Optofluidics

Optofluidics refers to manipulation of light using fluids, or vice-verse, on the micro to nano meter scale. By taking advantage of the microfluidic manipulation, the optical properties of the fluids can be precisely and flexibly controlled to realize reconfigurable optical components which are otherwise difficult or impossible to implement with solid-state technology. In addition, the unique behavior of fluids on micro/nano scale has given rise to the possibility to manipulate the fluid using light. In the Penn State Bio-NEMS laboratory, one of the ongoing efforts is to develop tunable microlenses that can adaptively focus light within lab-on-a-chip devices. Such lenses can greatly enhance the performance of a variety of on-chip biological/chemical assays that rely on optical characterization, such as cell sorting, single cell analysis, and single molecule detection. Recently we successfully demonstrated an optofluidic tunable microlens (Fig. 1) based on the dean flow fluid interface bending effect. The uniqueness of this lens is that it can fit in a planar lab-on-a-chip device while is still capable of focusing light perpendicular to the device plane (x-z plane). We are also exploring other on-chip reconfigurable optofluidic devices.

Figure 1: The mechanism of the tunable optofluidic microlens. CaCl2 solution (n = 1.445) bows outward into water (n = 1.335) due to the dean flow effect induced in the curve. Shorter focal length is obtained after flow transitions from (a) a low flow rate to (b) a high flow rate.

References

Xiaole Mao, John Robert Waldeisen, Bala Krishna Juluri, Tony Jun Huang, Hydrodynamically Tunable Optofluidic Cylindrical Microlens, Lab on a Chip, Vol. 7, pp. 1303-1308, 2007. [PDF]
Xiaole Mao, Tony Jun Huang, Focusing Fluids and Light in Micro/Nano Scale – Enabling Technologies for Single-Particle Detection, IEEE Nanotechnology Magazine, 2008 (in press).