Browsing by Author "Sun, Kai"

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Bacterial Concentration Detection using a PCB-based Contactless Conductivity Sensor
(2019-01-01)
Zhang, Xiao-Yan
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Li, Zhe-Yu
;
Zhang, Yu
;
Zang, Xiao-Qian
;
Ueno, Kosei
Capacitively coupled contactless conductivity detection ((CD)-D-4) is an improved approach to avoid the problems of labor-intensive, time-consuming and insufficient accuracy of plate count as well as the high-cost apparatus of flow cytometry (FCM) in bacterial counting. This article describes a novel electrode-integrated printed-circuit-board (PCB)-based (CD)-D-4 device, which supports the simple and safe exchange of capillaries and improves the sensitivity and repeatability of the contactless detection. Furthermore, no syringe pump is needed in the detection, it reduces the system size, and, more importantly, avoids the effect on the bacteria due to high pressure. The recovered bacteria after (CD)-D-4 detection at excitation of 25 Vpp and 60-120 kHz were analyzed by flow cytometry, and a survival rate higher than 96% was given. It was verified that (CD)-D-4 detection did not influence the bacterial viability. Moreover, bacteria concentrations from 10(6) cells/mL to 10(8) cells/mL were measured in a linear range, and relative standard deviation (RSD) is below 0.2%. In addition, the effects on bacteria and (CD)-D-4 from background solutions were discussed. In contrast to common methods used in most laboratories, this method may provide a simple solution to in situ detection of bacterial cultures.
On-chip MIC by Combining Concentration Gradient Generator and Flanged Chamber Arrays
(2020-02-01)
Zhang, Xiao-Yan
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Li, Zhe-Yu
;
Ueno, Kose
;
Misawa, Hiroaki
;
Ren, Nan-Qi
Minimum inhibition concentration (MIC) of antibiotic is an effective value to ascertain the agent and minimum dosage of inhibiting bacterial growth. However, current techniques to determine MIC are labor intensive and time-consuming, and require skilled operator and high initial concentration of bacteria. To simplify the operation and reduce the time of inhibition test, we developed a microfluidic system, containing a concentration generator and sub-micro-liter chambers, for rapid bacterial growth and inhibition test. To improve the mixing effect, a micropillar array in honeycomb-structure channels is designed, so the steady concentration gradient of amoxicillin can be generated. The flanged chambers are used to culture bacteria under the condition of continuous flow and the medium of chambers is refreshed constantly, which could supply the sufficient nutrient for bacteria growth and take away the metabolite. Based on the microfluidic platform, the bacterial growth with antibiotic inhibition on chip can be quantitatively measured and MIC can be obtained within six hours using low initial concentration of bacteria. Overall, this microfluidic platform has the potential to provide rapidness and effectiveness to screen bacteria and determine MIC of corresponding antibiotics in clinical therapies.
Soluble InP and GaP Nanowires: Self-Seeded, Solution-Liquid-Solid Synthesis and Electrical Properties
(2009)
Liu, Zhoping
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Sun, Kai
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Jian, Wen-Bin
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Xu, Dan
;
Lin, Yen-Fu
We demonstrate a facile method for self-seeded, solution-liquid-solid growth of soluble InP and GaP nanowires at it temperature of approximate to 300 degrees C. Both types of nanowires are single crystals with very small diameters. The synthesized InP nanowires are almost defect-free, whereas the GaP nanowires have some microtwins. The effect of reaction temperatures and input ligand/III/V (III and V indicate elements of Group 13 and 15 respectively) ratios oil wire formation is discussed, and two competitive chemical pathways involved in the nanowire formation are proposed. In addition, electrical properties of these III-V nanowires, generated from the solution-based approach, were investigated for the first time. The current-voltage (I-V) and room temperature resistance investigations indicate that both InP and GaP nanowires possess very low native point defects for carrier concentrations and they could be potentially promising building blocks in optoelectronic applications.