Chi-Chih Lai

A real-time dynamic imaging system for centrifugal microflow platforms

Based on the operational concept of quasi-static state and optoelectronic measurement technology, this research develops a real-time dynamic imaging system for centrifugal microfluidic platforms. Unlike the conventional centrifugal inspection system, which can only be used for examination of the final steady stage in microflow analysis, the developed system with a multi-speed controller and object tracking design is fabricated with low cost to recognize dynamic microflow patterns for different kinds of compact disc-type centrifugal microstructures. The characteristics of rotational control efficiency and image acquisition quality are obtained from fluidic microvalve experiments that are achieved in measuring microflow dynamic responses and in visualizing transient microflow patterns. A man–machine interface was connected with a computer to perform the control and alignment adjustments to catch exact image data for following analysis. The rotation stability of the system has been evaluated, and the rotation speed up to 4500 rpm with vertical vibration less than ±0.2 mm is achieved measured at radial distance of 5 cm. The image acquisition is transferred via USB 2.0 at a speed of up to 30 images per second to the display and memory module.

Nano-AAO-Based Microsensor for Monitoring Process Carbon Monoxide

This study developed a porous nano anodic aluminum oxide (AAO) based gas microsensor for detecting process carbon monoxide (CO) at room temperature. The small sensing microdevice has stable response with high sensitivity which includes porous AAO structures, gas sensing membrane, interdigitated sensing electrode, heater and temperature sensor. The tungsten oxide (WO3) sensing membrane covers AAO to enlarge total gas sensing surface area to enhance gas sensing response. The Pt interdigitated sensing electrode can also improve the sensitivity. The experimental results showed that the CO gas concentration sensitivity is proportional to temperature. As compared with the sensor without AAO, the concentration range of CO sensed by this microsensor is 100~1000 ppm, the gas sensing resistance change rate can be increased by 87.4 %.

Fabrication and application of a wireless inductance-capacitance coupling microsensor with electroplated high permeability material NiFe

A fully integrated wireless inductance-capacitance (LC) coupling microsensor was designed and fabricated by MEMS technology. The sensing loop was formed by connecting a deformable parallel-plated capacitor and a planar spiral inductor with a Ni(80)Fe(20) core. Polyimide and PMMA were used to isolate and package the devices. Typical dimension of the sensors was 5 × 5 mm2 × 0.77 mm. Different electroplated inductive coils (30, 40, and 60 turns) were fabricated to connect with a 4 × 4 mm2 plate capacitor in series. The LC sensing module for measuring liquid-level induced frequency responses was setup. Experimental results show that frequency response decreased as liquid level increased and sensitivity is about 7.01 kHz/cm with deviation less than 2%. Developed planar spiral inductor with high permeability magnetic core can provide a wide range of frequency variation in LC sensing applications.

Study on Light Intensity Enhancement of ZnO/ITO/P-GaN Light-Emitting Diodes

Light intensity enhancement of GaN-based blue light-emitting diodes (LEDs) is performed using different surface roughening technologies. Three roughening technologies are applied that contain surface roughening of p-GaN, textured indium tin oxide (ITO) on roughened p-GaN, and growing ZnO nanorods on textured ITO/p-GaN. A roughened p-GaN surface was grown on the c-plane sapphire substrate at temperature 800 °C. The morphologies of the textured LEDs with roughness in the range from 9.67 nm to 51.13 nm were observed. The light output efficiency of LED with roughened ITO layer is increased up to 73.8 %. Different dimensions of LEDs can be driven by constant injection current 20 mA without increasing threshold voltage, and larger size of ZnO/ITO/p-GaN LED shows higher luminance intensity. The LEDs with ZnO nanorods on roughened ITO/GaN have shown great performance to enhance the power conversion efficiency.

Evaluating solar microsensors packaged with MEMS covers for improving light tracking efficiency

A novel solar microsensor with microelectromechanical system (MEMS)-based packaging for improving solar tracking efficiency was proposed and a functional solar power sensing array was also developed. Solar energy as a renewable energy source in the world is the most important issue. The microsensor with different shapes of masks as light inlet was fabricated on silicon wafers to provide variable attenuation effect of the sunlight. To detect light incident elevation and azimuth accurately, a circuit module for a maximum power tracking system is developed conducting the automatic tracking function by feedback control technique. The best angle related sensitivity for the microsensors covered with inside-shrunk and inside-extended windows are 128.6 Ω/degree and 150.2 Ω/degree, respectively. The collimated process of the incident solar power by developed solar microsensor keeps maximum solar energy collection with the best long-term efficiency in photovoltaic energy conversion. The microsensor to sense collimated solar intensity is designed to promote solar energy collection efficiency and an intelligent bi-axes dynamic solar tracking device will develop in the future.

