Resonant nanophotonic biosensors
Optical sensing of biological targets is provided using a metasurface having guided mode resonances with electric field profiles that extend out from the metasurface. Surface functionalization of such metasurfaces can be used to provide sensing for biological targets, such as nucleic acids, proteins, small molecules, extracellular vesicles, and whole cells. Binding of the target to the surface functionalization can affect the resonance wavelength of the guided mode resonances, thereby providing a sensitive assay for the biological targets.
1 . An apparatus comprising: an electromagnetic metasurface, surface functionalized for selective molecular binding of one or more molecules or analytes in proximity to the electromagnetic metasurface, including one or more waveguides disposed on a substrate; wherein each of the one or more waveguides is to support one or more guided mode resonances and has a corresponding longitudinal perturbation, and a selected one or more of the guided mode resonances is to couple free-space radiation by the corresponding longitudinal perturbation; and the selected one or more guided mode resonances, in operation, have electric field distributions that extend outside the electromagnetic metasurface.
2 . The apparatus of claim 1 , further comprising an optical source configured to provide the free-space radiation, wherein the electric field distributions, that extend outside the electromagnetic metasurface, are associated with resonant wavelength shifts based on the surface functionalization and on the selective molecular binding of one or more molecules or analytes to the electromagnetic metasurface.
3 . The apparatus of claim 1 , further comprising an optical detector configured to receive output radiation from the electromagnetic metasurface, wherein the output radiation is selected from the group consisting of: reflected radiation, transmitted radiation, scattered radiation, diffracted radiation, and Raman-scattered radiation.
4 . The apparatus of claim 3 , wherein the optical detector is configured to determine a spectrum of the output radiation based on dispersion caused by the one or more waveguides, wherein the electric field distributions, that extend outside the electromagnetic metasurface, are associated with resonant wavelength shifts based on the surface functionalization and on the selective molecular binding of one or more molecules or analytes.
5 . The apparatus of claim 1 , further comprising the surface functionalization disposed on the electromagnetic metasurface to selectively bind one or more analytes in proximity to the electromagnetic metasurface.
6 . The apparatus of claim 5 , wherein the one or more analytes are selected from the group consisting of: nucleic acids, proteins, small molecules, extracellular vesicles, pathogens and whole cells.
7 . The apparatus of claim 5 , wherein a detection sensitivity of the one or more analytes is 10 fM (femtomolar) or better, whereby detection of the one or more analytes without a prior analyte amplification step is provided.
8 . The apparatus of claim 5 , wherein a dynamic range for detection of the one or more analytes is 10 dB (decibels) or more.
9 . The apparatus of claim 1 , wherein the electromagnetic metasurface is configured as an array of one or more sensor pixels, each sensor pixel including a corresponding part or all of one of the one or more waveguides.
10 . The apparatus of claim 9 , wherein the array of one or more sensor pixels is selected from the group consisting of 1-dimensional arrays and 2-dimensional arrays.
11 . The apparatus of claim 9 , further comprising per-pixel selective surface functionalization, whereby multiplexed sensing of two or more distinct analytes is provided.
12 . The apparatus of claim 1 , wherein the selected one or more guided mode resonances have a free-space fraction of electric field energy of 0.2 or more.
13 . The apparatus of claim 1 , wherein resonance wavelength shifts are enhanced in response to one or more complementary target-probe conditions and suppressed for non-specific binding, and the electric field distributions, that extend outside the electromagnetic metasurface, are associated with resonant wavelength shifts based on the surface functionalization and on the selective molecular binding of one or more molecules or analytes.
14 . The apparatus of claim 1 , further including an optical detector to respond to resonance wavelength shifts being enhanced due to one or more complementary target-probe conditions.
15 . The apparatus of claim 1 , further including an optical detector to respond to resonance wavelength shifts being enhanced, relative to a baseline reference, due to one or more complementary target-probe conditions.
16 . The apparatus of claim 1 , further including an optical detector to provide environmental sensing in response to the selected one or more guided mode resonances having electric field distributions that extend outside the electromagnetic metasurface, and to resonance wavelength shifts being enhanced due to one or more complementary target-probe conditions.
17 . The apparatus of claim 1 , wherein
the one or more waveguides are disposed on the substrate to mitigate light scattering losses out ends of the waveguides,
light is to be transmitted or reflected as incident light from the electromagnetic metasurface, and
the electromagnetic metasurface includes subwavelength nanoantennas to confine light in a near field region, which is proximal the subwavelength nanoantennas, and to control light scattering in a region distal to the subwavelength nanoantennas.
18 . The apparatus of claim 1 , wherein the one or more waveguides include or correspond to distinct and separated dielectric blocks.
19 . The apparatus of claim 1 , wherein the one or more waveguides include separated blocks, each including dielectric material, wherein sets of immediately adjacent ones of the separated blocks are spaced by respective gaps to facilitate exposure of the electric field energy into a medium surrounding the electromagnetic metasurface.
20 . A method comprising: using a functionalized electromagnetic metasurface, including one or more waveguides disposed on a substrate, to selectively molecular bind one or more molecules or analytes in proximity to the electromagnetic metasurface, wherein each of the one or more waveguides supports one or more guided mode resonances and has a corresponding longitudinal perturbation; and causing a selected one or more of the guided mode resonances to couple free-space radiation by the corresponding longitudinal perturbation and the selected one or more guided mode resonances to have electric field distributions that extend outside the electromagnetic metasurface.