Hao Pengfei

Particle acceleration for delivery deoxyribonucleic acid vaccine into skin in vivo

Skin represents an important immunogenic inductive site, 3%–4% epidermis cells are special antigen-presenting cells. Deoxyribonucleic acid (DNA) vaccine can elicit vigorous immune responses in epidermis cells. The means of delivering DNA vaccine into epidermis cells becomes an important step in DNA vaccine applications. This article presents a new type of gene gun based on the principle of two-stage injector acceleration. DNA coated particles are attached on an screen-type carrier located at the negative pressure inlet, the particles will be sucked into the accelerating channel by negative pressure and be accelerated at a great speed. FLUENT, a computation fluid dynamic application software is used to simulate the flow condition of the injector. Distribution of Mach number, total pressure on exit cross section, and negative pressure on negative pressure inlet are analyzed, by which the process of acceleration of particles is determined. We also measured these parameters in this study. The data show that t...

Experimental Study on Transitional Flow in a Circular Microtube

We investigate the characteristics of the transition from laminar to turbulent flow in the microtube with a diameter of 310 μm. The microscopic particle image velocimetry is used to measure the water flow at Re=1600–2500 in the microtube. It is found that the flow transition occurs at Re=1600–1900, and the streamwise streaks and vortices appear in the transitional flow fields. These experimental observations provide a validation for the theoretical prediction of unstable travelling waves in pipe flow.