Template-assisted electrodeposition, magnetic nanowires, PHR sensor, flow sensor
Over millennia of evolution, animals have developed exceptional receptors such as lateral line system of fishes and sensory hairs in insects. This hair-like structures is a part of sensory system used to detecting external stimuli and changes around the animals. With the aid of current fabrication technology, an engineering equivalent artificial hair-like (AHL) sensors were developed to imitate the structure and function of the biological hairs on animals. The AHL sensors can be operated based on several principles such as magnetic, piezoresistive, and piezoelectric. This Theses presents the results obtained during the development of magnetic based artificial hair-like sensor as a feasible flow sensor. Here, the study demonstrates the ability to fabricate vertically aligned multisegment nanowires on planar Hall resistance (PHR) sensor via template-assisted electrodeposition. Nanowires consisting of Au and CoNiP segments were grown into polycarbonate (PC) membrane with its corresponding length controlled during the fabrication process. The nanowires are 250 nm in diameter and 6 µm long with the average length of Au and CoNiP measured to be 5 µm and 1 µm respectively. Elemental composition of the nanowires specifically for CoNiP segment were also quantified to confirm the percentage of said element present inside the nanowires. The magnetic properties of the nanowires were measured in applied magnetic field parallel and perpendicular to nanowires long axis. Coercivity of the nanowires along and perpendicular to nanowire long axis were calculated to be 1850 Oe and 1820 Oe respectively. Additionally, the effect of nanowire’s crystal structure and CoNiP segment length on its magnetic properties were also investigated in this work. The PHR sensor profile was analyzed and its field sensitivity was calculated to be 1.1 µV/Oe in the low field region. An average voltage changes of 22 µV was observed after Au/CoNiP nanowires were deposited on the sensor surface. Voltage signal increase up to 0.06 µV from the baseline as air was blown towards the nanowires, thus proving the viability of this sensor to sense air flow.
Table Of Contents
ABSTRACT i Table of Contents iii List of Tables iv List of Figures iv I. INTRODUCTION 1 II. RESEARCH BACKGROUND 3 2.1 Template-assisted synTheses of metal nanowires 3 2.1.1 “Track-etched” polycarbonate membrane 4 2.2 Planar Hall magnetoresistive (PHR) sensor 5 III. EXPERIMENTAL 8 3.1 Materials 8 3.2 Fabrication of vertically aligned Au/CoNiP nanowires 8 3.2.1 Gold-coated Silicon Substrate 8 3.2.2 Polycarbonate membrane attachment on substrate 9 3.2.3 Electrodeposition of nanowires 11 3.3 Fabrication of sensor with Au/CoNiP nanowire 13 3.3.1 Fabrication of pattern 13 3.3.2 Fabrication of cross-type PHR sensor 14 3.3.3 Electrodeposition of nanowires 15 3.4 Characterization 15 3.4.1 Scanning Electron Microscopy (SEM) 15 3.4.2 X-ray diffraction (XRD) 16 3.4.3 Vibrating Sample Magnetometer (VSM) 16 3.4.3 Magnetoresistance (MR) measurement 17 IV. RESULTS AND DISCUSSION 19 4.1 Fabrication of vertically aligned nanowires 19 4.1.1 Nanowire dimension 19 4.1.2 Growth Mechanism 22 4.1.3 PC membrane attachment on substrate 25 4.2 Magnetic properties of nanowires 28 4.3 Characterization of sensor 34 V. CONCLUSION AND FUTURE OUTLOOK 38 REFERENCE 39 요 약 문 43