Laser Induced Graphene for Soft Actuators and Sensors

Laser Induced Graphene (LIG) is a 3D porous conductive carbon material produced by laser-induced pyrolysis of polymer precursors. In recent years it has found applications in soft and wearable electronics, energy storage devices, among others.^1–3 LIG conductive tracks, electrodes, sensors are created through a single synthesis/patterning step by laser scribing with a IR or UV laser onto some polymer precursors. Alternatively, biologically-derived precursors are investigated and employed.⁴ LIG technology represents a maskless and chemical-free alternative to other printing technologies but is also opening unprecedented possibilities for the realization of circuits onto virtually any surface.
In our LAMPSE group, we investigate LIG for the development of soft sensors and actuators, and their use in various Robotics applications.
We create stretchable conductive composites by embedding LIG within elastomeric matrices like polydimethylsiloxane PDMS, various silicone rubbers, or polyurethane PU. Their characteristic piezoresistive behavior can be fine-tuned through laser processing parameters. Strain, bending, pressure, temperature sensors are thus developed for a variety of applications: sensorization of soft pneumatic grippers for enabling proprioception, thin wearable sensors which conform to the human skin for personal monitoring, integration of sensing capabilities in wearable haptic devices.
On the other hand, by coupling those LIG/elastomer stretchable conductors with stimuli responsive polymers, new strategies for soft actuation can be devised. A smart humidity-responsive hydrogel (poly-(N-vinycaprolactam), pNVCL) is used to realize a multi-responsive soft bending actuator, capable of self sensing. Other approaches involve a Liquid Crystal Elastomer (LCE): a thermoresponsive material featuring excellent properties like large actuation strains and reversible linear actuation process. In both cases soft LIG/elastomer circuits served as Joule heating elements to resistively heat the active materials and trigger an actuation.

Finally, I will show some novel developments of LIG from new non-polymer precursors and from bio-sourced materials and how they can enable sustainable approaches to soft robotics and electronics.

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) Dallinger, A. et al. ACS Appl. Polym. Mater. 2021, 3, 1809.