Magnetic-nanoparticle-embedded “wireless” hydrogel microvalve

We propose and demonstrate remotely activated (“wireless”) microvalves that utilize the volume change of thermoresponsive gels, induced by the magnetic heating of magnetic nanoparticles (MNPs) embedded within these gels. The thermoresponsive gels were precisely patterned on Si substrates via photolithography. Notably, embedding MNPs in the gels did not compromise the patterning accuracy; the MNP concentration range of 1–3 wt% in the sols (the range of interest in this study) does not strongly affect the swelling behavior of the thermoresponsive gels. The microvalves exhibited strong actuation due to the magnetic heating of the MNPs when subjected to alternating magnetic fields. Our investigation of the valve switching response demonstrated that the opening and closing behavior closely follows the switching of the applied magnetic field.