This Small Business Innovation Research Phase I project aims to develop a novel type of nanodevice for label-free detection and identification of single, individual (bio)molecules. A unique nanomanufacturing technology has been developed for low-cost and reliable fabrication of micro/nanofluidic circuitry integrated with plasmonic nanostructures. Successful combination of these components will allow the confinement of light and liquid at the nanoscale, allowing the characterization of individual molecules flowing one-by-one along a plasmonic hot spot. This technology will enable a breakthrough in the detection and identification of single molecules, drastically simplifying the sample preparation by removing the need for labeling. The Phase I work will focus on the use of the nanochannel/nanoantenna system to detect the Raman signal of substances confined in tiny volumes (10^-21 L). This will serve as the basis for the development of a fully integrated system with on-chip read out capabilities for detection of toxins in fresh water in Phase II.
The broader impact/commercial potential of this project lies in the novelty and versatility of the sensor, which will be able to detect, discriminate and analyze individual molecules without the need for labels. Even further, the system will be portable, fully integrated with on-chip read out capabilities, and will require very small sample volumes (on the order of a few microliters). The first market to be targeted is environmental monitoring for water control: the device will be used to detect in real time the concentration of toxins in fresh water, and to track their evolution over time. Once the label-free detection and identification of single biomolecules on a portable chip is demonstrated, the applications will be expanded to the biomedical and point-of-care markets. The results of the research in Phase I will open a new route for the fabrication of a large variety of fully-integrated, ultrasensitive, portable, label-free biosensors.
In this project we have demonstrated the integration of a nanochannel with a plasmonic optical antenna for ultra-high sensitivity detection. The proposed device consists of a complete microfluidic system, with microchannels that deliver the liquid, and nanochannels with lateral dimensions as small as 30 nm x 30 nm. These have gold nanoantenna adjacent, which focuses and enhances the light in the nanochannel. The nanoantenna breaks the limitations given by the diffraction of light, creating a hot spot which dimensions are given by the antenna geometry and can be in the range of tens of nanometers. In addition, in this hot spot, the fields are much more intense, enhancing the excitation and emission optical signals coming from the nanometric area. We have first developed and optimized a novel technology for the fabrication of the devices, based on nanoimprint lithography, and all wafer scale processing. These technologies are compatible with the use of cheap, plastic materials, and are ready for mass production. The devices are all transparent. We have used the nanoantenna to enhance the Raman scattering signal from different liquids dropped on the sample. An enhancement of x150 has been observed when the antenna is present compared to the same measurement without antenna. We have also used the devices to detect and quantify single quantum dots. Each nanocrystal can be observed individually, independently of their concentration in solution, thanks to the focusing effect of the antenna. This allows for single particle counting, so the number of counts per time can be used to obtain the concentration of the sample. These results open the route for ultra-high sensitivity (bio)detection; target molecules can be functionalized with quantum dots, for individual molecule tracking, study and detection. These devices will have an impact in point-of-care diagnosis, environmental monitoring, and medical applications where ultra-high sensitivity is required - such as quantification of very low viral loads, or detection of cancer biomarkers at early stages.
