Nanolayer Sensors
This project phase is divided into various sub-phases:
Producing Nanolayer Sensors
This phase focuses on the development of two-dimensional layers with a high surface-to-volume ratio. Available materials include graphene and 2D TMDC layers (transition metal dichalcogenide) such as MoS2 and PtSe2. Various deposition processes (chemical vapor deposition, molecular beam epitaxy) are used to produce these layers. Low-dimensional, nanotechnology-based layers from metal oxides and organic layers are also examined.
Functionalizing Nanolayers
The requirements specification in work package 1 is used to identify suitable receptor groups for detecting target elements and procedures for producing functional nanolayers. Suitable chemical interactions between target elements and functional layers are examined on a laboratory scale and characterized with a view to their responsiveness.
Characterizing Nanolayers
In addition to characterizing the responsiveness of the functional layers, we analyze their surfaces. Elaborate methods such as TOF-SIMS, XPS and AFM are used as few materials are available, including monolayers. The physical and chemical properties of the layers as well as the adsorption, desorption and the dielectric properties of the elements to be measured are examined under defined environmental conditions, as is the stability of the layers during further processing (work package 4).
Stability and Reliability Testing of Nanolayer Sensors
The project will develop systems for the detection of elements in gases (exhaled breath) and liquids (sweat). The materials and methods for the production of functional layers will reflect this aspect. Particular challenges are expected with regard to mechanical and chemical stability in the development of reliable and stable materials for fluidics. Sensor materials should thus be characterized under controlled and realistic conditions. In coordination with the application partners, realistic scenarios for examining cross sensitivity and environmental stability are created using reagent simulants and climatic chambers.
Sensor Components
Materials from work package 3 provide the basis for the development of sensor components. Suitable interactions between receptors and elements have been identified which lead to concentration-dependent changes in sensor material properties when target elements are detected. These changes, for example in work function or electrical conductivity, can be measured electronically in transistor, transfer line measurement or diode structures. Signals can also be detected using optical methods (absorption, emission), in particular in waveguides. Mechanical changes can be recorded when thin layers are stretched as a free-floating membrane. The nanolayers examined here can be used in these nanoelectromechanical systems. The VITAL-SENSE project is developing current work carried out as part of a project sponsored by the Federal Ministry of Education and Research regarding pressure sensors on the basis of 2D layers. The project characterizes these sensor materials with respect to their responsiveness and then transforms them into sensor components using appropriate transducers. On the basis of the results from work package 3, suitable components are processed and modified if necessary, for example to improve the sensitivity of the sensor. Material screening is then conducted, followed by the corresponding transfer to suitable components.
In this project phase, the changes in work function and conductivity are used for electrical measurements of transistor and diode characteristics as well as impedance spectroscopy of interdigital structures. The optical absorption or emission is then measured on chip (intensity measurement of absorption peak / emission peak). The permittivity of functional coating will also be examined using split-ring resonators. The attenuation of the optical signal of on-chip waveguides can be examined in a collaborative effort. The last step in this project phase concerns electromechanical properties, namely piezoelectric effect and the change of conductivity with electric tension. This technology can be used to produce more sensitive, miniaturized pressure sensors.
