A global research team has established a near-field optical sensing platform that is capable of producing arrayed light beams with high-spatial and high-intensity constraints in semi-open areas.
Image Credit: Shutterstock.com/Dmitriy Rybin
The study was led by Prof. Hui Yang from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences and Prof. Zengbo Wang from Bangor University.
The sensing platform proposed by this study is based on an array of dielectric microsphere lenses that come with laser-machined semi-open microwells on top of each microsphere (μ-well lens). The platform can be employed in biosensors to identify and measure ultra-low concentration biochemical analytes.
The research was published on January 11th, 2022 in Sensors and Actuators B: Chemical.
Through photonic nanojet (PNJ) focusing, dielectric microsphere lenses could squeeze light into the subwavelength scale. The light is narrowed and focused into a tiny area, which results in a light field that is orders of magnitude greater than that of the incident light.
Therefore, an improved electromagnetic excitation, which activates strong light-matter interactions, is experienced by biochemical analytes in the concentration zone of the PNJ.
Thus, the PNJ-based optical convergence method is a hopeful technology in the near-field optical sensing field. Nevertheless, the understanding of this near-field optical sensing technology is still difficult.
Generally, the PNJ with a relatively small effective volume is produced perpendicular to the substrate comprising dielectric microspheres in free space. Hence, it is rather difficult to introduce the objects of interest to this volume.
Furthermore, owing to the heterogeneous distribution of the PNJ intensity field, when the spatial location of the object varies, signals reporting the strength of light-matter interactions among the objects and the PNJ can display server fluctuations.
For the first time in this field, we have proposed a near-field optical sensing platform based on localized photonic nanojets (L-PNJs).
Zengbo Wang, Professor, Bangor University
This resolved the aforementioned two difficulties and attained effective quantitative biosensing and signal amplification.
Researchers used a nanosecond laser to accurately machine micron-scale semi-open microwells above every dielectric microsphere lens.
The resulted μ-well lens could not only produce a potential L-PNJ but also accurately and passively capture a single micron-scale analyte to the L-PNJ. Thus, this new design enhances the efficacy of introducing targets into the L-PNJ and subdues their eventual signal fluctuations.
This sensing platform is promising for the development of next-generation on-chip signal amplification and quantitative detection systems as well as for investigating a wide range of light-matter interaction processes.
Hui Yang, Professor, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences
Journal Reference:
Zhang, P., et al. (2022) Localized photonic nanojet based sensing platform for highly efficient signal amplification and quantitative biosensing. Sensors and Actuators B: Chemical. doi.org/10.1016/j.snb.2022.131401.