Resumen:
A tunable phononic crystal based ultrasonic filter was designed by stimulating the phase of the
polymeric material embedded in a periodic structure using infrared radiation. The acoustic filter
can be tuned remotely using thermal stimulation induced by the infrared radiation. The filter is
composed of steel cylinder scatterers arranged periodically in a background of bulk poly
(N-isopropylacrylamide) polymer hydrogel. The lattice structure creates forbidden bands for
certain sets of mechanical waves that cause it to behave as an ultrasonic filter. Since the
bandstructure is determined by not only the arrangement of the scatterers but also the physical
properties of the materials composing the scatterers and background, modulating either the
arrangement or physical properties will alter the effect of the crystal on propagating mechanical
waves. Here, the physical properties of the filter are varied by inducing changes in the polymer
hydrogel using an electromagnetic thermal stimulus. With particular focus on the k00-wave, the
transmission of ultrasonic wave changes by as much as 20 dBm, and band widths by 22% for select
bands.