Metal Plated 3D Printed Devices for Basic Research
22 November 2017
Complex structures are required for research projects in fundamental studies of gas-phase chemical reactions. In these studies, the motion of molecules is controlled by using strong electric fields and tailored electrode shapes. These are best produced by electroplating 3D printed pieces.
We have demonstrated the use of additive manufacturing in combination with selective metal plating for applications in fundamental research. Our studies target the most fundamental aspects of chemical reactions in the gas-phase. In order to reach our goals we require full control over all degrees of freedom of the particles, in particular over the motion of the molecules. The basis of most such experiments is a technique called "molecular beams". Here, a gas is expanded from a high-vacuum reservoir into vacuum in a way that it forms a collimated jet that flies through the vacuum container. Reactions can then be studied for example by crossing two molecular beams at a given angle such that reaction products are formed at the crossing point.
A key aspect of our experiments is the ability to steer molecules from molecular beams inside the vacuum. The motion of some molecules can be controlled via the application of very strong electric fields which in turn are generated by applying high voltages (around 10000 V) to electrodes separated by only 1-2 mm. Stringent requirements apply to the surface properties and positioning of these electrodes since small defects can lead to electric arcing, thus making the experiment impossible.
A complication arises from the degree of complexity of the 3D electrode structures required in our experiments. Traditionally, such structures are prouduced from stainless steel, using standard machining and polishing technologies. The limitations of these, even in combination with multiaxis CNC devices, limit the viability of certain experiments. 3D printing resolves the limitations of the structural requirements, but by itself suffers from material restrictions. The electrode structures themselves need to be conductive, but they need to be mounted on electrically insulating materials. The surfaces have to be highly polished, bt the structures can be such that mechanical polishing is not possible.
We have overcome all these limitations by combining sterolithography with metal coating. The base structure for the electrodes and their mounting structures (which need to be electrically insulating) is printed as one piece. This piece is then electroplated selectively, such that some regions are conductive and used to apply the high voltages while other regions remain insulating and serve as supports and spacers.
This approach has been demonstrated by producing a so-called beam-splitter for neutral molecules. In a beam-splitter a single beam is split into two - this can be done for light beams, for example by using a partially reflective glass, or for fluids simply by using a Y-shaped piece connected to two ducts. For the low-density gas samples used in our experiments it is substantially more complex because it has to be obtained without mechanical forces but instead through the electric fields described above. The required electrode structure has been designed precisely according to the required electric fields, resulting in a device that would be highly challenging to produce by traditional means and require several months of work. The 3D printed, electroplated piece was produced in a week and had properties that were comparable, and in several aspects even better, than the traditionally manufactured piece.
More information about this project can be found on our website and at https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.7.044022