manipulation

Biological and biomedical microfluidic devices have been widely used to isolate rare cells. Although various techniques are available for analyzing rare cells, many are limited by high sample loss and low selectivity. Surface Acoustic Wave (SAW) technology offers a promising active approach for cellular analysis due to its simplicity, low cost, and compatibility with other microfluidic devices, making SAW-based microchips essential tools for manipulating rare cells. This review outlines the principles of acoustic isolation, introduces theoretical concepts and key equations, and examines recent experimental studies in this field. Findings indicate that SAW-based microfluidic devices have been effectively employed for manipulating, isolating, focusing, and patterning rare cells, achieving a cell separation efficiency of approximately 80-90%, though slightly lower than that for microparticles. This paper also discusses existing challenges and research gaps, recommending future directions such as the development of novel three-dimensional designs, optimization of acoustic devices through artificial intelligence, and the integration of acoustic methods with other techniques.

Nanotechnology involves the ability to see and control individual atoms and molecules which are about 100 nanometer or smaller. One of the major tools used in this field is atomic force microscopy which uses a wealth of techniques to measure the topography and investigates the surface forces in nanoscale. Friction force is the representation of the surface interaction between two surfaces and surface topology. In order to have more precise nano-manipulation, friction models must be developed. In this study a sensitivity analysis has been conducted for nano-manipulation of nanoparticles toward dimensional and environmental parameters based on Coulomb and Hurtado and Kim (HK) friction models using Sobol method. Previously graphical sensitivity analysis has been used for this target in which the percentage of importance of parameters is not taken into account. But in Sobol method as a statistical model this problem is solved. Results show that cantilever thickness is the most effective dimensional parameter on critical force value while cantilever length and width are of less importance. Environmental parameters such as cantilever elasticity modulus, substrate velocity and adhesion, respectively, take next orders.

The theory of contact mechanics deals with stresses and deformations which arise when the surfaces of two solid bodies are brought into contact. In elastic deformation contact occurs over a finite area. A regular method for determining the dimensions of this area is Hertz Contact Model. Appearance of atomic force microscope results in introduction of Contact Mechanics into biology. Low elasticity modulus of biologic particles, causes large deformation against foreign forces, therefore to understand them, studying their behavior is essential. Here, in studying these particles we have used finite element which is a new tool in biology. In this paper indentation of three prostate cancer cells CL-1, CL-2 and LNCaP which have low elasticity modulus and are considered ductile materials was conducted using Hertz contact mechanics model. For modeling, in this section the contact equations of two spheres were used and simulated by using finite element method (FEM). The results of these two steps were compared with available experimental data on these cells to verify simulations and results. These results include force-displacement diagram which shows particles behavior against foreign load. In this presentation we tried to study the behavior of these cells through different methods and make a comparison. Using finite element approach in studying characteristics of these particles was new.

In this paper, the effect of air relative humidity and capillary force on contact geometry of surfaces based on JKR model by Atomic force microscopy was investigated in order to manipulate nano-particles. With transition from macro to nano-scale, the effect of surface forces becomes more significant in comparison with inertial force. Because contact mechanics models are based on surface energy and there is a permanent humidity in surrounded environment. In order to precisely determine the forces in AFM dynamics equations and different environments and also their application in contact modeling, the effect of capillary forces must exactly be specified. Experimental results showed that the air relative humidity percentage affects the adhesion force. So, as AFM is used for fine and nano-scale particles. These forces have significant effect on operation accuracy and should not be neglected. In this paper, the effect of capillary forces has been modeled based on JKR contact mechanics model. The results obtained from this modeling have been compared with experimental data.

Contact mechanics is related to the deformation study of solids that meet each other at one or more points. The physical and mathematical formulation of the problem is established upon the mechanics of materials and continuum mechanics and focuses on computations involving bodies with different characteristics in static or dynamic contact. Contact mechanics gives essential information for the safe and energy efficient design of various systems. During manipulation process, contact forces cause deformation in contact region which is significant at nano-scale and affects the nano-manipulation process. Several nano-contact mechanics models such as Hertz, DMT, JKRS, BCP, MD, COS, PT, and Sun have been applied as the continuum mechanics approaches at nano-scale. Recent studies show interests in manipulation of biological cells which have different mechanical properties. Low young modulus and consequently large deformation makes their manipulation so sensitive. In this article small deformation contact mechanics models are used for biological cell, in air and liquid environment, then results will be compared with Tatara contact mechanics model which has been developed for hyperelastic materials with large deformation. Since biological cells are mostly modeled as viscoor hyper-elastic materials, this model will be more compatible with their condition. FE simulation has been done to investigate the applicability of these models and finite element approach in different ranges of deformations.