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Introduction Internet of things Smart New World Source : iamwire IoT has evolved multiple technologies including sensors, embedded systems, communication, real-time analytics or machine learning. For hardware concept, sensor network is one of key technologies. 2
Introduction Micro/ Nano size sensors Smaller size of sensor can make various applications Various micro/nano sensor concepts have been suggested. : Due to its size effect, it can minimize damages or harmful effects to embedded system. : Human body, Bridge, etc. However, a supply of power and a control signal transmission are rarely even considered. 3
RF communication technology RF communication Antenna Tuner Amp. Demod. RF signal (EM Wave) Electrical signal Design parameters L 2 RF antenna theory : = f (L) Dipole Antenna Antenna size : nanometer - micrometer level Working frequency : THz - PHz 4
RF communication technology Nano/micro size antenna Design of nano antenna Test of interference situation for multi antenna Nano antenna fabrication and analysis Micro size antenna 30 20 Power (db) 10 0-10 -20 Reference SiO 2 Rectenna -30-40 0 1 2 3 Frequency (THz) There are lots of issues to convert from EM wave to electrical signal. : No electrical components or electrical measurement devices for THz-PHz region 5
Optical communication technology Optical wireless communication Source : Li-Fi consortium Source : eng.bu.ac.th LED (Tx) + Image sensor (Rx) Micro LED & Micro image sensor SNR issues for outdoor environment Even IR wave, it is hard to penetrate into human body or walls of building. 6
Magnetic coupling communication Wireless transmission EM wave shows serious attenuation for liquid base matters Magnetic inductive coupling is appropriate to nano/micro sensor, since it can work inside of body or liquid base ambience. 7
Magnetic coupling communication Development of Antenna & TFT combined system 1. Antenna issue Transistor can be core element in electronic system. Transistor needs to be adopted to flexible system, so TFT is appropriate for this concept Decreasing WPT efficiency at low frequency level and small size of antenna Flat spiral coil is suitable in wireless TFT system due to fabrication process and design issue To apply to micro sensors. the size of antenna needs to be minimized as micro-size. 2. Thin film transistor (TFT) issue Decreasing mobility of TFT at high frequency level Not only magnetic antenna, but also some electrical components such as switch, rectifier or amplifier require for wireless power and signal transmission. As one of building block for various applications, antenna and TFT combined system were suggested and studied. 8
Results & Discussion I - antenna Micro magnetic antenna 14.0n 12.0n 1mm 800um Inductance (H) 10.0n 8.0n 6.0n 4.0n 2.0n 0.0 5.0M 10.0M 15.0M 20.0M 25.0M 30.0M Frequency (Hz) 1mm 800um 600um 500um 600um As scaling down the size of antenna, the wireless transmission efficiency is decreased. We should enhance this electromagnetic characteristics. 9 500um J. Kang, et.al, Micro-size Antenna Structure with Vertical Nanowires for Wireless Power Transmission and Communication, J. Nanoscience &Nanotechnology, 14, (2014)
Results & Discussion I - antenna Improvement using magnetic core structure B = μ r μ 0 H Absence of magnetic core Presence of magnetic core B = μ 0 H + μ 0 χ m H = μ 0 1 + χ m H = μ r μ 0 H B: Magnetic flux density H: Magnetic flux μ r : Relative permeability of magnetic core χ m : Susceptibility of magnetic core When the ferro-magnetic material is located in the center of coil pattern, the inductance value can be enhanced by inducing a higher magnetic flux in the center. Enhancement of magnetic flux leads to increase the inductance of coil. 10
Results & Discussion I - antenna Various core designs Presence of Magnetic Core (MC) Solution for size effect Suppressing eddy current effect Increasing area density 11
Results & Discussion I - antenna Characteristics according to MC effects I Inductance according to the MC effect Q = ωl R s η 12 = k 2 Q 1 Q 2 1 + k 2 Q 1 Q 2 Q 2 Q 2 + Q L Q 2 = Q 2Q L Q 2 + Q L Q2 factor according to the MC effect 12
Results & Discussion I - antenna Characteristics according to MC effects II Inductance according to the MC effect Inductance according to the MC effect 13
Results & Discussion I - antenna Geometry Effect of Transmission Coil (Tx) Solenoid coil #1 Diameter 10 cm Coil thickness 0.1mm 17turn (height 2cm) Receiving Coil (Rx) 1000 μm / 800 μm Contac pad : Al (170 nm) Coil: Cr/Au (50/120 nm) Width: 40 μm Spacing: 10 μm Solenoid coil #2 Diameter 5 cm Coil thickness 0.1mm 17turn (height 2cm) Solenoid coil #3 Diameter 1 cm Coil thickness 0.1mm 17turn (height 2cm) 14
Results & Discussion I - antenna Geometry Effect of Transmission Coil (Tx) Rx Tx Diameter Tx Working Distance Geometry effect of transmission (TX) coil for micro size magnetic induction coil V pp (mv) 35 30 25 20 15 10 5 0 Rx 1000 um + Tx 10 cm (54 MHz) Rx 800 um + Tx 10 cm (54 MHz) Rx 1000 um + Tx 5 cm (59 MHz) Rx 1000 um + Tx 5 cm (59 MHz) Rx 1000 um + Tx 1 cm (66.5 MHz) Rx 800 um + Tx 1 cm (66.5 MHz) 0 1 2 3 4 5 Distance (Rx-Tx) (cm) K, H. Lee, et.al., A study on geometry efrfect of transmission coil for micro size magnetic induction coil, Solid-State Electronics, 119, (2016) 15
Results & Discussion I - antenna Multi-Tx concept Double Coil System 16
Results & Discussion II - TFT Issues of Thin Film Transistor (TFT) Problem Source Drain Solution to increase the operating frequency of TFT Channel Insulator Gate α-igzo 17
Results & Discussion II - TFT Characteristics of a-igzo TFT 1. Wc(100 μm), Lc(10 μm), and Ci(17.4 nf) 2. Corresponding field-effect mobility μ FE(sat) : 13 cm 2 /V s 3. The following on-off ratio was about ~10 7 18
Results & Discussion III - Antenna + TFT Wireless signal transmission in TFT (Antenna connection to S-D) MC effect MC effect B. O. Jun, et.al., Wireless thin film transistor based on micro magnetic induction coupling antenna, Scientific Reports, 5, (2015) 19
Results & Discussion III - Antenna + TFT Wireless switching effect of TFT (Antenna connection to Gate) 10 3 20
Future applications more confined and smaller spaces and wireless transportation of the information 21
Future applications 22