Implantable MEAs are an essential tool for the elucidation of the functional circuitry of the brain. These devices offer a means of simultaneously recording from neurons to elucidate modular and hierarchical processing, as well as neural circuitry involved in adaptation. In addition, MEAs have the potential to serve as a clinical neuroprostheses. MEAs implanted in cortex record from motor regions to enable control of devices, systems, and can restore control of the patients own paralyzed limbs when combined with functional electrical stimulation systems. The majority of MEAs, and especially those that are available commercially, are fabricated from silicon and leverage techniques associated with integrated circuit microfabrication and packaging. Using industry standard approaches, the features of MEAs can be reproducibly created and the resulting devices can be manufactured and disseminated. Two well-known approaches are MEAs initially developed at the University of Utah and at the University of Michigan now available to the neuroscience research community through Blackrock Microsystems and Neuronexus, respectively.

It is now widely understood that these devices exhibit limited long term viability where recordings fail after 6 months – 1 year after implantation. One of the causes for this failure is believed to originate from the chronic foreign body response from microglia and astrocytes which extends well beyond the normal acute inflammatory response following initial implantation. This foreign body response has often been attributed, in large part, to the mechanical mismatch that exists between the MEAs and the surrounding brain tissue as well as the feature size of the MEAs. In this presentation, we will discuss a novel type of MEA that achieves compliance by material properties, specifically MEAs created from shape memory polymers (SMPs) where formulations allow tunable and dynamic mechanical properties. SMPs can be fabricated which are stiff at room temperature, but soften by 1-2 degrees of magnitude once inserted in the brain. This strategy, which leverages conventional photolithography, can be utilized to create devices customized for recording and stimulation within cortical and deep brain regions. An important aspect of this strategy is that it provides a pathway for translation and dissemination of novel, manufacturable neurotechnology. This presentation will provide an overview of work to date to create and demonstrate compliant and flexible MEAs and the electrochemical characterization of these devices both in vitro and in vivo.