Controlling the response of color tunable poly(N-isopropylacrylamide) microgel-based etalons with hysteresis.

We present the hysteresis of the response of the poly(N-isopropylacrylamide)-co-acrylic acid microgel-based etalons to solution temperature and pH changes. We find that the optical hysteresis of the etalon can be controlled using various solution ionic strengths and/or counterions, as well as by varying the microgel's acrylic acid concentration.