ancylostoma duodenale</em>, <em>Necator americanicu...
Abstract-Conventionalturbines are mostly reaction and impulse type or both. Often technical chall... more Abstract-Conventionalturbines are mostly reaction and impulse type or both. Often technical challenge faced by conventional turbines in Himalaya is erosion by sediment. Financial feasibility of power plants is depended upon innovations to prevent erosion of mechanical equipments or alternatives which better handle these conditions. Tesla turbine is an unconventional turbine that uses fluid properties such as boundary layer and adhesion of fluid on series of smooth disks keyed to a shaft. It has been garnering interest as Pico turbine where local communities could manage such stations in low capital. It provides a simple design which can be produced locally and maintained at low cost. It can be useful in plants for pumping of water and other viscous fluids. Tesla Turbine pump has been used as a blood pump. Due to its uniqueness it has its own cliché uses giving importance to identify the scope of use of Tesla Turbine in Nepal. This paper is presented in context of research project at...
Abstract- Having the hydropower potential of 42000 MW and other immense source of electrical ener... more Abstract- Having the hydropower potential of 42000 MW and other immense source of electrical energy, Nepal still faces the problem of load shedding. And this problem has catastrophic consequences as electricity rules the routine of our busy lives from micro to macro level; say to charge a cell phone (essence of today’s lives) or to fill tank by water for numerous purposes. However, the situation, when the daily busy schedule and the problem of load shedding intersect, can be addressed. The paper presents a system of an automatic water level controller with SMS notification. The project was carried out to assist user in load shedding based country like Nepal. SMS notification was added to automatic controller system so that water can be managed by user during load shedding. Two systems work synergistically; automatic level controller system and SMS system. The program was developed in Arduino program developing environment and uploaded to the Microcontroller. Water level in the syste...
The COVID-19 pandemic has highlighted the need of eco-friendly and locally or distributed manufac... more The COVID-19 pandemic has highlighted the need of eco-friendly and locally or distributed manufacturing of diagnostic and safety products. Here, we characterized five handmade papers for their potential application to make paper analytical device (PADs). The handmade papers were made from locally available plant fiber using eco-friendly method. Thickness, grammage, and apparent density of the paper samples ranged from 198 μm to 314 μm, 49 g/m2 to 117.8 g/m2, and 0.23 to 0.39 g/cm3, respectively. Moisture content, water filtration and wicking speed ranged from 5.2% to 7.1%, 35.7 to 156.7, and 0.062 to 0.124 mms-1, respectively. Further, water contact angle and porosity ranged from 76˚ to 112˚ and 79% to 83%, respectively. The best paper sample one was chosen to fabricate PADs which were used for the determination of metformin. The metformin assay on PADs followed linear range from 0.0625 to 0.5 mg/mL. The assay had limit of detection and limit of quantitation of 0.05 mg/mL and 0.18 m...
Continuous flow microfluidic cell inactivation with the use of insulating micropillars for multiple electroporation zones
ELECTROPHORESIS, 2019
Electroporation is a powerful tool for inactivating cells and transfecting biological cells and h... more Electroporation is a powerful tool for inactivating cells and transfecting biological cells and has applications in biology, genetic engineering, medicine, environment, and many others. We report a new continuous flow device embedded with insulating micropillars to achieve better performance of cell inactivation. The use of micropillars creates multiple electroporation zones with enhanced local electric field strengths. Using a model solution of Saccharomyces cerevisiae, we examined the inactivation performance of the device under various applied electric voltages and flow rates. Results from the numerical simulations and experiments showed that even with an induced transmembrane potential of 0.58 V, close to 63% of cell inactivation was achieved at a flow rate of 2.5 mL/h. This was higher than the 24% cell inactivation observed for a reference device without micropillars that was subjected to the same conditions.
Conventional turbines are mostly reaction and impulse type or both. Often technical challenge fac... more Conventional turbines are mostly reaction and impulse type or both. Often technical challenge faced by conventional turbines in Himalaya is erosion by sediment. Financial feasibility of power plants is depended upon innovations to prevent erosion of mechanical equipments or alternatives which better handle these conditions. Tesla turbine is an unconventional turbine that uses fluid properties such as boundary layer and adhesion of fluid on series of smooth disks keyed to a shaft. It has been garnering interest as Pico turbine where local communities could manage such stations in low capital. It provides a simple design which can be produced locally and maintained at low cost. It can be useful in plants for pumping of water and other viscous fluids. Tesla Turbine pump has been used as a blood pump. Due to its uniqueness it has its own cliché uses giving importance to identify the scope of use of Tesla Turbine in Nepal. This paper is presented in context of research project at Kathman...
