Physics of Life
  Soft and Living Matter Group

9. A  spongy material  made up of hard rigid spherical nano-particles  with large pores which is highly compressible  but spring back to its original shape.  The particles are enmeshed in a polymer gel which makes it deformable but also elasticity to give shape to the scaffold.

A multiscale modeling challenge : A nm thick polymer mesh surround 22 nm nano-particles
to form nano-composite walls of thickness of 1 micron, and dimentions of 10-50 microns which surround open void of size 100 microns to make a sponge of size 1cm. All length  contribute to the combined  elastic response of the composite material.

How does one do it ? Which degrees of freedom to coarse-grain out and how ?


MOVIE BY ANISH SUKUMARAN (IITB B Tech student).
 
Following the deformation of a single void.

       The junctions   surrounding the voids are made of hard nano-particles trapped in a polymer mesh. The polymer mesh gives the scaffold soft and deformable. 95% of the scaffold is Nano-P which are  hard particles of materials like SiO2. If the scaffold were fully made up of solid material like Calcium phosphate or SiO2, it would be brittle. The large voids make the substance very light.

 A 3 minute talk by Anish Sukumar on the system.














Box with 27 CONNECTED VOIDS.                    ONLY HALF OF THE  BOX IS SHOWN.The colour gradient along z-direction helps the viewer distinguish different  particle layers along z & has no other significance.

-  IN COLLABORATION with K. GURUSWAMY  (IITB)  and N. BACHHAR (IIT-Jodhpur)

--  Extension of project by Somesh Kurhatti:  Replace the spherical particles in the polymer mesh by ellipsoidal nano-particles, that is expected to significantly alter its elastic properties.

Future Plans:

Questions for future students: How  can this study be extended to understand mechanical properties of  Bones or Shells (of marine living organisms) and correlate it to their microscopic structure?   Basic info about porous bones.

--How can one make the system harder while maintaining the flexibility (remain non-brittle) ?

--  There should already quite some literature about mechanics and structures of (human) bones. Bird bones have large pores to make them light. Spinal cord fluids, which form a cushion between bones, have self assembling filaments floating in a fluid medium which give it the necessary elastic + flow properties.

--  How are Shells different from Bones ?  Shell of a turtle vs oyster shell vs clam shells vs...dont know what. How are these shell properties optimized for different organisms?

-- A collection of articles and basic information about micro-structure of BONES AND SHELLS
: the webpage  created by Aparna Jayaraj and Nishanga P: IISER Pune students.

--  Does this help ?  https://www.nio.org/profile/1219/dr-narsinh-thakur

--  Finally the question is how does nature manipulate micro structure to obtain the required stiffness/softness/brittleness/ductility/compressive strength/tensile strength/flexibility..? Whatever the organism needs to survive it's ecological niche