Novel magnetic indenter for rheological analysis of thin biological sheet for regenerative medicine.

A novel method is proposed for analyzing the mechanical properties of a thin sheet of cells or extracellular matrix cultured for regenerative medicine. A steel sphere is mounted onto the center of the sheet sample, placed over a circular aperture, and a loading force is exerted via an electromagnet with well-regulated current while the displacement of the sample center is optically detected. Details of the instrument and its performance are described.

Pulse-response measurement of frequency-resolved water dynamics on a hydrophilic surface using a Q-damped atomic force microscopy cantilever.

The frequency-resolved viscoelasticity of a hydration layer on a mica surface was studied by pulse-response measurement of a magnetically driven atomic force microscopy cantilever. Resonant ringing of the cantilever due to its 1st and 2nd resonance modes was suppressed by means of the Q-control technique. The Fourier-Laplace transform of the deflection signal of the cantilever gave the frequency-resolved complex compliance of the cantilever-sample system.

Magnetically-modulated atomic force microscopy for analysis of soft matter systems.

Experimental method of studying viscoelasticity, a common idea to understand properties of microscopic biological soft matter systems, especially single biopolymer chains, using atomic force microscopy (AFM) with magnetically- driven cantilever is surveyed. The experimental setup of applying well-characterized excitation to the cantilever and the analysis method to derive the viscoelasticity of the system under study are briefly introduced. Examples of measuring viscoelasticity of single peptide molecule and single titin molecule are shown.

Multifrequency high-speed phase-modulation atomic force microscopy in liquids.

We have developed a new technique, called multifrequency high-speed phase-modulation atomic force microscopy (PM-AFM) in constant-amplitude (CA) mode based on the simultaneous excitation of the first two flexural modes of a cantilever. By performing a theoretical investigation, we have found that this technique enables the simultaneous imaging of the surface topography, energy dissipation and elasticity (nonlinear mapping) of materials. We experimentally demonstrated high-speed imaging at a scan speed of 5 frames/s for a polystyrene (PS) and polyisobutylene (PIB) polymer-blend thin-film surface in water.

Step response measurement of AFM cantilever for analysis of frequency-resolved viscoelasticity.

Extension of AFM-based viscoelasticity measurement into a frequency-resolved analysis is attempted. A cantilever immersed into and interacting with distilled water was employed for the trial system. Using a home-built wideband magnetic excitation AFM, a step force with a transient time less than 1micros is applied to the AFM cantilever and its deflection is measured.