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Research Projects
3D Co-Printing of Ionic Hydrogel and Elastomer for Facile Fabrication of Wearable Sensors and Soft Robots
Shaojia Wang, Pengfei Xu, Runze Zuo, Xinyu Liu
In submission: RA-L
Soft and stretchable sensors and electronics hold great potential for application in wearable sensing, human-machine interaction, and soft robotics. On materials, double-network (DN) ionic hydrogels are a promising candidate because of their tunable mechanical properties, high toughness and stretchability, good conductivity, and excellent biocompatibility. Meanwhile, silicone-based elastomers like Ecoflex are commonly used structural materials for constructing wearable devices integrating ionic hydrogel-based sensing components. Moulding-based fabrication methods are limited for hydrogel-elastomer integration, inspiring us to develop 3D co-printing techniques for hydrogel-elastomer-based devices. Here we employ direct ink writing (DIW) for 3D co-printing of DN ionic hydrogel and Ecoflex, and adopt benzophenone (BP)-based chemistry to form covalent bonding of the two materials during cross-linking. We fabricate a wearable strain sensor and a sensory glove for demonstrations.
Conductive and elastic bottlebrush elastomers for ultrasoft electronics
Pengfei Xu, Shaojia Wang, Angela Lin, ..., Helen Tran, Xinyu Liu
Nat Commun 14, 623 (2023)
Understanding biological systems and mimicking their functions require electronic tools that can interact with biological tissues with matched softness. Conductive materials that match the softness of biological tissue are thus highly demanded for the construction of ultrasoft electronics. However, the commonly employed intrinsically stretchable materials usually contain solvents that limit stability for long-term use or possess low electronic conductivity. Additionally, integrating such ultrasoft and conductive materials into electronic devices is poorly explored. This article reports a solvent-free, ultrasoft and conductive PDMS bottlebrush elastomer composite with single-wall carbon nanotubes as conductive fillers. The conductive SWCNT/BBE with a filler concentration of 0.4−0.6 wt % reveals an ultralow Young’s modulus (<11 kPa) and satisfactory conductivity (>2 S/m) as well as strong wet-adhesion property. Furthermore, we fabricate ultrasoft electronics based on laser cutting and 3D printing of conductive and non-conductive BBEs and demonstrate their potential applications in wearable sensing, soft robotics, and electrophysiological recording.
A Cable-Driven Soft Biomimetic Robotic Hand with In-hand RGB-D Camera for Dexterous Grasping and Manipulation
Zhanfeng Zhou, ..., Shaojia Wang (4th Author), Xinyu Liu
In submission: IEEE Transactions on Robotics (T-RO)
Ultrasoft and Ionically Conductive Bottlebrush elastomer for bioelectronics
Siddhartha Challa, Pengfei Xu, Shaojia Wang, Xinyu Liu
In preparation: Advanced Functional Materials (AFM)
Biological tissues are soft and ionically conductive, but many tools that interact with them are composed of materials that are much stiffer and electronically conductive. Bottlebrush elastomers (BBEs) are ultra-soft but not conductive. Adding ionic liquid to BBEs could provide them with ionic conductivity while maintaining ultra-softness. The lowest Young’s modulus achieved is 1.3 kPa and the highest conductivity is 1.7 mS/cm. The PEG/IL BBE is hygroscopic and the IL could leak from the BBE. A hydrophobic IL could be copolymerized with the BBE to address this limitation. The Young’s modulus and charge carriers of the PEG/IL BBE match those of biological tissues. Our BBE is softer than most reported dry conductive elastomers. The material’s improved properties are beneficial for bioelectronics applications.
