Finger vein verification

At present, biometric system is well - liked as its high security level manage to reduce frauds, intrudes and forgeries. A biometric system utilizes physiological features and behavior characteristics of an individual such as face, finger mark, iris, handwriting, voice, signature and others. One of the recent biology feature used as biometric system is the finger vein. The vein features are robust, stable and most importantly unique for every individual. This trait offers a higher security because for gery is extremely difficult. The finger vein verification project verifies a person‟s identity based on the vein patterns. Generally, the finger vein images are pre - processed and a neural network algorithm is developed to verify the finger vein images. Las t but not least, the performance of the finger vein verification is evaluated. The project achieved an overall accuracy of 82.86%

Thermoelectric power generation enhancement of microfabricated metal-based planar thermopiles through geometrical and device structure optimizations

Thermoelectricity converts heat energy into electricity through a simple mechanism, in which a potential difference is generated due to the temperature difference between the hot and cold contact electrodes (AT) of coupled thermoelements. There are many types of thermoelements used in developing thermoelectric generators. However, metal thermoelements offer cheaper solutions, easier fabrication processes, and can produce substantial electricity at smaller AT. The strong correlations of electrical and thermal conductivities in metal thermoelements have resulted in lower Seebeck coefficients along with reduced thermoelectric power-generating performances. Alternatively, a thermoleg cross-sectional area (A ) optimization approach may optimize these disruptive correlations and improve their powergenerating effectiveness. A sandwiched planar structure can also allow more thermopiles to be integrated without affecting the generator’s size. In this study, thermoelectric devices based on a flexible copper (Cu)-clad polyimide substrate with simpler fabrications using Cu, nickel (Ni), and cobalt (Co) metal thermoelements were explored. Planar and lateral device structures may assist in generating larger A T and output power through their longer thermoleg length (l) and larger A . Thus, for the first time, Cu thermoleg-based generators were built on planar and lateral structures, and Co was introduced and implemented in this study too. This study also investigated the roles of previously unexplored geometrical structures such as the l and thermoleg width. Hereby, a sandwiched planar Cu/Co device was optimized by increasing the thermoleg thickness (t) of Co by 3.86 times the t of Cu, and this generator showed improvement factors of 23.5 and 40.2 times than the earlier-fabricated non-optimized Cu/Co and Cu/Ni generators, respectively. Promisingly, the A optimized sandwiched planar and lateral thick film device structures were found to be very compatible and favorable for metal-based thermoelectric generators

Copper-Nickel and copper-cobalt thermoelectric generators: power-generating optimization through structural geometrics

In this paper of thermoelectric generators, metals are used as the prospective thermoelectric materials or thermoelements on flexible copper (Cu)-clad polyimide substrate. The fabricated thick film generators have planar and lateral structures with lateral heat flow and lateral thermopile layout. Hereby, two prototypes of thermoelectric generators are made, the first employing Cu and nickel (Ni) and the second Cu and cobalt (Co) as their positive and negative thermoelements, respectively. This paper also investigates the roles of geometrical structures such as the thermoleg's length and width and the generator's size in promoting elevated thermoelectric power generation. Consequently, the highest performing thermoleg designs (length: 5-20 mm; width: 100- 1000 μm) for the two prototypes are identified as having a length, width, and thickness of 5 mm, 1000 μm, and 31μm, respectively, with generator dimensions of 1.1 cm length and 4.3 cm width. Collectively, this design has an accumulated average temperature difference, output power density, and thermoelectric efficiency factor of 60 K, 0.59μ Wcm-2, and 1.64×10 4 μ Wcm-2K-2, respectively, for the Cu-Ni generator, while the corresponding values for the Cu-Co generator are 64 K, 1.15 μ Wcm-2, and 2.81 × 10 4 μ Wcm-2K-2. An improvement factor of 1.71 is realized by the Cu-Co generator compared to the Cu-Ni one due to its larger Seebeck coefficient and figure of merit. This highlights the Cu-Co metallic couple as an encouraging thermoelement in thermoelectricity. Promisingly, the thick film and lateral device structures are more compatible and favorable for metal-based thermoelectric generators

