The research objective of this award is to provide a scanning probe-based, laser-assisted, cost-effective and controllable nanomanufacturing tool with sub-5nm resolution. The approach will be to develop a novel near-field scanning probe to concentrate optical energy by directly fabricating a nanometer-sized photonic confinement structure on a patterned silicon probe tip, and to use the probe for efficient laser light transmission and coupling at the nanoscale. The key technologies involve the fabrication of multi-layer optical phase gratings on the probe tip, and experimental characterization of probe actuation and light concentration on the probe tip. The focused laser beam out of the probe tip allows one to manipulate nanostructures, such as quantum dots, nanotubes and nanowires, on a variety of substrates. The new scanning probe can be batch fabricated in an array format, with the potential to be integrated in a commercial near-field scanning optical microscope so that one can detect the nanostructures during manufacturing.
If successful, this research will have a significant impact on the field of manufacturing integrated bio-nanosystems. It will pave the way for future development of a variety of hybrid nanoscale devices and systems critical to future electronics, healthcare, pharmaceutical and defense applications. The educational objective of this proposal is to train the next generation of bioengineers to configure nanoscale structures to dissect basic scientific phenomena at the cellular and molecular levels through developing undergraduate teaching modules, research training program and creating an online learning center and workshops.
The objective of this NSF award is to design and fabricate novel aperture-based and apertureless-based scanning probes suitable for near-field scanning optical microscopy (NSOM), which can potentially provide higher spatial resolution with enhanced optical power output for inspecting internal cellular structures and cellular processes. The main challenge for efficient near-field scanning is on one hand to provide highly localized electromagnetic energy localization near the tip of the NSOM probe, to illuminate only a sub-wavelength detail of the object of interest, and on the other to support high optical throughput, in order to be able to detect the scattering from the object over the background noise. With a conventional single aperture-based NSOM tip, the resolution of the measurement, inversely proportional to the aperture size, is also inversely related to the overall power throughput; and low optical throughput remains a challenge for high-resolution near-field scanning application. On the other hand, techniques exploiting surface plasmon polariton (SPP) waves have indeed shown promising results in enhancing the achieved field enhancement at the tip, since they allow focusing and localizing the electromagnetic wave within extremely small regions compared to the wavelength. Among possible SPP techniques, the ones that utilize SPP diffraction for directional excitation appears particularly attractive for NSOM measurements, as it can provide higher electromagnetic energy focusing for the local probe geometry of interest. Through this project, several NSOM probe designs have been put forward to complete our goal. By applying novel plasmonic patterns on the pyramidal shaped probe, designed NSOM probes have shown promising results in regard to spatial optical resolution and high near-field optical throughput: X100~X1000 field enhancement without degradation of spatial resolution. Four novel probe designs have been devised and plasmonic patterns were transferred on the surface of metalized pyramidal-shaped scanning probe; specifically two aperture based probes with optimized concentric corrugations and two apertureless probes utilizing efficient plasmonic generation schemes have been demonstrated to prove their performance. Plasmonic corrugations concentric-patterned on an aperture-based probe helps enhance the near-field intensity and further enhanced by the employment of nano rod placing at the apex of tip. Since the usual aperture based probe suffers low optical throughput because the most incident light energy is being cut-off by sharp probe geometry, we adopted nonlocal probe concept to our apertureless based probe geometry. The SPPs launcher, a slit perforated in the probe side where the incident light is not being cut-off, has performed as nonlocal SPP excitation source; and the excited SPPs on probe side are efficiently guided to tip apex through the utilization of two different unidirectional Schemes, which are applied to different apertureless based probe designs. By using optimized plasmonic patterns on aperture-based probe, light confinement with enhanced optical throughput from the aperture has been proven. And patterned surfaces on apertureless probe tip have boosted the spatial resolution and near-field power throughput tremendously. Armed with our studies on efficient plasmonic probe designs enabling high resolution scanning with high signal-to-noise ratio, NSOM will allow detection of individual fluorescent proteins as part of multimolecular complexes on the surface of fixed cells. This research supported by NSF is transformative and uniquely integrated with the design and fabrication of novel plasmonic probes with the capability of nanofabrication, detection, repair/remanufacturing, and perturbation with nanometer resolution to manipulate and image biological processes.
