Shuo-Hung Chang

An ultra-precision XY/spl theta//sub Z/ piezo-micropositioner. I. Design and analysis

A novel three degree-of-freedom micropositioner was developed for deep ultraviolet lithography applications. The design of the micropositioner utilizes the monolithic flexural mechanism with built-in multilayer piezoelectric actuators and sensors to achieve translations in the X- and Y-axes and rotation in the theta(Z)-axis. The compact design aims at high resolution, high stiffness, and extremely low crosstalk interference. Parametric analyses of harmonic and forced vibrations are conducted to solve the derived dynamic models for the near optimum geometry of the micropositioner. Furthermore, the error budget analysis is conducted to minimize the effects of the geometric tolerance, material variation, and hysteresis errors.

Fabrication of single-walled carbon nanotube flexible strain sensors with high sensitivity

This work demonstrates a fabrication technique of high sensitivity flexible strain sensors at room temperature. The grown well-aligned millimeter-long single-walled carbon nanotube (SWCNT) was transferred from the silicon substrate to the pretrenched flexible substrate. The sensor design allows effective adhesion between SWCNT and flexible substrate for SWCNT lengthwise strain and piezoresistivity change. Experimental results show that the sensor achieves a high strain resolution of 0.004%. The measured piezoresistive gauge factor of the flexible sensor is 269. The demonstrated fabrication technique of flexible sensors shows advantage of high sensitivity, high quality, and is suitable for mass production.

Bubble growth and ink ejection process of a thermal ink jet printhead

The present study investigated bubble growth and the ink ejection process of a thermal ink jet (TIJ) printhead with a thin-film heater on the bottom-wall of the ink nozzle. Numerical predictions are presented for bubble volume, temperature, and pressure, and ink jet ejection length under various heating conditions. An inexpensive optical system was set up to visualize the transient ink ejection process. Experimental results to show the effect of the heating pulse conditions on the ejected droplet volume and ejected ink length are also presented. The experimental and numerical results agree well on both the ejected ink length for shorter time history (< 6 μs) and the threshold operating voltage for the ink ejection.

An ultra-precision XY/spl Theta//sub Z/ piezo-micropositioner. II. Experiment and performance

For pt I see ibid., vol. 46, no. 4 (July 1999). The performance of an ultra-precision three dimensional micropositioner using the built-in multilayer piezoelectric actuators and sensors is presented. The compact design utilizes the monolithic mechanism to achieve translation in the X- and Y-axes and rotation in the /spl theta//sub Z/ axis with high stiffness and high damping. Hysteresis, nonlinearity, and drift of piezoelectric effects are improved by incorporating the sensors in a feedback control. Experiments demonstrate that the micropositioner is capable of a 10 nm resolution over the travel range of 17.8 /spl mu/m in the X- and Y-axes and a 0.15 /spl mu/rad resolution over the range of 585 /spl mu/rad in the /spl theta//sub Z/ axis. The crossaxis interferences are within 1.14% of the full range. The results agree well with predictions by theoretical models.For pt I see ibid., vol. 46, no. 4 (July 1999). The performance of an ultra-precision three dimensional micropositioner using the built-in multilayer piezoelectric actuators and sensors is presented. The compact design utilizes the monolithic mechanism to achieve translation in the X- and Y-axes and rotation in the /spl theta//sub Z/ axis with high stiffness and high damping. Hysteresis, nonlinearity, and drift of piezoelectric effects are improved by incorporating the sensors in a feedback control. Experiments demonstrate that the micropositioner is capable of a 10 nm resolution over the travel range of 17.8 /spl mu/m in the X- and Y-axes and a 0.15 /spl mu/rad resolution over the range of 585 /spl mu/rad in the /spl theta//sub Z/ axis. The crossaxis interferences are within 1.14% of the full range. The results agree well with predictions by theoretical models.

A six-DOF prismatic-spherical-spherical parallel compliant nanopositioner

A nanopositioner using a 6-prismatic-spherical-spherical parallel (PSS) linked compliant mechanism driven by 6 multilayered piezoelectric actuators (PZT) is presented. Compared with a traditional Gough-Stewart platform in which each actuator was installed between the end effector and the base, this nanopositioner installed the PZT directly on the base to achieve much smaller mechanical loop, higher stiffness, faster response, and compactness. This nanopositioner consists of one fixed plate; three 2-PSS compliant mechanisms; and one end effector. The kinematics characteristics of the nanopositioner were analyzed through the pseudo-rigid-body model. The behavior of the compliant mechanism was intensively simulated by the finite element method (FEM). Tracking a 5 nm radius circle of the 15 times 15 times 5 cm3 prototype was experimentally demonstrated. The measurement results showed the nanopositioner achieved 8 mum travel with 5 nm resolutions and 200 murad rotation with 0.7 murad resolutions. The nanopositioner can be used to manipulate nano scale devices, fabricate nano components, or operate nano machines.