Micro-scale energy harvesting devices: review of methodological performances in the last decade

Power harvesting devices which harness ambient surrounding energies to produce electricity could be a good solution for charging or powering electronic devices. The main advantages of such devices are that they are ecologically safe, portable, wireless, and cost effective and have smaller dimensions. Most of these power harvesting devices are realized by utilizing the microelectromechanical systems (MEMS) fabrication techniques. In this paper, the capabilities and efficiencies of four micro-power harvesting methods including thermoelectric, thermo-photovoltaic, piezoelectric, and microbial fuel cell renewable power generators are thoroughly reviewed and reported. These methods are discussed in terms of their benefits and applications as well as their challenges and constraints. In addition, a methodological performance analysis for the decade from 2005 to 2014 are surveyed in order to discover the methods that delivered high output power for each device. Moreover, the outstanding breakthrough performances of each of the aforementioned micro-power generators within this period are highlighted. From the studies conducted, a maximum energy conversion of 2500 mW cm-2 is reached by thermoelectric modules. Meanwhile, thermo-photovoltaic devices achieved a rise in system efficiency of up to 10.9%. Piezoelectricity is potentially able to reach a volumetric power density of up to 10,000 mW cm-3. Significantly in microbial fuel cell systems, the highest power density obtained reached up to 6.86 W m-2. Consequently, the miniaturized energy harvesters are proven to have credibility for the performance of autonomous power generation

State-of-the-art reviews and analyses of emerging research findings and achievements of thermoelectric materials over the past years

This review is focused on state-of-the-art thermoelectric materials (or thermoelements), from which the thermoelements with the highest figures of merit (z) along with the those having the greatest research interest and findings were surveyed and analyzed. These were in addition to the statistical analyses made in this review for categorizing z achievement ranges for all types of thermoelements. Almost 56% of positive thermoelements and 39.6% of negative thermoelements were discovered from 1950 to 2017, and a total of 62.2% of thermoelement research findings were reported in 2010–2017. Furthermore, nearly 47.65% of the discovered thermoelements preserved z in the range of 1–4.99 × 10−3 K−1, and only about 2.52% possessed less than 9.9 × 10−6 K−1. Chalcogenide was the major type of thermoelement studied to date, with overall representation of 37.2%. Nearly 68.9% of chalcogenide thermoelements were capable of reach 1–4.99 × 10−3 K−1, while 53% of metal oxide thermoelements ranged within 0.1–0.499 × 10−3 K−1. Nanostructure thermoelements achieved the highest z of 47 × 10−3 K−1 and 17 × 10−3 K−1 at 300 K, for Bi2Te3 quantum wires and Bi2Te3 quantum wells, respectively. Correspondingly, hybrid and conducting polymer thermoelements also reached z as high as 16 × 10−3 K−1 at 300 K for positive thermoelement: nano-Ag/regioregular poly(3-octylthiophene-2,5-diyl) and negative thermoelement: graphdiyne

Methodological reviews and analyses on the emerging research trends and progresses of thermoelectric generators

Thermoelectric generator is among the earliest initiated electricity-harvesting methods. It is a very potential power harvester that can convert wasteful thermal energy into electricity. However, it often suffers from low energy conversion rate due to its inconsistent heat source, inefficient thermoelectric material (or thermoelement) performance, and incompetent structural issues. Progressively for the first time, detailed methodological surveys and analyses are made for bulk, thick, and thin films in this review. This is in order to accommodate better insights and comprehensions on the emerging trends and progresses of thermoelectric generators from 1989 to 2017. The research interests in thermoelectric generators have started back in 1989, and have continuously experienced emerging progresses in the number of studies over the last years. The methodological reviews and analyses of thermoelectric generator showed that almost 46.6% of bulk and 46.1% of thick and thin film research works, respectively, are actively progressed in 2014 to 2017. Nearly 86.2% of bulk and 44.1% of thick and thin film thermoelectric generators are realizing in between 0.001 and 4 μW cm−2 K−2, while 43.1% of thick and thin films are earning among 10−6 to 0.001 μW cm−2 K−2. The highest achievement made until now is 2.5 W cm−2 at a temperature difference of 140 K and thermoelectric efficiency factor of 127.55 μW cm−2 K−2. This achievement remarked positive elevation for the field and interest in thermoelectric power generation. Consecutively, the research trends of fundamental devices' structure, thermoelement, fabrication, substrate, and heat source characteristics are analyzed too, along with the desired improvement highlights for the applications of thermoelectric generators

