Mohammad Reza Nikmaneshi - Center of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran - MSc student
Amir Ghasemi - Center of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran-PhD student
Bahar Firoozabadi - Center of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran-Professor
Mohammad Said Saidi - Center of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran-Professor

There is a network of protein filaments in the front part of a motile cell, which is called actin network. The actin filaments (F-actins) are constantly polymerizing and elongating at the leading edge of the cell. Indeed, these filaments want to move forward. However, the cell membrane resists against actins movement and causes actin retrograde flow. Based on the actin flow velocity and structure of actin filaments, the front part of the cell is organized into a lamellipodium and a lamellum. Any moving cell adheres to the extracellular matrix (ECM) via focal adhesions. A certain lamellipodium-lamellum boundary is associated with the focal adhesions and consists of a series of arclike segments linking neighboring focal adhesions. In this work, a simple continuum model from the front part of the cell for lamellipodium-lamellum boundary generation with stress distribution in the actin network is presented. The actin network is assumed as a highly viscous Newtonian fluid. Since, the lamellipodium-lamellum boundary is a critical region for stress, the actin filaments probably are disintegrated on this boundary and the new structure of them will be formed. The critical stress for actin filaments in fluid is also obtained.

Lamellipodium-Lamellum boundary, Actin network, Focal adhesion, Actin retrograde flow, Main stress