Peristaltic waves in a responsive gel sustained by a halogen-free non-oscillatory chemical reaction

Formerly, we demonstrated in three chemical systems how the combination of the shrinking response of an appropriate responsive gel and a pH-switch type chemical reaction, which is not capable of oscillations by itself, can lead to self-oscillations in size and in pH in a piece of gel surrounded by a constant environment. We demonstrate that this can be realized at very mild chemical conditions: at ionic strength similar to 0.015 M, with acid generated in concentrations similar to 10 micromol/liter, and without halogen-containing oxidant. We discuss in detail how to adjust the gel-response to the chemical reaction for sustained motion. Travelling contraction wave trains along a long thin cylinder (R-sw < 0.50 mm) were sustained for more than 2 days. Considering the environmentally neutral reaction wastes, free from halogens or metal ions, biomaterials become attainable matrices in contrast to former chemomechanical oscillators which all operated under much harsher chemical conditions. (C) 2015 Elsevier Ltd. All rights reserved.