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Objective. Brain-Machine Interfaces (BMIs) hold great promises for advancing neuroprosthetics, robotics, and for providing treatment options for severe neurological diseases. The objective of this work is the development and in vivo evaluation of electrodes for BMIs that meet the needs to record brain activity at sub-millimeter resolution over a large area of the cortex while being soft and electromechanically robust (i.e. stretchable). Approach. Current electrodes require a trade-off between high spatiotemporal resolution and cortical coverage area. To address the needs for simultaneous high resolution and large cortical coverage, the prototype electrode array developed in this study employs a novel bilayer routing of soft and stretchable lead wires from the recording sites on the surface of the brain (electrocorticography, ECoG) to the data acquisition system. Main results. To validate the recording characteristics, the array was implanted in healthy felines for up to 5 months. Neural signals recorded from both layers of the device showed elevated mid-frequency structures typical of local field potential (LFP) signals that were stable in amplitude over implant duration, and also exhibited consistent frequency-dependent modulation after anesthesia induction by Telazol. Significance. The successful development of a soft and stretchable large-area, high resolution micro ECoG electrode array (lahrμECoG) is an important step to meet the neurotechnological needs of advanced BMI applications.

The prevalence of cardiovascular risk factors is expected to increase the occurrence of cardiovascular diseases (CVDs) worldwide. Cardiac organoids are promising candidates for bridging the gap between in vitro experimentation and translational applications in drug development and cardiac repair due to their attractive features. Here we present the fabrication and characterization of isogenic scaffold-free cardiac organoids derived from human induced pluripotent stem cells (hiPSCs) formed under a supplement-deprivation regimen that allows for metabolic synchronization and maturation of hiPSC-derived cardiac cells. We propose the formation of coculture cardiac organoids that include hiPSC-derived cardiomyocytes and hiPSC-derived cardiac fibroblasts (hiPSC-CMs and hiPSC-CFs, respectively). The cardiac organoids were characterized through extensive morphological assessment, evaluation of cellular ultrastructures, and analysis of transcriptomic and electrophysiological profiles. The morphology and transcriptomic profile of the organoids were improved by coculture of hiPSC-CMs with hiPSC-CFs. Specifically, upregulation of Ca2+ handling-related genes, such as RYR2 and SERCA, and structure-related genes, such as TNNT2 and MYH6, was observed. Additionally, the electrophysiological characterization of the organoids under supplement deprivation shows a trend for reduced conduction velocity for coculture organoids. These studies help us gain a better understanding of the role of other isogenic cells such as hiPSC-CFs in the formation of mature cardiac organoids, along with the introduction of exogenous chemical cues, such as supplement starvation.

Microcracked gold films on elastomeric substrates can function as stretchable and deformable interconnects and sensors. In response to stretch or deformation, the design would seek to minimize the change in resistance for stretchable or deformable interconnects; if used as resistive sensors, a large change in resistance would be desired. This research examines the change in resistance upon bending of a microcracked conductor and compares the results with stretching such a conductor. The resistance depends on the strain in the film, which, for bending, is a function of the bending radius and the location of the film within the structure with respect to the neutral plane. The resistance decreases when the gold conductor is under compression and increases when it is under tension. The decrease in resistance under compression is small compared to the increase in resistance under tension, marginally depending on the bending radius. In contrast, the resistance under tension significantly increases with decreasing bending radius. The mechanics model presented here offers a mechanistic understanding of these observations. These results provide guidance for the design of interconnects for flexible and stretchable electronics and for flexible sensors to monitor the magnitude and direction of bending or stretching.