Simulation of droplet generation through electrostatic forces

Rahman, Khalid,Ko, Jeong-Beom,Khan, Saleem,Kim, Dong-Soo,Choi, Kyung-Hyun 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1

This paper represents the multiphysics simulation of droplet generation of ink containing conductive nano-particles through electrostatic forces on substrate. The main focus is to investigate the phenomena by generating the drops through a nozzle with the help of electrostatic forces. The electrostatic based deposition system has vast application in printed electronics and biotechnology. In electrostatic deposition mechanism for droplet generation, a strong electric potential is applied at the tip of the nozzle; due this electric potential, the liquid containing the nano-particles experience strong electrostatic static forces at the interface with the air (at the tip of the nozzle). When these electrostatic forces exceed the internal (viscous forces) and external forces (surface tension), a deformation takes place which results in the flow of the liquid in the form of droplets. The size of the droplet is dependent on different parameters like applied voltage, properties of the ink, dimension of the nozzle. To have better understanding of this, a numerical simulation was performed based on multi-physics approach. Multiple simulations were performed by changing the position of electrode in nozzle and varying the applied voltage. Droplet size with respect to applied voltage was evaluated; electric field with respect to applied voltage and time for the droplet generation was also evaluated through these simulations. This study will help in better understanding the parameters of droplet generation phenomena and optimal design of the nozzle for the electrostatic inkjet system.

Study of Drop-on-Demand Printing Through Multi-Step Pulse Voltage

Khalid Rahman,Arshad Khan,Nguyen Minh Nam,최경현,김동수 한국정밀공학회 2011 International Journal of Precision Engineering and Vol.12 No.4

This paper presents study of the Electrohydrodynamic Drop-on-Demand (DOD) phenomena by applying the multi-step pulse voltage. The multi-step voltage was generated through the high voltage power source connected with pulse generator. A DOD phenomenon was observed with the help of high speed camera. For study purpose the experiments were performed on ethanol by changing the operating parameters such as multi-step pulsed voltage, frequency of applied pulsed voltage and flow-rate. For DOD printing purpose conductive ink is used and patterns were made on the glass substrate and analyzed on different operating conditions. The minimum droplet diameter of approximately 40μm at 325Hz frequency was achieved on the glass substrate. The printed pattern exhibited the linear ohmic behavior and pattern material is characterized through XRD. This study will help in better understanding of the Electrohydrodynamic DOD phenomena for the printing purpose.

Effect of flow rate in the generation of printed line in electrostatic inkjet system

Ahsan Rahman(아산 라만),Jeong-Beom Ko(고정범),Hyung-Chan kim(김형찬),Su-Jin Kim(김수진),Khalid Rahman(카리드 래만),Asif Ali(아시프 알리),Bong-Su Yang(양봉수),Adnan Ali(아드난 알리),Yang-Hoi Doh(도양회),Kyung-Hyun Choi(최경현),Dong-Won Je 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-

The Electrostatic Inkjet system has a huge number of applications in cost and time effected manufacturing of printed electronics like RFID, flexible display, solar cell, sensors, batteries etc. So, the fundamental focus will be to investigate the drop generation phenomena by applying the electrostatic forces. Electrostatic inkjet printing for printed electronics technology is advancing rapidly but it s still in its infancy as inkjet printing system is not able to design complicated devices. This paper explains the behavior of the multiphysics phenomena of the Drop on Demand (DOD) electrostatic Inkjet system for printed electronics devices.

TWO-PHASE EVAPORATIVE BATTERY THERMAL MANAGEMENT TECHNOLOGY FOR EVs/HEVs

Rahman Ataur,Mohammed Nurul Amin Hawlader,Helmi Khalid 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.5

Electric vehicle’s motor draws power from battery to meet its power demand in different road profiles. Battery high discharged currents are causes of warming battery’s cells. The temperature of 40 ºC and above reduces battery life span. The rationale of fuzzy controlled evaporative battery thermal management system (EC-BThMS) development from this study is to control the battery temperature in the range of 20 ~ 40 ºC both in charging/discharging modes. The proposed system has been developed with estimating the total cooling loads and thermal behavior of the battery cells. A fuzzy controlling system has been introduced with the EC-BThMS to control the electro-compressor and the expansion valve based on the response of battery temperature sensors.A battery pack of 8.6 kWh equipped EV has been operated with 60 km/h on 0 % gradient and 40 km/h on 5 % gradient in IIUM campus while 130 km/h on 0 % gradient and 50 km/h on 3.67 % gradient in Malaysia International Formula circuit to study the battery temperature profile and percentage of battery power saving. Comparison has been made on the performance of EC-BThMS with air cooling battery thermal management system (AC-BThMS) by using same vehicle. Result shows that EC-BThMS can save energy 17.69 % more than AC-BThM 1 and 23 % more than AC-BThM 2.

