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Multiparametric investigation of cardiac physiology is crucial for the diagnosis and therapy of heart disease. However, no method exists to simultaneously map multiple parameters that govern cardiac (patho)physiology from beating hearts in vivo. Here, we present a cardiac sensing platform that addresses this challenge, functioning with a wireless interface. Advanced fabrication and assembling strategies enable the heterogeneous integration of transparent microelectrodes, light-emitting diodes, photodiodes, and optical filters into a multilayer array structure on soft substrates. The microelectrodes exhibit superior electrochemical performance for measuring electrical potentials and excellent transparency for co-localized fluorescence measurement. The device shows excellent biocompatibility and records the fluorescence of calcium reporter with performance comparable to imaging cameras. Multiparametric in vivo mapping of electrical excitation, calcium dynamics, and their combined effects on cardiac excitation-contraction coupling is demonstrated during normal rhythm, arrhythmia, and treatment. This technology offers potential widespread use in cardiac research to support scientific discoveries and advance clinical life-saving diagnostics and therapies. 

The Hilbert transform is widely used in biomedical signal processing and requires efficient implementation. We propose the implementation of the discrete Hilbert transform based on emerging memristor devices. It uses two matrix multiplication layers using weights programmed in the memristor array and a linear Hadamard product calculation layer mappable to CMOS. The functionality was tested on a dataset of optical cardiac signals from the human heart. The results show negligible <1% angle error between the proposed implementation and the MATLAB function. It also has robustness to non-idealities. This proposed solution can be applied to bio-signal processing at the edge. 

Transparent microelectrode arrays (MEAs) that allow multimodal investigation of the spatiotemporal cardiac characteristics are important in studying and treating heart disease. Existing implantable devices, however, are designed to support chronic operational lifetimes and require surgical extraction when they malfunction or are no longer needed. Meanwhile, bioresorbable systems that can self-eliminate after performing temporary functions are increasingly attractive because they avoid the costs/risks of surgical extraction. We report the design, fabrication, characterization, and validation of a soft, fully bioresorbable, and transparent MEA platform for bidirectional cardiac interfacing over a clinically relevant period. The MEA provides multiparametric electrical/optical mapping of cardiac dynamics and on-demand site-specific pacing to investigate and treat cardiac dysfunctions in rat and human heart models. The bioresorption dynamics and biocompatibility are investigated. The device designs serve as the basis for bioresorbable cardiac technologies for potential postsurgical monitoring and treating temporary patient pathological conditions in certain clinical scenarios, such as myocardial infarction, ischemia, and transcatheter aortic valve replacement. 

Recently developed optically transparent microelectrode technology provides a promising approach for simultaneous high-resolution electrical and optical biointerfacing with tissues in vivo and in vitro. A critically unmet need is designing high-performance stretchable platforms for conformal biointerfacing with mechanically active organs. Here, we report silver nanowire (Ag NW) stretchable transparent microelectrodes and interconnects that exhibit excellent electrical and electrochemical performance, high optical transparency, superior mechanical robustness and durability by a simple selective-patterning process. The fabrication method allows the direct integration of Ag NW networks on elastomeric substrates. The resulting Ag NW interface exhibits a low sheet resistance (Rsh) of 1.52–4.35 Ω sq−1, an advantageous normalized electrochemical impedance of 3.78–6.04 Ω cm2, a high optical transparency of 61.3–80.5% at 550 nm and a stretchability of 40%. The microelectrode arrays (MEAs) fabricated with this approach exhibit uniform electrochemical performance across all channels. Studies on mice demonstrate that both pristine and stretched Ag NW microelectrodes can achieve high-fidelity electrophysiological monitoring of cardiac activity with/without co-localized optogenetic pacing. Together, these results pave the way for developing stretchable and transparent metal nanowire networks for high-resolution opto-electric biointerfacing with mechanically active organs, such as the heart.