Biocompatible contactless electrically responsive hydrogel‐based force maker

Abstract

We present a biocompatible contactless gel actuator based on poly(methacrylic acid) with magnesium counterions (MgPMA) that, being placed in sodium chloride solution, is able to generate a high value of active mechanical force in a DC electric field. Force generation of the gel goes simultaneously with its swelling due to the osmotic pressure provided by the ionic exchange in the MgPMA polyelectrolyte matrix induced by the electric current. An increase in the charge density of the polymeric network enhances the mechanical stiffness of the gel, which provides negative feedback to force generation. The extent of such influence depends on the networking density of the gel matrix. As a result, soft MgPMA gels with low networking density show higher level of force generation than dense gels with high networking density. It is shown that cylindrical gel samples of ca 8 mm in length and ca 11 mm in diameter immersed in NaCl solution some distance apart from platinum electrodes are able to exert a force of up to 0.4 N in a DC electric field for a constant length of sample with a rate of ca 1.0 mN per second on average.