Microfluidic and Biosensing System
Miniaturization of a biological/chemical analysis system (micro- or nano-TAS) is not merely reduction of analysis time and materials cost required for completing the investigation procedure, comparing with the conventional bench process. The length scale matching between the miniaturized devices and the biological objectives enables the direct manipulation of molecules and localization of molecular-surface interaction that facilitate high efficient molecular mixing, separation, and molecular recognition, such that sensitivity and specificity can be significantly enhanced.
As the flow passage downscales to micro flow region pressure-driven forces becomes less effective; conversely, electrokinetic force dominates at the scale. The main focus of the laboratory is to understand the scaling effects of the electrokinetics in liquid in contrat to molecular forces and the accompanying electrothermal issues in order to make an integrated system that is able to utilize the force fields for effective molecular/fluidic control and sensing.
Ultra-sensitive Mirrormirror Embedded Biosensor
The low light collection efficiency in a conventional optical detection system limits the sensitivity of fluorescence based biomolecule sensing due to the spatial mismatch between the 2-D light collection optics and 3-D fluorescence emission from a molecule. Taking the advantage of microfabrication technology, we fabricated a micro biosensor with all its sidewalls integrated with crystal-plane smooth micromirrors that redirect the 3-D emitted fluorescence light to a 2-D opening of an optical detection system. The sensitivity, as a result, was enhanced by two orders of magnitude.
Specific DNA Detection without Separation
In most biosensing methods such as ELISA and DNA assay, the combination of high specificity and sensitivity relies on an efficient separation scheme that isolates the target-probe complexes from the non-binding molecules in order to avoid false positive signal. The separation usually is carried out on a solid surface through the steps of immobilization and washing. In a micro biosensor, this separation basing on washing scheme becomes ineffective due to the huge drag force resulted from the dramatic increase of surface-to-volume. Using a molecular beacon, an oligo probe that forms a hairpin structure and becomes fluorescent upon hybridizes with its complementary strand, for DNA detection, separation becomes unnecessary as the non-binding molecular beacon still remains non-fluorescent and does not generate false signal. Moreover, since immobilization is also not required, the target-probe hybrids are free to be manipulated in liquid and can be moved, trapped, and concentrated to the detection region of a laser induced fluorescence (LIF) system, thereby enhancing the system sensitivity.