Sepehr Emamian

Screen Printing of Multilayered Hybrid Printed Circuit Boards on Different Substrates

This paper reports on the successful fabrication of a multilayered hybrid printed circuit board (PCB) for applications in the consumer electronics products, medical technologies, and military equipment. The PCB was fabricated by screen-printing silver (Ag) flake ink, as metallization layer, and UV acrylic-based ink, as dielectric layer, on different substrates such as paper, polyethylene terephthalate, and glass. Traditional electronic components were attached onto the printed pads to create the multilayered hybrid PCB. The feasibility of the hybrid PCB was demonstrated by integrating an embedded microcontroller to drive an liquid-crystal display (160 × 100 pixels). In addition, the amount of the ink spreading after printing, the effect of bending on the printed lines, and the effect of the roughness of the substrates on the resistance of the printed lines was investigated. It was observed that the resistance of the lines increased by ≈1.8%, after 10000 cycles of bending, and the lowest resistance of 1.06 Ω was measured for the 600 μm printed lines on paper, which had a roughness of 0.175 μm. The advantage of fabricating PCBs on flexible substrates is the ability to fold and place the boards on nearly any platform or to conform to any irregular surface, whereas the additive properties of printing processes allow for a faster fabrication process, while simultaneously producing less material waste in comparison with the traditional subtractive processes. The results obtained show the promising potential of employing screen printing process for the fabrication of flexible and light-weight hybrid PCBs.

Robust Control of an Islanded Microgrid Under Unbalanced and Nonlinear Load Conditions

This paper presents a robust control strategy for the autonomous operation of a microgrid consisting of electronically coupled distributed generation (DG) units. The DG units are connected to a point of common coupling, and supply a load, which can be unbalanced and/or nonlinear. In practice, the load is usually unknown in terms of network topology and parameters. However, it is assumed that the load current is measurable and bounded. In this case, considering the load current as a measurable disturbance signal, the controller design is formulated to an H∞ optimization problem in order to minimize the adverse impact of harmonics and negative-sequence voltage due to nonlinear and unbalanced loads. The optimization problem is then converted into a convex linear matrix inequality (LMI) condition, which is simply solved using MATLAB LMI toolbox. The performance of the proposed controller is verified using hardware-in-the-loop (HIL) real-time simulations carried out in OPAL-RT technologies. The HIL results show that the proposed controller provides the load with a set of sinusoidal, three-phase balanced voltages despite several unbalanced and nonlinear load conditions.

A novel flexographic printed strain gauge on paper platform

A novel flexible printed strain gauge was fabricated successfully on a flexible paper substrate using flexography printing process. Silver (Ag) ink was printed on the paper substrate as metallization layer. The performance of the printed device was investigated by subjecting the strain gauge to a 3-point bend test, with a displacement of 1 mm and 2 mm at 3 Hz operating frequency for 500 cycles. The electro-mechanical response of the strain gauge for the 1 mm displacement demonstrated an overall resistance change of 6.4 % and 6.5 % for the base resistance and bend resistance, respectively after 500 cycles of bending. Similarly an overall resistance change of 87.97 % and 28.8 % was observed for the base resistance and bend resistance, respectively after 500 cycles of bending for 2 mm displacement. The response of the fabricated strain gauge, as a function of electrical resistance, is analyzed and presented in this paper.

A new decentralized voltage control scheme of an autonomous microgrid under unbalanced and nonlinear load conditions

This paper presents an effective voltage control strategy for the autonomous operation of a medium voltage (MV) microgrid under nonlinear and unbalanced load conditions. The main objectives of this strategy are to effectively compensate the harmonic and negative-sequence currents of nonlinear and unbalanced loads using distributed generation (DG) units. The proposed control strategy consists of a multi-proportional resonant controller (MPRC) whose parameters are assigned with particle swarm optimization (PSO) algorithm. The optimization function is defined to minimize the tracking error at the specific harmonics considering the stability limitations. In this paper the performance of the proposed controller is investigated for a single DG unit. Due to the fact that DG units can be decentralized, this strategy generalizes for multi-DG unit networks. The performance of the proposed control scheme is verified by using digital time-domain simulation studies in the PSCAD/EMTDC software environment.

Fully printed and flexible piezoelectric based touch sensitive skin

A fully printed piezoelectric based touch sensitive skin has been successfully fabricated using screen printing technique. The device, consisting of a 4×4 array of printed sensors and interconnect lines, was fabricated on a flexible polyethylene terephthalate (PET) substrate, using silver (Ag) ink. Screen printed polyvinylidene fluoride (PVDF), as a piezoelectric layer, was sandwiched between the printed Ag top and bottom electrode metallization layers. The effective polarization of the printed piezoelectric PVDF layer was verified using capacitance-voltage analysis. Piezoelectric-voltage analysis demonstrated the capability of the device to generate voltage peaks as high as 10 V as well as the ability to turn on location based light-emitting diodes (LEDs). The response of the touch sensitive skin is analyzed and presented in this paper.

