Resin design in stereolithography 3D printing for microfluidic applications

Additive manufacturing (AM), also known broadly as 3D printing, has enticed the research community and industries alike in the past few decades. The advancement in AM techniques has influenced the material quality and product design in addition to how these products are being perceived and utilized by the consumers . The 3D printing techniques have greatly simplified prototype manufacturing and the translation of conceptual designs. Moreover, AM techniques have made it possible to complete complex designs in a shorter time with the desired lot size and according to the consumer demand. Customized designs and products can also be manufactured without making drastic changes to the entire production set-up.

According to the ASTM standard, AM techniques can be divided into seven groups: stereolithography (SLA), fused deposition modeling (FDM), selective laser sintering (SLS), material jetting, binder jetting, direct energy deposition and laminated object manufacturing (LOM). These techniques are already being used for the industrial preparation of several products covering various fields; for example, construction industry, garments, dental and medical care products and equipment, automobiles and robots, military supplies, and electronics. In 2020 alone, the global spending on 3D printing systems and related equipment was valued at 16 billion U.S. dollars and is predicted to grow at a rate of 26.4% in the coming years, with a projected revenue of approximately 40 billion U.S. dollars in 2024.

Advances in additive manufacturing (often referred to as “3D printing”) technologies have greatly impacted the field of microfluidic device fabrication over the past decade. One particular class of 3D printing, namely stereolithography, and its variants has particular appeal for microfluidic manufacturing due to its ability to create objects with small feature size and high resolution. In this chapter, we consider the underlying chemistry of resins for stereolithography in addition to the optical properties of both the resin and the light source with a specific view to successfully printing microfluidic devices consisting of enclosed channels with small crosssectional area. The main advantages and disadvantages of stereolithography, relative to other 3D printing techniques, are addressed in addition to how the material properties of the final printed object can be tuned through resin additives such as nanoparticle fillers or precursors, in addition to multi-material printing. Lastly, the performance and application of printed devices is discussed.