Yang Hoi Doh

Optical security system for the protection of personal identification information

A new optical security system for the protection of personal identification information is proposed. First, authentication of the encrypted personal information is carried out by primary recognition of a personal identification number (PIN) with the proposed multiplexed minimum average correlation energy phase-encrypted (MMACE_p) filter. The MMACE_p filter, synthesized with phase-encrypted training images, can increase the discrimination capability and prevent the leak of personal identification information. After the PIN is recognized, speedy authentication of personal information can be achieved through one-to-one optical correlation by means of the optical wavelet filter. The possibility of information counterfeiting can be significantly decreased with the double-identification process. Simulation results demonstrate the effectiveness of the proposed technique.

Hybrid Surface Acoustic Wave- Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PEDOT:PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films’ characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics.

New morphological detection algorithm based on the hit-miss transform

A new hit-miss transform (HMT) algorithm is proposed to de- tect distorted multiple objects in clutter. The HMT in morphology is used to locate a specific object in an input image. But the standard algorithm of the morphological HMT may cause problems in detecting various true- class objects. To provide efficient recognition of various true-class ob- jects in the input image, a new optical hit-miss morphological transform using the synthetic structuring element (SE) is proposed. The synthetic hit SE is composed of the intersection of all true-class hit SEs, and the synthetic miss SE is composed of the complement of the union of all true-class hit SEs. Simulation results show that the proposed algorithm can be used for the recognition of various true-class objects in an un- known input scene with only one HMT operation.

Electrohydrodynamic Spray Deposition of ZnO Nanoparticles

This paper presents the electrospray deposition of solution-based ZnO nanoparticles. Transparent thin film transistors in active matrix displays have become the most interested research area. Electrospray assures direct deposition by eliminating etching steps required after deposition by other techniques. Uniform layers of minimum thickness 87 nm on glass and 356 nm on polyimide using electrospray experiment is achieved. Contact angle analyzer has been used for finding properties like wetting energy, spreading coefficient and work of adhesion of the ink on glass and polyimide substrates. All experiments were performed in ambient conditions.

Exploring resistive switching in poly(4-vinylphenol)–graphene nano-composite films

In this study the organic resistive switching devices having sandwich structure of indium tin oxide (ITO)-coated glass/poly(4-vinylphenol) (PVP)–graphene composite/silver (Ag) were fabricated and characterized. The active layers were fabricated using blended, semiblend and layer-by-layer approaches, sandwiched between two electrodes. The film thicknesses of the active layers were measured to be about 200 nm. The surface morphology was characterized by field-emission scanning electron microscopy. Electrical current–voltage (I–V) analyses confirmed the memristive behavior of the sandwich devices. The effect of active layer fabrication approach was analyzed by comparing the resistive switching characteristics. The devices showed characteristic OFF to ON (high resistance to low resistance) transition at low voltages, when operated between ±2 V, characterized at 100 µA and 5 mA compliance currents. The memristive behavior of PVP–graphene active layer fabricated by blended approach showed more stability and robustness compared to non-blended approaches. The devices fabricated by blended approach exhibited a room temperature V–I hysteresis and ROFF/RON ≈ 5.

Electrohydrodynamic Inkjet – Micro Pattern Fabrication for Printed Electronics Applications

In electronic industry the manufacturing of conductive patterning is necessary and ineluctable. Traditionally, lithography is widely used for fabrication of the conductive patterns. However, lithographic processes require the complicated equipments, are time consuming and the area throughput is limited. In order to reduce the material usage, process time and large area fabrication, different fabrication technique is required. Nonlithographic-direct fabrication method (Pique & Chrisey, 2001) such as inkjet (Gans et al., 2004) and roll-to-roll (Gamota et al., 2004) printing (also known as printed electronics) are predominant examples for reasonable resolution and high throughput as compared to lithography techniques. This direct fabrication technology can be further classified into two different technologies depending on the fabrication method as contact (gravure, offset or flexographic etc) and non-contact (inkjet) method. Non-contact inkjet printing method has moved beyond graphic printing as a versatile manufacturing method for functional and structural materials. Commercially available inkjet printer can be divided into two modes based on the ejection of the fluid: Continuous, where jet emerges from the nozzle which breaks in stream of droplets or Drop-on-Demand, the droplet ejects from the nozzle orifice as required (Lee, 2002). Inkjet printing offers the advantages of low cost, large area throughput and high speed processing. The most prominent examples of inkjet printing includes the direct patterning of, printed circuit board, conductive tracks for antenna of radio frequency identification tags (RFID) (Yang et al., 2007), Photovoltaic (Jung et al., 2010), thin film transistors (Arias et al., 2004), micro arrays of the DNA (Goldmann & Gonzalez, 2000), biosensors, etc. In case of continuous inkjet printing, the deflector directs the stream of droplets into a waste collector or onto substrate, for start and stop of the printing. This wastage of the ink issue has been addressed by the introduction drop-on-demand inkjet printing (thermal and piezoelectric). In drop-on-demand, thermal or vibration pulse are used to eject the liquid droplet from the nozzle to the substrate. However, the current printing technologies have constrained due to limitation of the ink viscosity, clogging of small size nozzles, generation of pattern smaller than the nozzle size and limitation of material to be deposited (Le, 1998). In order address these limitations, many researchers are focusing on electrohydrodynamic inkjet printing (continuous and drop-on-demand) (Park et al., 2007). Electrohydrodynamic jet printing uses electric field energy to eject the liquid from