Copper–cobalt thermoelectric generators:Power improvement through optimizedthickness and sandwichedplanar structure

In this paper, metallic thermoelectric generators were studied and fabricated using copper (Cu) and cobalt (Co) as their respective positive and negative thermoelements. Thus, the chosen Cu-clad polyimide substrate alleviated the deposition of Cu and eased the microfabrication. A lateral device structure might assist in generating larger output power through its longer thermoleg length. Hence, the fabricated thick-film devices had planar and lateral structures with lateral heat flow and lateral thermopile layout. The strong correlations of electrical and thermal conductivities in metal thermoelements have resulted in lower Seebeck coefficient along with reduced thermoelectric power-generating performances. Alternatively, a thermoleg cross-sectional area ( A ) optimization approach may optimize these disrupting correlations and improve their power-generating effectiveness, whereas a sandwiched planar structure can allow more thermopiles to be integrated without influencing the generator's size. Both A optimization and sandwiched planar structure have rarely been applied and studied in the past works and have never been implemented using metal thermoelements. Hereafter, a Cu-Co device was enhanced through A optimization by increasing the thickness of Co over 3.86 times the Cu thickness, and the implementations of a sandwiched planar structure. Herein, a flexible sandwiched planar thermoelectric generator was fabricated for the first time, using simpler microfabrication. This enhanced Cu-Co generator achieved a thermoelectric efficiency factor of 6.6 × 10-3 μ Wcm-2K-2(12.89 μ Wcm-2) at a temperature difference of 44.2 K. It remarked 3.1 times of improvement (by stacking three sets of thermopile) than its similar single Cu-Co thermopile of ten thermocouples

Copper–cobalt thermoelectric generators: power improvement through optimized thickness and sandwiched planar structure

In this paper, metallic thermoelectric generators were studied and fabricated using copper (Cu) and cobalt (Co) as their respective positive and negative thermoelements. Thus, the chosen Cu-clad polyimide substrate alleviated the deposition of Cu and eased the microfabrication. A lateral device structure might assist in generating larger output power through its longer thermoleg length. Hence, the fabricated thick-film devices had planar and lateral structures with lateral heat flow and lateral thermopile layout. The strong correlations of electrical and thermal conductivities in metal thermoelements have resulted in lower Seebeck coefficient along with reduced thermoelectric power-generating performances. Alternatively, a thermoleg cross-sectional area (A) optimization approach may optimize these disrupting correlations and improve their power-generating effectiveness,whereas a sandwichedplanar structure can allow more thermopiles to be integrated without influencing the generator’s size. Both A optimization and sandwiched planar structure have rarely been applied and studied in the past works and have never been implemented using metal thermoelements. Hereafter, a Cu–Co device was enhanced through A optimization by increasing the thickness of Co over 3.86 times the Cu thickness, and the implementations of a sandwiched planar structure. Herein, a flexible sandwiched planar thermoelectric generatorwas fabricated for the first time, using simpler microfabrication. This enhancedCu–Co generator achieved a thermoelectric efficiency factor of 6.6×10−3 μWcm−2K−2 (12.89 μWcm−2) at a temperature difference of 44.2 K. It remarked 3.1 times of improvement (by stacking three sets of thermopile) than its similar single Cu–Co thermopile of ten thermocouples