Stanford Advisors

All Publications

  • Soft, bioresorbable, transparent microelectrode arrays for multimodal spatiotemporal mapping and modulation of cardiac physiology. Science advances Chen, Z., Lin, Z., Obaid, S. N., Rytkin, E., George, S. A., Bach, C., Madrid, M., Liu, M., LaPiano, J., Fehr, A., Shi, X., Quirion, N., Russo, B., Knight, H., Aduwari, A., Efimov, I. R., Lu, L. 2023; 9 (27): eadi0757


    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.

    View details for DOI 10.1126/sciadv.adi0757

    View details for PubMedID 37406128

    View details for PubMedCentralID PMC10321742

  • Graphene Biointerface for Cardiac Arrhythmia Diagnosis and Treatment. Advanced materials (Deerfield Beach, Fla.) Lin, Z., Kireev, D., Liu, N., Gupta, S., LaPiano, J., Obaid, S. N., Chen, Z., Akinwande, D., Efimov, I. R. 2023; 35 (22): e2212190


    Heart rhythm disorders, known as arrhythmias, cause significant morbidity and are one of the leading causes of mortality. Cardiac arrhythmias are frequently treated by implantable devices, such as pacemakers and defibrillators, or by ablation therapy guided by electroanatomical mapping. Both implantable and ablation therapies require sophisticated biointerfaces for electrophysiological measurements of electrograms and delivery of therapeutic stimulation or ablation energy. In this work, a graphene biointerface for in vivo cardiac electrophysiology is reported for the first time. Leveraging sub-micrometer-thick tissue-conformable graphene arrays, sensing and stimulation of the open mammalian heart are demonstrated both in vitro and in vivo. Furthermore, the graphene biointerface treatment of atrioventricular block (the kind of arrhythmia where the electrical conduction from the atria to the ventricles is interrupted) is demonstrated. The graphene arrays show effective electrochemical properties, namely interface impedance down to 40 Ω cm2 at 1 kHz, charge storage capacity up to 63.7 mC cm-2 , and charge injection capacity up to 704 µC cm-2 . Transparency of the graphene structures allows for simultaneous optical mapping of cardiac action potentials, calcium transients, and optogenetic stimulation while performing electrical measurements and stimulation. The report presents evidence of the significant potential of graphene biointerfaces for advanced cardiac electrophysiology and arrhythmia therapy.

    View details for DOI 10.1002/adma.202212190

    View details for PubMedID 36965107

  • Transparent and Stretchable Au─Ag Nanowire Recording Microelectrode Arrays. Advanced materials technologies Chen, Z., Nguyen, K., Kowalik, G., Shi, X., Tian, J., Doshi, M., Alber, B. R., Guan, X., Liu, X., Ning, X., Kay, M. W., Lu, L. 2023; 8 (10)


    Transparent microelectrodes have received much attention from the biomedical community due to their unique advantages in concurrent crosstalk-free electrical and optical interrogation of cell/tissue activity. Despite recent progress in constructing transparent microelectrodes, a major challenge is to simultaneously achieve desirable mechanical stretchability, optical transparency, electrochemical performance, and chemical stability for high-fidelity, conformal, and stable interfacing with soft tissue/organ systems. To address this challenge, we have designed microelectrode arrays (MEAs) with gold-coated silver nanowires (Au─Ag NWs) by combining technical advances in materials, fabrication, and mechanics. The Au coating improves both the chemical stability and electrochemical impedance of the Au─Ag NW microelectrodes with only slight changes in optical properties. The MEAs exhibit a high optical transparency >80% at 550 nm, a low normalized 1 kHz electrochemical impedance of 1.2-7.5 Ω cm2, stable chemical and electromechanical performance after exposure to oxygen plasma for 5 min, and cyclic stretching for 600 cycles at 20% strain, superior to other transparent microelectrode alternatives. The MEAs easily conform to curvilinear heart surfaces for colocalized electrophysiological and optical mapping of cardiac function. This work demonstrates that stretchable transparent metal nanowire MEAs are promising candidates for diverse biomedical science and engineering applications, particularly under mechanically dynamic conditions.

