Nanoindentation Methods to Measure Viscoelastic Properties of Single Cells Using Sharp, Flat, and Buckling Tips Inside ESEM

Abstract

In this paper, methods to measure viscoelastic properties of time-dependent materials are proposed using sharp, flat, and buckling tips inside an environmental SEM. Single W303 yeast cells were employed in this study. Each of the tips was used to indent single cells in a nanoindentation test. Three loading histories were used: 1) a ramp loading history, in which a sharp indenter was used; 2) a step loading history, in which a flat indenter was implemented; and 3) a fast unloading history, in which a buckling nanoneedle was applied. Analysis of the viscoelastic properties of single cells was performed for each of the loading histories by choosing an appropriate theory between the correspondence principle and the functional equation. Results from each of the tests show good agreement, from which strong conclusion can be drawn.

Recent advances in nanorobotic manipulation inside scanning electron microscopes

“…When AFM probes are used for force sensing, an applied force can be determined from Hooke's law 85,86 . The stiffness of an AFM probe can be calibrated using a reference cantilever of a known stiffness 87 . Image processing can be conducted to measure AFM probe deflections and determine the applied force.…”

“…The AFM cantilever structure can be modified by FIB etching and deposition to create various types of application-specific tools. For instance, AFM probes were modified to have a flat tip 86,89 , stiff needle tip 87,[90][91][92][93] , knife blade tip 94 and fork tips 95,96 for cellular and intracellular characterization and cell manipulation. Tungsten probes are fabricated and sharpened by electrochemical etching to obtain a high-aspect ratio.…”

“…90 was constructed inside an ESEM, which consists of two units for manipulation with seven DOFs and one cooling stage for holding samples and sample temperature control. This system performed simultaneous realtime observation and manipulation of biological samples for cell property characterization and surgery 87,91,95,156 . To prepare the TEM samples, a hybrid nanomanipulation system that was integrated with an eight-DOF manipulator and a six-DOF manipulator inside an SEM and a TEM, respectively, was constructed 3,13,153 , as shown in Figure 3g.…”

“…These tools were mounted on a nanomanipulation system in ESEM to perform indentation to determine cell stiffness and viscoelastic properties 87,90 . The nanomanipulation system was also employed to lift and push a cell to measure adhesion forces between the cell and substrate 89,95,156,168 ; to measure cell-cell adhesion force 96 ; and to electrically characterize intracellular properties 36 , as shown in Figures 6d and e. Figure 6f shows the use of a nano-knife for performing cell surgery of a yeast cell 94 .…”

Acoustic cardiac signals analysis: a Kalman filter–based approach

“…Two important steps have to be carried out before nanoneedles are used to measure cell stiffness: fabrication of soft and hard nanoneedles, and calibration of soft nanoneedles. 5,6 In related work, a finite element methodcode Abaqus was used for numerical analysis to ensure that only good-quality nanoneedles were selected for measurement of reliable data. In this research, 3 it was possible to detect defective nanoneedles, which should not be used to measure stiffness variation among single cells.…”