Shu-Sheng Lee

Phase-shifting algorithms for electronic speckle pattern interferometry

A set of innovative phase-shifting algorithms developed to facilitate metrology based on electronic speckle pattern interferometry (ESPI) are presented. The theory of a phase-shifting algorithm, called a (5,1) algorithm, that takes five phase-shifted intensity maps before a specimen is deformed and one intensity map after a specimen is deformed is presented first. Because a high-speed camera can be used to record the dynamic image of the specimen, this newly developed algorithm has the potential to retain the phase-shifting capability for ESPI in dynamic measurements. Also shown is an algorithm called a (1,5) algorithm that takes five phase-shifted intensity maps after the specimen is deformed. In addition, a direct-correlation algorithm was integrated with these newly developed (5,1) or (1,5) algorithms to form DC-(5,1) and DC-(1,5) algorithms, which are shown to improve significantly the quality of the phase maps. The theoretical and experimental aspects of these two newly developed techniques, which can extend ESPI to areas such as high-speed dynamic measurements, are examined in detail.

Ellipsometric surface plasmon resonance

We develop a new multifunctional optical biochip system that integrates an ellipsometer with a surface plasmon resonance (SPR) feature. This newly developed biochip biosensor, which we call ESPR for an ellipsometric SPR, provides us with a system to retrieve detailed information such as the optical properties of immobilized biomolecular monolayers, surface concentration variations of biomedical reactions, and kinetic affinity between biomolecules required for further biotech analysis. Our ESPR can also serve as both a research and development tool and a manufacturing tool for various biomedical applications.

A schematic-based design model for microphone and circuit integration

The transistor-level elements for condenser microphone design have been implemented in an IC design environment. Arbitrary diaphragm shapes can be composed and simulated by using our basic elements. The sensitivity and frequency response are obtained by co-simulation with the microphone and the readout circuit using Cadence/Spectrereg simulator. The new model is capable of dealing with the multi-field coupling effects including acoustical, mechanical and electrostatic behavior. Comparing to the ANSYS static simulation by using shell63 elements, our design model gives matched results based on the same mesh condition. Both the finite element analysis and theoretical calculated natural frequency agree with the nodal simulation results. Co-simulation enables trade-off analysis between the acousto-electro-mechanical and electronic design parameters. Furthermore, this platform provides a unified design interface between mechanical and electrical engineers, which is critical for top-down design of monolithic microsystems.

The study of the piston driving and position sensing for a linearly moving piston pump

The major component of the left ventricular assist device (LVAD) is the pump and the pulsatile pump can generate the pulsatile flow which is similar to the circulation human body. In this research work, the control method of the piston movement for a linearly moving piston pump has been developed. The pump owned 24-sets coils outside the tube and a piston inlaid with a permanent magnet was inside. An induced magnetic field was interact to the magnet and generated repulsive or attractive force to drive the piston when the current was applied to the coil. Some simulation of the magnetic field distribution with different numbers of coils carrying the different direction current has been done. To verify the simulation and the real situation of the piston moving, the Hall Effect sensors were used to sense the piston. The sensing signals showed the piston moved smoothly and controllable in the air under attractive force. However, the combination of repulsive or attractive forces was needed when the water was pumped in a simple channel by it. The flow rate was about 5.5 liters per minute when the pump was connected to the blood circulation simulation machine provided by Keelung Chang Gung Memorial Hospital. The developed control signals was successful to drive the linearly moving piston pump and achieve the minimum required flow rate for a LVAD.

Design and verification of the miniature optical system for small object surface profile fast scanning

As the progress of optical technologies, different commercial 3D surface contour scanners are on the market nowadays. Most of them are used for reconstructing the surface profile of mold or mechanical objects which are larger than 50 mm×50 mm× 50 mm, and the scanning system size is about 300 mm×300 mm×100 mm. There are seldom optical systems commercialized for surface profile fast scanning for small object size less than 10 mm×10 mm×10 mm. Therefore, a miniature optical system has been designed and developed in this research work for this purpose. Since the most used scanning method of such system is line scan technology, we have developed pseudo-phase shifting digital projection technology by adopting projecting fringes and phase reconstruction method. A projector was used to project a digital fringe patterns on the object, and the fringes intensity images of the reference plane and of the sample object were recorded by a CMOS camera. The phase difference between the plane and object can be calculated from the fringes images, and the surface profile of the object was reconstructed by using the phase differences. The traditional phase shifting method was accomplished by using PZT actuator or precisely controlled motor to adjust the light source or grating and this is one of the limitations for high speed scanning. Compared with the traditional optical setup, we utilized a micro projector to project the digital fringe patterns on the sample. This diminished the phase shifting processing time and the controlled phase differences between the shifted phases become more precise. Besides, the optical path design based on a portable device scanning system was used to minimize the size and reduce the number of the system components. A screwdriver section about 7mm×5mm×5mm has been scanned and its surface profile was successfully restored. The experimental results showed that the measurement area of our system can be smaller than 10mm×10mm, the precision reached to ±10μm, and the scanning time for each surface of an object was less than 15 seconds. This has proved that our system own the potential to be a fast scanning scanner for small object surface profile scanning.

