Pulsating pH-responsive nanogels.

A novel method is presented for the design of robust, sustained nanochemomechanical oscillators. The approach is based on the switching of chemoresponsive nanogel beads between their collapsed and swollen state by coupling them to an appropriately chosen nonlinear reaction. The presented system utilizes a proton activated oscillatory reaction and pH-sensitive nanobeads of gel that provide more than an order of magnitude volume change. A key point of our approach is the control of the colloid stability of the nanobeads of gel in a wide range of experimental parameters (pH, ionic strength, temperature) without interfering with the swelling characteristics of the nanogel particles. This was achieved by utilizing the interaction of nanogels with ionic surfactants.