|Title:||Systematic Optimization for the Design of Si-NW Biosensor|
|Keywords:||Si-NW, Sensitivity, P Electrostatic screening, Poisson Boltzmann Equation|
Biomolecular analysis at very low concentrations is becoming
increasingly important. Semiconducting nanowires have been reported as
highly sensitive biosensors. Biosensor based on Si-NW has already
demonstrated ultrasensitive detection of DNA, proteins, pH levels, etc.
Although it is generally accepted that NWs with lower doping density and
smaller diameter provides better sensitivity, the influence of factors
like electrostatic screening due to the ions in the solution, analyte
concentration, pH of the electrolyte solution on NW sensor performance
needs to be explained for the systematic optimization of sensor design.
In this theoretical study a simple analytical model, based on
reaction-diffusion theory is developed to obtain the minimum detectable
concentration by a Si-NW biosensor. Investigating the average response
time this study shows that, for a reasonable incubation time (500 sec),
Si-NW sensor can detect down to about 350 fM concentrations. Also the
Poisson Boltzmann Equation is solved analytically based on the result of
the diffusion-capture model to show that the electrostatic screening
within an ionic environment limits the response of a Si-NW biosensor. In
this research work, maximum pH sensitivity achieved for Si-NW sensor is
45 mV/pH. This study concludes that, the parameters such as the
dimension of the Si-NW, the doping level of the Si-NW, analyte
concentration, the ions concentration in the solvent, pH of the solution
etc must be optimized for high sensitivity biomolecule detection.