Integrating SPR-ellipsometry and Electrochemical Measurements for Performance Evaluation of Label-free Thiophene-based Biosensor

The surface plasmon resonance reflectance changes measured with a circularly polarized ellipsometry and an electrochemical impedance spectroscopy were identified to be able to characterize the critical roles of biomolecules for vastly different biological functions and processes. Throughout the course of this study, interferon-gamma (IFN-γ) was chosen as the biomarker to test and to verify the performance of this newly developed system for Tuberculosis detection. The interactions of IFN-γ with immobilized anti-IFN-γ antibody at various concentrations were interrogated both optically and electrochemically. A semi-conductive linker bis-thiophene was thiolated to ensure the cross-linked monoclonal human IFN-γ antibody got self-assembled onto the gold thin film and form a label-free biosensor. The functional features of the bis-thiophene coated-gold film were characterized by cyclic voltammetry and impedance spectroscopy methods. The association of IFN-γ to the bis-thiophene bridging units via antibody-antigen interactions provided the basis for ultrasensitive detection of IFN-γ by tracking the conformation changes in surface-bound protein molecules. The phase shift can be attributed to the average thickness and the real-time index of refraction of the protein layer in different protein layer. Experimental results obtained by impedance spectroscopy and by phase-interrogation SPR showed linear dynamic range. Our experimental results verified that an increase in the concentration of the IFN-γ usually accompanied by phase increase in SPR and an impedance decrease in EIS. These results indicated that our newly developed integrated biosensing system can potentially provide new insight into various conjugate phenomena and interfacial processes for observing molecular conformation changes.

An integrated platform for biomolecule interaction analysis

We developed a new metrology platform which can detect real-time changes in both a phase-interrogation mode and intensity mode of a SPR (surface plasmon resonance). We integrated a SPR and ellipsometer to a biosensor chip platform to create a new biomolecular interaction measurement mechanism. We adopted a conductive ITO (indium-tinoxide) film to the bio-sensor platform chip to expand the dynamic range and improve measurement accuracy. The thickness of the conductive film and the suitable voltage constants were found to enhance performance. A circularly polarized ellipsometry configuration was incorporated into the newly developed platform to measure the label-free interactions of recombinant human C-reactive protein (CRP) with immobilized biomolecule target monoclonal human CRP antibody at various concentrations. CRP was chosen as it is a cardiovascular risk biomarker and is an acute phase reactant as well as a specific prognostic indicator for inflammation. We found that the sensitivity of a phaseinterrogation SPR is predominantly dependent on the optimization of the sample incidence angle. The effect of the ITO layer effective index under DC and AC effects as well as an optimal modulation were experimentally performed and discussed. Our experimental results showed that the modulated dynamic range for phase detection was 10E-2 RIU based on a current effect and 10E-4 RIU based on a potential effect of which a 0.55 (°/RIU) measurement was found by angular-interrogation. The performance of our newly developed metrology platform was characterized to have a higher sensitivity and less dynamic range when compared to a traditional full-field measurement system.

Analyzing biomolecular interactions by variable angle ellipsometry

In this paper, an innovative ellipsometer is developed and applied to metrology of the biomolecular interaction on a protein biochip. Both the theory, optical and opto-mechanical configurations of this newly developed ellipsometer and methodologies adopted in system design to improve the system performance are presented. It will be shown that by measuring the ellipsometric parameters, the corresponding concentration variation in biochemical reaction can be calculated according to stoichiometry analysis. By applying the variable angle ellipsometry to analysis of a multi-layered sample, the thickness and concentration are resolved. It is believed that the newly developed ellipsometer biosensor is able to undertake an accurate measurement on biomedical interaction.

Measuring the arterial-induced skin vibration by geometrical moiré fringe

The demand for self-measured blood pressure self-monitoring device has much increased due to cardiovascular diseases have become leading causes of death for aging population. Currently, the primary non-invasive blood pressure monitoring method is cuff-based. It is well developed and accurate. However, the measuring process is not comfortable, and it cannot provide a continuous measurement. To overcome this problem, methods such as tonometry, volume clamp method, photoplethysmography, pulse wave velocity, and pulse transit time are reported. However, the limited accuracy hindered its application for diagnostics. To perform sequential blood pressure measurement with a high accuracy and long-term examination, we apply moiré interferometry to measure wrist skin vibration induced by radial artery. To achieve this goal, we developed a miniaturized device that can perform moiré interferometry around the wrist region. The 0.4-mm-pitched binary grating and tattoo sticker with 0.46 mm-pitched stripe pattern are used to perform geometric moiré. We demonstrated that the sensitivity and accuracy of this integrated system were sufficient to monitor arterialinduced skin vibration non-invasively. Our developed system was validated with ECG signals collected by a commercial system. According to our studies from measurement, the repeatability of wrist pulsation measurement was achieved with an accuracy of 99.1% in heart rate. A good repeatability of wrist pulse measurement was achieved. Simulations and experiments are both conducted in this paper and prove of geometrical moiré method a suitable technique for arterial-induced skin vibration monitoring.

Development of a simple LDV system for tube micro particles flow rate measurement

Laser Doppler velocimetry (LDV) is one of the recent applied technologies in optical detection, and it has become an important research topic recently. In this research work, a previous developed Laser Doppler velocimetry system has been modified and applied to the tube flow rate measurement. We used optical fiber components as waveguides to make it easier to guide and focus the sampling light to tube flow. The scattered light was collected and coupled with the reference light to produce an interference beam. When the fluid flowed in the tube, the Doppler shift frequency according to the flow rate would exist in the interference beam. The Doppler shift frequency is calculated by using short-time Fourier transformation (STFT) algorithm to obtain the flows velocities. The tube flow contained the microparticles, therefore Mie scattering phenomena needed to be investigated. In the experiments, the 1 micron polystyrene suspension was used with a concentration of 1:50 and a peristaltic pump was used to pump the fluid flowing through the tube at the velocity of 5 mm/s, 10mm/s, 20mm/s, and 30 mm/s. The STFT algorithm programmed by matlab was used to acquire the spectrum and the variation of frequency. The measurement results confirmed that the particle flow rate has a linear relationship with the frequency of the STFT analysis. In this study, an LDV system has been established, which can measure the flow rate of tube particles by Doppler shift measurement and can be easily manipulated during the process.