Flexoelectric Effect Of Microcantilever-DNA Chip

Flexoelectric theory of liquid crystal biofilm, Zhang′s two-variable method of laminated beam, scaling method and continuum electrostatics theory and etc., are utilized to establish a simplified single-layered silicion membrane flexoelectric model and four-layered electromechanical liquid crystal model for nanomechanical analysis of DNA chips in label-free biodetection to obtain the relationship among DNA biofilm electrostatic potential, chip deflections and factors such as DNA fragment length, packing density, salt solution concentration. And DNA biofilm potential is detected in experimental conditons.For single-stranded DNA(ssDNA) chips, from the view point of bioelectricity, based on nonlinear Poisson-Boltzmann equation (NLPB) and Liu′s simplified single-layered silicion membrane flexoelectric theory, with the help of Fogolari′s corrected formula, an approximate analytical relation among ssDNA molecule structure feature, salt solution concentration and biofilm electrostatic potential, chip deflection is formulated. According to Wu′s experimental data of ssDNA chip, the ssDNA biofilm height and the flexoelectric coefficient are fitted. The influences of ssDNA fragment length, packing density on chip deflection are investigated.For double-stranded DNA(dsDNA) chips, based upon the ssDNA nonlinear flexoelectric model, considering the hybridization effect on monomer concentration, charge density and biofilm equilibrium height, with the help of Fogolari′s corrected formula, an approximate analytical relation among dsDNA molecule structure feature, salt solution concentration, DNA hybridization rate and biofilm electrostatic potential, chip deflection is formulated. According to Wu′s experimental data of dsDNA chip, the dsDNA biofilm height and the flexoelectric coefficient are fitted. The influences of DNA fragment length, packing density on the height, potential, charge density of biofilm and chip deflection before and after hybridyzation are investigated.For DNA biofilm potential, using thiol self-assembled technology and digital potential difference comprehensive tester, ssDNA biofilm potential difference before hybridyzation and dsDNA biofilm potential difference after hybridization are detected. The relation among DNA fragment length, salt solution concentration, pH value and DNA biofilm potential is investigated. The difference between DNA potential experiment data and theoretical predictions by Fogolari′s corrected method and Chen′s iteration method is dicussed.For ssDNA chip, considering chip deformation and structure charactistic, based upon the simplified single-layered silicion membrane flexoelectric model, according to Gao′s free energy analysis of biofilm, a four-layered electromechanical liquid crystal model for nanomechanical analysis of DNA chips is established. With the help of Taylor′s expension method, an approximate analytical relation among ssDNA molecule structure feature, salt solution concentration, non-biolayer macroscopic mechanical energy, biofilm electrostatic potential, and chip deflection is formulated. According to Mckendry′s ssDNA chip experimental data, the biofilm height and the flexoelectric coefficient are fitted. The influences of ssDNA fragment length, packing density on biofiom potential and chip deflection are investigated.