The Research Of Improving Detection Limit Of Microfluidic Biosensor

Microftuidic, also known as lab on chip, can integrate lots of operation units on one chip such as sample separation, preparation, reaction, detection and information processing in chemistry and biology fields. Moreover, the advantages including convenient operation, rapid detection, compact in size, convenient to carry and less sample consumption can be found in Microftuidic. Optofluidics are analytical field in Microftuidic that provide lots of excellent characteristics on enhancing the sensing performance and simplifying the design of microsystems. Meanwhile, the optical refractive index (RI) detection is a prominent method on biosensing, due to its high precision, real-time results and label-free detection. The nanowier biosensor is widely researched and applied in Microftuidic by scholars because of its high sensitivity. For biosensors used in Microftuidic, the detection limit (DL) is one of the most important parameters wich can estimate the detectability of biosensor.In this paper a series of research has been carried out around detection limit for Microftuidic biosensor based on Fabry-Perot cavity (FPC) and nanowires. The main contents are as follows:1. Smooth and flat surfaces of the microchannelare obtained by using a silicon on insulator (SOI) substrate, in which the oxide layer functions as an etch-stop layer. Thus, high-Q FPC biosensor can be obtained by deposition SiO2/Ta2O5 dielectric DBR on the smooth channel surface. The measured Q-factor and sensitivity of the FPC biosensor are 861 and 1100±121 nm/RTU (RI units), respectively, and the corresponding DL reaches 1.1 ×10-5 RIU, which is the best result of optofluidics FPC till now.2. The FPC sensor with integrated dual-channel structure, which is fabricated on a SOI (silicon-on-insulator) substrate for eliminating the etching roughness of channel surface and enhancing the Q-factor, is proposed for optical differential detection (ODD). with employing ODD, system noise such as drift of wavelength, power, and temperature can be effectively suppressed. Moreover, the small signal can be extracted from the large output value, which enables sufficient amplification of the small signal. A DL of 5.5 × 10-8 RIU is experimentally demonstrated, which is one of the best results of optofluidics till now.3. The promotion of nanowire biosensor DL is discussed from the point of electronic mobility in nanowire field effect transistor (FET). Due to appropriate InP shell thickness (3.3 nm), optimized SiO2 layer and contact electrode (Au/Ti), and strain-induced built-in electric field (including piezoelectric field) along the NW, a recorded room-temperature electron mobility of 22,300 cm2/Vs was achieved, which is the best result of nanowire FET at room-temperature till now.4. Nanowire diode based on strain-engineered band-gap was realized by using tapered InAs/InP core/shell structure. A band-gap variation of 0.21 eV along the InAs wire was obtained with an InP shell thickness of 6.5 nm. The strain-engineered structure would increase the design freedom of NW devices.