High-Speed Nanomechanical Property Measurement in Liquid Using Inversion-Based Iterative Feedforward-Feedback Control

This article presents an inversion-based iterative feedforward-feedback (II-FF/FB) approach to achieve high-speed nanomechanical property measurement of soft materials in liquid. Measurement of nanomechanical properties in liquid is needed for studying a wide variety of soft materials, particularly live biological samples such as live cell. Moreover, high-speed nanomechanical property measurement is needed when dynamic evolution of the sample occurs and/or the rate-dependent viscoelasticity of materials is measured. Nanomechanical measurement in liquid, however, is challenged by the adverse effects including the thermal drift effect, the reduction of the signal to noise ratio, and the hysteresis and the vibrational dynamics effects of the piezoelectric actuators (used to position the probe relative to the sample). Thus, the main contribution of the article is the development of the II-FF/FB approach to tackle these challenges. The proposed method is illustrated through force-curve measurement on a poly (dimethylsiloxane) (PDMS) sample in liquid at high-speed. The experimental results demonstrated the efficacy of the proposed approach in achieving high-speed force-curve measurements of soft samples in liquid.