Browsing by Author "Hsu, CP"

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A two-way membrane-type micro-actuator with continuous deflections
(2000-09-01)
Hsu, CP
;
Hsu, WS
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機械工程學系
;
Department of Mechanical Engineering
This paper presents design, simulation, fabrication, and testing of a novel two-way micro-membrane actuator able to deflect in both upward and downward directions with continuous deflections. The design concept, to realize two-way continuous movement, is achieved by arranging different bimorph structures at different regions of the actuator with two kinds of boundary conditions. The actuator comprises of a square membrane with four bimorph beams and one central bimorph plate on it. The material (e.g. aluminum) on the top layer of the bimorph beams and plate has a larger thermal expansion coefficient than the material (e.g. silicon dioxide) of the membrane. The driving voltages in the two operating modes are both less than 3.5 V at about 350 mW maximum power consumption for an 1 mm(2) membrane actuator. The upward and downward deflections achieved up to 50 and 15 mu m with maximum simulated temperatures less than 420 and 150 degrees C, respectively. A finite-element model is built to simulate the thermal mechanical behaviors that are compared with the experimental results. The design parameters influencing the deflections of the actuator are also discussed.
Ab initio characterization of electron transfer coupling in photoinduced systems: Generalized Mulliken-Hush with configuration-interaction singles
(2005-12-29)
Chen, HC
;
Hsu, CP
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應用化學系分子科學碩博班
;
Institute of Molecular science
To calculate electronic couplings for photoinduced electron transfer (ET) reactions, we propose and test the use of ab initio quantum chemistry calculation for excited states with the generalized Mulliken-Hush (GMH) method. Configuration-interaction singles (CIS) is proposed to model the locally excited (LE) and charge-transfer (CT) states. When the CT state couples with other high lying LE states, affecting coupling values, the image charge approximation (ICA), as a simple solvent model, can lower the energy of the CT state and decouple the undesired high-lying local excitations. We found that coupling strength is weakly dependent on many details of the solvent model, indicating the validity of the Condon approximation. Therefore, a trustworthy value can be obtained via this CIS-GMH scheme, with ICA used as a tool to improve and monitor the quality of the results. Systems we tested included a series of rigid, sigma-linked donor-bridge-acceptor compounds where "through-bond" coupling has been previously investigated, and a pair of molecules where "through-space" coupling was experimentally demonstrated. The calculated results agree well with experimentally inferred values in the coupling magnitudes (for both systems studied) and in the exponential distance dependence (for the through-bond series). Our results indicate that this new scheme can properly account for ET coupling arising from both through-bond and through-space mechanisms.
Constructing quantitative models from qualitative mutant phenotypes: preferences in selecting sensory organ precursors
(2006-06-01)
Hsu, CP
;
Lee, PH
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Chang, CW
;
Lee, CT
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應用化學系分子科學碩博班
Motivation: To study biology from the systems level, mathematical models that describe the time-evolution of the system offer useful insights. Quantitative information is required for constructing such models, but such information is rarely provided. Results: We propose a scheme-based on random searches over a parameter space, according to criteria set by qualitative experimental observations-for inferring quantitative parameters from qualitative experimental results. We used five mutant constraints to construct genetic network models for sensory organ precursor formation in Drosophila development. Most of the models were capable of generating expression patterns for the gene Enhancer of split that were compatible with experimental observations for wild type and two Notch mutants. We further examined factors differentiating the neural fate among cells in a proneural cluster, and found two opposite driving forces that bias the choice between middle cells and the peripheral cells. Therefore, it is possible to build numerical models from mutant screening and to study mechanisms behind the complicated network.