A Novel Electro-Optical Magnetic Microsensor with Reducing Interference Packaging

A novel electro-optical magnetic microsensor with reducing interference packaging mechanism for sensing magnetic field strength is demonstrated. Both capacitive and optical fiber sensing microstructures surrounded magnetic shields are fabricated in a chip using low temperature silicon-based MEMS compatible technology. Varied NiFe permalloy flaps embedded on polyimide membranes were used as flexible sensing mechanisms to actuate side-polished fiber and capacitor plate. The fiber Bragg gratings are used as optical sensors with high sensitivity. Results of simulations and experiments show that the structures can reduce interference and then increasing sensitivity and performance effectively. A sensitivity of 0.35nm/T is achieved by evaluating the peak shift of Bragg wavelength excited by Nd-Fe-B magnets with residual magnetic strength up to 1.12 T.

An Automatic Anemometer Based on the Technology of Double-Ring Thermoelectric Sensing Structure

The research presents a novel automatic anemometer based on the technology of automatic multi-dimensional thermoelectric sensor array. The multi-dimensional thermoelectric sensor array was designed to form a double-ring structure using commercial thermocouples to detect real-time airflow temperature distribution, velocity and direction. The sensing arrays and a controllable heater and a human-machine interface that is calibrated by a hot-wire anemometer. The anemometer has advantages of low cost, real-time detection with fast response. Related air flow information has measured accurately and repeatability.

A Magnetic Microsensor with Temperature Compensation Based on Optical Mechatronic Technology

An optical mechatronic magnetic microsensor with temperature compensation based on fiber Bragg grating (FBG) and microelectromechanical system (MEMS) technologies is demonstrated. Parallel nickel-electroplated cantilever beams are fabricated as an attractive bending mechanism for pushing the optical fiber. Related stress induced cantilever bend caused by magnetic force driving reflective wavelength shift that exactly corresponds with photo-elastic coupling effect to characterize microsensors. Two different cycles of gratings in the same fiber have fabricated to perform the function of magnetic sensing and temperature compensation for reducing temperature-induced bias in magnetic measurement automatically. The sensitivity of 2.238 T/nm with null temperature response has obtained which excited by Nd-Fe-B magnets with residual magnetic strength up to 1.26 Tesla.

Pneumatic-Controlled Fluidic Microdevices for Executing NOT, NOR, and NAND Logic Functions

Novel pneumatic-controlled logic microdevices based on a microelectromechanical system (MEMS) compatible process and microfluidic control technology have been developed for executing the universal basic logic functions of NOT, NOR, and NAND. The main fabrication processes for the logic microdevices include anisotropic silicon bulk etching, silicone rubber membrane formation, wafer bonding and packaging. The dynamic characteristics and pneumatic-controlled performance of the elastic membranes have been measured using an equipped fluidic instrument, which indicates their potential application to safety monitoring for preventing electric-induced disasters. All logic functions of the microdevices have been demonstrated to correspond exactly to the related truth tables. The newly developed logic microdevices are capable of controlling a liquid or gas system with high sensitivity in a wide dynamic range, and with strong immunity from temperature fluctuations.

Micromachined Packaging for Ultrasonic Transducers with Particle Restraint Mechanisms

The ultrasonic transducers micropackaging with particle pollution restraint mechanisms using micromachining process is proposed. The developed packaging with active dustproof mechanisms is very promising, because it permits the advantages of shielding, protection, reliability and signal connection. Technical approaches to the capacitive micro-ultrasonic transducer packaging are divided into three parts: micromachining cap structures, die attachments, and dustproof mechanisms. Simulations for handling the packaging issues are relatively developed. Features of the technology for restraint electrodes on microcap are described. The measurements for various physical and electrical parameters and the packaging needed to make optimal measurements is given. Future directions and potentials of the packaging technology are discussed