Browsing by Author "Liu, Tzu-Wei"

Now showing 1 - 6 of 6

A MICRO KINETIC ENERGY HARVESTER DEMONSTRATING ENERGY HARVESTING FROM 3-D MECHANICAL MOTION AND POWER INCREASING THROUGH MAGNETIC-BASED FREQUENCY RECTIFICATION
(2012)
Chung, Tien-Kan
;
Wang, Chieh-Min
;
Tseng, Chia-Yuan
;
Liu, Tzu-Wei
;
Yeh, Po-Chen
In this paper, we report a micro 3-D kinetic energy harvester demonstrating an energy conversion from environmental mechanical-energy (3-D mechanical motion) to electrical energy (voltage output). In addition to energy harvesting/conversion from 3-D motion, we demonstrate a non-contact frequency-up rectification approach which converts an incoming lower vibration frequency to a higher frequency in order to increase the power output of the harvester.
A Three-Axial Frequency-Tunable Piezoelectric Energy Harvester Using a Magnetic-Force Configuration
(2014-09-01)
Chung, Tien-Kan
;
Wang, Chieh-Min
;
Yeh, Po-Chen
;
Liu, Tzu-Wei
;
Tseng, Chia-Yuan
To date, researchers have utilized energy harvesters to power wireless sensor nodes as self-powered wireless sensors to create many innovative wireless sensors network applications such as medical monitoring, machining-condition monitoring, and structural-health monitoring. Regarding to energy harvesters, some researchers demonstrated wideband or frequency up-converted vibrational energy harvesters using magnetic force together with piezoelectric materials. However, these harvesters are not able to harness 3-D or three-axial mechanical energy through using one single mechanism or configuration. To address this problem, we report a novel magnetic-force-configured three-axial frequency-tunable piezoelectric energy harvester in this paper. Due to the magnetic-force configuration, the harvester converts ambient three-axial mechanical vibration/motion to piezoelectric voltage-response (i.e., three-axial energy harvesting). Simultaneously, the harvester also converts the ambient vibration/motion at a lower frequency to higher frequency without mechanical wear-out (i.e., noncontact frequency up-conversion). Through modifying the configuration, the oscillating frequency is tunable. By frequency tuning, the harvester\'s oscillating frequency and ambient vibration frequency are able to be matched to maximize the power output. Experimental results show the peak voltage, peak power, and frequency conversion of one single piezoelectric beam of the harvester under an in-plane and out-of-plane vibration is up to 800 mV, 640 nW, and from 7 to 56 Hz, and 27 mV, 729 pW, and from 1 to 294 Hz, respectively. These results confirm the harvester is capable of harnessing energy from 3-D and three-axial mechanical motion/vibration, addressing frequency-mismatching issue, avoiding mechanical wear-out problems, and producing a stable voltage output. Due to these, the energy-harvesting approach will enable more novel and practical wireless sensors network applications in the future.
Characteristics of GaN-based photonic crystal surface emitting lasers
(2008-09-15)
Lu, Tien-chang
;
Chen, Shih-Wei
;
Kao, Tsung-Ting
;
Liu, Tzu-Wei
;
光電工程學系
Characteristics of GaN-based photonic crystal surface emitting lasers (PCSELs) were investigated and analyzed. The GaN-based PCSEL emits a blue wavelength at 401.8 nm with a linewidth of 1.6 angstrom and shows a threshold energy density about 2.7 mJ/cm(2) under the optical pumping at room temperature. The lasing wavelength emitted from PCSELs with different lattice constants occurs at the calculated band edges showing different polarization angles due to the light diffracted in specific directions, corresponding exactly to Gamma, K, and M directions in the K-space. Furthermore, the PCSEL also shows a spontaneous emission coupling efficiency beta of about 5 X 10(-3) and a characteristic temperature of 148 K. (C) 2008 American Institute of Physics.
Electromagnetic/Magnetic-Coupled Targeting System for Screw-Hole Locating in Intramedullary Interlocking-Nail Surgery
(2014-12-01)
Wong, Tze-Hong
;
Chung, Tien-Kan
;
Liu, Tzu-Wei
;
Chu, Hou-Jen
;
Hsu, Wensyang
At present, intramedullary interlocking nails are widely used for bone-fracture fixation in orthopedic surgeries. Surgeons often use X-ray imaging to find the actual location of the distal screw-holes of the nail after the nail is inserted into the medullary canal of a bone for fixation. Thus, the patients and medical team are inevitably exposed to radioactivity. In this paper, we report a radiation-free electromagnetic/magnetic-coupled targeting system to locate the distal screw-holes of the nail used in interlocking-nail surgery. The targeting system consists of a c-shaped electromagnet with a pick-up coil, a highly permeable curved silicon-steel strip embedded on the nail, a guiding mechanism, and electronic measuring instruments. An alternative current is applied to the electromagnet to generate a uniform magnetic field/flux in the electromagnet\'s air gap. When the nail inserted into the medullary canal of a bone is scanned through or rotated in the air gap of the electromagnet, the magnetic flux in the air gap is influenced by the silicon-steel strip embedded on the nail. The variation of the magnetic flux induces a voltage response in the pick-up coil due to electromagnetic induction. The pattern of the voltage response is analyzed to establish a criterion for screw-hole targeting. The results obtained using this criterion reveal that the maximum targeting error of the location and orientation targeting for a screw-hole with a diameter of 5 mm is <2 mm and 10 degrees, respectively. Thus, the system/approach is sufficiently simple and accurate to be used by surgeons in clinical surgery.
Lasing Characteristics of GaN-based Photonic Crystal Surface-Emitting Lasers
(2009)
Chen, Shih-Wei
;
Kao, Tsung-Ting
;
Liu, Tzu-Wei
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
We successfully demonstrated and analyzed the characteristics of GaN-based photonic-crystal surface emitting lasers at room temperature at different band edges (Gamma, K, and M), showing specific thresholds and polarization angles
Self-Magnetization-Switchable Micro-Magnetic Track Based Magnetic-Bead Manipulation
(2018-01-01)
Chung, Tien-Kan
;
Fang, Lin-Huei
;
Liu, Tzu-Wei
;
Chu, Hou-Jen
;
Ranabotu, Jaganmohan Reddy
In this paper, we report a self-magnetizationswitchable magnetic-track based magnetic-bead manipulation on a silicon wafer. The manipulation approach consists of a thermomagnetic NiCu micro-disc track (which is deposited on the silicon wafer), micro magnetic bead, a thermoelectric generator (TEG; which is placed beneath the silicon wafer), and four external electromagnets (which are used to produce a directional magnetic field). The Curie temperature of the NiCu micro-disc track is approximate room temperature. Due to this, when the TEG cools the NiCu micro-disc track lower than its Curie temperature (i.e., lower than room temperature), the track becomes ferromagnetic. However, when the TEG heats the NiCu micro-disc track higher than its Curie temperature (i.e., about or higher than room temperature), the track becomes paramagnetic. Therefore, by alternative cooling and heating, the track is switched between ferromagnetic and paramagnetic (i.e., magnetic moment is changed between normal and very small). This achieves on-chip self-magnetization-switchable track. Furthermore, when a directional magnetic field is applied to the track which becomes ferromagnetic, the track can guide the bead manipulation. Alternatively, when the track becomes paramagnetic, the track cannot guide the bead manipulation. This novel selfmagnetization-switchable magnetic-track-guided bead manipulation provides an important alternative bead manipulation for biomedical NIEMS/NEMS systems.