Rotational manipulation of massive particles in a 2D acoustofluidic chamber constituted by multiple nonlinear vibration sources

Rotational manipulation of massive particles and biolo gical samples is essential for the development of miniaturized lab-on-a-chip platforms in the fields of chemical,medical,and biological applications.In this paper,a device concept of a two-dimensional acoustofluidic chamber actuated by multiple nonlinear vibration sources is proposed.The functional chamber enables the generation of acoustic streaming vortices for potential applications that include strong mixing of multiphase flows and rotational manipulation of micro-/nano-scale objects without any rotating component.Using numerical simulations,we find that diversified acoustofluidic fields can be generated in the chamber under various actuations,and massive polystyrene beads inside can experience different acoustophoretic motions under the combined effect of an acoustic radiation force and acoustic streaming.Moreover,we investigate and clarify the effects of structural design on modulation of the acoustofluidic fields in the chamber.We believe the presented study could not only provide a promising potential tool for rotational acoustofluidic manipulation,but could also bring this community some useful design insights into the achievement of desired acoustofluidic fields for assorted microfluidic applications.

Influence of lumbar disc degeneration on the efficacy of lumbar fixed-point rotation manipulation in sitting position:a finite element study

Objective：To investigate the influence of lumbar disc degeneration on the efficacy of lumbar fixed-point rotation manipulation in sitting position in treating lumbar intervertebral disc herniation（LIDH）.Methods：We simulated lumbar fixed-point rotation manipulation of sitting position using three finite element models including a normal model,a mild degeneration model and a moderate degeneration model of L3-5,in which the herniated disc was assumed at the left rear of L4 disc and the rotation manipulation was carried out on the right side.The displacement and stress at the left rear of L4 disc of the three models were analyzed.Results：When lumbar fixed-point rotation manipulation in sitting position was carried out,a displacement and stress were generated at the left rear of L4 intervertebral disc of the three models directing forward.The displacement and stress in degeneration models were less than those in the normal model,and the smallest values were found in the moderate degeneration model.From normal model to mild and then to the moderate degeneration model,the displacement decreased by 36% and 59%,and the stress decreased by 22.3% and 45.2%,respectively.Conclusion：The lumbar disc degeneration affects adversely the effectiveness of lumbar fixed-point rotation manipulation in sitting position in the treatment of LIDH.The severer the lumbar degeneration,the greater the influence.