To determine the morphology and the inner structure of the ALGPODES beads, SEM measurements were performed. For this purpose, plain and split beads were deposited onto carbon tape, and placed in the microscope. SEM micrographs show that ALGPODES beads feature a rather homogeneous external surface (shell-like, Figure ) with small pores (~100 nm) that would allow analytes to permeate. In contrast, the inside of the beads showed a layered structure, leading to the formation of large internal cavities (25-100 µm), as it can be seen in Figure . This internal foam-like structure is common to the other Ca-alginate beads investigated (formed using either 1% ALG, Figure SI 2 or 5% ALG, Figure 3) as well as to those reported in the literature. It is relevant to mention the work from Voo et al, who reported that beads formed with 100 mg/mL ALG also displayed a layered structure, effect that was attributed to the coalescence of the partiallygelled Ca-alginate, trapped within the highly-crosslinked shell. Additionally, optical images collected from as-prepared beads (Figure ) showed the expected spherical shape with a glossy, homogeneous, and smooth surface; indicating the compatibility of the new ALGPODES with established spherification processes. The size distribution of the selected beads (1% ALG, 5% ALG, or ALGPODES) was also investigated. For that purpose, 300 beads of each composition were photographed, and their diameter measured using ImageJ software. As it can be observed in Figure , beads formed with 1% ALG displayed the smallest size, with a diameter of 2.2 ± 0.3 mm and the beads formed with 5% ALG showed a diameter of 3.4 ± 0.2 mm. These dimensions are in agreement with previously reported values for ALG beads produced under various experimental conditions (including the size dependence with respect to the concentration of the polymer), although beads covering a much wider range (20 μm to 7 mm) have been reported. ALGPODES beads presented a narrower size distribution, featuring an average diameter of 2.9 ± 0.1 mm (ranging from 2.4 mm to 3.2 mm), matching other reports and showing a significant difference with respect to the ALG control beads. This difference can be attributed to the decreased surface tension of the ALGPODES (with respect to the 5% ALG), due to the presence of glycerol in the dripping solution that has a dominant effect on the size of the droplet released from the needle. Figure 2: Size distribution of the selected beads (1% ALG, 5% ALG, or ALGPODES). 300 beads of each composition were photographed, and their diameter measured using ImageJ software.