Nowadays, the major challenging issues in the manufacture of lab-on-a-chip devices is the difficulties in the additional packaging and assembly.In general, the microlenses can find important applications in lab-on-a-chip devices such as light focusing, fluorescence collecting and optical imaging. However, incorporation of microoptical components with good optical property into the fused silica chip by femtosecond laser has not been achieved yet, because the surface after chemical etching usually exhibits poor smoothness,which gives rise to strong scattering and loss of light.

To overcome this issue, Researchers at Shanghai Institute of Optics and Fines Mechanics (SIOM/China) and RIKEN-Advanced Science Institute(Japan)recently showed that the surface roughness can be significantly reduced with an oxyhydrogen (OH) flame polish method(Applied Physics A-Materials Science & Processing 102(1),179-183,2011 ).

In the paper, they demonstrate the integration of microfluidics and microoptics on a fused silica glass chip, which possesses the capacity to detect and magnify the image of fluorescent beads fed in microfluidic channels. The opportunity to perform the one-continuous integration of microoptics and microfluidics is offered by the extremely high intensity of the tightly focused fs laser pulses which can enable highly nonlinear interaction between light and matter [23], thereby providing an efficient way for local modification of transparent materials. This chip may find great potential in compact bioimaging and detection implementations. At this moment,the imaging quality of the microlens still cannot compete to that of the conventional microscope, mainly due to the aberration of a singe spherical lens. To eliminate the imaging aberration, one can use either a combination of carefully designed microlenses or a nonspherical microlens. At present, both strategies are under consideration for solving this aberration problem with the 3D femtosecond laser direct writing technique.