The sustainability of polymer microparticle production processes was evaluated. A different viewpoint was provided to encourage researchers to use simple yet effective green chemistry metrics calculations in the development of these processes.

The microfluidic production of simple (microspheres) and core–shell (microcapsules) polymer microparticles, often called microencapsulation, has been the scope of several research works since the 1980s. It is a fast, thrifty, and efficient process because of its controlled properties, tuneability, and yield, which can reach 100%. However, the question of its greenness, sustainability, and scalability remains unclear, and more awareness/education is required in this field. The sustainability of production processes using microfluidic techniques can be realized/discussed based on three pillars: (i) waste generation, (ii) the solvents employed, and (iii) raw materials. On the other hand, although the scaling-up of these processes was reported on in several papers as procedures in which hundreds or thousands of microfluidic chips are set in parallel, the sustainability of this scale-up has not been addressed to our knowledge. This opinion paper highlights the advantages of microfluidic encapsulation processes, their greenness according to the above-mentioned pillars, (i–iii) and the necessary considerations to scale them up while preserving their sustainability.

The use of sustainable raw materials is now a necessity in all industries, including the production of porous microparticles. Cyrene™ is a cellulose-derived compound that is readily prepared through the reduction of the α,β-unsaturation of levoglucosenone (LGO)—a wood-based platform molecule. In this work, the importance of Cyrene™ as a potential bio-based molecule to produce sustainable porous microparticles is demonstrated. First, a methacrylic derivative of Cyrene™ (m-Cyrene) was synthesized. A microfluidic co-flow device was then established to produce m-Cyrene-based oil-in-water (O/W) controlled-size emulsions and to polymerize them by ultraviolet (UV) radiation in a vial. The continuous phase was a sodium dodecyl sulfate aqueous solution, and the dispersed phase was a mixture of m-Cyrene with methacrylic anhydride (MAN) at two different mass concentrations (i.e., 1 wt.% MAN and 92 wt.% MAN) and 2,2-dimethoxy-2-phenylacetophenone (DMPA) as a photoinitiator. The process used the lowest possible quantity of raw materials and avoided excessive purifications to produce homogeneous porous m-Cyrene-MAN microparticles. The controlled size and homogeneous size distribution of the produced polymer microparticles were confirmed by scanning electron microscope (SEM) images. The 3D microstructure as well as the porosity were determined using X-ray microtomography. The high-resolution 3D images produced indicate that the pores of the microparticles are homogeneous and that their porosity is controllable through the concentration of MAN in the monomer mixture (porosity of 30% for a 1 wt.% MAN ratio and 2% for a 92 wt.% MAN ratio). Such porosity control is very important for future potential encapsulation processes that require precise release control.

Understanding microbial growth and metabolism under controlled environments is critical for both fundamental research and bioprocess development. In this study, we present a cost-effective droplet-based microfluidic device enabling high-throughput screening of GFP expression in Escherichia coli (E. coli) under varying glucose concentrations. Fluorinated Ethylene Propylene (FEP) tubing was selected for its low cost and compatibility with stable water-in-oil emulsification, facilitating robust droplet generation. The system achieved a 33333-fold reduction in media consumption compared to traditional Erlenmeyer flask cultures. Growth kinetics and GFP expression were assessed in both Erlenmeyer flasks and microdroplets, showing high qualitative correlation between platforms. Low glucose levels (5-10 g/L) supported rapid initial growth and early GFP production, followed by a fluorescence decline due to nutrient depletion. In contrast, higher glucose concentrations (25-50 g/L) prolonged the exponential phase and enhanced GFP production per unit biomass, though growth was slowed by overflow metabolism. In microdroplets, delayed GFP expression at 25 and 50 g/L were observed, and parallel bioreactor experiments confirmed that this delay is caused by oxygen limitation at high glucose concentrations. Importantly, the microfluidic device enables controlled variation of oxygen availability simply by adjusting droplet size or generation frequency, providing a powerful means to probe oxygen-sensitive metabolic behaviors. These results validate the microfluidic platform's ability to mimic Erlenmeyer flask-scale dynamics, while uniquely allowing precise modulation of oxygen transfer conditions at the microscale. The system offers a reliable, miniaturized alternative for optimizing microbial bioprocesses with drastically reduced reagent use and increased experimental throughput.