This paper presents a tunable optofluidic circular liquid fiber through the numerical simulation. Fiber is a significant optical device and has been widely applied on optical fiber communication. But the fiber based solid has limited tunability. Compared to solid fiber, the fiber based liquid material is relatively infrequent. Cause for the liquid optical device has more freedom tunable properties than solid counterpart, it has attracted more interest. The traditional optofluidic waveguide is designed like a sandwich in planar channel. This two-dimensional (2D) structure liquid waveguide will face huge transmission loss in the perpendicular direction of the flow streams. In this paper, a curving microchannel is designed inside the microchip to produce centrifugal effect. Two different liquids are injected into the chip by external pumps. In a particular situation, the core flow will be totally surrounded by the cladding flow. So the liquid can form an optical waveguide. Its structure is similar to an optical fiber which high refractive index (RI) liquid is core of the waveguide and the low RI liquid is cladding of the waveguide. Profit from the reconfigurability of liquid material, this liquid fiber has excellent tunability. The diameter of the core flow can be tuned in a wider range by changing the volume ratio of the flows through the finite element analysis. It is predictable that such a tunable liquid fiber may find wider applications in lab-on-a-chip systems and integrated optical devices.
Gold nanoparticles have very unique physical, chemical and biological characters, which makes them have widespread applications in many fields. Sorting gold nanoparticles with different size is of great importance because the unique properties of gold nanoparticles relate with their sizes extremely close. Optical sorting is an excellent way due to much better sorting precision compared with the traditional sorting methods. In this paper, a new chip design sorting gold nanoparticles is presented and results of sorting two different nanoparticles have been analyzed as well. Mie theory is used to calculate the optical force of nanoparticles in different diameter, and finite element analysis is used to analysis the variation of flow field and sorting process of gold nanoparticles.