Eric Huang

Wide field super-resolution surface imaging through plasmonic structured illumination microscopy.

We experimentally demonstrate a wide field surface plasmon (SP) assisted super-resolution imaging technique, plasmonic structured illumination microscopy (PSIM), by combining tunable SP interference (SPI) with structured illumination microscopy (SIM). By replacing the laser interference fringes in conventional SIM with SPI patterns, PSIM exhibits greatly enhanced resolving power thanks to the unique properties of SP waves. This PSIM technique is a wide field, surface super-resolution imaging technique with potential applications in the field of high-speed biomedical imaging.

Spatially-Resolved Proteomics: Rapid Quantitative Analysis of Laser Capture Microdissected Alveolar Tissue Samples

Laser capture microdissection (LCM)-enabled region-specific tissue analyses are critical to better understand complex multicellular processes. However, current proteomics workflows entail several manual sample preparation steps and are challenged by the microscopic mass-limited samples generated by LCM, impacting measurement robustness, quantification and throughput. Here, we coupled LCM with a proteomics workflow that provides fully automated analysis of proteomes from microdissected tissues. Benchmarking against the current state-of-the-art in ultrasensitive global proteomics (FASP workflow), our approach demonstrated significant improvements in quantification (~2-fold lower variance) and throughput (>5 times faster). Using our approach we for the first time characterized, to a depth of >3,400 proteins, the ontogeny of protein changes during normal lung development in microdissected alveolar tissue containing only 4,000 cells. Our analysis revealed seven defined modules of coordinated transcription factor-signaling molecule expression patterns, suggesting a complex network of temporal regulatory control directs normal lung development with epigenetic regulation fine-tuning pre-natal developmental processes.

Experimental Demonstration of Localized Plasmonic Structured Illumination Microscopy

Super-resolution imaging methods such as structured illumination microscopy and others have offered various compromises between resolution, imaging speed, and biocompatibility. Here we experimentally demonstrate a physical mechanism for super-resolution that offers advantages over existing technologies. Using finely structured, resonant, and controllable near-field excitation from localized surface plasmons in a planar nanoantenna array, we achieve wide-field surface imaging with resolution down to 75 nm while maintaining reasonable speed and compatibility with biological specimens.

TIRF microscopy with ultra-short penetration depth

Total internal reflection fluorescence microscopy (TIRF), in both commercial and custom-built configurations, is widely used for high signal-noise ratio imaging. The imaging depth of traditional TIRF is sensitive to the incident angle of the laser, and normally limited to around 100 nm. In our paper, using a high refractive index material and the evanescent waves of various waveguide modes, we propose a compact and tunable ultra-short decay length TIRF system, which can reach decay lengths as short as 19 nm, and demonstrate its application for imaging fluorescent dye-labeled F-actin in HeLa cells.

Ultrafast Imaging using Spectral Resonance Modulation.

CCD cameras are ubiquitous in research labs, industry, and hospitals for a huge variety of applications, but there are many dynamic processes in nature that unfold too quickly to be captured. Although tradeoffs can be made between exposure time, sensitivity, and area of interest, ultimately the speed limit of a CCD camera is constrained by the electronic readout rate of the sensors. One potential way to improve the imaging speed is with compressive sensing (CS), a technique that allows for a reduction in the number of measurements needed to record an image. However, most CS imaging methods require spatial light modulators (SLMs), which are subject to mechanical speed limitations. Here, we demonstrate an etalon array based SLM without any moving elements that is unconstrained by either mechanical or electronic speed limitations. This novel spectral resonance modulator (SRM) shows great potential in an ultrafast compressive single pixel camera.

Etalon Array Reconstructive Spectrometry

Compact spectrometers are crucial in areas where size and weight may need to be minimized. These types of spectrometers often contain no moving parts, which makes for an instrument that can be highly durable. With the recent proliferation in low-cost and high-resolution cameras, camera-based spectrometry methods have the potential to make portable spectrometers small, ubiquitous, and cheap. Here, we demonstrate a novel method for compact spectrometry that uses an array of etalons to perform spectral encoding, and uses a reconstruction algorithm to recover the incident spectrum. This spectrometer has the unique capability for both high resolution and a large working bandwidth without sacrificing sensitivity, and we anticipate that its simplicity makes it an excellent candidate whenever a compact, robust, and flexible spectrometry solution is needed.

Spectrum engineering for reconstructive spectrometry

We demonstrate a novel method spectrometry using etalons on a CCD camera. This prototype enables compact, high resolution, and high efficiency spectrometry with no moving parts.

Three-dimensional fluorescent microscopy via simultaneous illumination and detection at multiple planes

The conventional optical microscope is an inherently two-dimensional (2D) imaging tool. The objective lens, eyepiece and image sensor are all designed to capture light emitted from a 2D ‘object plane’. Existing technologies, such as confocal or light sheet fluorescence microscopy have to utilize mechanical scanning, a time-multiplexing process, to capture a 3D image. In this paper, we present a 3D optical microscopy method based upon simultaneously illuminating and detecting multiple focal planes. This is implemented by adding two diffractive optical elements to modify the illumination and detection optics. We demonstrate that the image quality of this technique is comparable to conventional light sheet fluorescent microscopy with the advantage of the simultaneous imaging of multiple axial planes and reduced number of scans required to image the whole sample volume.

Spectral engineering for reconstructive imaging and spectrometry(Conference Presentation)

Conventional sensing techniques work by doing a point-by-point mapping of information from a signal to a detector, whether in spectrometry or imaging. However, there are alternative ways to acquire a signal of interest. By structuring the spectral properties of a measurement, it is possible to impose a sensing pattern onto the signal of interest, and then algorithmically recover the signal from the detected measurements. This allows for a computational isolation of the signal from the measurement, which has potential benefits in flexibility, speed, or resolution. To that end, we have developed a device for spectral engineering using an array of optical resonators. We can then multiplex the properties of our device onto the signal, and the signal then becomes encoded with a known pattern. From this, we recover the signal. The flexibility in our device is shown as we use it for both imaging and spectrometry. We anticipate this method to be useful for a wide variety of applications from high-speed imaging to compact spectrometry.