One of the great challenges in optics is to break the diffraction limit to achieve optical superresolution for applications in imaging, sensing, manufacturing and characterization. In recent years we witnessed a number of exciting developments in this field, including for example super-resolution fluorescent microscopy, negative-index metamaterial superlens and superoscillation
lens. However, none of them can perform white-light super-resolution imaging
until the development of microsphere nanoscopy technique, which was pioneered by the current PhD’s research group. The microscope nanoscopy technique was developed based on all-dielectric microsphere superlens which is fundamentally different from metal-based superlenses. In this research,
we aim to significantly advance the technology by: (1) increasing superlens resolution to sub- 50 nm scale and (2) improving superlens usability and demonstrate application in wider context including lab-on-chip devices. Our longer-term vision is to bring the all-dielectric superlens technology to market so that each microscope user can have superlens in hand for their daily examination of nanoscale objects including viruses. To improve the superlens resolution, a systematic theoretical study was first carried out on the optical properties of dielectric microsphere superlens. New approaches were proposed
to obtain precise control of the focusing properties of the microsphere lens. Using pupil mask engineering and two-material composite superlens design, one can precisely control the focusing properties of the lens and effectively surpass the diffraction limit λ/2n. To further improve the resolution, we incorporated the metamaterial concept in our superlens design. A new all-dielectric nanoparticle metamaterial superlens design was proposed. This is realized by 3D stacking of high-index nanoparticles to form a micro-sized
particle lens. This man-made superlens has unusual optical properties not found in nature: highly effective conversion of evanescent wave to propagating wave for unprecedented optical super-resolution. By using 15 nm TiO2 nanoparticles as building blocks, the fabricated 3D all-dielectric metamaterial-based solid immersion lens (mSIL) can produce a sharp image with a super-resolution of at least 45 nm under a white-light optical microscope, significantly exceeding the classical diffraction limit and previous near-field imaging techniques. In
additional to mSIL where only one kind of nanoparticle was used, we also studied twoVII nanomaterial hybrid system. High-quality microspheres consisting of ZrO2/polystyrene elements were synthesised and studied. We show precise tuning of the refractive index of microspheres can effectively enhance the imaging resolution and quality. To increase superlens usability and application scope, we proposed and demonstrated a new microscope objective lens that features a two times resolution improvement over conventional objective. This is accomplished by integrating a conventional microscope objective lens with a superlensing microsphere lens with a customised lens adaptor. The new objective lens was successfully demonstrated for label-free super-resolution static and scanning imaging of 100 nm features in engineering and biological samples. In an effort to reduce superlens technology entrance barrier, we studied several spider silks as naturally occurring optical superlens. These spider silks are transparent in nature and have micron-scale cylinder structure. They can distinctly resolve λ/6 features with a large field-of-view under a conventional white-light microscope. This discovery opens a new door to develop biology-based optical systems and has enriched the superlens category.
Because microsphere superlenses are small in size, their application can be extended to lab-on-chip device. In this thesis, microsphere superlens was introduced to a microfluidic channel to build an on-chip microfluidic superlensing device for real-time high-resolution imaging of biological objects. Several biological samples with different features in size, transparency, low contrast and strong mobility have been visualised. This integrated device provides a new way to allow researchers to directly visualise details of biological specimens in real-time under a conventional white light microscope. The work carried out in this research has significantly improved the microsphere superlens technology which opens the door for commercial exploitation.