Thiol concentration, structural characteristics and gelling properties of bovine heart protein concentrates

Rahman, M. Shafiur,Go, Gwang-woong,Seo, Jin-Kyu,Gul, Khalid,Choi, Sung-Gil,Yang, Han-Sul Elsevier 2019 LWT- Food science and technology Vol.111 No.-

<P><B>Abstract</B></P> <P>Consumer demand for proteins from animal sources has been increasing with economic growth of the populations. Freeze-dried ground bovine heart was treated using supercritical-CO<SUB>2</SUB> (SC–CO<SUB>2</SUB>) at different pressures (20, 30 and 40 MPa) and hexane to produce a protein concentrate. Thiol concentration, structural and gelling properties of the control bovine heart and bovine heart protein concentrates (BHPCs) were investigated. SC-CO<SUB>2</SUB> treatment at 20 MPa led to an increased (<I>p</I> < 0.05) thiol (–SH) content (74.08 nmol/mg protein) than those for the control and other BHPCs. Fourier–transform infrared (FT–IR) spectroscopy showed increased secondary structure of α–helix and parallel β–sheet content for SC-CO<SUB>2</SUB>–treated bovine heart protein when compared to the control and hexane–treated bovine heart protein. Integrated light scattering in protein suspension showed SC-CO<SUB>2</SUB>–treated samples had higher cumulative values (Q3) and density (q3) for the particle size distribution. SC-CO<SUB>2</SUB>–treated BHPC had better physicochemical properties without structural deterioration of proteins resulting in increased functional properties such as solubility (31.08 g/100 g bovine heart), viscosity and gelling capacity (least gelation concentration 10 g/100 mL water). Bovine heart proteins may serve as a good source of quality proteins for different food applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bovine heart was treated using SC-CO<SUB>2</SUB> and hexane to produce a protein concentrate. </LI> <LI> SC-CO<SUB>2</SUB>–treated sample had higher thiol (-SH) content than the control and other samples. </LI> <LI> FT-IR spectra showed SC-CO<SUB>2</SUB>–treated samples had higher α–helix and β–sheets. </LI> <LI> Integrated light scattering showed greater particles in solution for SC-CO<SUB>2</SUB>–treated sample. </LI> <LI> SC-CO<SUB>2</SUB> treatment resulted in increased functional properties of the protein concentrates. </LI> </UL> </P>

Physicochemical characteristics and microbial safety of defatted bovine heart and its lipid extracted with supercritical-CO₂ and solvent extraction

Rahman, M. Shafiur,Seo, Jin-Kyu,Choi, Sung-Gil,Gul, Khalid,Yang, Han-Sul Elsevier 2018 FOOD SCIENCE AND TECHNOLOGY -ZURICH- Vol.97 No.-

<P><B>Abstract</B></P> <P>The demand for healthier meat and meat products with low fat is increasing rapidly to reduce cardiovascular and other chronic diseases. Bovine heart was defatted using supercritical-CO<SUB>2</SUB> (SC-CO<SUB>2</SUB>) at a constant temperature (40 °C) with three different pressures (20, 30, and 40 MPa) and using solvent extraction. The objective of this study was to produce a low-fat meat ingredient such as defatted bovine heart (DBH), and investigate its physicochemical characteristics and microbial safety, including the extraction yield and fatty acid composition of bovine heart lipid. SC-CO<SUB>2</SUB> treatment at high pressure results in higher removal of fat i.e. a higher extraction yield (93.60%). The DBH prepared using SC-CO<SUB>2</SUB> at 30 and 40 MPa had significantly higher proteins (82.07 and 82.67 g/100 g DBH, respectively), amino acids (80.39 and 79.05 g/100 g DBH, respectively), and minerals (2910 and 2901 mg/100 g DBH, respectively) and with lower microbial contents compared to those of the control and other DBHs. SC-CO<SUB>2</SUB>-extracted lipid had significantly higher unsaturated fatty acids (53.09 g/100 g fatty acids) than the control (45.62) and hexane-extracted lipid (44.65). SC-CO<SUB>2</SUB>-treatment leads to higher fat removal without deterioration of nutritional quality and significantly reduces the microbial content in defatted meals.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bovine heart was defatted by SC-CO<SUB>2</SUB> and hexane to produce a low-fat meat ingredient. </LI> <LI> SC-CO<SUB>2</SUB> treatment at high pressure resulted in higher removal of fat. </LI> <LI> Protein, amino acid and mineral contents of bovine heart increased after SC-CO<SUB>2</SUB> treatment. </LI> <LI> SC-CO<SUB>2</SUB> process significantly reduced microbial contamination in defatted samples. </LI> <LI> SC-CO<SUB>2</SUB>–extracted lipids had significantly higher unsaturated fatty acids. </LI> </UL> </P>

