Kuo-Liang Liu

Novel microchip for in situ TEM imaging of living organisms and bio-reactions in aqueous conditions

A novel and disposable microchip (K-kit) with SiO(2) nano-membranes was developed and used as a specimen kit for in situ imaging of living organisms in an aqueous condition using transmission electron microscopy (TEM) without equipment modification. This K-kit enabled the successful TEM observation of living Escherichia coli cells and the tellurite reduction process in Klebsiella pneumoniae. The K. pneumoniae and Saccharomyces cerevisiae can stay alive in K-kit after continuous TEM imaging for up to 14 s and 42 s, respectively. Besides, different tellurite reduction profiles in cells grown in aerobic and anaerobic environments can be clearly revealed. These results demonstrate that the K-kit developed in this paper can be useful for observing living organisms and monitoring biological processes in situ.

Indium-doped molybdenum oxide as a new p-type transparent conductive oxide

New p-type transparent conductive oxide materials, MoO3:In single crystal nanowires and amorphous films, are synthesized in this work. Both nanowires and amorphous films exhibit high optical transmittance, 80–88% for 80 nm thick films at 400–800 nm wavelength, and low resistivity (down to 5.98 × 10−4 Ω cm) suitable for photovoltaic device applications. The amorphous films are also deposited on flexible polyimide substrates and exhibit excellent electrical properties even after bending. Besides, p-MoO3:In/i-ZnO/n-AZO devices are fabricated to demonstrate the potential for all-transparent flexible electronic applications.

Quantitative Characterization of Nanoparticles in Blood by Transmission Electron Microscopy with a Window-Type Microchip Nanopipet

Transmission electron microscopy (TEM) is a unique and powerful tool for observation of nanoparticles. However, due to the uneven spatial distribution of particles conventionally dried on copper grids, TEM is rarely employed to evaluate the spatial distribution of nanoparticles in aqueous solutions. Here, we present a microchip nanopipet with a narrow chamber width for sorting nanoparticles from blood and preventing the aggregation of the particles during the drying process, enabling quantitative analysis of their aggregation/agglomeration states and the particle concentration in aqueous solutions. This microchip is adaptable to all commercial TEM holders. Such a nanopipet proves to be a simple and convenient sampling device for TEM image-based quantitative characterization.

Structural and Mechanical Properties of Klebsiella pneumoniae Type 3 Fimbriae

This study investigated the structural and mechanical properties of Klebsiella pneumoniae type 3 fimbriae, which constitute a known virulence factor for the bacterium. Transmission electron microscopy and optical tweezers were used to understand the ability of the bacterium to survive flushes. An individual K. pneumoniae type 3 fimbria exhibited a helix-like structure with a pitch of 4.1 nm and a three-phase force-extension curve. The fimbria was first nonlinearly stretched with increasing force. Then, it started to uncoil and extended several micrometers at a fixed force of 66 ± 4 pN (n = 22). Finally, the extension of the fimbria shifted to the third phase, with a characteristic force of 102 ± 9 pN (n = 14) at the inflection point. Compared with the P fimbriae and type 1 fimbriae of uropathogenic Escherichia coli, K. pneumoniae type 3 fimbriae have a larger pitch in the helix-like structure and stronger uncoiling and characteristic forces.

Identification of Protein Domains on Major Pilin MrkA That Affects the Mechanical Properties of Klebsiella pneumoniae Type 3 Fimbriae

The Klebsiella pneumoniae type 3 fimbriae are mainly composed of MrkA pilins that assemble into a helixlike filament. This study determined the biomechanical properties of the fimbriae and analyzed 11 site-directed MrkA mutants to identify domains that are critical for the properties. Escherichia coli strains expressing type 3 fimbriae with an Ala substitution at either F34, V45, C87, G189, T196, or Y197 resulted in a significant reduction in biofilm formation. The E. coli strain expressing MrkAG189A remained capable of producing a normal number of fimbriae. Although F34A, V45A, T196A, and Y197A substitutions expressed on E. coli strains produced sparse quantities of fimbriae, no fimbriae were observed on the cells expressing MrkAC87A. Further investigations of the mechanical properties of the MrkAG189A fimbriae with optical tweezers revealed that, unlike the wild-type fimbriae, the uncoiling force for MrkAG189A fimbriae was not constant. The MrkAG189A fimbriae also exhibited a lower enthalpy in the differential scanning calorimetry analysis. Together, these findings indicate that the mutant fimbriae are less stable than the wild-type. This study has demonstrated that the C-terminal β strands of MrkA are required for the assembly and structural stability of fimbriae.

Low Temperature Electroless Ni–P Catalyst Deposition Enhanced by UV Exposure for Carbon Nanofiber and Nanotube Growth

Electroless Ni-P nanoparticles deposition enhanced by UV exposure was investigated to catalyze the synthesis of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) by thermal chemical vapor deposition at 400°C for interconnect formation that can reduce process complexity. The Ni-P nanoparticles with a size of 6-15 nm were deposited by using a UV-assisted electroless plating on the SiO 2 trench wall at ~28°C for CNF wiring formation. Besides, the Ni-P nanoparticles were selectively deposited at the bottom of the via-hole with a size of 100 nm by using electroless plating at 70°C for CNT-via formation.

Carbon nanotube formation by laser direct writing

This letter presents carbon nanotube (CNT) formation by laser direct writing using 248nm KrF excimer pulsed laser in air at room temperature, which was applied to irradiate amorphous carbon (a-C) assisted by Ni catalysts underneath for the transformation of carbon species into CNTs. The CNTs were synthesized under appropriate combination of laser energy density and a-C thickness. The growth mechanism and key parameters to determine the success of CNT formation were also discussed. The demonstration of the CNT growth by laser direct writing in air at room temperature opens an opportunity of in-position CNT formation at low temperatures.

Uncoiling mechanism of Klebsiella pneumoniae type 3 pili measured by using optical tweezers

Pili are bacterial appendages that play many important roles in bacterial behaviors, physiology and interaction with hosts. Via pili, bacteria are able to adhere to, migrate onto, and colonize on host cells, mechanically. Different from the most studied type 1 and P type pili, which are rigid and thick with an average of 6~7 nm in diameter, type 3 pili are relatively tiny (3-5 nm in diameter) and flexible, and their biophysical properties remains unclear. By using optical tweezers, we found that the elongation processes of type 3 pili are divided into three phases: (1) elastic elongation, (2) uncoiling elongation, and (3) intrinsic elongation, separately. Besides, the uncoiling force of the recombinant pili displayed on the surface of E. coli [pmrkABCDV1F] is measured 20 pN in average stronger than that of E. coli [pmrkABCDV1]. This suggests that pilin MrkF is involved in determining the mechanical properties of the type 3 pili.