Hangbo Zhao

Simultaneous interrogation of cardiac electrophysiological and metabolic processes is essential for investigating and treating heart disease. Key challenges remain in creating stretchable multimodal bioelectronic devices capable of organ-scale, label-free probing of electrophysiology and metabolism in vivo. Here, we present stretchable, scalable, large-area transparent microelectrode arrays (MEAs) that integrate up to 144 microelectrodes and interconnects, enabling a centimeter-scale field of view to tackle these challenges. The microelectrodes consist of conductive polymer-coated metal nanowire composites with outstanding optical transparency and electrochemical performance for both electrophysiological sensing and electrical pacing. These large-area arrays exhibit excellent yield, uniformity, biocompatibility, and mechanical deformability like native cardiac tissue. They successfully achieve in vivo spatiotemporal mapping of electrophysiological activity together with colocalized label-free autofluorescence imaging of metabolism across all four beating heart chambers under clinically relevant conditions in small animals, including ischemia, arrhythmia, and device-delivered electrotherapy. The platform offers methodological opportunities to advance basic and clinical cardiology.

Stretchable antennas are increasingly important for wearable electronics, soft robotics, and conformal wireless systems that require mechanically compliant radiofrequency components capable of operating under deformation. Among various approaches, liquid metal-based antennas offer a promising combination of high conductivity and mechanical compliance. However, most existing liquid metal antennas rely on embedded microfluidic channels and cleanroom-based fabrication, which limit scalability, design flexibility, and rapid prototyping. Here, we introduce a cleanroom-free, stencil-based fabrication strategy that combines 3D printing, replica molding, and templated blade coating of oxidized eutectic gallium–indium to produce stretchable patch antennas on soft silicone substrates. By integrating multilevel fractal-inspired slot geometries, the antennas achieve lower operating frequencies within the same footprint and tunable, direction-sensitive frequency shifts under uniaxial, transverse, and biaxial stretching of up to 40%. Full-wave finite-element simulations confirm the frequency-tuning behavior. When mounted on the human elbow, the antenna conforms to joint motion and enables direction-sensitive wireless strain sensing. This platform provides a scalable, miniaturized, and mechanically robust route to stretchable liquid metal patch antennas for wearable sensing applications.

This protocol describes acute experiments involving sacral stimulation of minipigs while monitoring distal colon motility. Stimulation at various amplitudes and frequencies is applied to the S2 or S3 sacral roots using a bipolar cuff. Colon motility is monitored using multiple sensing modalities including electromyography (EMG), colon wall strain sensing, intraluminal pressure manometry, and electrochemical dopamine sensing.

This dataset contains electrophysiological and sensor data on the effects of sacral root stimulation on colon motility. Sensors include manometry, strain sensing, electromyography, and electrochemical measurement of neurotransmitters.

Liquid metal–based stretchable electronics offer high electrical performance and seamless integration with deformable systems but face challenges in achieving scalable, high-resolution patterning. In this work, we present a method for micropatterning liquid metal particle (LMP) films with feature sizes as small as 5 micrometers by integrating electrostatically enabled colloidal self-assembly and microtransfer printing. The resulting cold-welded LMP micropatterns exhibit exceptional electromechanical properties, high conductivity (2.4 × 10 6 siemens per meter), stretchability (more than 1200%), and strain- and pressure-insensitive resistance, owing to their multiscale and dynamic morphologies. Demonstrations in highly stretchable strain sensors and cardiac mapping devices highlight the capabilities of this method for creating high-performance, highly stretchable electronic systems. Notably, balloon catheter–integrated LMP microelectrode arrays show low impedance under extreme deformations and enable high-resolution endocardial electrogram mapping inside the human heart. This method expands the potential of liquid metal–based stretchable electronics for a wide range of applications, including implantable biomedical devices and soft robotics.

Implantable strain sensors integrated on organ surfaces can monitor organ deformations, such as bladder filling and stomach motility, thereby providing important information about their functional states. A major challenge lies in achieving large strain ranges while ensuring biocompatibility and long-term stability inside physiological fluid environments. Commonly used stretchable materials have relatively high water permeability, which can lead to degradation of sensing performance. This work presents a method to provide highly stretchable, biocompatible, compliant, and stable encapsulation for implantable capacitive strain sensors. Conformal deposition of parylene, a widely used encapsulation material with limited stretchability, followed by controlled mechanical buckling, creates microscale wrinkles in the parylene coating. A thermal annealing step reduces Young’s modulus of parylene, which converts globally buckled thick (>5 μm) parylene coating into microscale wrinkles. This simple annealing step effectively enhances the stretchability and barrier properties of the parylene coating. The resulting biocompatible wrinkled parylene encapsulation provides over 60% mechanical stretchability and a normalized water vapor transmission rate of 0.07 g mm/m 2 /day, offering one of the best combinations of barrier properties and stretchability among different encapsulation materials. In addition, the uniaxially microwrinkled encapsulation results in a more than doubled gauge factor for capacitive strain sensing by suppressing the Poisson effect. Thermally accelerated dynamic testing of encapsulated strain sensors validates their long-term stability. Additionally, strain sensing using encapsulated sensors sutured on a bladder phantom and ex vivo porcine bladders demonstrates their potential for real-time organ deformation sensing. The versatility of this encapsulation method makes it promising for a wide variety of stretchable implantable devices, supporting continuous organ monitoring and targeted therapy.

