Laser Induced Graphene for Soft Robotics

Laser Induced Graphene (LIG) is a three-dimensional porous conductive carbon material created through the laser-induced pyrolysis of polymer precursors. Recently, it has been utilized in soft and wearable electronics, as well as energy storage devices, among other applications.^1–3 LIG conductive tracks, electrodes, and sensors are produced in a single synthesis/patterning step using laser scribing with an IR or UV laser on polymer precursors. Additionally, biologically-derived precursors are being explored and utilized.^4,5 LIG technology provides a maskless and chemical-free alternative to conventional printing methods, while also opening up unique possibilities for embedding circuits on a wide range of surfaces.
In our LAMPSE group, we investigate LIG for developing soft sensors and actuators, and their use in various Robotics and Bioengineering applications.
We produce stretchable conductive composites by incorporating LIG into elastomeric matrices such as polydimethylsiloxane (PDMS), various silicone rubbers, or polyurethane (PU). The distinctive piezoresistive properties can be adjusted by modifying the laser processing parameters.³ This leads to the development of strain, bending, pressure, and temperature sensors for a range of applications, including sensorization of soft pneumatic grippers for proprioception and exteroception, thin wearable sensors that conform to human skin for personal monitoring, and the integration of sensing capabilities in wearable haptic devices. Recently, LIG/elastomer composites have been combined with Au-based nanostructured neuromorphic devices to explore embodied intelligence in soft robots, able to interact with the surrounding environment.⁶
Conversely, by integrating LIG/elastomer stretchable conductors with stimuli-responsive polymers, new strategies for soft actuation can be developed. A smart humidity-responsive hydrogel (poly-(N-vinylcaprolactam), pNVCL) enables the creation of a multi-responsive soft bending actuator that can self-sense.⁷ Another approach utilizes a Liquid Crystal Elastomer (LCE), a thermoresponsive material featuring large actuation strains and a reversible linear actuation process. In both instances, soft LIG/elastomer circuits functioned as Joule heating elements, resistively heating the active materials to trigger the actuation.
Novel directions are explored by investigating LIG obtained from bio-sourced materials as they can enable sustainable approaches to soft robotics and electronics.
Ultimately, our recent discovery of an entirely new type of LIG precursor, which includes certain selected dyes and inks/paints, enables the scribing of LIG sensors on nearly any surface or object, including soft robots. I will present some proof of concept of soft sensors realized with a “Paint & Scribe” approach, greatly expanding the reach of this research.⁸

References
(1) Lin, J. et al. Nat. Commun. 2014, 5, 5714.
(2) Ye, R.; James, D. K.; Tour, J. M. Adv. Mater. 2019, 31, 1803621.
(3) Dallinger, A. et al. ACS Appl. Mater. Interfaces 2020, 12, 19855
(4) Bressi A.C. et al. ACS Appl. Mater. Interfaces 2023, 12, 19855.
(5) Thaikkattu Sankaran, S. et al. Small 2024, DOI: 10.1002/smll.202405252, In Publication.
(6) Nadalini, G. et al. Adv. Electron. Mater. 2024, under review.
(7) Dallinger, A. et al. ACS Appl. Polym. Mater. 2021, 3, 1809.
(8) Dallinger, A. et al. Adv. Science 2024, under review.