Phototactic motion of Tetrahymena pyriformis in the light circle. The T. pyriformis display in-plane rotational motion when exposed to the UV light, where the cells rotate counter-clockwise and after a short period of time move out of plane, continuing in a corkscrew motion. No response is observed when exposed wavelengths are over 570 nm using a long pass filter and in the 450 - 550 nm range using both blue and green dichroic filters [PDF].

A bacteria-powered microrobot is controlled with electric stimulus for the micro-assembly experiment. The C-type structure is a microbiorobot (MBR)on which the bacteria attached and another small square structure is a target microstructure on which bacteria are not attached. Only the MBR moved toward the microstructure by controlling the direction of the applied electric fields [PDF].

Transmission electron microscope (TEM) tomography, based on tilt series, can be used to create three-dimensional structure of solid-state nanopore, which is formed by high intensity of electron beam. After collecting the tilted (- 45 degree to 45 degree) 2-D images, we can reconstructure the 3-D nanopore structure using an advanced back-projection algorithm in Automated Reconstruction of Tomographic Tilt Series (ARTS). With single-digit nanometer pores, we are able to investigate ssDNA/dsDNA/RNA kinetics as well as DNA sequencing at single base resolution. The pore shown in this video has a 8 nm diameter [PDF].

Our objective is to understand and model the mechanics of bacterial flagellar bundling. Full-scale flagella are 10 micron meters in length, 20 nm in diameter, and turn at a rate of 100 Hz. To accurately simulate bundling at a more easily observable scale, we built a scale model in which 20 cm long helices are rotated in 100,000 cp silicone oil (poly-di-methyl-siloxane). The highly viscous oil ensures an appropriately low Reynolds number. We developed a macroscale particle image velocimetry (PIV) system to measure the full-field velocity distribution for rotating rigid helices and rotating flexible helices [PDF].