Design of a Novel MEMS Microgripper with Rotatory Electrostatic Comb-Drive Actuators for Biomedical Applications.

Luis Velosa-Moncada,Max González-Palacios,Jean-Pierre Raskin,Luz Aguilera-Cortés,Agustin Herrera-May

doi:10.3390/s18051664

Abstract

Primary tumors of patients can release circulating tumor cells (CTCs) to flow inside of their blood. The CTCs have different mechanical properties in comparison with red and white blood cells, and their detection may be employed to study the efficiency of medical treatments against cancer. We present the design of a novel MEMS microgripper with rotatory electrostatic comb-drive actuators for mechanical properties characterization of cells. The microgripper has a compact structural configuration of four polysilicon layers and a simple performance that control the opening and closing displacements of the microgripper tips. The microgripper has a mobile arm, a fixed arm, two different actuators and two serpentine springs, which are designed based on the SUMMiT V surface micromachining process from Sandia National Laboratories. The proposed microgripper operates at its first rotational resonant frequency and its mobile arm has a controlled displacement of 40 µm at both opening and closing directions using dc and ac bias voltages. Analytical models are developed to predict the stiffness, damping forces and first torsional resonant frequency of the microgripper. In addition, finite element method (FEM) models are obtained to estimate the mechanical behavior of the microgripper. The results of the analytical models agree very well respect to FEM simulations. The microgripper has a first rotational resonant frequency of 463.8 Hz without gripped cell and it can operate up to with maximum dc and ac voltages of 23.4 V and 129.2 V, respectively. Based on the results of the analytical and FEM models about the performance of the proposed microgripper, it could be used as a dispositive for mechanical properties characterization of circulating tumor cells (CTCs).

Highlights

Cancer is a major public health problem worldwide and the second leading cause of death in the world, which generated 8.8 million deaths in 2015 [1]
The mechanical properties of polysilicon employed in finite element method (FEM) models springs have refined mesh and are regarded fixed at their base, which are are the follows: Young modulus of 160 GPa, Poisson ratio of 0.23 and density of 2330 kg m−3
V surface micromachining process from Sandia National Laboratories. This microgripper is formed by a compact structure of four polysilicon layers that operate at its rotational vibration mode in plane xy

Summary

Introduction

Cancer is a major public health problem worldwide and the second leading cause of death in the world, which generated 8.8 million deaths in 2015 [1]. Circulating tumor cells (CTCs) inside the human blood represent the beginning of the process of blood-borne cancer metastasis [3,4]. These cells escaped from primary tumors of patients to flow inside their blood [5], whose CTCs levels is correlated with the onset of later metastatic relapse [6,7,8] or with the survival of patients with overt metastasis [9,10,11]. Devices that capture CTCs of patient blood samples could be used to detect earliest signs of tumor metastasis

Methods

Results

Conclusion