Abstract
Owing to bio-polymer’s low-cost, environmental friendliness and mechanically stable nature, calcium alginate microcapsules have attracted much interest for their applications in numerous fields. Among the common production methods, the Electrospraying technique has shown a great potential due to smaller shape capsule production and ease of control of independent affecting parameters. Although one factor at a time (OFAT) can predict the trends of parameter effect on size and sphericity, it is inefficient in explaining the complex parameter interaction of the electrospray process. In the current study, the effects of the main parameters affecting on size and sphericity of the microcapsules using OFAT were optimized to attain calcium alginate microcapsules with an average diameter below 100 µm. Furthermore, we propose a statistical model employing the Surface Responses Methodology (RSM) and Central Composite Design (CDD) to generate a quadratic order linear regression model for the microcapsule diameter and sphericity coefficient. Experimentally, microcapsules with a size of 92.586 µm and sphericity coefficient of 0.771 were predicted and obtained from an alginate concentration of 2.013 w/v, with a flowrate of 0.560 mL/h, a needle size of 27 G and a 2.024 w/v calcium chloride concentration as optimum parameters. The optimization processes were successfully aligned towards formation of the spherical microcapsules with smaller average diameter of less than 100 µm, owing to the applied high voltage that reached up to 21 kV.
Highlights
The 6% w/v microcapsules produced from the electrospray technique were elongated and misshapen due to increased surface tension at the needle-droplet surface, and as such, complexity in breaking off the viscous fluid at the needle tip [18,19]
The higher viscosity of the solution could cause deformation of the microcapsule as it is electrosprayed into the crosslinking solution
Two forces act on an electrosprayed microcapsule as it moves from the tip of the needle into the crosslinker: the viscous forces and drag forces
Summary
Alginate is a broad definitive term for a group of naturally occurring unbranched polysaccharides consisting of 1.4 linked β-D-mannuronic acid, a C-5 epimer and an Lguluronic acid. It is abundant in nature and mainly produced from seaweed, bacteria and algae, with around 30,000 metric tons of annual production [1]. Due to their abundance and versatility in application, alginates have seen significant applications as beads [2], fibers [3] and capsules of micro and nano sizes [4] in diverse fields ranging from biological and medical to chemical and mechanical use. Alginate beads have a wide range of applications as encapsulating anti-corrosion materials due to their ease of use, low cost, lack of toxicity, mechanical stability and resilience to acidic and basic environments [8]
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