    View details for DOI 10.1002/admt.202201716

    View details for PubMedID 38644939

    View details for PubMedCentralID PMC11031257

  • Flexible Electro-Optical Arrays for Simultaneous Multi-Site Colocalized Spatiotemporal Cardiac Mapping and Modulation ADVANCED OPTICAL MATERIALS Obaid, S. N., Chen, Z., Madrid, M., Lin, Z., Tian, J., Humphreys, C., Adams, J., Daza, N., Balansag, J., Efimov, I. R., Lu, L. 2022; 10 (23)
  • Flexible and Transparent Metal Nanowire Microelectrode Arrays and Interconnects for Electrophysiology, Optogenetics, and Optical Mapping ADVANCED MATERIALS TECHNOLOGIES Chen, Z., Boyajian, N., Lin, Z., Yin, R. T., Obaid, S. N., Tian, J., Brennan, J. A., Chen, S. W., Miniovich, A. N., Lin, L., Qi, Y., Liu, X., Efimov, I. R., Lu, L. 2021; 6 (7)
  • Advanced Electrical and Optical Microsystems for Biointerfacing ADVANCED INTELLIGENT SYSTEMS Obaid, S. N., Chen, Z., Lu, L. 2020; 2 (9)
  • Flexible and Transparent Metal Oxide/Metal Grid Hybrid Interfaces for Electrophysiology and Optogenetics. Advanced materials technologies Chen, Z., Yin, R. T., Obaid, S. N., Tian, J., Chen, S. W., Miniovich, A. N., Boyajian, N., Efimov, I. R., Lu, L. 2020; 5 (8)


    Flexible and transparent microelectrodes and interconnects provide the unique capability for a wide range of emerging biological applications, including simultaneous optical and electrical interrogation of biological systems. For practical biointerfacing, it is important to further improve the optical, electrical, electrochemical, and mechanical properties of the transparent conductive materials. Here, high-performance microelectrodes and interconnects with high optical transmittance (59-81%), superior electrochemical impedance (5.4-18.4 Ω cm2), and excellent sheet resistance (5.6-14.1 Ω sq-1), using indium tin oxide (ITO) and metal grid (MG) hybrid structures are demonstrated. Notably, the hybrid structures retain the superior mechanical properties of flexible MG other than brittle ITO with no changes in sheet resistance even after 5000 bending cycles against a small radius at 5 mm. The capabilities of the ITO/MG microelectrodes and interconnects are highlighted by high-fidelity electrical recordings of transgenic mouse hearts during co-localized programmed optogenetic stimulation. In vivo histological analysis reveals that the ITO/MG structures are fully biocompatible. Those results demonstrate the great potential of ITO/MG interfaces for broad fundamental and translational physiological studies.

    View details for DOI 10.1002/admt.202000322

    View details for PubMedID 38404692

    View details for PubMedCentralID PMC10888205

  • Wireless, battery-free subdermally implantable photometry systems for chronic recording of neural dynamics. Proceedings of the National Academy of Sciences of the United States of America Burton, A., Obaid, S. N., Vázquez-Guardado, A., Schmit, M. B., Stuart, T., Cai, L., Chen, Z., Kandela, I., Haney, C. R., Waters, E. A., Cai, H., Rogers, J. A., Lu, L., Gutruf, P. 2020; 117 (6): 2835-2845


    Recording cell-specific neuronal activity while monitoring behaviors of freely moving subjects can provide some of the most significant insights into brain function. Current means for monitoring calcium dynamics in genetically targeted populations of neurons rely on delivery of light and recording of fluorescent signals through optical fibers that can reduce subject mobility, induce motion artifacts, and limit experimental paradigms to isolated subjects in open, two-dimensional (2D) spaces. Wireless alternatives eliminate constraints associated with optical fibers, but their use of head stages with batteries adds bulk and weight that can affect behaviors, with limited operational lifetimes. The systems introduced here avoid drawbacks of both types of technologies, by combining highly miniaturized electronics and energy harvesters with injectable photometric modules in a class of fully wireless, battery-free photometer that is fully implantable subdermally to allow for the interrogation of neural dynamics in freely behaving subjects, without limitations set by fiber optic tethers or operational lifetimes constrained by traditional power supplies. The unique capabilities of these systems, their compatibility with magnetic resonant imaging and computed tomography and the ability to manufacture them with techniques in widespread use for consumer electronics, suggest a potential for broad adoption in neuroscience research.

    View details for DOI 10.1073/pnas.1920073117

    View details for PubMedID 31974306

    View details for PubMedCentralID PMC7022161

  • Recent advances in organic optoelectronic devices for biomedical applications OPTICAL MATERIALS EXPRESS Chen, Z., Obaid, S. N., Lu, L. 2019; 9 (9): 3843-3856
  • All-Solid-State Asymmetric Supercapacitors with Metal Selenides Electrodes and Ionic Conductive Composites Electrolytes ADVANCED FUNCTIONAL MATERIALS Chen, Z., Yang, Y., Ma, Z., Zhu, T., Liu, L., Zheng, J., Gong, X. 2019; 29 (38)