Biochip technology is highly effective method that allows monitoring of biomaterials e.g., yeast and bacteria at a time in computerized automatic operations. Miniaturized nanostructure p-n junction test sites, which are arranged on a solid substrate, are proposed to sense and count the biomaterials. This PhD thesis reports on the impedance of p-n junction-based Si biochips with gold ring top electrodes and unstructured gold bottom electrodes, which allows for counting target biomaterial in a liquid-filled ring top electrode region. The phosphor and boron implanted biochips prepared in dissimilar annealing and doping conditions have been considered and three different types of top electrodes designed and tested to check the influence of the properties of the top electrode on the biochips to achieve more convenient samples for bio sensing technology. The systematic experiments on p-n junction-based Si biochips fabricated by two different sets of implantation parameters (i.e., biochips PS5 and BS5) are studied and the comparable significant change of impedance characteristics in the biochips in dependence on the number of bacteria suspensions, i.e., Lysinibacillus sphaericus JG-A12, in Deionized water at optical density at 600 nm from OD600 = 4–16 in the electrode ring region is demonstrated. The number of biomaterials and the microscopic images can be linked to the impedance changes of the biochip. The electrical equivalent circuit models for the devices have been proposed by using characterized frequency dependent capacitance and conductance of biochips. While the Nyquist spectrum of the biochips are not compromise on perfect semicircle, combination of constant phase elements with resistor in parallel fashion and series inductor and resistor have been utilized to model the impedance of the biochips. Corresponding parameters i.e., capacitors, resistors and inductors have been extracted from the modeling results and the changes in their values by adding the biomaterials obtained. As the result, the linear relation between the numbers of the biomaterial and the impedance of the biochips has been showed. Furthermore, Deionized water and glucose with yeast (Saccharomyces cerevisiae) at optical density OD600 ranging from 4 to 16 has been put in the ring electrode region of impedance biochips and impedance has been measured in dependence on the added volume (20, 21, 22, 23, 24, 25 µL). Modeled impedance of the biochip reveals a linear relationship between the impedance model parameters and yeast concentration. Presented biochips allow for continuous impedance measurements without interrupting the cultivation of the yeast. A multiparameter fit of the impedance model parameters allows to determine the concentration of yeast cy in the range from cy = 3.3x10^7 to cy = 17x10^7 cells/mL. This work shows that independent on the liquid, DI water or glucose, the change of the impedance model parameters with increasing added volume of the liquid is clearly distinguishable from the change of impedance model parameters with increasing concentration of added yeast in the ring electrode region of the impedance biochips. We also counted bacterial cells of E. coli strain K12 in several-microliter DI water or in several-microliter PBS at the low optical density (OD) range (OD = 0.05–1.08) in contact with the surface of Si-based impedance biochips with ring electrodes by impedance measurements. The multiparameter fit of the impedance data allowed calibration of the impedance data with the concentration cb of the E. coli cells in the range of cb = 0.06 to 1.26 × 10^9 cells/mL. The results showed that for E. coli in DI water and in PBS, the modelled impedance parameters depend linearly on the concentration of cells in the range of cb = 0.06 to 1.26 × 10^9 cells/mL, whereas the OD, which was independently measured with a spectrophotometer, was only linearly dependent on the concentration of the E. coli cells in the range of cb = 0.06 to 0.50 × 10^9 cells/mL. with the help of the newly developed ring electrode structure, the modeled capacitance and resistance parameters of the electrical equivalent circuit describing the p-n junction-based biochips depend linearly on the number of bacteria in the ring top electrode region, which successfully proves the potential performance of p-n junction-based Si biochips in observing the bacterial suspension. The proposed p-n junction-based biochips reveal perspective applications in medicine and biology for diagnosis, monitoring, management, and treatment of diseases.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:91334 |
| Date | 29 May 2024 |
| Creators | Kiani, Mahdi |
| Contributors | Schmidt, Heidemarie, Kanoun, Olfa, Technische Universität Chemnitz |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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