Mechanics of the Small
|A pigmy shrew consumes much more food than a whale per unit volume of their body weights. The shrew looses lot more energy through its large body surface compared to its volume - a consequence of scaling.|
Our primary focus is the mechanics of the small. We have two objects of study: a living cell and a material sample, both at micro to sub-micro meter scale. We are interested at the fundamental mechanisms that arise from the small size. We use both theory and experiment to explore the mechanisms. We develop micro and nano-machines to explore the world of small. Currently we are exploring the questions: How small size of material samples (such as thin films or nano wires) or their microstructures determine their properties? Does the mechanical stiffness of cancer tumors play a role in initiating metastasis, and if so, how? Do memory and learning in animals depend on mechanical forces in neurons?
For a material sample, the smallness may appear in various forms, e.g., the physical size, the layer thickness of a multilayer system, or the grain size in a polycrystalline metal. Size brings interfaces. Smaller the size, higher the interface to volume ratio. At nano scale, interfaces are abundant, and they play important roles in defining macroscopic properties of materials such as mechanical strength, energy dissipation and conductivity. Interfaces interfere with the mechanisms by which macroscopic materials behave, and may generate new mechanisms.
One of our central goals is to explore and understand the interaction between the macroscopic mechanisms and the interfaces, and the new mechanisms that interfaces may generate (structure-property relation, a fancier way of saying). For example, when the grains of a crystalline metal is large, dislocations (crystal defect) can move through the crystal when sheared to accommodate deformation. When the grain size is small, grain boundaries impede the dynamics of dislocation (deformation mechanism of the macro), and changes the deformation characteristics and strength of the metal.
Single cells are basic units of life. There is increasing experimental evidence suggesting that extracellular and intracellular mechanical forces have a profound influence on a wide range of cell behavior such as growth, differentiation, apoptosis (programmed cell death), gene expression, adhesion and signal transduction. Study of cell mechanics has drawn considerable attention from diverse fields, including biology, physics, biochemistry, and bioengineering.