Chiang-Ho Cheng

Investigation of a piezoelectric valveless micropump with an integrated stainless-steel diffuser/nozzle bulge-piece design

To meet a growing need in biological and medical applications, innovative micro-electro-mechanical system (MEMS) technologies have realized important progress on the micropump as one of the essential fluid handling devices to deliver and control precise amounts of fluid flowing along a specific direction. This research proposes a piezoelectric (PZT) valveless micropump adopting an integrated diffuser/nozzle bulge-piece design. The pump mainly consisted of a stainless-steel structured chamber with dimensions of 8 mm in diameter and 70 μm in depth to enhance its long-term reliability, low-cost production, and maximized liquid compatibility. A PZT diaphragm was also used as a driving source to propel the liquid stream under actuation. As commonly used indices to describe pump operation, the delivered volumetric flow rates and pressures were determined at bulge-piece diameters of 2, 4 and 6 mm, with a driving voltage of 160 Vpp and frequency ranging from 50 to 550 Hz. Measurements and simulations have successfully shown that this micropump is capable of operating at a greater volumetric flow rate of up to 1.2 ml min−1 with a maximum back pressure of 5.3 kPa. In addition, the time-recurring flow behavior in the chamber and its relationship to the pumping performance were examined in detail.

Hybrid motion planning of a planar robot for a tracking problem with singularity

A motion planning problem for a planar robot on a path with singularity is studied in this paper. The motion planning problem is solved by a proposed hybrid motion planning method to guarantee the robustness of singularity and to reduce the computing load of the optimal-perturbation problem. To verify the proposed method, a tracking path with singularity is studied to compare the proposed method from the inverse Jacobin method. Moreover, a planar robot is designed and controlled via the PC-base architecture to implement the proposed method.

Characterization of droplet ejection process for a full-size piezoelectric inkjet printhead

Numerical simulations are performed to explore the fluid physics of droplet ejection process for a full-size piezoelectric inkjet printhead. In the analysis, the theoretical model takes account of a set of three-dimensional transient conservation equations of mass and momentum, with the incorporation of the continuous surface force model for treating the interfacial surface tension effect. The resultant governing equations are solved using an iterative semi-implicit method for pressure-linked equations consistent (SIMPLEC) algorithm for determining the flow properties. The volume-of-fluid (VOF) method in conjunction with the multi-dimensional piecewise linear interface construction (PLIC) technique is applied to characterize the behavior of liquid surface movement. Using the design configuration of a test piezo-diaphragm printhead, the time evolution of the gas-liquid interface is calculated for a complete ejection cycle of 164 μs. The flow and transport phenomena in various stages, including the ink filling, ejection, and droplet formation, are thoroughly examined in this work.