Novel rGO-based gas sensor platform for low-power gas sensing applications

Chemoresistive gas sensors based on semiconducting metal oxides (MOX) have been successful realized and fabricated for many years. They are used in many applications, such as automotive, indoor air quality and smart phones. They offer many advantages in compare to other gas sensing principles. They are inexpensive, simple, cheap, stable and can be very sensitive. There is continuous effort to improve the performance of these sensors. All MOX gas sensors used deposited sensing layer over insulating substrate provided with electrodes and heaters. First sensors have used thick film in alumina subtrates or on alumina tubes. Such sensors are still successful on the market. Such gas sensors typically are exhibiting a power consumption of 0.2 to 1 W. Silicon micromachining technology offers some important advantages such as high volume production and small feature size. Typically a thermally insulated heating elements suspended on a dialectric membrane such SiN, SiO or SiC is realized. Au or Pt electrodes are patterned on top of the membrane. This concept helps to reduce the power consumtion. With this concept MOX gas sensors with lower power (<200mW) have been realized.

In this paper we report on novel gas sensors platform using standard MEMS micromachining technology and the rGO material as concept to increase the sensing surface with the goal to increase the sensitivity and reduce the power consumption. A standard IDE (Au Interdigital Electrodes) platform has been used as substrate. On top of the IDE elecrodes a thin rGO-layer with 3D arrangement has been deposited using the Electrophoretic Deposition (EPD) technique. This increases the sensor surface significantly. To fabricate the novel 3D arranged Graphene biosensor, the reduced Graphene Oxide - Polyethylene Glycol - Amine (rGO-PEG-NH2) was suspended in Isopropyl alcohol. The ζ-potential of the in-solution Graphene flakes was optimized adding MgCl2 · 6H2O and enhanced to +46 mV. A high performance ultrasonic mixer is used to crumple and disperse the rGO-PEG-NH2 flakes within the solvent. The layer thickness can be tuned by using deposition time and current. The sensing MOX material (nano particles like CuO, ZnO) has been deposited by drop casting on the surface of the 3D arranged rGO-layer. First results show very promising behavior of the new platform – alcohol, CO and CO₂ have been detected even at room temperature.