Papers by Author: W.W. Zhang

Abstract: Microfluidic channel and micro-cavities were fabricated from polyhydroxyalkanoate biodegradable polymer using a direct 20ns, 248 nm excimer laser writing method. First we give a design of the micro-analytical device; second we discussed the laser ablation of biodegradable ppolymer material. The morphology, dimensional accuracy, and surface conditions of the fabricated micro-devices were studied using atomic force microscopy, scanning electron microscopy, optical microscopy, and X-ray photoelectron spectroscopy. Melting of the biodegradable polymer was observed at a fluency of 50mJ/cm2 while ablation was observed at a fluency of 100mJ/cm2.The different width between bottom and top surface are studied in our research. The particle deposited on the polymer surface is seen from the SEM of 248nm laser ablation of PHA. However, the direct burning of PHA can be seen from the optical photo by 355nm laser. Compare to results of PHA with two different lasers, we can see that the 248nm laser is a suitable choice.

Abstract: Molecular dynamics simulations are carried out to characterize the mechanical properties of [001] and [110] oriented silicon nanowires, with the thickness ranging from 1.05nm to 3.24 nm. The nanowires are taken to have ideal surfaces and (2×1) reconstructed surfaces, respectively. A series of simulations for square cross-section Si nanowires have been performed and Young’s modulus is calculated from energy–strain relationship. The results show that the elasticity of Si nanowires is strongly depended on size and surface reconstruction. Furthermore, the physical origin of above results is analyzed, consistent with the bond loss and saturation concept. The results obtained from the molecular dynamics simulations are in good agreement with the values of first-principles. The molecular dynamics simulations combine the accuracy and efficiency.