3D Printing & Conductivity: Fabricating Ultra-Stretchable Conductors

August 19, 2019 by Bridget O'Neal 3D Printing 3D Printing Materials

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Researchers in Shanghai are delving further into 3D printing conductors, with their findings recently published in ‘A highly transparent and ultra-stretchable conductor with stable conductivity during large deformation.’ Authors Zhouyue Lei and Peiyi Wu follow up on the increasing development of stretchable conductors and improvements being made in their electromechanical properties, along with studying issues with deformation and defects—and ways to break through such limits.

Molecular synergistic design. a Schematic illustration of the molecular synergistic design, including the optimized ion-rich structure predicted by DFT and the dynamic hydrogen-bond networks. b The true tensile stress–strain curves of the conductors with different contents of the IL. The strain rate is 0.17 s−1. c The SAXS profile of the intrinsically stretchable conductor. The inset picture is the AFM phase image of the conductor. (scale bar: 100 nm) d IR spectra and corresponding second derivative curves of the intrinsically stretchable conductor, PAA, PDMAPS, and IL in the region of 1750–1600 cm−1

Soft materials, and especially conductive ones, are critical in applications for artificial intelligence and biological systems; however, it takes some doing to get them into a softer and more flexible form. Plasticizers and flexible segments added to the polymers are one way to create softer regions, along with adding conductive elements like electronic fillers or ionic electrolytes and then managing the paths and networks.

The researchers endeavored to create soft nanochannels, connected with crosslinked networks:

“Herein, we introduce a type of intrinsically stretchable conductors. Small-molecular liquid-like electrolytes, such as ILs, provide charge carriers; polymers with similar ionic structures, e.g., polyzwitterions, realize ionic synergy with the liquid electrolytes and thus assemble conductive nanochannels to avoid aggregates or leaking risk of the electrolytes; dynamic networks are constructed by polymers that also have molecular synergy with the conductive nanochannels, to guarantee the structural integrity, deformation adaptability and environmental stability.”

The conductor can store, create, and send electrical signals through the flow and distribution of ions and nanochannels, with the paths ‘dynamically adapting’ to deformation. The authors point out that the material is also suitably stable, demonstrating a three percent change of conductivity in 24 hours, and exhibiting no melting point or glass transition in extreme temperatures.

Electrical properties in dynamic environments. a Schematic illustration of the conductive paths in this material adapting to deformation. Blue lines represent ion nanochannels and the purple parts represent the dynamic networks. b Photographs of the 3D-printing conductor during a stretch-release cycle (scale bar: 2 cm). c The stability of the ionic conductivity during the deformation process. d The relative changes in ionic conductivity in the temperature range of −10 to 100 °C (error bars: standard deviations). e The stability of the ionic conductivity at extreme low or high temperatures for a long period. These measurements are humidity control (60 RH%)

The research team found the stretchable conductor to be promising for use in soft robotics, and the ability to provide sensing capabilities. The nanoscale paths could be suitable for adapting to larger deformation issues, along with direct exposure to outside elements.

“Benefiting from the rational designs, this material not only breaks through the limits encountered in current electronic and ionic conductors, with good transparence, ultra-stretchability, high modulus, reconfiguration of the elastic networks, etc., but also greatly improve the stability in dynamic environments,” concluded the researchers.

“We believe that current work addresses a long-lasting challenge in the field of intrinsically stretchable conductors, provides general inspiration for the nanostructural designs and device fabrications, and could also promote the development of intelligent robots with the requirements for entire softness, high transparence, multiple sensory capabilities, and environmental stability.”

3D printing and conductive materials are often paired up in the fabrication of electronic components, from desktop filament to composites, and research into studies using silicone. What do you think of this news? Let us know your thoughts; join the discussion of this and other 3D printing topics at 3DPrintBoard.com.