3D-printing of a complete modular ion mobility spectrometer

Abstract: Three-dimensional printing (3D-printing) is an asset for rapid prototyping. Therefore, this technology is applied in amateur, fundamental as well as in applied research communities. Moreover, the fused deposition modeling even allows a cheap and fast 3D-printing of functional filaments such as conductive or ferro-magnetic materials. Further applicable materials enable the production of electronic circuits, electrodes or even complete analytical sensors.

Here, a 3D-printed stand-alone drift tube ion mobility spectrometer (IMS) completely manufactured in one process is presented. The ionization chamber, the Bradbury-Nielsen gate, the partly conductive drift tube, and the detector including an aperture grid and a Faraday plate were printed by dual extrusion 3D-printing. Therefore, non-conductive polylactic acid (PLA) was utilized for the housing and conductive PLA was used for the electrodes, the ion gate and the detector. Due to a magnetic quick lock system and a modular design, each part of this innovative ion mobility spectrometer can be exchanged in an instant. All parts were validated individually and as a whole by comparing them to an ion mobility spectrometer produced by computerized numerical control machining consisting of polytetrafluoroethylene (PTFE).

To investigate the performance, parameters regarding the resolution, resolving power, signal-to-noise ratio, running-in period and long-term stability were used involving a set of isomeric volatile organic compounds (VOCs). Notably, every single 3D-printed component as well as the completely 3D-printed IMS could keep up with the traditionally produced ones. Furthermore, the signal intensity was comparable to the signal intensity of the PTFE-IMS in exemplary optimization steps. The resolution, resolving power and signal-to-noise ratio could be improved by the variation of the Bradbury-Nielsen gate design, thus demonstrating the potential of the 3D-printing for design optimization and rapid prototyping of analytical instrumentation.