DATE: Sunday, December 08, 2019
TIME: 12:00 PM - 12:30 PM
LOCATION:Auditorium Between Buildings 4 & 5
Abstract: Biosensors monitor physiological activities for diagnosis and treatment of disease. Molecularly imprinted polymers (MIPs) are a viable synthetic approach for molecular recognition in biosensing. For biosensing purposes, the most important properties in MIP optimization are sensitivity and selectivity towards a desired analyte. This study aims to optimize MIP sensitivity and selectivity by varying the amount and type of cross-linker used in the synthesis of cortisol and melatonin. The four cross-linkers tested were trimethylpropane trimethacrylate (TRIM), ethyleneglycodimethacrylate (EGDMA), divinylbenzene (DVB), and pentaerythritol triacrylate (PETRA). Based on literature, the following ratios were used for the template molecule to functional monomer to cross-linker in MIP synthesis: for EGDMA cross-linked polymers, 1:6:30; for TRIM and PETRA cross-linked polymers, 1:8:8, 1:6:3, and 1:8:35; for DVB cross-linked polymers, 1:6:30, 1:4:16, and 4:1:60. The polymers were ground and washed, then suspended in a polyvinyl matrix which was spin-coated onto an organic electrochemical transducer (OECT). The device performance was evaluated using electrochemical impedance spectroscopy. For each device, the impedance was measured in electrolyte solutions containing target molecules in concentrations ranging from 1 pM to 100 uM. The impedance was plotted against the analyte concentration to give the sensing slope, which is a measurement for the binding affinity of the polymer. For a device to be considered sensitive, its sensing slope should be greater than its non-imprinted counterpart by a factor above the error margin (+/- 1.79). Of the devices tested, CM1835T (highly cross-linked with TRIM) showed sensitivity towards cortisol, but lacks selectivity towards cortisol over its structural analog, estradiol. Of the melatonin selective polymers, MM163T (low cross-linking with TRIM), MM1630D, and MM4160D (both highly cross-linked with DVB) all showed promising results in sensitivity to melatonin. Overall, the results indicate that high degrees of cross-linking in MIPs improve sensitivity for large, rigid, non-aromatic molecules such as cortisol; however there is no correlation between selectivity and the degree of cross-linking. Meanwhile, divinylbenzene as a cross-linker improves sensitivity and selectivity towards aromatic analytes such as melatonin and estradiol. This study could be improved upon by further characterization of imprinted and non-imprinted polymers, investigation of molecular dynamics, and optimization of devices.
TIME: 12:30 PM - 01:00 PM
Abstract: "Polystyrene homopolymer and copolymer were synthesized via atom transfer radical emulsion polymerization (ATRP). Water soluble initiator was synthesized by reacting diethanolamine and α-bromoisobutyrate bromide. Polystyrene homopolymer was made by using the synthesized water soluble initiator with varied initiator concentration. The synthesis of diblock copolymer of Poly (ethylene glycol)-b-poly (styrene) was carried out with different non-ionic surfactants. The synthesized water soluble initiator and homopolymer as well as diblock polymers were characterized by nuclear magnetic resonance (NMR), Gel permeation chromatography (GPC), and Dynamic light scattering (DLS)".
DATE: Wednesday, December 11, 2019
TIME: 03:00 PM - 05:00 PM
LOCATION:Ubn Sina Building (ldg. 3), Room 5209
ABSTRACT: Gaseous pollution has become a global issue and its presence above certain limits is hazardous to human health and environment. Detection of such gases is an immediate need and researchers around the world are trying to solve this problem. Metal oxides are being used as sensing materials for a long time, but a high operating temperature limits applications in many areas. On the other hand, two-dimensional materials with high surface-to-volume ratio and chemical stability are promising candidates in the field of gas sensing. This includes monolayer transition metal dichalcogenides, such as MoS2 and WS2, which are direct band gap materials. While few layer transition metal dichalcogenides are indirect band gap materials, they are easier to synthesize than monolayers. Therefore, it is important to understand whether few layer transition metal dichalcogenides possess the same sensing behavior as the corresponding monolayers. For this reason the first part of this dissertation compares the sensing behavior of monolayer and few layer MoS2 and WS2. Two dimensional hexagonal boron nitride is a highly stable structural analogue of graphene. However, its insulating behavior with large band gap is not suitable for sensing. Recently, monolayer Si2BN has been proposed to exist. As the presence of Si makes this material reactive, the second part of this dissertation addresses its application as sensing material. In the final part of this dissertation, in search of a metal free, non-toxic, and earth abundant sensor material, further structural analogues of graphene are considered, namely monolayer C3N, monolayer C3Si, and monolayer C6BN. In particular, different theoretical approaches for studying the sensing performance of materials are compared to each other.
