Polymers are building blocks of biological systems. They are composed of linear macromolecular structures where atoms or molecules connect together by covalent bonds. In the strongest bonds in nature. Each monomer in the backbone of the polymer undergoes thermal fluctuations due to constant collision of solvent molecules with them. The thermal fluctuations of monomers causes the whole polymer chain to undergo deformations and in the long time the chain takes all possible configurations. In this case, the there is a possibility to assign an average chain length to it. The simple linear chain has an average length of a N 1/2 for the monomers without excluded volume interactions and an average length of a N ν . Here, a is the Kuhn length which is measure of monomer size, N is the number of monomers or degree of polymerization and ν = 3/5 or more precisely ν = 0.588 is the Flory exponent. More precise expression for the chain length is obtained by the density functional theory (DFT) as (5a 2 b/8π) 1/5 N ν where b is the second Virial coefficient and it has all the information regarding interactions between monomers and solvent. If b > 0 the monomers repel each other and the solvent is good, if b < 0 the monomers attract each other and the solvent is poor, and finally, if b = 0 the monomers do not interact and the solvent is Θ. Polymer brushes form when linear chains are densely grafted to a surface. The surface density of the chains or number of chains per surface area is called grafting density σ g . Polymer brushes have many applications in lubrication, stabilization of cells and colloidal particles, modification of surface properties and functional surfaces. There have been many theoretical, numerical and experimental works on polymer brushes. Polymer brush bilayers are two opposing brush covered surfaces where the top and bottom chains interpenetrate moderately. Polymer brush bilayers could be found in many biological systems, for instance, as Glycol in the outside of cells and as aggregan in the synovial joint of mammals. In most situations, there are macromolecular inclusions that are suspended in the solvent.