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.^1–3LIG 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.<br/>In our LAMPSE group, we investigate LIG for the development of soft sensors and actuators, and their use in various Robotics applications.<br/>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.<br/>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.<br/> <br/>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.<br/> <br/><u>References</u><br/>(1) Lin, J. et al. <i>Nat. Commun.</i> <b>2014</b>, <i>5</i>, 5714.<br/>(2) Ye, R.; James, D. K.; Tour, J. M. <i>Adv. </i><i>Mater.</i> <b>2019</b>, <i>31</i>, 1803621. <br/>(3) Dallinger, A. et al. <i>ACS Appl. Mater. Interfaces</i> <b>2020</b>, <i>12</i>, 19855<br/>(4) Bressi A.C. et al. ACS <i>Appl. Mater. Interfaces</i> <b>2023</b>, <i>12</i>, 19855.<br/>(5) Dallinger, A. et al. <i>ACS Appl. Polym. </i><i>Mater.</i> <b>2021</b>, <i>3</i>, 1809.