Democratise Microfluidics in Industry and Education With 3D Printing

The field of microfluidics is a rapidly expanding discipline that is causing a major revolution in many scientific and industrial domains, including chemistry. The basis of this field is the manipulation of fluids at the micrometric scale using miniaturised devices, thus providing precise control of chemical reactions. The benefits of microfluidics include the following: reduced volumes, better management of mass and heat transfers, as well as increased automation. Consequently, it is possible to improve the efficiency of chemical processes while reducing the consumption of reagents and the production of waste.

In the domain of chemistry, this technology boasts a plethora of applications, encompassing the synthesis of high-added-value compounds, chemical analysis and controlled crystallisation. The integration of microfluidics within chemical processes has precipitated substantial advances in pharmaceutical development and catalysis, with a particular emphasis on the optimisation of kinetics in water, the ideal solvent in green and sustainable chemistry. Moreover, the capacity to couple these devices with advanced analytical instruments enables real-time monitoring of reactions.

Notwithstanding the numerous advantages attendant in the adoption of microfluidics in the domain of chemistry, the process is encumbered by several significant challenges. These primarily address concerns regarding development and production costs, the availability of suitable materials, and the level of acceptance within the scientific and industrial community.

Indeed, a primary impediment to the advancement of microfluidics concerns the financial investment required for the conception and fabrication of these devices. In comparison to conventional chemistry apparatus, microfluidic systems necessitate not only specialised manufacturing processes, frequently modelled on the semiconductor industry, but also sophisticated and costly associated equipment (e.g. sensors, syringe pumps, microscopes).The machining of microchannels, the integration of sensors and the assembly of these devices demand costly infrastructures and advanced technical expertise. Furthermore, the necessity to customise microfluidic chips according to specific applications results in increased research and development costs.

Moreover, the selection of materials for the fabrication of microfluidic devices poses an additional challenge. While glass and silicon are efficient, they are costly and challenging to manipulate. Polymers such as polydimethylsiloxane (PDMS) offer a more economical alternative, but they have limitations in terms of chemical compatibility, thermal stability and longevity. Furthermore, chemical reactions occurring at the microfluidic scale necessitate meticulous management of wetting phenomena, adsorption of reagents on the walls, and evaporation, which complicates their implementation.

The integration of microfluidics within the domain of chemistry is impeded by several factors. Firstly, the constraints mentioned earlier, and secondly, a novel paradigm within the field. This necessitates a shift in practices and mindsets, which represents a significant barrier to its adoption.A considerable number of laboratories and industries remain reliant on conventional methods and are reluctant to invest in a technology that is perceived as intricate and costly.Additionally, the absence of established standards and protocols further complicates the transition to microfluidics, particularly for companies seeking to implement it on a large scale. Finally, the training of researchers and engineers in this technology is still insufficient, which slows down its diffusion and adoption.

Notwithstanding the challenges encountered, research in the field of microfluidics persists in its advancement, characterised by the emergence of more efficient materials, the establishment of standardised methodologies, and the diminution of manufacturing expenses. As the technology becomes increasingly accessible and seamlessly integrated into prevailing practices, its adoption is anticipated to undergo a marked acceleration, thereby laying the foundation for subsequent advancements in the domain of chemistry.

The potential of 3D printing to democratise microfluidics in industry and education

The advent of low-cost, easy-to-use 3D printing has precipitated a paradigm shift in numerous scientific and technological domains, including microfluidics.Conventionally, the fabrication of microfluidic devices entailed costly and intricate techniques such as photolithography, polymer molding, and precision machining. The advent of conventional 3D printing has emerged as a flexible, expeditious, and cost-effective alternative for designing microfluidic systems tailored to diverse applications.

One of the primary benefits of 3D printing applied to microfluidics is its capacity to produce complex structures in a single step, provided that a straightforward assembly protocol can be developed using common and cost-effective products.

Additionally, it enables advanced customisation of devices to meet the specific requirements of researchers and manufacturers. The advent of increasingly printing resolutions has enabled the fabrication of channels with dimensions that are compatible with the requirements of conventional chemistry (a few hundred microns). 3D printing also facilitates the integration of additional elements, such as sensors or electrodes, directly into microfluidic chips. Furthermore, it significantly reduces the development time of prototypes, thereby accelerating innovation in this field.

