Single 12 nm Au-Nanoparticle Attachments on AFM Tips for Single Quantum Dot Pick-up (J.Phy.Chem.C 2013, 2014)
A novel method for single, sub-4 nm nano-object pick-up is developed by the employment of a 1.8 nm Au-NP attached to an AFM tip vertex directly without tip surface modification. The 1.8 nm Au-NP is selectively attached to the vertex of the AFM tip by the application of a short and current-limited voltage bias between the Au-NP and the AFM tip. Through an interaction combining evaporation and electrostatic attraction, the Au-NP can be transferred from the substrate onto the AFM tip in a controllable manner. This method provides the advantages such as: (1) the AFM probes need no surface pre-treatment, (2) various sizes of Au-NPs can be attached on-demand and (3) the entire process can be rapidly completed in minutes. Transmission electron microscope (TEM) observation is used to verify whether a single 4 nm QD is picked up by a single 1.8 nm Au-NP attached on the probe. This probe could be potentially used for picking up a single protein molecule in the future.
Self-Aligned Wet-Cell for Hydrated Microbiology Observation in TEM (Lab Chip, 2012, Soft Matter 2013)
This work proposes a Self-Aligned Wet (SAW) Cell suitabl e for direct-cell or bacteria incubation and observation in a wet environment inside a transmission electron microscope. This SAW cell is fabricated by a bulk-micromachining process and composed of two structurally complementary counterparts (an out-frame and an in-frame) where each contain a silicon nitride film based observation window. The in10 and out-frames can be self-aligned via a mechanism of surface tension from a bio-sample droplet without the aid of positioning stages. The liquid chamber is enclosed between two silicon nitride membranes that are thin enough to allow high energy electrons to penetrate while also sustaining the pressure difference between the TEM vacuum and the vapor pressure within the liquid chamber. A large field of view (150 μm x 150 μm) in a SAW cell is favored and formed from a larger sized observation window in the out15 frame, which is fabricated using a unique circular membrane formation process. In this work, we introduce a novel design to circumvent the challenges of charging/heating problems in silicon nitride that arise from interactions with an electron beam. This paper also demonstrates TEM observations of D.Radiodurans growth in a liquid environment within a thicker chamber (20 μm) within a SAW cell.