Optofluidics

Previous research highlight in optofluidics:

Three-dimensional composite metallodielectric nanostructure for enhanced surface plasmon resonance sensing

Current research highlight: Optofluidics with nanoresonator platforms: Co-localization of biomolecules with ultrasmall resonant optical fields for detection of Raman signals from single molecules

Multilayer nanofluidics

Figure 1. Schematic diagram of the multilayer nanofluidic architecture. a) Nanoparticles flow in the chamber. b) When an electric field is applied, the nanoparticles are captured onto the underlying nanochannel membrane defined by the nanohole pattern, which connects the top PDMS to the bottom PDMS chamber. c) Experimental setup of the multilayer nanophotonic chip. d) 200-nm nanoparticles were captured onto the underlying 600-nm-pitch nanochannel array after a voltage was applied to form a 2D nanoparticle array.

With the rise of microfluidics in the 1990s and the continued focus on microscale lab-on-a-chip models, the Ultrafast Nanoscale Optics group has been studying fluidic channels that are compatible with other nanofabricated devices. By being able to selectively manipulate where nanoparticles, or any type of molecule, flow on a chip, we are able to control particle placement down to the nanoscale level. The integration between nanofluidics and nanoplasmonics will aid in our goal of creating a platform that can be used for sensing of specific analytes, whether they be of the biological, environmental, or chemical nature.

The nanochip fabricated in our lab consists of arrays of nanoopenings, or nanoholes, all integrated with micro- and nanofluidic channels (see Fig. 1). As the nanoparticles pass through the sample (Fig. 1a), the nanoparticles are captured at the opening of the nanochannel where the nanoholes are contained (Fig. 1b). The molecules are controlled via electroosmotic forces (Fig. 1c), in which an applied electric field forces the target molecules into the designated areas (Fig. 1d). The stability of the nanoparticles being contained within the nanoholes is sufficient, as the nanoparticles are shown to have remained in the holes long after the potential has been removed.

The ability to have flow control over molecules is an important step when implementing the concept of lab-on-a-chip. While previous work required binding agents, our method is label-free and thus the analytes can be controlled without additional chemical labeling. This platform can be expanded further by putting nanoresonators in place of the nanoholes, allowing for localization onto a resonant platform that can be used for biodetection.

References

  1. H. M. Chen, L. Pang, M. S. Gordon, Y. Fainman, Small, 7, 2750-2757 (2011).
  2. H. M. Chen, L. Pang, A. King, G. M. Hwang, Y. Fainman, submitted
  3. L. Pang, H. M. Chen, L. M. Freeman, Y. Fainman, Lab Chip, C2LC40467B, (2012).