电激励下基于挠曲电效应的外毛细胞力电耦合分析

Electromechanical coupling analysis of outer hair cells based on flexoelectric effect under the electrical stimulation

耳蜗内的外毛细胞在电激励下的力电耦合运动是耳蜗放大主动机制的重要基础.以耳蜗外毛细胞为研究对象,基于外毛细胞侧壁的特殊膜结构,推导膜曲率变化、轴向伸缩与跨膜电位差之间的相互关系,建立外毛细胞挠曲电-压电线性等效模型,进而获得整体的等效压电系数.建立外加电激励下细胞轴向振动的动力学控制方程和动态电学方程,并结合相应的力学和电学边界条件进行分析,从频域上讨论细胞材料参数和流体阻力对外毛细胞电动性机制的影响.计算结果表明:在高频区域随着激励频率的增加,流体阻力限制机械功的输出;机械功输出大小和峰值所对应的激励频率与细胞长度、外膜挠曲电系数和细胞基部电阻抗有关,当细胞越长、挠曲电系数或细胞基部电阻抗越大时,机械功输出越大,其对应峰值的激励频率越小.

The electromechanical coupling response of cochlear outer hair cells under the electrical stimulation contitutes an important basis for the active mechanism of cochlear enlargement.Based on the special membrane structure of outer hair cell sidewall,the relationship among membrane curvature,axial stretching and transmembrane potential difference is deduced.The effective flexoelectric-piezoelectric linear model of outer hair cells is established,and the effective piezoelectric coefficient has been obtained.The dynamic governing equation and dynamic electrical equation of the axial vibration under the external electrical stimulation are derived.With corresponding mechanical and electrical boundary conditions,the influence of material parameters and fluid resistance on electromotility mechanisms of outer hair cells are analyzed and discussed in the frequency domain.Calculation results show that the fluid resistance will restrict the mechanical power output with increasing stimulus frequencies in the high frequency zone.The mechanical power output and peak frequency are related to the cell length,flexoelectric coefficient of outer membrane and electrical impedance at the end of cells.The long cells,the large flexoelectric coefficients and electrical impedances will lead to the large mechanical power output and smaller peak frequencie.