Proprioception in soft robots is essential for enabling autonomous behaviors, allowing them to navigate and interact safely in unstructured environments. Previous sensorization-based shape reconstruction methods, which often rely on machine learning techniques, have limitations in their broad applicability for different robotic systems and environments. In this work, we present a shape reconstruction scheme enabled by sparsely distributed soft strain sensors on the surfaces of soft robots, combined with a model-based reconstruction framework. Our approach utilizes miniaturized stretchable capacitive strain sensors with large stretchability and low hysteresis, which can be easily attached to soft robot surfaces for accurate local strain measurements. These measurements are fed into an optimization algorithm with embedded mechanical constraints. Our approach can predict all deformation modes in a soft bar with a maximum displacement error of less than 4% of the bar length and accurately reconstruct the shapes of soft pneumatic grippers during grasping actions. Additional reconstructions of a bioinspired arm in complex contact scenarios further demonstrate the versatility of our approach. This shape reconstruction scheme using distributed strain sensors offers a convenient and broadly applicable solution for enhancing proprioception in soft robots.

Abstract Implantable sensors can provide access to accurate, continuous, and minimally invasive monitoring of physiological signals from internal organs and tissues, thereby facilitating timely diagnosis, closed-loop intervention, and advanced health management. Among the various types of implantable sensors, those capable of measuring physical parameters–such as temperature, force, and flow–are particularly important due to their ability to monitor physical conditions critical to nearly all organs and to provide insights into a wide range of health conditions. This review presents recent progress in four key types of implantable physical sensors: strain sensors, pressure sensors, temperature sensors, and flow sensors. It covers their engineering principles, design considerations, in vivo performances, and clinical relevance. The review also addresses critical challenges and future opportunities in the development of implantable physical sensors, such as flexibility and stretchability, biocompatibility, long-term stability, and the translation of these sensing technologies from bench to clinic. Graphical Abstract

Implantable systems with chronic stability, high sensing performance, and extensive spatial-temporal resolution are a growing focus for monitoring and treating several diseases such as epilepsy, Parkinson's disease, chronic pain, and cardiac arrhythmias. These systems demand exceptional bendability, scalable size, durable electrode materials, and well-encapsulated metal interconnects. However, existing chronic implantable bioelectronic systems largely rely on materials prone to corrosion in biofluids, such as silicon nanomembranes or metals. This study introduces a multielectrode array featuring a wide bandgap (WBG) material as electrodes, demonstrating its suitability for chronic implantable applications. Our devices exhibit excellent flexibility and longevity, taking advantage of the low bending stiffness and chemical inertness in WBG nanomembranes and multimodalities for physical health monitoring, including temperature, strain, and impedance sensing. Our top-down manufacturing process enables the formation of distributed electrode arrays that can be seamlessly integrated onto the curvilinear surfaces of skins. As proof of concept for chronic cardiac pacing applications, we demonstrate the effective pacing functionality of our devices on rabbit hearts through a set of ex vivo experiments. The engineering approach proposed in this study overcomes the drawbacks of prior WBG material fabrication techniques, resulting in an implantable system with high bendability, effective pacing, and high-performance sensing.

Stretchable three-dimensional (3D) penetrating microelectrode arrays have potential utility in various fields, including neuroscience, tissue engineering, and wearable bioelectronics. These 3D microelectrode arrays can penetrate and conform to dynamically deforming tissues, thereby facilitating targeted sensing and stimulation of interior regions in a minimally invasive manner. However, fabricating custom stretchable 3D microelectrode arrays presents material integration and patterning challenges. In this study, we present the design, fabrication, and applications of stretchable microneedle electrode arrays (SMNEAs) for sensing local intramuscular electromyography signals ex vivo. We use a unique hybrid fabrication scheme based on laser micromachining, microfabrication, and transfer printing to enable scalable fabrication of individually addressable SMNEA with high device stretchability (60 to 90%). The electrode geometries and recording regions, impedance, array layout, and length distribution are highly customizable. We demonstrate the use of SMNEAs as bioelectronic interfaces in recording intramuscular electromyography from various muscle groups in the buccal mass of Aplysia .

