Real-time processing and manipulation of biological signals require bioelectronic devices with integrated components capable of signal amplification, processing, and stimulation. Transistors form the backbone of such circuits, but numerous criteria must be met for efficient and safe operation in biological environments. Here, we introduce an internal ion-gated organic electrochemical transistor (IGT) that uses contained mobile ions within the conducting polymer channel to permit both volumetric capacitance and shortened ionic transit time. The IGT has high transconductance, fast speed, and can be independently gated to create scalable conformable integrated circuits. We demonstrate the ability of the IGT to provide a miniaturized, comfortable interface with human skin using local amplification to record high-quality brain neurophysiological activity. The IGT is an effective transistor architecture for enabling integrated, real-time sensing and stimulation of signals from living organisms.
Neuroelectronic devices are critical for the diagnosis and treatment of neuropsychiatric conditions, and are hypothesized to have many more applications. A wide variety of materials and approaches have been utilized to create innovative neuroelectronic device components, from the tissue interface and acquisition electronics to interconnects and encapsulation. Although traditional materials have a strong track record of stability and safety within a narrow range of use, many of their properties are suboptimal for chronic implantation in body tissue. Material advances harnessed to form all the components required for fully integrated neuroelectronic devices hold promise for improving the long‐term efficacy and biocompatibility of these devices within physiological environments. Here, it is aimed to provide a comprehensive overview of materials and devices used in translational neuroelectronics, from acquisition and stimulation interfaces to methods for power delivery and real time processing of neural signals.
Transcranial electrical stimulation is a noninvasive neurostimulation technique with a wide range of therapeutic applications. However, current electrode materials are typically not optimized for this abiotic/biotic interface which requires high charge capacity, operational stability, and conformability. Here, a plant‐based composite electrode material based on the combination of aloe vera (AV) hydrogel and a conducting polymer (CP; poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, PEDOT:PSS) is reported. This material system is fabricated into films and provides biocompatibility, conformability, and stability, while offering desirable electrical properties of the PEDOT:PSS. AVCP films are also molded onto the rough surface of the skull leading to a mechanically stable and robust interface. The in vivo efficacy of the AVCP films is verified to function as stimulating and recording electrodes by placing them on the skull of a rat and concomitantly inducing focal seizures and acquiring the evoked neural activity. AVCP films pave the way for high‐quality biological interfaces that are broadly applicable and can facilitate advances in closed‐loop responsive stimulation devices.
Implanted bioelectronic devices require data transmission through tissue, but ionic conductivity and inhomogeneity of this medium complicate conventional communication approaches. Here, we introduce ionic communication (IC) that uses ions to effectively propagate megahertz-range signals. We demonstrate that IC operates by generating and sensing electrical potential energy within polarizable media. IC was tuned to transmit across a range of biologically relevant tissue depths. The radius of propagation was controlled to enable multiline parallel communication, and it did not interfere with concurrent use of other bioelectronics. We created a fully implantable IC-based neural interface device that acquired and noninvasively transmitted neurophysiologic data from freely moving rodents over a period of weeks with stability sufficient for isolation of action potentials from individual neurons. IC is a biologically based data communication that establishes long-term, high-fidelity interactions across intact tissue.
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