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A novel upgraded molecular mechanics framework has been developed by improving the flexural and torsional behavior in bonds between atoms based on modified couple stress theory (MCS-MM). The MCS-MM approach drives a considerable advancement in predicting the mechanical behavior of nanostructures. Due to applying the modified couple stress theory in the beam energy equations, the length scale parameter is added to the equations. The presented method provides a better prediction for the elastic and geometric properties of the equivalent beams in the atomic structure. In order to show the efficiency of this upgraded proposed model, various aspects of graphene sheets were considered, such as energy deviation, mechanical properties, buckling behavior, and crack opening displacement (COD). The results confirm the efficiency and accuracy of the model and are consistent with molecular dynamics modeling. The MCS MM method leads to a significant improvement in strain energy deviation. It predicts the elastic properties and mechanical behavior of graphene sheets more accurately. The MCS-MM method can be replaced with previous ones as an appropriate approach.

Particulate separation has many applications in medicine, biology and industry. In this research, the separation of polystyrene particles with a diameter of 10, 20 and 30 μm in the fluid flow of a microchannel is investigated. The microchannel consists of a spiral region and a straight region under the influence of acoustic waves. In the spiral region, the particles under hydrodynamic effects undergo the initial separation; then the particles enter the straight region of the microchannel, and the