Abstract Robotic manipulators can be used to deposit materials on non-planar surfaces. Conventional sensor-based industrial robots can only work on stationary surfaces, relying on the scanned data prior to printing. As a result, performing depositions that involve changes in plane motion presents significant challenges. The deposition of conformal materials on a time-varying deformable surface requires the manipulators to update coordinates in real time on the plane for positioning and orientation. This can be achieved by employing multiple sensors for manipulator motion planning and control, in order to prevent collisions between the tool and the surface. In this paper, we propose simple tool center point calibration, initial point coordinate estimation, and a gap compensation scheme to combine real-time feedback control and direct conformal deposition. Combining these elements allows us to maintain a controlled gap between the tooltip and the deformable surface during the deposition. We test the efficacy of the proposed approach by printing a single layer of ink patterns with approximately 950 μm line width on a deformable surface. We also characterize the printing quality with different gaps and printing steps and show that sensor-based control is critical in smooth printing. Finally, the effects of changing the relative position of the tooltip, different surface colors, and laser sensor position are characterized.

Stretchable strain sensors are essential for various applications such as wearable electronics, prosthetics, and soft robotics. Strain sensors with high strain range, minimal hysteresis, and fast response speed are highly desirable for accurate measurements of large and dynamic deformations of soft bodies. Current stretchable strain sensors mostly rely on deformable conducting materials, which often have difficulties in achieving these properties simultaneously. In this study, we introduce capacitive strain sensor concepts based on origami-inspired three-dimensional mesoscale electrodes formed by a mechanically guided assembly process. These sensors exhibit up to 200% stretchability with 1.2% degree of hysteresis, <22 ms response time, small sensing area (~5 mm 2 ), and directional strain responses. To showcase potential applications, we demonstrate the use of distributed strain sensors for measuring multimodal deformations of a soft continuum arm.

Stretchable Microarchitectures In article number 2211781, Hoang-Phuong Phan, Hangbo Zhao, and co-workers develop an innovative soft lithography process to create three-dimensional electronics using wide bandgap material nanomembranes. This class of unusual electronic devices enables new functionalities for advanced organ-on-chip technology and long-term implant applications.

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Abstract Wide bandgap (WBG) semiconductors have attracted significant research interest for the development of a broad range of flexible electronic applications, including wearable sensors, soft logical circuits, and long‐term implanted neuromodulators. Conventionally, these materials are grown on standard silicon substrates, and then transferred onto soft polymers using mechanical stamping processes. This technique can retain the excellent electrical properties of wide bandgap materials after transfer and enables flexibility; however, most devices are constrained by 2D configurations that exhibit limited mechanical stretchability and morphologies compared with 3D biological systems. Herein, a stamping‐free micromachining process is presented to realize, for the first time, 3D flexible and stretchable wide bandgap electronics. The approach applies photolithography on both sides of free‐standing nanomembranes, which enables the formation of flexible architectures directly on standard silicon wafers to tailor the optical transparency and mechanical properties of the material. Subsequent detachment of the flexible devices from the support substrate and controlled mechanical buckling transforms the 2D precursors of wide band gap semiconductors into complex 3D mesoscale structures. The ability to fabricate wide band gap materials with 3D architectures that offer device‐level stretchability combined with their multi‐modal sensing capability will greatly facilitate the establishment of advanced 3D bio‐electronics interfaces.

To achieve high-performance printed electronic devices, scalable and cost-effective printing of high-quality metallic electrodes with narrow gaps, such as for transistors with short channel lengths, is desirable. Here, we demonstrate short channel (<10 μm) transistors, using thin (<100–200 nm) electrodes fabricated by flexographic printing with nanoporous stamps, with single-wall carbon nanotubes (SWCNTs) as the network semiconductor. The nanoporous stamps comprise polymer-coated vertically aligned carbon nanotubes and facilitate control of the printed ink thickness in the 50–200 nm range. The measured on–off ratio and mobility meet or exceed those of previously reported SWCNT network transistors fabricated by alternative printing methods.

Bioengineering approaches that combine living cellular components with three-dimensional scaffolds to generate motion can be used to develop a new generation of miniature robots. Integrating on-board electronics and remote control in these biological machines will enable various applications across engineering, biology, and medicine. Here, we present hybrid bioelectronic robots equipped with battery-free and microinorganic light-emitting diodes for wireless control and real-time communication. Centimeter-scale walking robots were computationally designed and optimized to host on-board optoelectronics with independent stimulation of multiple optogenetic skeletal muscles, achieving remote command of walking, turning, plowing, and transport functions both at individual and collective levels. This work paves the way toward a class of biohybrid machines able to combine biological actuation and sensing with on-board computing.