[paper] Cantilever with Carbon Piezoresistor

Jongmoon Jang, Giulia Panusa, Giovanni Boero and Juergen Brugger 

SU-8 Cantilever with Integrated Pyrolyzed Glass-Like Carbon Piezoresistor

Microsyst Nanoeng 8, 22 (2022)

DOI:10.1038/s41378-022-00351-9

Abstract: Glass-like carbon (GC) is a nongraphitizing material composed entirely of carbon atoms produced from selected organic polymer resins by controlled pyrolysis in an inert atmosphere. The GC properties are a combination of the properties of glass, ceramic, and graphite, including hardness, low density, low thermal conductivity, high chemical inertness, biocompatibility, high electrical conductivity, and microfabrication process compatibility. Despite these unique properties, the application of GC in mechanical sensors has not been explored thus far. Here, we investigate the electrical, structural, and chemical properties of GC thin films derived from epoxy-based negative photoresist SU-8 pyrolyzed from 700 to 900°C. In addition, we fabricated microGC piezoresistors pyrolyzed at 700 and 900 °C and integrated them into nonpyrolyzed SU-8 cantilevers to create microelectromechanical systems (MEMS) mechanical sensors. The sensitivities of the GC sensor to strain, force, surface stress, and acceleration are characterized to demonstrate their potential and limits for electromechanical microdevices.

Fig: Design and layout of the glass-like carbon (GC)-based sensor:

a.) Schematic drawing of the GC strain sensor, and

b.) Enlarged optical microscopic image of a fabricated GC piezoresistor

Acknowledgements: The authors thank the Center of Micro/Nanotechnology (CMi) of EPFL for the microelectromechanical system (MEMS) fabrication support and Bio-Micro Robotics laboratory with Professor Hongsoo Choi of DGIST for the microforce probe system facility support. This work received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Project “MEMS 4.0”, ERC-2016-ADG, Grant Agreement No. 742683) and the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2020R1F1A107422211).