|In this paper we present
a microrobotic system that integrates microscope vision and microforce
feedback for characterizing biomembrane mechanical properties. We describe
robust visual tracking of deformable biomembrane contours using physics-based
models. A multi-axis microelectromechanical systems based force sensor
is used to determine applied forces on biomembranes and to develop a novel
biomembrane mechanical model. By visually extracting biomembrane deformations
during loading, geometry changes can be used to estimate applied forces
using a biomembrane mechanical model and the determined elastic modulus.
Forces on a biomembrane can be visually observed and controlled, thus
creating a framework for vision and force assimilated cell manipulation.
The experimental results quantitatively describe a stiffness increase
seen in the mouse zona pellucida (ZP) after fertilization. Understanding
this stiffness increase, referred to as "zona hardening", helps
provide an understanding of ZP protein structure development, i.e., an
increase in the number of cross links of protein ZP1 between ZP2 and ZP3
units that is conjectured to be responsible for zona hardening. Furthermore,
the system, technique, and model presented in this paper can be applied
to investigating mechanical properties of other biomembranes and other
cell types, which has the potential to facilitate many biological studies,
such as cell injury and recovery where biomembrane mechanical propertychanges
need to be monitored.