Design and fabrication of a three-dimensional long-stretch micro drive by electroplating
(2003)
Wu, CT
;
Tai, WC
;
Hsu, CP
;
Hsu, W
;
機械工程學系
Although lots of works have been devoted to develop the microactuators or microstructures, few researches have been done on three-dimensional microactuators. Here the feasibility investigation on a three-dimensional electrothermally driven long-stretch micro drive (LSMD) is proposed by integrating the LSMD and mechanical hinge mechanism. The LSMD (about 2000 mum x 500 mum) consists of two cascaded compliant structures in parallel. Each cascaded structure is formed by connecting several basic actuation units in series. The mechanical hinge is used to allow the LSMD to be lifted as a three-dimensional structure. One of the important issues in fabricating the three-dimensional microactuator is the conducting circuit to actuate the microactuator. Here the Ni electroplating process is used to fabricate the mechanical hinge structure and the LSMD, then the mechanical hinge itself can act as the conductive circuit easily. From the LSMD simulation results, several design parameters are found to have significant influence on the output displacements. Larger out-stretching displacements are feasible by proper choice of design parameters. Preliminary fabrication results of nickel-made LSMD exhibit output displacement of 190 mum at input voltage of 3 volts. Fabrication results of nickel-made three-dimensional LSMD are also presented.
Electrothermally driven long stretch micro drive with modlithic cascaded actuation units in ompact arrangement
(2003)
Hsu, CP
;
Liao, TS
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Hsu, WY
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機械工程學系
;
Department of Mechanical Engineering
An electrothermally-driven long stretch micro drive (LSMD) is presented for in-plane rectilinear motions in hundreds of micrometers with very compact arrangement. High output performance (output displacements over device area excluding electrical contact pads) of 200 mum/mm(2) has successfully achieved for devices made of 10similar to12 mum thick electroplated nickel. The proposed device (N=5) features large output displacements with low operation temperatures (< 350degreesC) and driving voltages (< 4 volts). It can be operated up to 100 Hz at 3 volts without displacement degradations. Experiments and simulations are conducted to verify two design issues, bent beam angle and constraint bar width, with good agreements. The output displacements can be effectively magnify by cascading more actuation units in cascaded structures of the micro drive.
Influence of initial curvature effect on micromachined thermal bimorph actuation
(2001)
Hsu, CP
;
Hsu, WY
;
機械工程學系
;
Department of Mechanical Engineering
While the micro bimorph structures are fabricated with enough initial curvatures or so-called geometrical imperfections, structural instability may occur to result in snap-through behaviors and exhibit large deflection strokes. The bimorph structures with various initial deflections ratios and various heating area ratios are simulated and fabricated to predict the stable and unstable regions of the curved bimorph structures with clamped boundary condition. Four major types of load-deflection curves are described and discussed. Testing results and some observations are reported.
Instability in micromachined curved thermal bimorph structures
(2003-11-01)
Hsu, CP
;
Hsu, WY
;
機械工程學系
;
Department of Mechanical Engineering
For the micromachined thermal bimorph structure, there is often initial deflection, or so-called geometrical imperfection, which may affect the stability of the structure. Here, finite element simulations and experiments are conducted to study the influences of initial deflection and actuating region on mechanical behaviors of a curved bimorph structure with clamped boundary condition. Devices are fabricated by adjusting the internal stresses of polysilicon layers on bimorph structures to achieve various initial deflections. Various actuation regions are achieved by designing different sizes of top layers covering the bottom layers of the bimorph structures. Stable and unstable regions in terms of two design factors, initial deflection ratio and bimorph ratio, are characterized by simulations and experiments. It is found that the curved bimorph structure is stable when the bottom layer is fully covered with the top layer or the initial deflection is much smaller than the structure thickness. The stable device is found to deflect in one direction only. The bimorph structure becomes unstable while the initial deflection is close to or larger than structure thickness. For unstable curved bimorph structures, we find the snap buckling effect with two-way deflections and a hysteresis loop.
