Improved Dual Electrothermal Microgripper based on a Chevron actuator

In Micro-Electro-Mechanical Systems (MEMS) technology, there is an important interest in the
characterization of devices using dynamic analysis, which is a technique to determine the dynamic
behavior of a structure or component, involving time, inertia and the possibly damping of the structure.
This paper is focused on the analysis and simulation of an improved dual microgripper and its
components: microcantilever and chevron. In addition, a movement amplifier based on an
arrangement of beams was also designed in order to improve the opening of each jaw of the top
gripper.
Dual microgrippers are designed on silicon and implemented using Professional Autodesk Inventor.
Top gripper is initially closed, while the down one is initially open.
The analytical response of the microgripper components was acquired with Steady-State Thermal,
Static Structural, and Modal modules of Ansys Workbench Software.
The dynamic behavior, resonance frequencies for chevron actuator and dual microgrippers are
presented. Simulation results show the modal shapes of all analyzed devices, determining their
respective modal frequencies.
A comparison between initial and improved dual microgrippers was also performed. About the top
grippers, the increment showed by the improved microgripper in total displacement is of 24.4%, and
the temperature distribution only showed a little reduction (7%). For the case of the down gripper, the
total displacement decrease in approximately 50%, force remains without change and its temperature
shows a little decrement (7.2%).
In both dual microgrippers, the biggest temperature value resides in the chevron inside, at the top part
of its shuttle, with 162.76°C. Supply voltage was considered from 0 to 7 V. This swept could be useful
to determine the more appropriate voltage level to obtain a desirable response. In each analyzed
device, their corresponding modal shapes, using FEA, were determined. The modal shapes analysis
allow to understand the performance of the analyzed devices, at the correspondent frequency. From
the comparison between initial and improved dual microgrippers, implemented with Silicon, special
attention was given to the top grippers. Total displacement showed by the improved microgripper has
a maximum value of 0.86 μm. Third natural frequency remains almost without change (4.7%),
increasing at 70.38 kHz and the temperature distribution only showed a little reduction (7%, maximum
temperature was of 131.49°C), which is better for practical applications. For the case of the down
grippers of improved dual microgripper, the total displacement decrease in approximately 50% (with a
value of 0.18 μm), force remains without change (3.8 μN) and its temperature decreases (7.2%), at
162.77°C, which is also better for practical applications. These parameters values of the improved
dual microgripper are illustrative for possible applications.