Cellular mechanical properties are closely related to cell physiological functions and status, and their analysis and measurement help understand cell mechanism. In this study, a microfluidic platform was built to measure the mechanical properties of cells by using dielectrophoretic (DEP) force. The electrodes generally used to stretch cells are made of indium tin oxide, Au, and Pt, which have inherent disadvantages. In this paper, galinstan alloy liquid metal was first introduced as microelectrode to form non-uniform electric filed for red blood cell stretching manipulation. The liquid metal microelectrode is easy to manufacture, low in price, stable at high voltage, and reusable. An effective microfluidic chip integrated with liquid metal electrode was designed and simulated, and a series of experiments to capture and stretch red blood cells was performed. The length of the red blood cells increased from 6 µm to 8 µm under the DEP force from 0 pN to 103 pN. This work also revealed the potential use of liquid metal as microelectrode to manipulate the microparticles and cells in a microfluidic chip.

Introduction

Cells are the basic unit of life. The in-depth study of biological cell is the key to uncover physiological processes and cure diseases [1], [2], [32]. Cellular properties have been studied using a series of techniques via effective cell manipulation, which mainly includes cell rotation, separation, transportation, injection, and stretching [4]–[۹]. Biological processes, such as cell growth, differentiation, division, and apoptosis in life, are directly affected by the mechanical properties of the cell [10], [11]. Cellular physiological function deterioration leads to abnormalities in cell mechanical properties and eventually various diseases [12]–[۱۴]. Cell stretching is one of the most important tasks in cell manipulation and can obtain the mechanical properties of cells. The mechanical properties of cells directly affect their cell morphology and structure and thereby dominate their biological functions [15], [16]. The methods for evaluating the cell mechanical properties can be divided into contact and noncontact techniques. Contact measurement, such as micropipette suction, microinjection, and atomic force microscopy, stretches or compresses the cell through mechanical contact [17]–[۲۲].