Characterizing Viscoelastic Properties Of The Living Cell With A Probe Nanot-Weezer

Cell structure and functionalities, as well as cell growth, multiplication, aging apop-tosis，and cytopathy are closely related with the cell mechanics. The external force and celldeformation directly influence cell functionalities. Therefore, study on the cell mechanicshas the vital significance for understanding the cell and its functionalities. To measuringcell mechanics, numerous methods and tools have been developed. Among them, atomicforce microscope (AFM) is one of mostly used tools for cell mechanics study due to itshigh-precision, wide-range of force measurement, as well as easy sample preparation.In this work, living cell mechanics were measured by employing newly designednanotweezer installed on the nanorobotics system. The system is capable of measuringliving cell’s static and dynamic viscoelastic properties in the liquid environment. The pro?posed novel nanotweezer provides a new approach to measure the viscoelastic propertiesof living cell that could a potential tool for biomechanics. Main research issues of thisdissertation are shown as follows:A nanotweezer consists of two microassembled AFM probe cantilever beams and cor?responding method for cell viscoelastic properties were developed. The cantilever beamswere cut by using focused ion beam (FIB) and nanotweezer probe is fabricated using themicroassembly technique. The nanotweezer formed by two oppositely aligned probes haspotential to measure the cell mechanics by compressing, stretching and shear modes.The mechanical modeling of the cell’s viscoelastic properties were described by tworepresentative models, namely power-Law principle and Zener’s model. The former is usedto qualitatively describe the cell’s creep and relaxation properties, and the later is used togenerate the cell’s creep and relaxation functions, and then the cell’s viscoelastic parame?ters.A temperature control system was designed that was used to maintain temperature(37士0.5。C) of the cell’s physiological solution. The chamber is filled with5%CO2ofconcentration. Therefore the experiments can be performed for a long duration while keep?ing the cell alive.Finally, a measure and control system was developed for the cell’s static and dynamicviscoelastic properties measurement with the developed nanotweezer. Compared with theindentation method performed by the conventional AFM probe that is used to measure thecell’s local viscoelastic properties, the developed nanotweezer can be used to measure thecell’s whole viscoelastic properties. The developed method is capable of evaluation thecomplete viscoelastic properties of the cell.We have proposed a new method for measuring the cell’s viscoelastic properties. The newly developed method has the following advantages:1) The loading force and cell de?formation are more uniform due to the dual-parallel-plate structure of the nanotweezer, andthe cell slip can be eliminated.2) The nanotweezer can simultaneously measure the normalthe lateral forces applied on the cell. Thus, the nanotweezer is available for stretching,compressing and shear modes of the cell’s mechanics measurement.3) By adjusting struc?ture parameters, the nanotweezer can meet requirements of different force ranges and forceaccuracies of the cell’s mechanics measurement.