The design and additive manufacturing of functional continuous flow reactors

In recent years, the search for new synthetic methods has moved beyond the traditional quest for new reactions and reagents. The scope of the search has now broadened to incorporate new practical preparative methods for increasingly complex chemical transformations. One of the most exciting and potentially significant developments is the innovative incorporation of flow chemistry into lab based synthesis platforms. In flow chemistry, chemical reactions are performed within the confines of a tube or pipe, under precise reaction parameters in order to accurately control the reaction outcome. These tubes or pipes often come in the form of flow reactors, which are either micro-bore tubing or chips featuring patterned fluidic pathways.

Current micro-fabrication techniques used for the formation of many of these flow reactors are limited as a result of complex and expensive manufacturing processes acting to limit many researchers access to this technology. This is compounded by the continued desire for chemist’s to integrate analytical techniques within these reactors, which leads to additional complexities during fabrication. Additive manufacturing (AM) is a layer based manufacturing process in which 3D objects can be manufactured through selected material deposition in sequential 2D layers. This manufacturing technique is becoming more popular in the development of fluidic devices for various chemo and biological applications, including flow chemistry. The majority of these reported devices however lack the desired complexity, functionality and resolution required for many modern chemical applications.

In this study, the polymer-based AM technique of stereolithography (SL) and the metal-based technique of ultrasonic additive manufacturing (UAM) were employed to fabricate a range of 3D reactor devices. The ability to incorporate additional analytical elements within these devices was established in the form of both optical and electrical elements. In the first part of the study, hybrid manufacturing approaches were investigated in order to increase both the complexity of parts formed via stereolithography and facilitate the integration of sensing elements within the resulting flow devices. The effectiveness of these techniques was then confirmed through the direct monitoring specific analytes and the optimisation of a selected test reaction. In the second part of the study, highly complex flow reactors were manufactured from targeted metal alloys to mark the first ever example of UAM being used to manufacture a flow reactor device. The ability for these reactors to perform complex organic synthesis was then established through a variety of metal mediated organic transformations. Following this, studies into the exploitation of associated phenomena to allow the embedding of sensors within the metallic structures was performed to facilitate potential future applications across a broad range of future chemical applications.

The investigation showed that SL is highly suitable for the formation of geometrically complex devices ideal for early stage research. This was a direct result of the ability to rapidly design and manufacture devices in order to optimise equipment configurations and reactor conditions. UAM was demonstrated to be ideal for the formation of highly robust and complex metallic devices suitable for performing high temperature and high pressure chemistry. The additional functionality that can be imparted to these devices as a result of the research outlined in this work adds substantial functionality to the reactors, suitable for a wide range of potential applications.