3D printed composites that are light weight, durable, and have tunable conductivity are difficult to achieve and are of considerable interest for numerous applications which include electrostatic dissipation, EMI shielding, and soft conducting material applications. 3D printing of these materials into complex shapes such as grids, strain gauges, and thermocouple interfaces would also be greatly useful for measuring temperature, strain, and strain rate of materials. The unique redox properties of conjugated polymers (CPs) allow for this type of material utility to be possible. Here, we report on the direct ink write printing of polyaniline (PANI). We use dinonylnapthalene sulfonic acid as a surfactant, dopant and bulky counterion to endow both solubility in a range of organic solvents (e.g. toluene, xylenes) as well as conductivity. Imparting high solubility allows us to use various additives and processing conditions to tune both the rheological behavior of the ink, as well as the electrical properties of the resultant printed structures to advance the production of 3D conductive PANI devices. Specifically, we take advantage of fumed silica and ultra-high molecular weight polystyrene (PS) to tune the rheological and mechanical properties of the resulting composites. We demonstrate the ability to tune the conductivity of these printed structures over a range of six orders of magnitude (<10^-6 – 10⁰ S/cm), which is decidedly apt for many of the aforementioned applications. Our approach provides an effective and simple approach to printing PANI-based 3D architectures that will contribute to the ongoing effort of bringing the promising properties of CPs to the future of micro- and nano-electronic devices.

3D printing of PANI-based inks in an antennae geometry on PET before and after bending.

Brandon DiTullio

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