Droplet formation of a thermal sideshooter inkjet printhead

The present study aims to provide numerical predictions on the droplet formation process for a thermal sideshooter inkjet printhead, which directly aAects the printing quality of the printhead. The calculation procedure starts from the heat up of the printhead by an input electrical pulse, then obtains the pressure impulse response curve due to the formation and collapse of a bubble in the ink, the ink flow motion in the ink nozzle, and finally the evolution process of the ejected ink droplet outside the ink nozzle. The governing continuity and momentum equations for the flow motion in the ejected ink droplet are solved on the Eulerian frame by an implicit finite-diAerence scheme. The ink droplet leading is then updated to the new location from the newly obtained velocity. A comparison is made between the present numerical predictions with experimental results. A good agreement has been found. In addition, the present study shows the eAects of the operating voltage of electrical pulse, the ink properties, and the gravity on the breakoA time of ejected droplet from the ink nozzle exit and the separation time of the long tail from main droplet. ” 1998 Elsevier Science Inc. All rights reserved.

Electro-elastic characteristics of asymmetric rectangular piezoelectric laminae

The electro-elastic characteristics of clamped rectangular piezoelectric laminated plates were analytically investigated. A fully covered electrode piezoelectric layer was laminated on an elastic layer to form a nonsymmetrical laminated plate. Using the electro-elastic theory with the Kirchhoff-Love hypothesis, formulation of analyses for mechanical, electrical, and electromechanical characteristics of the laminae are presented. Numerical analysis was carried out using the extended Kantorovich method to yield eigenvalues and eigenfunctions. Theoretical predictions of dynamic characteristics were validated by comparing results with finite element analysis data. The calculated natural frequencies are presented in easy-to-use figures that are useful for sensor and actuator design in microelectromechanical systems (MEMS).

Determining Mechanical Properties of Carbon Microcoils Using Lateral Force Microscopy

Mechanical properties of amorphous carbon microcoil (CMC) synthesized by thermal chemical vapor deposition method were examined in compression and tension tests, using the lateral force mode of atomic force microscope (AFM). The AFM cantilever tip was manipulated by a piezoelectric scanner to contact, pull, and push an individual CMC. The lateral force that was exerted by the CMC deformation causes the twist of the AFM cantilever. It was monitored by the laser and photodetector of the AFM during the experiments. A linear response of the CMC was observed in the range of 25 nm to 5 mum of tension experiments. The results show that the spring constant of the CMC is reasonably proportional to the coil number. The shear modulus of the amorphous CMC is estimated to be 3 plusmn 0.2 GPa. The proposed method is promising to manipulate the compression and tension of the CMC and to measure the lateral force exerted in an ambient environment.

Fabrication of High Sensitivity Carbon Microcoil Pressure Sensors

This work demonstrates a highly sensitive pressure sensor that was fabricated using carbon microcoils (CMCs) and polydimethylsiloxane (PDMS). CMCs were grown by chemical vapor deposition using various ratios of Fe-Sn catalytic solution. The pressure sensor has a sandwiched structure, in which the as-grown CMCs were inserted between two PDMS layers. The pressure sensor exhibits piezo-resistivity changes in response to mechanical loading using a load cell system. The yields of the growth of CMCs at a catalyst proportion of Fe:Sn = 95:5 reach 95%. Experimental results show that the sensor achieves a high sensitivity of 0.93%/kPa from the CMC yield of 95%. The sensitivity of the pressure sensor increases with increasing yield of CMCs. The demonstrated pressure sensor shows the advantage of high sensitivity and is suitable for mass production.

Flow-induced melting of condensed domains within a dispersed Langmuir film

During phase transition from the liquid-expanded to the liquid-condensed state, a dispersed Langmuir film of pentadecanoic acid is submitted to an annular shear flow of moderate Reynolds number (Re=10–100). The mesoscopic morphology of this two-phase Langmuir film is investigated based on area fraction distribution of the condensed phase after a permanent regime is established. The distribution demonstrates radially inwards packing along the liquid surface induced by centripetal flow originating from centrifugation of the subphase along the rotating floor. For a growing level of centrifugation, a circular Reynolds ridge arises along the liquid surface. The Langmuir film experiences a strong morphological transition driven by a balance between surface shear and reduced line tension. As a result, a shear-induced melting of the condensed domains generates a new patterning which can be described as a regular and monodispersed matrix of tiny condensed droplets.