Porous microstructure multi layer spectroscopy and biosensing

Abstract

A preferred embodiment biosensor is a multi-layer micro-porous thin film structure. Pores in a top layer of the micro-porous thin film structure are sized to accept a first molecule of interest. Pores in a second layer of the micro-porous thin film structure are smaller than the pores in the top layer and are sized to accept a second molecule of interest that is smaller than the first molecule of interest. The pores in the second layer are too small to accept the first molecule of interest. The pores in the top layer and the pores in the second layer are sized and arranged such that light reflected from the multi-layer micro-porous thin film structure produces multiple superimposed interference patterns that can be resolved. In preferred embodiments, the multi-layer micro-porous thin film structure is a porous silicon thin film multi-layer structure formed on a silicon substrate, such as a silicon wafer. Specific and nonspecific binding can be detected with biosensors of the invention. The position of peaks in the Fourier transform of the reflection spectrum and the shift in peak amplitudes can be used to determine the presence and quantity of targeted biological molecules of interest.

1 . A biosensor, comprising: 
 a multi-layer micro-porous thin film structure;    pores in a top layer of the micro-porous thin film structure being sized to accept a first molecule of interest;    pores in a second layer of the micro-porous thin film structure being smaller than said pores in the top layer and being sized to accept a second molecule of interest that is smaller than said first molecule of interest, said pores in the second layer being too small to accept the first molecule of interest;    wherein said pores in the top layer and said pores in said second layer are sized and arranged such that light reflected from the multi-layer micro-porous thin film structure produces multiple superimposed interference patterns that can be resolved.    
   
   
       2 . The biosensor of  claim 1 , wherein said multi-layer micro-porous thin film structure is oxidized.  
   
   
       3 . The biosensor of  claim 2 , wherein said multi-layer micro-porous thin film structure is thermally oxidized.  
   
   
       4 . The biosensor of  claim 2 , wherein said multi-layer micro-porous thin film structure is ozone oxidized.  
   
   
       5 . The biosensor of  claim 3 , wherein said multi-layer micro-porous thin film structure is pre-treated with at least one of said first and second molecules of interest.  
   
   
       6 . The biosensor of  claim 1 , multi-layer micro-porous thin film structure is formed of porous silicon.  
   
   
       7 . A method for biosensing, the method comprising: 
 exposing a biological analyte to a multi-layer micro-porous thin film structure that has a top layer with larger pores than a second layer, the pores being sized to produce multiple superimposed interference patterns that can be resolved in the reflectivity spectrum;    exposing the multi-layer micro-porous thin film structure to light to produce a reflectivity spectrum;    sensing the reflectivity spectrum to obtain reflectivity data;    extracting optical parameters from the reflectivity data;    determining, from the optical parameters, whether at least one biomolecule of interest is present in said biological analyte.    
   
   
       8 . The method of  claim 7 , wherein said step of extracting comprises computing a fast Fourier transform of the reflectivity spectrum.  
   
   
       9 . The method of  claim 8 , wherein said step of determining comprises determining a position shift of peaks in the Fourier transform of the reflectivity data.  
   
   
       10 . The method of  claim 7 , wherein said step of determining comprises determining an amplitude shift of peaks in the Fourier transform of the reflectivity data.