Jingda Wu

Photonic Crystal Optical Tweezers with High Efficiency for Live Biological Samples and Viability Characterization

We propose and demonstrate a new optical trapping method for single cells that utilizes modulated light fields to trap a wide array of cell types, including mammalian, yeast, and Escherichia coli cells, on the surface of a two-dimensional photonic crystal. This method is capable of reducing the required light intensity, and thus minimizing the photothermal damage to living cells, thereby extending cell viability in optical trapping and cell manipulation applications. To this end, a thorough characterization of cell viability in optical trapping environments was performed. This study also demonstrates the technique using spatial light modulation in patterned manipulation of live cell arrays over a broad area.

Inkjet Printable Flexible Thin-Film NCQD Photodetectors on Unmodified Transparency Films

We proposed and experimentally demonstrated a cost-efficient and easy-to-fabricate flexible thin-film nanocrystal quantum dot (NCQD) photodetector, by sandwiching a piece of NCQD-soaked tracing paper between two PEDOT:PSS electrodes. The highly conductive and transparent multilayer polymer electrodes are printed with an office inkjet printer without further patterning on commercial unmodified transparency films. The tracing paper is able to act as both the bed for NCQD attachment and the interspacing layer to prevent short-circuiting in vertical devices. Consistent increase in device performance is observed when the bending radius becomes smaller. Linear I-V characteristics are obtained, which show our device structure works as a photoconductor.

Fluorescent porous silicon biological probes with high quantum efficiency and stability

We demonstrate porous silicon biological probes as a stable and non-toxic alternative to organic dyes or cadmium-containing quantum dots for imaging and sensing applications. The fluorescent silicon quantum dots which are embedded on the porous silicon surface are passivated with carboxyl-terminated ligands through stable Si-C covalent bonds. The porous silicon bio-probes have shown photoluminescence quantum yield around 50% under near-UV excitation, with high photochemical and thermal stability. The bio-probes can be efficiently conjugated with antibodies, which is confirmed by a standard enzyme-linked immunosorbent assay (ELISA) method.

MEMS resonant mass sensor with enabled optical trapping

Microresonators have an unmatched ability to detect the minute masses of single particles or biological cells. Precise measurement of cell mass, and its physical properties, is necessary to answer fundamental biological questions, with implications in cell biology, pharmacology, and medicine. This paper investigates the use of photonic-crystal-mediated optical trapping toward increasing the precision and applicability of this highly sensitive technique, discussing device design, fabrication, implementation, and preliminary results.

Optical modulation and manipulation of neurons and cells with high efficiency through quantum dots and photonic crystals

Nanomaterials such as semiconductor quantum dots and nanostructures such as photonic crystals can interact with light in unique ways due to their nms to sub-μm feature size. This enables versatile applications with high efficiencies. In this paper, we focus on biological applications, specifically, photostimulation and optical manipulation of cells. We report photostimulation and activation of neurons with very low optical intensity (0.0036 mW/mm2) through colloidal quantum dots. We also demonstrate efficient optical manipulation of cells and nanoparticles on a 2-D photonic crystal platform. Particles as small as 100 nm can be trapped with ∼16 μW/μm2 optical intensity.

MEMS Resonator and Photonic Crystal Integration for Enhanced Cellular Mass Sensing

This work describes the design and fabrication steps of a MEMS resonant-beam structure that utilizes optical trapping technology and microfluidics in an attempt to enhance the precision and accuracy of cellular-mass sensing devices.