Cubic Nanoantennas Eyed for NEMS Biosensors

Lab-on-a-chip applications could benefit from cubic nanoantennas that direct light more effectively than spherical ones.

The cubes, which are composed of insulating rather than conducting or semiconducting materials, are easier to fabricate and suffer little or no loss due to heat and scattering, according to researchers at Monash University.

The team simulated a chain of 200-nm dielectric nanoncubes placed in the path of visible and near-infrared light sources. The space between the nanocubes was adjusted to fine-tune the light beam for various applications. As the separation between cubes increased, the angular width of the beam narrowed and directionality improved, the researchers said.

Schematic of unidirectional cubic nanoantennas inducing directionality to omnidirectional nanoemitters to precisely focus light with adjustable beam width and intensity. These ultranarrow directional beams can play multiple roles in lab-on-a-chip devices such as illumination sources in microfluidic analysis or minute deflection registers in nanocantilever-based sensors. Signals are detected in the photodetectors and get processed by on-chip signal processing circuitry for biomolecular identification. Courtesy of D. Sikdar and M. Premaratne/Monash University.

“Unidirectional nanoantennas induce directionality to any omnidirectional light emitters like microlasers, nanolasers or spasers, and even quantum dots,” said doctoral student Debabrata Sikdar. “Analogous to nanoscale spotlights, the cubic antennas focus light with precise control over direction and beam width.”

The nanoantennas could play a role in nanoelectromechanical systems (NEMS) that would allow complete sensor systems on microchips. Such “lab-on-a-chip” systems could be used to measure food safety, identify air pollution and even quickly diagnose and treat cancer.

“These unidirectional nanoantennas are most suitable for integrated optics-based biosensors to detect proteins, DNA, antibodies, enzymes, etc., in truly portable lab-on-a-chip platforms of the future,” Sikdar said. “They can also potentially replace the lossy on-chip IC (integrated circuit) interconnects, via transmitting optical signals within and among ICs, to ensure ultrafast data processing while minimizing device heating.”

Sikdar and colleagues plan to begin constructing unidirectional cubic NEMS antennas in the near future at the Melbourne Center for Nanofabrication.

The research was published in the Journal of Applied Physics (doi: 10.1063/1.4907536).

For more information, visit www.monash.edu.