Design and Fabrication of Microspiral Inductive Coils for the Applications in Cell Culturing, Low Power Electromagnetic Actuation and Electricity Monitoring of Household Appliances

• Main Authors: Chen, Yung-Chang, 陳永昌
• Other Authors: Cheng, Yu-Ting
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/94432894836481043476

博士 === 國立交通大學 === 電子工程學系 電子研究所 === 101 === With the rapid evolution of science and technology, miniaturization is the major development trend in recent decades. As the CMOS technology continues scaling, smart hand-held devices combined with the capabilities of wireless communication and varieties of sensing functions for real-time monitoring of the natural environment conditions or physiological signals become the most convenient and powerful tool in our future life. Instead of CMOS technology, micro-electro-mechanical systems (MEMS) technology has been recognized one of the key technologies for developing pervasive transducers by realizing a microscale 3D structure to provide various sensing and actuating functionalities in next generation. It has been widely applied in electrical, mechanical, optical, acoustic, chemical, biomedical system,…etc., such as the well-known MEMS pressure sensors, inertial sensors and microphones in the automotive and consumer electronic industry. Nowadays, inductive coils have been applied everywhere in our environment, like the transformer with several floors high at the power plant and the substation, and small on-chip spiral inductors inside the CMOS chips in consumer electronics. The objectives of this dissertation are aimed to demonstrate and extend the microcoil applications in biotechnology, acoustic and electricity monitoring systems for the improvement of our life. In this dissertation, a platform technology with experimental results has been developed and utilized to rapidly investigate and analyze the biological effects of localized extremely low frequency (ELF) electromagnetic field (EMF) on living cells. The proximity effect of the localized ELF-EMF on living cells is revealed using the bio-compatible microplatform on which an on-glass inductive coil array, the source of the localized ELF-EMF in micro scale, is designed, fabricated and operated with a field strength of 1.2 ± 0.1 mT at 60 Hz for cell culturing study. After a 72 h ELF-EMF exposure, HeLa (human cervical cancer) and PC-12 (rat pheochromocytoma) cells exhibit about 18.4% and 12.9% cell proliferation rate reduction, respectively. Furthermore, according to the presented dynamic model, the reduction of the proliferation can be attributed to the interference of signal transduction processes due to the tangential currents induced around the cells. In addition, this dissertation also presents an optimized Cu-Ni nanocomposite coil synthesized based on the trade-off of resistivity and permeability of the nanocomposite for low-power electromagnetic microspeaker fabrication. A 200μm wide composite coil plated in an alkaline noncyanide copper based bath that is added with 2g/L of Ni nanopowders can realize ~40% power saving of the speaker performed in a frequency range of 1 to 6kHz as compared with the coil made of pure Cu for the same speaker design. In addition, a PDMS membrane is employed for the low-power milliwatt electromagnetic microspeaker fabrication. For a 1.76 mW power input, the speaker with a 3.5 mm in diameter and 3.3 µm thick membrane can generate a sound with the sound pressure level (SPL) of 106 dB @1 kHz in a 2 c.c. coupler. In the last part of this dissertation, a flexible inductive coil tag is presented to sense the electric current in the two-wire power cords of household goods. The tag is fabricated using a CMOS compatible SU-8 flexible technology which provides unique device characteristics of low-cost, reliable, and pervasive. With a 30-turns coil design in an area of 0.5 x 1 cm2, the coil tag can provide a sensitivity of 18 µV/A and 21 µV/A for detecting 50 and 60 Hz electric current in the ampere regime, respectively. Moreover, by integrating with the voltage sensor part, a flexible non-intrusive power sensor tag with good proximity is presented for accurate power detection of the household appliances using typical zip-cord power lines. Both current and voltage sensors with the design of a 50-turns inductive coil and two capacitive electrodes, respectively, in an area of 1.3 x 1 cm2 are fabricated on a 100 μm-thick flexible PET substrate as a sensor tag. The tag exhibits a sensitivity of 271.6 mV/A and 0.38 mV/V via active low-pass filter circuits for the current and voltage detection. Meanwhile, a compensation circuit inputted with the signals of voltage sensor signals is proposed for the interference reduction of in the current sensor that will be electrically coupled from the power cord, so that the current sensor can achieve over 40dB signal-to-noise ratio for measuring the loaded current of 1A, 60Hz on the power line. Furthermore, a sensitivity enhancement scheme is presented for the flexible inductive coil tag used for the current detection of household two-wire power lines. Experimental results show that the inductive coil tag can exhibit a larger induced voltage by the introduction of the magnetic C-clamp stripes that can guide and concentrate the magnetic flux in the center area of the inductive coil. For a 30-turns inductive coil, the incorporation of a 2 μm thick Ni and NiFe C-clamp stripes with 14.5 mm in length and ~20μm in height onto the coil can provide 15.5% and 37.2% sensitivity enhancement, respectively, for detecting 1 A, 60 Hz electric current flow in a SPT-2 16AWG power line. At final, it’s our belief that the proposed coil designs and fabrication processes combined with the theoretical modeling have great potential for the applications of magnetic field investigation of cell culturing in biological system, low power electromagnetic actuation in acoustic system, and electricity monitoring of household appliances.