Soft Robots Meet Bioelectronic Interfaces: A Promising Use-Case of Bio-Based and Biomimetic Polymers for Minimally Invasive Implantable Devices

This presentation shares an emerging research field of minimally invasive implantable devices that utilize soft robotics, which offers promising applications for bio-based and biomimetic polymers. The talk first highlights a recent work published in Science Robotics (<i>1</i>) concerning the development of deployable electrocorticography (ECoG) electrode arrays enabled by soft robotic sensing and actuation. ECoG is a minimally invasive method commonly used to map epileptogenic regions of the brain. It aids in lesion resection surgery and is increasingly explored in brain-machine interface applications. However, current devices present limitations, leading to trade-offs in cortical surface coverage, spatial electrode resolution, aesthetics, and risk factors. These limitations often restrict the use of the mapping technology to the operating room.<br/><br/>The presented work introduces a scalable technique for fabricating large-area soft robotic electrode arrays. These arrays can be deployed on the cortex through a square-centimeter craniotomy using a pressure-driven actuation termed "eversion”. The design of these eversion-based electrode arrays is akin to a rubber glove with finger-shaped air pockets. To prepare for deployment, this glove is inverted and folded within a cylindrical loader. During deployment, liquid is introduced into each "finger," enabling the array to revert and expand over the brain. Each section incorporates soft, microfabricated electrodes and strain sensors for real-time deployment monitoring. In a proof-of-concept acute surgery, the soft robotic electrode array was successfully deployed on a minipig's cortex to record sensory cortical activity without causing significant morphological damage.<br/><br/>The talk will also discuss insights into the future prospects of soft robotic implant technologies, which hold potential for multifunctional chronic health monitoring and treatment. Beyond the everting actuation mentioned, there are opportunities to explore various soft robotic actuation to adapt to the geometries and movements of specific target organs, such as bending, unfurling, coiling, and undulating. Additionally, there are promising applications for these robotic implants to deploy a diverse range of sensing or stimulating components. Examples include strain sensors for cardiac activity monitoring, microfluidic systems for drug delivery, and optical elements for optogenetic stimulation. Bio-based and tissue-mimetic soft polymers are especially significant, ensuring the implants' long-term biocompatibility and reliability. While the deployable ECoG arrays mentioned above utilized a soft polydimethylsiloxane (PDMS) matrix—comparable in mechanical properties to the brain's dura mater—employing even softer and more flexible polymers like hydrogels can decrease mechanical irritation on tissues, thus minimizing immune responses. Furthermore, antifouling materials like zwitterionic polymers can inhibit protein adhesion on the implant surface, a key factor in mediating immune responses. The integration of soft robotic implants with bio-based and bio-mimetic materials can open high-impact avenues in active implantable device technologies, enabling minimally invasive, chronic health monitoring and therapeutic applications previously deemed impossible.<br/><br/><b>References</b><br/>1. S. Song, F. Fallegger, A. Trouillet, K. Kim, S. P. Lacour, Deployment of an electrocorticography system with a soft robotic actuator. <i>Science Robotics</i> <b>8</b>, eadd1002 (2023).