Poly(acrylic acid)-Poly(vinyl alcohol) hydrogels for reconfigurable lens actuators

Reconfigurable lens provides variable-focus in optics without any moving part. The material for a reconfigurable lens should be deformable in the presence of external stimuli meanwhile maintaining its optical transparency for the lens function. This article reports the fabrication and actuation property of the Poly(acrylic acid)-Poly(vinyl alcohol) (PAP) hydrogels for reconfigurable active lens. The PAP hydrogels were prepared by free radical and freeze-thaw technique using N,N1-methylenebisacrylamaide and potassium persulfate/N,N,N1,N1-tetramethylethylenediamene as crosslinker-initiator pair system. The formation of the hydrogels was conformed form Fourier transform infrared spectra and thermogravimetric analysis. The prepared hydrogels were characterized by swelling studies and optical transparency measured with UV-visible spectroscopy and actuation test in the presence of electric field. There is an optimal concentration of acrylic acid concentration that shows maximum displacement output with less optical transparency loss. Displacement output increased with increasing the voltage and the maximum displacement output of 15.5 μm was achieved in the presence of electrical field. This corresponds to 4% strain.