This paper presents an electroporation device with high bacterial inactivation performance (~4.75... more This paper presents an electroporation device with high bacterial inactivation performance (~4.75 log removal). Inside the device, insulating silica microbeads are densely packed between two mesh electrodes that enable enhancement of the local electric field strength, allowing improved electroporation of bacterial cells. The inactivation performance of the device is evaluated using two model bacteria, including one Gram-positive bacterium (Enterococcus faecalis) and one Gram-negative bacterium (Escherichia coli) under various applied voltages. More than 4.5 log removal of bacteria is obtained for the applied electric field strength of 2 kV/cm at a flowrate of 4 mL/min. The effect of microbeads on the inactivation performance is assessed by comparing the performance of the microbead device with that of the device having no microbeads under same operating conditions. The comparison results show that only 0.57 log removal is achieved for the device having no microbeads—eightfold lower ...
Computational Fluid Dynamics (CFD) analysis of Pelton runner of Khimti Hydro-power Project of Nepal
Nepal, with its diverse topological features and rich water resources, boasts a huge hydro energy... more Nepal, with its diverse topological features and rich water resources, boasts a huge hydro energy potential with ability to generate 42000 MW of electricity. Higher mountains providing higher heads and seasonal variation in flow rates appropriates thechoice of Pelton turbines for hydro power projects in the country. The flat efficiency curve maintained by Pelton turbine on wide operating ranges counters for the seasonal variations seen in the rivers of Nepal. However, the design and manufacturing cost of actual Pelton prototype is very high. Redesigning and optimization process becomes even more costly and time consuming. However, the introduction of numerical tools has changed the design engineer's procedures in the process of new Pelton turbines design. The research was carried out in order to perform CFD analysis of Pelton runner of Khimti Hydropower. The runner was scaled down by meeting IEC 60193 standard. Whole simulation was performed in ANSYS-CFX. The results obtained fr...
Large‐Scale Fabrication of 3D Scaffold‐Based Patterns of Microparticles and Breast Cancer Cells using Reusable Acoustofluidic Device
Advanced Engineering Materials, 2021
Having the hydropower potential of 42000 MW and other immense source of electrical energy, Nepal ... more Having the hydropower potential of 42000 MW and other immense source of electrical energy, Nepal still faces the problem of load shedding. And this problem has catastrophic consequences as electricity rules the routine of our busy lives from micro to macro level; say to charge a cell phone (essence of today's lives) or to fill tank by water for numerous purposes. However, the situation, when the daily busy schedule and the problem of load shedding intersect, can be addressed. The paper presents a system of an automatic water level controller with SMS notification. The project was carried out to assist user in load shedding based country like Nepal. SMS notification was added to automatic controller system so that water can be managed by user during load shedding. Two systems work synergistically; automatic level controller system and SMS system. The program was developed in Arduino program developing environment and uploaded to the Microcontroller. Water level in the system is c...
Microfluidics based electroporation for inactivation of microorganisms
Enhanced sample pre-concentration by ion concentration polarization on a paraffin coated converging microfluidic paper based analytical platform
Biomicrofluidics
Microfluidic paper-based analytical devices (μPADs) represent a modest and feasible alternative f... more Microfluidic paper-based analytical devices (μPADs) represent a modest and feasible alternative for conventional analytical methods. However, the inadequate sensitivity of these devices limits the possible applications of μPADs. In this scenario, inducing ion concentration polarization (ICP) on μPADs has shown promise to overcome this limitation by preconcentrating the analytes of interest. Here, we report a μPAD implementing ICP using an off-shelf Nafion® membrane as the perm selective membrane. Two types of devices with a geometrical configuration of a straight channel converging at the middle connecting to circular reservoirs at the end of channels were fabricated. The devices are comprised of a single input channel and an absorption channel. The Nafion membrane is attached to the absorption channel of the device, which is encased by heating with paraffin films at both sides to lower the electro-osmotic flow generated by an applied DC electric field that is needed for ICP. The field induced ICP enables obtaining a maximum concentration factor of more than 2000 folds for fluorescein sodium salt solution on the μPAD. Also, since evaporation of the sample solution was reported to be of great influence on the concentration factor, we analyze the effect of sample solution evaporation on sample preconcentration. Furthermore, our reported fabrication method for μPAD can lower the fabrication cost down to 0.3 USD. This device shows the potential to be developed for serving as a diagnostic and environmental monitoring platform.
Bacterial inactivation via microfluidic electroporation device with insulating micropillars
Electroporation is a promising method to inactivate cells and it has wide applications in medical... more Electroporation is a promising method to inactivate cells and it has wide applications in medical science, biology and environmental health. Here, we investigate the bacteria inactivation performance of two different microfluidic electroporation devices with rhombus and circular micropillars used for generating locally enhanced electric field strength. Experiments are carried out to characterize the inactivation performance (i.e., the log removal efficiency) of two types of bacteria: Escherichia coli (E. coli, gram‐negative) and Enterococcus faecalis (E. faecalis, gram‐positive) in these two microfluidic devices. We find that under the same applied electric field, the device with rhombus micropillars performs better than the device with circular micropillars for both E. coli and E. faecalis. Numerical simulations show that due to the corner‐induced singularity effect, the maximum electric field enhancement is higher in the device with rhombus micropillars than that in the device wit...
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Papers by Sanam Pudasaini