Influence of Electrode Position and Electrostatic Forces on the Generation of Meniscus in Dielectric Ink

This paper analyzes and reports the influence of electrodes positioning on dielectric ink for the formation of stable meniscus in the electrostatic inkjet head, experimentally. To introduce the electrostatic inkjet head for the fabrication of different printed devices, it is important to know the best position of electrode in the inkjet head for the optimal electrification of the ink. The paper also examines electrode position and electrically driven liquid handling operations. From experiments, it has been deduced that the head performs best when the electrode position is at orifice in dielectric ink. For better understanding and evaluation of this phenomenon, simulations were also performed. The finite element model of the head with dielectric fluid has been developed to analyze the behavior under electric field. And to optimize the analysis, the research is also supported by the statistical techniques. Furthermore, the meniscus shape and response on applied voltage is studied and analyzed. Paper also elaborates and addresses issues like the meniscus generation using dielectric ink and ejections at low voltage with stability problems.

Distortion-invariant pattern recognition based on a synthetic hit-miss transform

A new synthetic hit-miss transform (SHMT) algorithm is proposed for distortion-invariant recognition of various objects in noisy and cluttered input images. The proposed SHMT algorithm uses synthetic structuring elements (SEs), which are synthesized based on a synthetic discriminant function (SDF) filter algorithm. The synthetic hit SE is composed of the linear combination of the reference hit SEs, and the synthetic miss SE is composed of the linear combination of the reference miss SEs. Based on various simulations, it is shown that the proposed algorithm can be applied to an HMT correlator to improve its ability to detect various objects with distortions in noisy and cluttered scenes.

Development of Electrostatic Inkjet Head by Integrating Metallic and Silica Capillaries for Stable Meniscus

This article discusses the stability and analysis of meniscus for electrohydrodynamic printing (EHDP) system and printed results on flexible substrate. Conventionally, an electrode is inserted vertically into the fluid for generating electric field to induce charges that move towards the surface of the liquid. Disturbances and vibrations in the inkjet head, caused by the application of high electric potential is the main problem affecting the stability of the meniscus. Centralization, obstruction to the fluid flow, and the fixed position of vertically inserted electrode in the inkjet head adds to the complexity of the system design. In order to overcome all these limitations, a new technique has been developed and verified experimentally. A metallic capillary enclosed by tapered glass capillary results in removing obstructions to the fluid flow caused by inserting electrodes from top into the capillary head. The voltage applied in new setup for extraction is reduced around 1.2 kV, analyzed by simulation, and also verified by experiments. Electrode within the fluid channel remains at fixed point eliminating the positioning problems for repeatable parameters. With this head design, uniformity of the patterned lines is enhanced by obtaining a stable meniscus. Resolution of the printed patterns on flexible polyimide substrate is minimized. Ink having properties of 39.68 wt% of Ag nanoparticles, viscosity of 39 cps, and 5 dyn/cm of surface tension is used. All experiments are performed in ambient environment.

Development of hybrid SAW-ED system for conductive thin-layer

In the hybrid SAW-ED deposition system for conductive thin-layer, droplets generation depend upon the SAW. Also, the electrostatic field can help pull off the droplets to the substrates. In this paper, the efficiency of hybrid SAW-ED head is studied analytically. For the development of hybrid SAW-ED deposition system, the optimized parameters for conductive thin-layer can be ascertained from the results discussed here. The background of this research is to get micro droplets and successive spray and the optimal conditions for the development of conductive thin-layer needed for devices of printed electronics through hybrid SAW-ED deposition system.