Conductive Hydrogels: Mechanically Robust Hybrids for Use as Biomaterials Rylie A. Green,* Rachelle T. Hassarati, Josef A. Goding, Sungchul Baek, Nigel H. Lovell, Penny J. Martens, Laura A. Poole-Warren 1. Introduction With the advent of more sophisticated electronics, con- ductive polymers (CPs) [1] have enormous potential for a wide range of uses. CPs have significant promise in medical electrode applications due to their low impedance, [2] but are limited by their poor mechanical performance, charac- terised by brittle failure [3] and poor cohesion, [4] which results in material loss and delamination. [5] This research presents a new hybrid CP system, termed a conductive hydrogel (Figure 1), which is both mechanically stable and retains the electrical property of the homogeneous CP. For biomedical applications, it has been recognised that incorporation of biological molecules into CPs, such as laminin peptides and growth factors, enhances their capacity to interact with cells and tissues. However, it is clear from recent studies that the physical and mechanical properties can be significantly altered after incorporation of biological molecules. [6,7] Modulation of mechanical properties may be achieved via alternate synthesis and processing approaches, [8] through composite or nano- composite approaches [9,10] or by blending or producing layered CPs with other polymer types. [11–13] The latter approach is the focus of this research as it provides a means for not only improving mechanical properties, but maintaining electrical properties and introducing capacity for improved incorporation of biological molecules. Several groups have focused on using a second polymer that is softer and more elastic than the CP component to form a hybrid CP. Typically, this second polymer has no inherent conductivity. The key challenges in forming an appropriate hybrid, is in combining the CP and non-CP component to preserve the overall electroactivity while imparting the desired mechanical softness and elasti- city. [14] Although variants of silicone rubber, [15,16] poly- urethanes, [17,18] polystyrenes [19–21] and polyvinyls [11] have been explored, hydrogels present the most promising option for producing hybrid CPs with physico-chemical and mechanical properties which can be tailored for specific applications. [14,22–24] Full Paper Dr. R. A. Green, R. T. Hassarati, J. A. Goding, S. Baek, Prof. N. H. Lovell, Dr. P. J. Martens, Prof. L. A. Poole-Warren Graduate School of Biomedical Engineering, University of New South Wales, Sydney 2052, Australia E-mail: r.green@unsw.edu.au A hybrid system for producing conducting polymers within a doping hydrogel mesh is presented. These conductive hydrogels demonstrate comparable electroactivity to conven- tional conducting polymers without requiring the need for mobile doping ions which are typically used in literature. These hybrids have superior mech- anical stability and a modulus significantly closer to neural tissue than materials which are commonly used for medical electrodes. Additionally they are shown to support the attach- ment and differentiation of neural like cells, with improved interaction when compared to homogeneous hydrogels. The system provides flexibility such that biologic incorporation can be tailored for application. 494 Macromol. Biosci. 2012, 12, 494–501 ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com DOI: 10.1002/mabi.201100490