Optimization of the Retardance in Citrate Coated Ferrofluids Using Integrated Genetic-Sequential Quadratic Programming Technique

The citrate (citric acid, CA) coated ferrofluids with great magneto-optical retardance could meet the highly magnetic responsive demand, especially in their potential biomedical applications such as hyperthermia and magnetic resonance imaging. In this study, the measured retardances are based on Taguchi method with nine tests for four parameters, including pH of suspension, molar ratio of CA to Fe
3
O
4
, CA volume, and coating temperature. Three optimization algorithms including sequential quadratic programming (SQP), genetic algorithm (GA) and integrated GA-SQP are executed to obtain high retardance. Five initial points chosen from the orthogonal test are input into the SQP, the GA is applied to the regression equation, and while executing the integrated GA-SQP algorithm, the parametric combination obtained by GA is adopted as the initial point in the SQP simulation. The global optimum retardance and the corresponding parameter values are effectively assured by the global search ability of a GA and the ability of local searching by using SQP.