Twodimensional nanohole array surface plasmon resonance biosensor Aditya Kher, Lin Pang, H' Matthew

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Two-dimensional nanohole array surfaceplasmon
resonance biosensorAditya Kher, Lin Pang, H.
Matthew Chen, and Yeshaiahu Fainman
Background
Experiment

• A microfluidic channel is mounted onto the
  nanohole array
• Monitor changes on the surface of the nanohole
  array by looking at the SPP resonant wavelength
• Different liquids in the fluidic channel means
  different refractive indices at the interface,
  detected as different resonant wavelengths for
  the SPP

• A surface plasmon-polariton (SPP) is an
  electromagnetic wave that is confined to the
  interface between a metal and a dielectric.
• SPPs are very sensitive to changes on this
  surface, such as changes in refractive index
• Because of the SPP dispersion relation, a grating
  coupler is used in order to excite them
• In our case, this grating is a two-dimensional
  nanohole array

Fabrication
Measuring surface hydrophilicity

• We have developed a novel bottom-up approach to
  fabricating these nanohole arrays
• Resist is patterned using low-cost holographic
  lithography
• Gold is sputtered at an angle, on top of the
  resist pillars, leaving holes where there are
  holes in the resist layerno etching required
• The size of the gold nanoholes can be changed by
  changing the sputter deposition time longer
  deposition yields smaller holes, and smaller
  holes produce a better SPP signal

• We can use this setup to measure the
  hydrophilicity, or wetting ability, of the
  nanohole array surface with respect to various
  fluids
• Begin monitoring the SPP resonant wavelength
  after flowing all of the liquid through the
  chamber (so that air is left inside)
• The adsorption thickness is related to the time
  it takes for the wavelength to shift, and
  determines the hydrophilicity by the following
  equation

Recent and future work

• Measuring the binding affinity between
  biomolecules by flowing them successively over
  the nanohole array surface
• Increasing the sensitivity in several ways, for
  example by employing a reference channel to
  subtract off environmental changes

Sample with smaller hole diameter has smaller SPP
linewidth
Side view of sample with gold sputtered onto
resist pillars