The selection of materials remains a significant challenge. A significant proportion of polymers utilised in 3D printing do not possess the physicochemical properties necessary for microfluidics, particularly with regard to optical transparency, chemical compatibility and thermal stability. Consequently, it is imperative to integrate the 3D printing process with a subsequent assembly process that can yield the requisite transparencies.

The solutions provided by SciencExpert should accelerate the adoption of microfluidics in training establishments, and with a view to the development of chemistry in water for sustainable development, a protocol has been established for the creation of microfluidic plates. This combines :

1. the simplicity of 3D printing with channels of the order of 300 microns to 500 microns;
2. the use of simple and inexpensive materials. These materials are found in everyday objects and are sometimes recycled;
3. a simple and effective assembly protocol.

The fabrication of the microfluidic plates is initiated with the utilisation of plates that have been 3D-printed to create channels. The dimensions of these plates are precisely measured at 50x50x1 mm, with each plate exhibiting a meticulously designed profile.

In order to manufacture the requisite microfluidic plates, the following components are required:

- Double-sided adhesive, characterised by transparency and high adhesion.

- Plates with 3D-printed channels, measuring 50x50x1 mm. the dimension is chosen according to the dimension of the double-sides adhesive.

- 3D-printed inlets and outlets.

- Plates (cover and bottom) made from polystyrene, sourced from reused CD or DVD boxes.

- Commercial or home made Rubber Gaskets. The internal diameter of the rubber gasket is 6 mm.

- Epoxy glue and tube.

The medium for 3D printing is constituted by STL files. These plates are 500-micron microfluidic circuits for the channels. The plates have dimensions of 50x50x1 (H, W, T) mm. The formats are ready-to-use STLs.

The channels are categorised into three distinct families: emulsion, T-junction and mixer. In addition, two further mixer families are distinguished: simple and high density :

The STL file for the low density mixer, with 300 microns channel, is attached below. The other files are available on SciencExpert Website.

The decision was taken to utilise UNF1/4" 28G thread plugs. This standard, which originates in the USA, is most frequently employed for HPLC and GPC chromatographic tubes. The expense and scarcity of the connectors intended for use by males and females has necessitated the creation of a special design that can be printed on a 3D printer using PLA as the material. The female component is a cube with a 1/4-inch thread hole, which is affixed to the plate using epoxy glue. The male component is designed to accommodate a 6-mm external tube, which is a standard aquarium component. As illustrated below, the construction of the piece is demonstrated. The female component has been printed in yellow PLA in order to facilitate greater clarity and distinction between the female (yellow) and male (black) components.

From the 5x5x1 mm printed microfluidic plate, the position of the inlets and outlets is marked on the part that is protected by a PE sheet of the double-sided adhesive. This procedure is then repeated on the polystyrene plate, which is cut to a size of 6x6 mm.

The perforations in the double-sided adhesive tape are created through the application of heat from a soldering iron to the adhesive layer. The perforations in the polystyrene plate are produced by drilling with a 3 mm drill bit.

Subsequently, the adhesive is carefully positioned on the microfluidic plate by adjusting the housings provided for the inlets and outlets. It is imperative to avoid the formation of air bubbles, and the adhesive is compressed on the plate to enhance adhesion across the entire surface.

Once the adhesive has been adequately applied to the plate, the polyethylene sheet is removed, which protects the second side. The polystyrene plate is then affixed by adjusting the housings provided for the inlets and outlets.

It is evident that the PS plate (6x6) is of a larger dimension than the microfluidic plate (5x5). The superfluous material from the PS plate (top and bottom) is then removed using a cutter. Subsequent to this process, the final design is achieved without the outlets and inlets :

Following the attachment of the outlets and inlets to the plate, a tube is inserted into the outlet and a M6 screw plug (M6 screws close to a UNF 1/4) is inserted into the inlets to close them.

The plate is then Subsequently, the plate is to be immersed in a bottle of water, and the impermeability is then tested by introducing air into the system.In the event that the system is not impermeable at the plate (a rare occurrence, as this has never happened in our case), the plate must be corrected.Leaks are more generally found at the interface of the female outlets and inlets and the male plugs.

It is evident that a rubber gasket is required at the interface between the male and female plugs. The fabrication of a homemade rubber gasket is achieved by utilising a used inner tube and a 6 mm diameter hole punch.

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