Biomolecular screening with encoded porous-silicon photonic crystals

Nat Mater. 2002 Sep;1(1):39-41. doi: 10.1038/nmat702.


Strategies to encode or label small particles or beads for use in high-throughput screening and bioassay applications focus on either spatially differentiated, on-chip arrays or random distributions of encoded beads. Attempts to encode large numbers of polymeric, metallic or glass beads in random arrays or in fluid suspension have used a variety of entities to provide coded elements (bits)--fluorescent molecules, molecules with specific vibrational signatures, quantum dots, or discrete metallic layers. Here we report a method for optically encoding micrometre-sized nanostructured particles of porous silicon. We generate multilayered porous films in crystalline silicon using a periodic electrochemical etch. This results in photonic crystals with well-resolved and narrow optical reflectivity features, whose wavelengths are determined by the etching parameters. Millions of possible codes can be prepared this way. Micrometre-sized particles are then produced by ultrasonic fracture, mechanical grinding or by lithographic means. A simple antibody-based bioassay using fluorescently tagged proteins demonstrates the encoding strategy in biologically relevant media.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies / immunology*
  • Antigens / analysis
  • Antigens / immunology*
  • Biosensing Techniques / instrumentation*
  • Biosensing Techniques / methods*
  • Cattle
  • Crystallization
  • Fluorescence
  • Goats
  • Immunoassay / instrumentation
  • Immunoassay / methods
  • Membranes, Artificial*
  • Molecular Probes / analysis
  • Porosity
  • Rabbits
  • Rats
  • Serum Albumin / analysis
  • Serum Albumin / immunology
  • Silicon Compounds / chemistry*


  • Antibodies
  • Antigens
  • Membranes, Artificial
  • Molecular Probes
  • Serum Albumin
  • Silicon Compounds