Electrochemically color tunable poly(N-isopropylacrylamide) microgel-based etalons

In this submission, pH responsive poly(N-isopropylacrylamide)-based microgels were used to fabricate optical devices (etalons). We demonstrate that the optical properties of the etalons could be manipulated upon the application of an appropriate electric potential between the etalon and a counter electrode, both in an electrolyte solution. An appropriate electrical potential hydrolyzes the water of the electrolyte solution, which subsequently changes the pH of the electrolyte solution. Since solution pH is able to change the solvation state of the microgels, and the etalon's optical properties depend on the microgel's solvation state, the etalon's optical properties can be tuned with an applied electrical potential. We show that the etalon's optical properties (color) is stable for many hours, until an appropriate potential is applied to bring the solution pH back to its initial value. The device's color switching kinetics were also probed, and showed significant color changes on the minute time scale. The dramatic optical property changes coupled with the reversibility of the device's color makes this system potentially useful for display device applications.