Structured illumination microscopy using a photonic chip

Structured illumination microscopy (SIM) enables live-cell super-resolution imaging of subcellular structures at high speeds. At present, linear SIM uses free-space optics to illuminate the sample with the desired light patterns; however, such arrangements are prone to misalignment and add cost and complexity to the microscope. Here, we present an alternative photonic chip-based two-dimensional SIM approach (cSIM) in which the conventional glass sample slide in a microscope is replaced by a planar photonic chip that importantly both holds and illuminates the specimen. The photonic chip reduces the footprint of the light illumination path of SIM to around 4 × 4 cm2. An array of optical waveguides on the chip creates standing wave interference patterns at different angles, which illuminate the sample via evanescent fields. High-refractive-index silicon nitride waveguides allow a 2.3 times enhancement in imaging spatial resolution, exceeding the usual 2 times limit of SIM. In summary, cSIM offers a simple, stable and affordable approach for performing two-dimensional super-resolution imaging over a large field of view

Chip-based wide field-of-view nanoscopy

Present optical nanoscopy techniques use a complex microscope for imaging and a simple glass slide to hold the sample. Here, we demonstrate the inverse: the use of a complex, but mass-producible optical chip, which hosts the sample and provides a waveguide for the illumination source, and a standard low-cost microscope to acquire super-resolved images via two different approaches. Waveguides composed of a material with high refractive-index contrast provide a strong evanescent field that is used for single-molecule switching and fluorescence excitation, thus enabling chip-based single-molecule localization microscopy. Additionally, multimode interference patterns induce spatial fluorescence intensity variations that enable fluctuation-based super-resolution imaging. As chip-based nanoscopy separates the illumination and detection light paths, total-internal-reflection fluorescence excitation is possible over a large field of view, with up to 0.5 mm × 0.5 mm being demonstrated. Using multicolour chip-based nanoscopy, we visualize fenestrations in liver sinusoidal endothelial cells