S.H. Chang

A precision piezodriven micropositioner mechanism with large travel range

A micropositioning stage with large travel range has been designed and built. The stage combines a piezoelectric driving element, flexure pivoted multiple Scott–Russell linkage, and a parallel guiding spring. Quality engineering techniques are used to optimize the configuration of the device in order to achieve the maximum displacement gain and the minimum angular deviation. A simple open-loop compensator is applied to reduce the hysteresis of the dynamic response of the stage. The experiment shows that the stage achieved a vacuum-compatible device with a travel of greater than 100 μm, a resolution of 0.04 μm, and an angular deviation of less than 31.1 μrad. The first natural frequency of the stage is 80 Hz and the settling time is approximately 50 ms. Compared with the uncontrolled condition, the controlled hysteresis is reduced significantly.

A high resolution long travel friction-drive micropositioner with programmable step size

A piezoelectric-driven Scott–Russel linear micropositioner utilizing the stick-slip effect of friction to drive a slider is presented. Effects of sawtooth, impulse, and transcendental electrical wave forms on the device performance are studied via numerical simulation and experiment test. The experiment demonstrates that positioning step sizes of 0.05–120 μm can be achieved at low input voltages of 2–25 V and essentially with unlimited travel range.

Miniature piezoelectric actuators: design concept, fabrication and performance evaluation

Magnifying mechanisms, which include bimorph configurations, waveguides, resonance, mechanical levers etc, that can convert a large-force, small-displacement piezoelectric material to become a smaller-force, large-displacement actuator are examined in detail. Sputtering processes for zinc oxide and lead-zirconate-titanate films, which are important for fabricating miniature laminated piezoelectric actuators, are presented. A newly developed laser Doppler interferometer that is especially designed for evaluating the performance of miniature piezoelectric actuators is also described. The design concept, optimization process, fabrication techniques and evaluation approach for such things as a piezoelectric impact hammer, a resonant dual-dimensional piezoelectric scanner, a Langevin type ultrasonic motor and a high-precision piezoelectric positioning stage are also discussed.

A novel design of piezo-driven dual-dimension optical scanning mechanism

An optical scanning mechanism capable of dual-dimension scanning is presented. The mechanism uses a piezoelectric element to drive a V-shaped reflecting mirror surface through two pairs of elastic beams. The design entails the use of various vibration modes to reflect the incident light in orthogonal directions. The design, fabrication, and mechanical, electrical, and optical performance of this scanning mechanism are presented. The scanning sensitivities of 88.8 and 19.3 μrad/V in each scanning direction are measured when operated at frequencies of 23.8 and 48.8 kHz, respectively. The capability of fine scanning sensitivity, high operating frequency, and wide scanning range is applicable for fine adjustment of the laser beam.

Dynamically programmable surface micro-wrinkles on PDMS-SMA composite

We report on the development of a PDMS-SMA composite whose surface micro wrinkles can be dynamically programmed by an electrical current supplied to the SMA wire. It is advantageous over other techniques for surface topographical modulation, including portability, real-time programmability, no requirement for specific surface chemistry, operability under ambient conditions, and relative ease of control. A simplified mechanical model is also developed to describe the force-deflection balance of the PDMS-SMA composite. The wavelengths and amplitudes of the wrinkles when different currents applied to the SMA are characterized, and the experimental results agree with the theoretical model. The developed composite device can be applied to programmable modulations of surface adhesion, friction, wettability, etc.

Damping characteristics of the Ti-rich TiNi melt-spun ribbon measured by using a dynamic mechanical analyzer

Damping characteristics of melt-spun Ti51Ni49 ribbons are investigated by using a dynamic mechanical analyzer (DMA). The as-spun Ti51Ni49 ribbons are crystalline and possess a uniform grain size distribution with an average diameter of 3 μm. The DMA results reveal that the tan δ value of the martensitic transformation peak increases with an increase in the temperature rate and applied deformation amplitude but decreases with an increase in the deformation frequency. Compared to amorphous or crystallized Ti50Ni25Cu25 melt-spun ribbons, the as-spun Ti51Ni49 ribbon was found to have a higher damping capacity during martensitic transformation when DMA tests were conducted at a cooling rate of 3 °C min−1 and a deformation frequency of 10 Hz. Besides, the as-spun Ti51Ni49 ribbon also exhibits a much higher inherent internal friction than bulk Ti50Ni50 or Ti51Ni39Cu10 shape memory alloys under isothermal conditions. The Ti51Ni49 melt-spun ribbon does not exhibit a relaxation peak, which is usually obtained in bulk Ti–Ni-based alloys or crystallized Ti50Ni25Cu25 melt-spun ribbons at about −75 °C in the DMA tan δ curve.

Surface modification of carbon cloth anodes for microbial fuel cells using atmospheric-pressure plasma jet processed reduced graphene oxides

In this study, we report on an easy, rapid, economical, and environmentally friendly method for surface modification of carbon cloth anodes applicable in microbial fuel cells (MFCs) by screen-printing reduced graphene oxide (rGO) followed by calcining using an atmospheric-pressure plasma jet (APPJ). Screen printing of rGO and APPJ treatment significantly increased the surface area of the effective materials for bacterial adhesion. The combination of screen printing of rGO and APPJ treatment also made the carbon cloth highly hydrophilic, which benefits the growth of bacteria on the surface of the carbon cloth. The rGO and APPJ-treated modified MFCs exhibited a maximum power density of 10.80 ± 0.19 mW m−2, whereas that of the unmodified MFCs was 6.02 ± 0.01 mW m−2. Both screen printing of rGO and APPJ treatment can be used for large-area surface modification, which is promising for manufacturing large-scale MFC stacks.