Cross-talk effect in electrostatic based capillary array nozzles

최경현,Khalid Rahman,Arshad Khan,김동수 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12

Electrohydrodynamic printing is a promising technique for printed electronics application. Most researchers working in this field are using a single nozzle configuration. However, for large area printing a multi-nozzle setup will be required for time and cost effective process. In this paper the influence of electric field and flow-rate on jetting angle on multi-nozzle array has been investigated experimentally. A three nozzle setup has been used in a linear array by using glass capillary as a nozzle with independent voltage applied on each nozzle and independent ink supply. The experiments are performed by changing the nozzle to nozzle gap and the effect on the jetting angle has been investigated. It has been observed that by increasing the applied voltage the jetting angle also increases at fixed flow-rate. In case of increasing the flow-rate, the jetting angle first increases with increase in flow-rate, but as the flow-rate increases at certain level the jetting angle decreases; moreover, at a high flow-rate the cone-jet length starts increasing. Numerical simulation has been performed to have a better understanding of the electric-field with respect to jetting angles. The influence of one nozzle on another nozzle is also investigated by operating the nozzle independently by using different operating cases. The cross-talk effect is also minimized by reducing the nozzle diameter. At 250 μm nozzle diameter the cross-talk effect was negligible for 5 mm nozzle-to-nozzle gap. This study will help in better understanding of the interaction between different nozzles in multi-nozzle cases and better design of the multi-nozzle system by minimizing the effects of adjacent nozzles for multi-nozzle electrohydrodynamic printing system.

Multi-nozzle electrohydrodynamic inkjet printing of silver colloidal solution for the fabrication of electrically functional microstructures

Khan, Arshad,Rahman, Khalid,Hyun, Myung-Taek,Kim, Dong-Soo,Choi, Kyung-Hyun Springer-Verlag 2011 Applied physics. A, Materials science & processing Vol.104 No.4

Low dimensional Ni-ZnO nanoparticles as marker of toxic lead ions for environmental remediation

Mohammed M. Rahman,Sher Bahadar Khan,Hadi M. Marwani,Abdullah M. Asiri,Khalid A. Alamry,Malik Abdul Rub,Anish Khan,Aftab Aslam Parwaz Khan,Abdullah H. Qusti 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.3

We have synthesized Ni-ZnO nanoparticles (NPs) by a wet-chemical route using reducing agents. Thestructural and optical properties of Ni-ZnO NPs were investigated by various conventional methods. Theanalytical potential of the Ni-ZnO NPs was studied for a selective detection of toxic Pb(II) ion usingrecognized ICP-OES method for environmental remediation. Data obtained from the selectivity studyindicated that the selectivity of Ni-ZnO NPs phase was the most toward Pb(II) ion. However, theadsorption isotherm data of Pb(II) on Ni-ZnO NPs phase was good-match with the Langmuir-Adsorption-Isotherm, strongly supporting that the adsorption process was mainly monolayer on homogeneousadsorbent surfaces.

Sensitive and selective m-tolyl hydrazine chemical sensor development based on CdO nanomaterial decorated multi-walled carbon nanotubes

Mohammed M. Rahman,M.M. Alam,Khalid A. Alamry 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.77 No.-

In this approach, the wet-chemical (co-precipitation) technique was used to prepare the cadmium oxide(CdO) nanoparticles (NPs) decorated with multi-walled carbon nanotubes (CNT) at low temperature. Thepowder XDR, UV–vis, TEM, XPS, and FTIR spectroscopy were used for detail characterization of thesynthesized CdO/CNT nanocomposite (NCs). A thin layer of CdO/CNT NCs was deposited onto a glassycarbon electrode (GCE) with conducting coating binder to obtain a chemical sensor which wassubsequently used to detect m-tolyl hydrazine hydrochloride (m-THyd) in buffer medium byelectrochemical approach for environmental safety. The proposed m-THyd chemical sensor exhibitedlong-term stability, good selectivity, broad linear dynamic range, lower detection limit, and enhancedelectrochemical response. The calibration curve of the current vs concentration of m-THyd was found tobe linear (r2 = 0.9903) over the linear dynamic range (LDR) of 0.01 nM to 0.1 mM. The sensitivity(25.7911 mA mM cm 2) of chemical sensor was calculated from the slope of calibration curve and surfacearea of GCE (0.0316 cm2) and the detection limit (4.0 0.2 pM) was estimated from the signal to noiseratio at 3. These preliminary results suggest that the newly developed CdO/CNT NCs nanocompositecould be promising electrochemical sensors for the detection of hazardous toxins to clean theenvironment in broad scales.