Nanoscale mass spectrometer: Co-resonant coupled mass-sensitive nanoscale oscillator

• Applicants: Dr.-Ing. Jens Twiefel; Professor Dr.-Ing. Marc Christopher Wurz; Professor Dr.-Ing. Stefan Zimmermann
• Subject Area: Measurement Systems
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 541658875

The objective of the project is to establish the scientific ground for the development of a novel nanoscale mass spectrometer based on mass-sensitive nanostructures in resonant oscillation. In the case of a spring bar in resonant oscillation, which serves as the mass-sensitive element in our approach, mass sensitivity and mass resolution mainly depend on the intrinsic mass of the spring bar, its elastic properties and the damping. Due to the advantages regarding excitation and observation, a nanoscale spring bar will be integrated into a co-resonant oscillating system, where a coupled microscale oscillator is piezoelectrically excited and observed. This approach requires an accurate tuning of the resonance frequencies of the resonators to be coupled. A detailed theoretical consideration and accurate modeling of the planned geometry by means of numerical simulation is therefore of crucial importance for the system design. Compared to the state of the art, simple and reproducible fabrication with available manufacturing technologies will be considered already in the design phase. In addition, operation at reduced pressure is proposed for high quality factors and defined particle adsorption. The temporal and local manipulation of particle adsorption and desorption at the surface of the nanoscale spring bar by means of pressure and temperature is intended to temporally attach a defined number of particles. In particular, numerical simulations will be used to develop new concepts that allow for local adsorption in order to minimize the effect of the position of adsorbed particles on the resonance frequency. A geometry-dependent inhomogeneous distribution of a heating current density in the sensitive element in combination with a differential approach seems very promising and will be experimentally investigated here for the first time. For high mass resolution, a very accurate detection of the oscillation state is necessary. Therefore, another important aspect of this project is the development of new excitation and measurement concepts and their implementation in low-noise measurement electronics. For continuous monitoring of the resonance frequency, active oscillator circuits and phase-locked loops will be investigated. The scientific challenge is the practical hardware implementation at high frequencies and accurate frequency counting. In addition, a new concept for continuous monitoring of the resonance frequency based on power control will be investigated. For suppressing parasitic common mode signals, a new differential concept is proposed, which will be implemented in this form for the first time.

• DFG Programme: Research Grants