Tdesign and fabrication of a three-dimensional long-stretch micro drive by electroplating
(2004)
Tai, WC
;
Wu, CT
;
Hsu, CP
;
Hsu, W
;
機械工程學系
Here a three-dimensional micoractuator is proposed by integrating an electro-thermal long stretch micro drive (LSMD) and mechanical hinge mechanism. The mechanical hinge is used to allow the LSMD to be lifted. One of the important issues in fabricating the lifted microactuator is the conducting circuit to actuate the microactuator. Here the electroplating process is used to fabricate the mechanical hinge structure and the LSMD, and then the mechanical hinge itself can act as the conductive circuit easily. The fabrication and testing result show that the three-dimensional LSMD of 2000 mum wide and 500 mum high can stand vertically with output displacement up to 56 mum at input voltage of 2 volts. However, it is found that the output displacement of three-dimensional LSMD is smaller than planar LSMD with substrate beneath due to the lacking of heat conduction at the same input voltage.
The dynamical correlation in spacer-mediated electron transfer couplings
(2006-06-28)
Yang, CH
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Hsu, CP
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應用化學系分子科學碩博班
;
Institute of Molecular science
The dynamical correlation effect in electron transfer (ET) coupling was studied in this work, for cases where electrons tunnel through a many-electron environment. The ET couplings for three different bridge-mediated model systems were calculated: (I) trans-alkyl chains [H2C-(CH2)(n)-CH2, n=2-10], (II) two isomers of trans-1,4-dimethylenecyclohexane, and (III) two ethylenes spaced by a saturated ethane molecule. The couplings were calculated as half energy gaps of the two lowest adiabatic states. The dynamical correlation was included with spin-flip (SF) and ionization potential or electron affinity coupled-cluster singles and doubles (SF-CCSD and IP/EA-CCSD) and a Delta CCSD scheme. The direct coupling (DC) scheme is also used as a way to obtain a solution with nondynamical correlation, since DC uses approximated eigenstates that are symmetry-restoring linear combinations of two symmetry-broken unrestricted Hartree-Fock configurations. For all cases tested except for one, results from the DC scheme closely follow the CCSD data, indicating that the dual-configuration solutions can be a good approximation of wave functions with nondynamical correlation included, but there exist exceptions. Comparing the DC results with SF-CCSD and IP or EA-CCSD data, we concluded that the dynamical correlation effect is small for most of the cases we tested. (c) American Institute of Physics.
Triplet-triplet energy-transfer coupling: Theory and calculation
(2006-01-28)
You, ZQ
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Hsu, CP
;
Fleming, GR
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應用化學系分子科學碩博班
;
Institute of Molecular science
Triplet-triplet (TT) energy transfer requires two molecular fragments to exchange electrons that carry different spin and energy. In this paper, we analyze and report values of the electronic coupling strengths for TT energy transfer. Two different methods were proposed and tested: (1) Directly calculating the off-diagonal Hamiltonian matrix element. This direct coupling scheme was generalized from the one used for electron transfer coupling, where two spin-localized unrestricted Hartree-Fock wave functions are used as the zero-order reactant and product states, and the off-diagonal Hamiltonian matrix elements are calculated directly. (2) From energy gaps derived from configuration-interaction-singles (CIS) scheme. Both methods yielded very similar results for the systems tested. For TT coupling between a pair of face-to-face ethylene molecules, the exponential attenuation factor is 2.59 A(-1)(CIS/6-311+G(**)), which is about twice as large as typical values for electron transfer. With a series of fully stacked polyene pairs, we found that the TT coupling magnitudes and attenuation rates are very similar irrespective of their molecular size. If the polyenes were partially stacked, TT couplings were much reduced, and they decay more rapidly with distance than those of full-stacked systems. Our results showed that the TT coupling arises mainly from the region of close contact between the donor and acceptor frontier orbitals, and the exponential decay of the coupling with separation depends on the details of the molecular contacts. With our calculated results, nanosecond or picosecond time scales for TT energy-transfer rates are possible. (c) 2006 American Institute of Physics.