Gravure printed paper based substrate for detection of heavy metals using surface enhanced Raman spectroscopy (SERS)

A novel paper based surface enhancemed Raman spectroscopy (SERS) substrate was fabricated by gravure printing single and double layers of silver nanoparticle (NP) ink, with a particle size of ~20-50 nm, as metallization layer on a paper from Mitsubishi (NB-RC3GR120). The capability of the SERS substrate for detection of toxic heavy metal compounds such as mercury sulfide (HgS) was demonstrated. The SERS based response of the printed substrate produced an enhanced Raman signal when compared to target molecules adsorbed on bare paper. An enhancement factor of five orders of magnitude, due to existence of hot spots between NP, was obtained. In addition, the effect of bending of the flexible paper substrate on the intensity of the Raman spectrum was also investigated. An enhancement of 500 % in the intensity of Raman spectra was obtained for a bending of 70°. The SERS based response of the printed substrate is analyzed and presented in this paper.

Detection of heavy metals using fully printed three electrode electrochemical sensor

A flexible three electrode electrochemical sensor was successfully screen printed on a polyethylene terephthalate (PET) film. Silver (Ag) ink, silver/silver chloride (Ag/AgCl) ink and carbon ink was used for the counter, reference and working electrodes, respectively. The feasibility of the fully printed sensor for detecting very low concentrations of toxic heavy metal ions was demonstrated. The electrochemical impedance spectroscopy (EIS) response of the printed sensor revealed a very high sensitivity at nano molar (nM) concentration levels of lead nitrate (Pb(NO3)2) and cadmium nitrate (Cd(NO3)2). A percentage change of 18 %, in impedance, was observed for the 1 nM concentration of Pb(NO3)2 when compared with DI water. The response of the electrochemical sensor is analyzed and presented in this paper.

Development of a Microfluidic Sensing Platform by Integrating PCB Technology and Inkjet Printing Process

A microfluidic sensing platform (MSP) for the detection of bio/chemicals has been successfully developed. Polydimethylsiloxane (PDMS)-based microfluidic channels were fabricated using master molds created with printed circuit board (PCB) technology. Silver (Ag)-based ink was employed to inkjet print interdigitated electrodes on flexible polyethylene terephthalate (PET) substrate. The printed PET substrate and PDMS were bonded to form the MSP. The capability of the fabricated MSP for detecting very low concentrations of heavy metal compounds was investigated. The electrochemical impedance spectroscopy response of the MSP revealed picomolar concentration levels of detection for mercury sulfide and cadmium sulfide. The results obtained demonstrated the feasibility of integrating conventional PCB and printing technology to create flexible MSPs for heavy metal sensing applications.

Robust decentralized voltage control of an islanded microgrid under unbalanced and nonlinear load conditions

This paper presents a new decentralized control strategy for the islanded operation of a microgrid under unknown load conditions. In the islanded mode of operation, the microgrid should provide the load with a set of regulated balanced three-phase voltages. The load which is parametrically and topologically uncertain can also be unbalanced and/or nonlinear. Thus, the use of conventional control strategies results in the poor performance and even instability of the microgrid system. The proposed method assumes that the load current is a measurable disturbance signal. The robust optimal control approaches are used to design a controller to overcome the disturbances resulting from the unknown loads dynamics. The optimization problem is converted to a convex problem and is solved using the linear matrix inequalities (LMIs). The performance of the designed controller is verified using time-domain simulations carried out in PSCAD/EMTDC software.

Investigation of SH-SAW sensors for toxic heavy metal detection

In this study, a guided shear horizontal mode surface acoustic wave (SH-SAW) sensor with 64° YX-LiNbO3 based piezoelectric substrate and gold (Au) interdigitated electrodes (IDE) was used for the detection of toxic heavy metal compounds. A flow cell, with a reservoir volume of 3 μl, which employs inlet and outlet valves for the microfluidic chamber and polydimethylsiloxane (PDMS) based microfluidic channels, was also designed and fabricated using an acrylic material. As the SAW propagates through the substrate between input and output IDEs, a change in the velocity of the wave due to the varying concentrations of the test analytes, causes a change in the resonant frequency. This frequency based response of the SAW sensor towards mercury sulfide (HgS) and lead sulfide (PbS) demonstrated the capability of the system to detect picomolar level concentrations. The response of the SAW sensor is analyzed and presented in this paper.