LOW-FREQUENCY MICROMOTION OF DEP-LEVITATED BIOPARTICLES .2. SPECTRAL AND STABILITY ANALYSIS

In Part I of this series of papers the experimental observations regar ding the phenomenon of micromotion observed during the levitation of b iological cells has been described along with a simple model. In this paper we examine the inadequacies of the simple model in reproducing t he experiment in the frequency region below 10 Hz. In particular a los s in the gain signal in this region is not predicted by the model of P art I due to the omission of some rather crucial terms in the lineariz ation process, The interpretation of this region requires an extended model which is discussed in this paper. Moreover, the model discussed in Part I is only applicable to a single-frequency levitator, while in this paper we include a dual-frequency levitator, A good approximatio n to the exact equation of motion is first of all selected by employin g a Runge-Kutta fifth- and sixth-order algorithm; this approximation i s then examined by the application of Fourier analysis. The exact cond itions for stabilization of the periodic motion to occur depends upon the particle charge and are presented in a quantitative form. (C) 1994 Academic Press, Inc.