Session: 14-06-01: Applied mechanics and materials in micro- and nanosystems

Paper Number: 165167

Mechanical Characterization of Stretchable Ecoflex Thin Films for Microengineering Applications 

Stretchable elastomers are growing in demand with applications in soft robotics, wearable technology, smart skin, and stretchable electronics.  With the growing demand there is also a keen interest in integrating these materials into microfluidics or other microelectromechanical systems (MEMS) applications. The most commonly used elastomer in MEMS is polydimethylsiloxane (PDMS) which has been extensively investigated especially in bioMEMS and microfluidic applications. However, PDMS has a relatively high elastic modulus (MPa) range and has a low elongation to break <200%. Previous research demonstrated that manufacturing PDMS at the micro-scale can have a significant effect on the mechanics of the material.

In recent years there has been significant research on using Ecoflex-based elastomer for a variety of applications including microfluidics, artificial skin, wearable technology, stretchable antenna and speakers and numerous other applications. Ecoflex is an elastomer with a lower elastic modulus < 50 kPa with high elongation to break 400-1000%. The mechanical properties vary depending on the type of Ecoflex used. However, there is limited data on the mechanics of the material and even less on mechanical properties at the micro-scale and impacts of manufacturing. This paper investigates methods to fabricate and integrate Ecoflex materials at the micro-scale including spin coating and etching parameters. However, the main goal of the paper is to investigate how manufacturing methods can impact the mechanical properties of the material.  The study investigated the impact of mixing the ecoflex and how it impacts mechanical properties and bubble formation. Demonstrating that hand mixing ecoflex had significantly lower elastic modulus and higher elongation to break than ecoflex that was mixed using a speedmixing technique. The paper also investigates curing temperatures effect on ecoflex mechanical properties. Ecoflex with various shore hardnesses were investigated including Ecoflex 00-10, 00-30, and 00-50 and Gel which has a shore hardness of less than 00 standards.

In addition to determining key manufacturing conditions and their effect on the final ecoflex material, the paper also investigated manufacturing composite films consisting of multiple ecoflex materials in order to finely tune the mechanical properties to meet specifications for various applications. The results presented in this study demonstrate that manufacturing methods can have a significant impact on the mechanics of the material.  Eliminating bubble generation is especially important for higher viscosity ecoflex’s and the role of curing is important when making composites as the various ecoflex materials cure at different rates.  Adding composities to the material to make them functional has been developed and only further complicates the predictability of the mechanical properties.  The paper demonstrates manufacturing methods of integrating ecoflex into a typical MEMS microfabrication process.

Presenting Author: Nathan Jackson University of New Mexico

Presenting Author Biography: Nathan Jackson is an Associate Professor at the University of New Mexico in the Mechanical Engineering Department and is the Director of the Nanoscience and Microsystems Engineering Program. His interests are in functional materials and integration of these into MEMS devices including energy harvesting, wearable technology, biosensor, atomizers, and acoustic resonators.

Authors:

Emily Weigel University of New Mexico
Ranjith Janardhana University of New Mexico
Nathan Jackson University of New Mexico