DATE: Wednesday, January 29, 2020
TIME: 04:15 PM - 05:15 PM
LOCATION:Lecture Hall 1 (2322), Engineering and Science Hall (Building 9)
DATE: Wednesday, February 05, 2020
Abstract: Ion transport is ubiquitous in aqueous environments in biological, geological, chemical and environmental systems. Electrokinetics plays a very important and key role in some special cases where pore size is comparable to the screening length of electrical double layer. The applications include tight oil/gas exploration and development, radiative waste disposal, high-quality water purification, and even ion channels in cells. This talk will present (1) electrokinetic and interface theories for ion transport in micro/nanoporous media; (2) a mesoscopic numerical framework for predictions and the validations by comparisons with theories and experimental data; (3) multiscale analysis in both spacial and temporal scales for special applications.
DATE: Wednesday, February 12, 2020
DATE: Wednesday, February 19, 2020
DATE: Monday, February 24, 2020
TIME: 12:00 PM - 01:00 PM
LOCATION:Building 9, Lecture Hall 2
Since their discovery, microelectromechanical systems (MEMS) has reached a certain level of maturity that, nowadays, they are being used in numerous daily-used machines ranging from all kind of sensors in automobiles to inertial sensors, accelerometers, and gyroscopes in the recent video games and smart mobile phones. Therefore, with the increasing demand for small sensors and actuators of distinguishing functionalities such as: large stroke, self-powering, self-calibration, high tunability, etc…, these tiny systems are expected to remain the exclusive technology in this regards for the coming years. However, with this growing demand come great challenges that these structures would have to withstand such as: the pull-in instability, all sort of internal resonances, auto-parametric resonances, mode localization, etc... Indeed, mode localization in MEMS has gathered significant attention over the past few years due to the potential to developing ultra-high sensitive micro-sensors. This dynamic phenomenon can be defined as the confinement of vibration energy to one of the modes of the coupled system in response to an external stimulus. Another phenomenon that is closely related in coupled systems exhibiting mode localization is the eigenvalue curve veering. Veering occurs when frequencies of two linearly coupled modes approach each other and deviate away interchanging the path trajectories as an external control parameter is varied. In the veering zone the respective mode-shapes of the two modes are affected by each other and get hybridized.
In this talk, the phenomenon of mode localization and mode veering will be discussed and explored for a specific MEMS design consisting of two electrostatically actuated and mechanically coupled microbeam based resonators. Continuous mechanical models will be used for the theoretical prediction of the dynamic responses of the two coupled resonators. The eigenvalue problem will be discussed under different stiffness perturbations and coupling strengths. The influence of the main input resonator electrode bias on the mode localization point will be also considered. The dynamics of the two coupled resonators will be presented and compared using their frequency response curves under different actuation, coupling strength, and output resonator stiffness perturbation scenarios.
Dr. Hassen M. Ouakad was born in Bizerte (Tunisia) in 1983. He received the B.Sc. degree, with honors, in Mechanics and Structures in 2007 from Tunisia Polytechnic School. In 2008 he received a master degree in Computational Mechanics from a joint graduate program between Tunisia Polytechnic School, Tunisia, and Virginia Tech, VA, USA. Then he joined the MEMS characterization and Motion Lab of the State University of New-York at Binghamton (NY, ISA), where he received the Ph.D. degree in 2010. In January 2011, he joined the Petroleum Engineering Department at the Texas A&M University in the Education City of Doha, State of Qatar, as a Postdoc Research Assistant. In September 2011 he joined the Mechanical Engineering Department of King Fahd University as an Assistant Professor. He got promoted to the rank of Associate Professor since April 2016. Since September 2018, he joined the Mechanical and Industrial Engineering Department of Sultan Qaboos University (SQU) in Oman as Associate Professor where he currently heads the Mechanical Systems Laboratory.
Dr. Ouakad is the recipient of the 2010 Excellence in research award granted by the Watson School of the State University of New-York at Binghamton, NY, USA. He was also awarded both the Excellence in Teaching and the Excellence in Academic Advising from the Engineering College of King Fahd University in May 2016 and April 2017 respectively. Moreover, He was awarded the Excellence in Research Award from the Deanship of Scientific Research at KFUPM back in May 2018. Dr. Ouakad developed and examined numerical/experimental techniques to characterize miniaturized devices rely on non-parallel plates electric actuating fields. He authored and co-authored more than ninety scientific articles published in highly ISI ranked international journals and referred conference proceedings. His work has been cited more than 1300 times and his H index is 15.
Dr. Ouakad is a member in the Institute of Electrical and Electronic Engineers (IEEE), and the American Society of Mechanical Engineering (ASME). He currently serves as an Associate Editor for the imminent journals of Vibration and Control, the IEEE ACCESS Journal, the Springer Microsystem Technologies. In addition, he served on few scientific committees of national and international symposiums and conferences.
DATE: Wednesday, March 11, 2020
DATE: Wednesday, March 25, 2020
DATE: Sunday, December 08 - Tuesday, December 10, 2019
TIME: 12:00 AM - 12:00 AM
DATE: Tuesday, December 10, 2019