PORTEFEUILLE

The emission of harmful gases, either deliberate or by accident, can cost both money and human lives. To mitigate the impact of such events, it is necessary for the emergency responders (e.g. firefighters, police, military) to have a prompt analysis of the situation, in particular knowing which gases are present and in what concentrations. It is therefore crucial to develop gas sensors that are: highly sensitive (capable of detecting tiny concentration changes) and selective (capable of discerning between different gases), fast and portable (real-time information all-around the event’s site).
In addition, these sensors would be applicable also as portable breath analyzers, which have the potential to radically change health-care. It has been shown that breath contains markers for a plethora of different diseases (from lung to breast cancer, including also organ transplant rejection, radiation poisoning, etc.), thus a personal breath analyzer could be used as a first stage in the health care system.
To achieve such system, we will combine gas micro-columns (long micro-channels that slow down some gases more than others) together with graphene sensors. Graphene (a carbon monolayer) is a novel material that in late-years has received a lot of attention for its exciting possibilities in many disciplines. In particular, it holds a great potential for gas sensing applications as both its mechanical and electrical properties change significantly when gas molecules are adsorbed to its surface. GraphGAS’ main objective is to develop a prototype of such a graphene-based gas sensor, so that its market potential can be evaluated at the end of the project. In addition, basic knowledge on the fundamental properties of the interactions between gases and graphene will be unveiled along the project, which could lead to new multi-functional systems and applications.

Combination of gas columns with graphene and other 2D materials, to achieve gas sensors that we call «multi-physical» detection, where no chemical functionalization is required to separate complex mixtures.

Gas micro-columns have been designed, fabricated and characterized
These are long (2 meters) tubes that are packed within a 1cm*1cm*1mm silicon cube, fabricated using standard microfabrication techniques available at the EPFL facilities. After coating the walls with a polymer, these tubes have the capability of physically separating the different gases that flow through them, a characteristic which is paramount for our application, because a mixture of gases becomes a succession of individual gases in the outlet of the tubes.

Graphene mechanical resonators have been fabricated and optimized
Suspended 2D resonators have been fabricated using graphene, an ultra-thin (mono-)layer of graphite. The mechanical resonators have been fabricated with electrical contacts on both ends as well as a third separate electrode placed below the resonator. These electrodes will enable us to create electrostatic forces to generate motion of the resonator and, at the same time, will enable the collection of charges generated by the motion of the resonator. The electrical and mechanical characteristics of the devices have been measured extensively.

A gas measurement setup has been designed and fabricated
The setup consists on the connection between a home-built gas-testing chamber, and a gas generator to produce minute concentrations of VOCs in the carrier gas (Nitrogen). This measurement setup has enabled us to test the performance of our fabricated monolayer gas sensors.

S. Rumyantsev et al., IEEE Sensors Journal, 2818-2822 (2013);
S. Rumyantsev et al., Nano Letters, 2294-2298 (2012);
F. Schedin et al., Nature Materials, 652-655 (2007).