A soft two-tailed microrobot in low Reynolds number fluids does not achieve forward locomotion by identical tails regardless to its wiggling frequency. If the tails are nonidentical, zero forward locomotion is also observed at specific oscillation frequencies (which we refer to as the reversal frequencies), as the propulsive forces imparted to the fluid by each tail are almost equal in magnitude and opposite in direction. We find distinct reversal frequencies for the two-tailed microrobots based on their tail length ratio. At these frequencies, the microrobot achieves negligible net displacement under the influence of a periodic magnetic field. This observation allows us to fabricate groups of microrobots with tail length ratio of 1.24 ± 0.11, 1.48 ± 0.08, and 1.71 ± 0.09. We demonstrate selective actuation of microrobots based on prior characterization of their reversal frequencies. We also implement simultaneous flagellar propulsion of two microrobots and show that they can be controlled to swim along the same direction and opposite to each other using common periodic magnetic fields. In addition, independent motion control of two microrobots is achieved toward two different reference positions with average steady-state error of 110.1 ± 91.8 μm and 146.9 ± 105.9 μm.

Enzymes are powerful versatile biocatalysts, however, industrial application of enzymes is usually hampered by their susceptibility. Bio-inspired Eudragit-α-amylase conjugate (E-AC) was proposed as a biocatalyst for various pharmaceutical and industrial applications. In this study, α -Amylase (E.C. 3.2.1.1) was immobilized by covalent conjugation to Eudragit L-100 under mild conditions. The effect of polymer, carbodiimide and enzyme concentrations on optimization of (E-AC) was investigated. In addition, characterization of the free α -Amylase and E-AC with regard to pH, temperature, kinetic parameters, reusability and operational and storage conditions was carried out. Results showed a shift of the optimum pH of E-AC towards the alkaline side whereas, E-AC exhibited higher thermal stability at all tested temperatures. The kinetic parameters, K_m values were 2.87 mg/ml and 3.15 mg/ml and V_max values were 8.35 mg/ml/min and 8.98 mg/ml/min for free and E-AC, respectively. E-AC retained 85% of the initial activity after five consecutive amylolytic cycles, thus emphasizing its powerful potentials. Operational storage and thermal stability were highly improved as well for E-AC conjugate with an 11.6 stabilization factor in comparison to the free α-amylase. In this study, Eudragit L-100 polymer was successfully used as smart immobilization support to create a reversibly soluble-insoluble enzyme biocatalyst to enforce and extend biotechnological applications of α-amylase in the pharmaceutical industry.