3D printed microstructures for flexible electronic devices.

Flexible and stretchable electronics have attracted increasing attention and been widely used in wearable devices and electronic skins, where the circuits for flexible and stretchable electronics are typically in-plane-based 2D geometries. Here, we introduce a 3D microprinting technology that can expand one more dimension of the circuit in flexible electronics. We fabricated three-dimensional serpentine microstructures based on direct laser writing. These microstructures with a thin metal coated layer can be used as stretchable conducting meshes. Soft silicone serving as a substrate and encapsulations for these 3D microstructures enables great light transmittance (>90% in visible light range) and flexibility with 114° bending and 24° twisting. Further optimization of the mechanical design of the 3D microstructures can also enhance the stretchability up to 13.8%. These results indicate 3D flexible electronics can be realized by simple microprinting methods. Furthermore, 3D microprinting would also allow for the precise fabrication of other 3D structures, such as mechanically active 3D mesostructures, for the function of mechanical and electrical testing.

Wireless, Battery-Free Epidermal Electronics for Continuous, Quantitative, Multimodal Thermal Characterization of Skin.

Precise, quantitative measurements of the thermal properties of human skin can yield insights into thermoregulatory function, hydration, blood perfusion, wound healing, and other parameters of clinical interest. The need for wired power supply systems and data communication hardware limits, however, practical applicability of existing devices designed for measurements of this type. Here, a set of advanced materials, mechanics designs, integration schemes, and wireless circuits is reported as the basis for wireless, battery-free sensors that softly interface to the skin to enable precise measurements of its temperature and thermal transport properties. Calibration processes connect these parameters to the hydration state of the skin, the dynamics of near-surface flow through blood vessels and implanted catheters, and to recovery processes following trauma. Systematic engineering studies yield quantitative metrics in precision and reliability in real-world conditions. Evaluations on five human subjects demonstrate the capabilities in measurements of skin hydration and injury, including examples of continuous wear and monitoring over a period of 1 week, without disrupting natural daily activities.

Flexible and stretchable opto-electric neural interface for low-noise electrocorticogram recordings and neuromodulation in vivo.

Optogenetic-based neuromodulation tools is evolving for the basic neuroscience research in animals combining optical manipulation and electrophysiological recordings. However, current opto-electric integrated devices attaching on cerebral cortex for electrocorticogram (ECoG) still exist potential damage risks for both brain tissue and electrode, due to the mechanical mismatch and brain deformation. Here, we propose a stretchable opto-electric integrated neural interface by integrating serpentine-shaped electrodes and multisite micro-LEDs onto a hyperelastic substrate, as well as a serpentine-shaped metal shielding embedded in recording electrode for low-noise signal acquisition. The delicate structure design, ultrasoft encapsulation and independent fabrication followed by assembly are beneficial to the conformality, reliability and yield. In vitro accelerated deterioration and reciprocating tensile have demonstrated good performance and high stability. In vivo optogenetic activation of focal cortical areas of awaked mouse expressing Channelrhodopsin-2 is realized with simultaneous high-quality recording. We highlight the potential use of this multifunctional neural interface for neural applications.

Skin-interfaced biosensors for advanced wireless physiological monitoring in neonatal and pediatric intensive-care units.

Standard clinical care in neonatal and pediatric intensive-care units (NICUs and PICUs, respectively) involves continuous monitoring of vital signs with hard-wired devices that adhere to the skin and, in certain instances, can involve catheter-based pressure sensors inserted into the arteries. These systems entail risks of causing iatrogenic skin injuries, complicating clinical care and impeding skin-to-skin contact between parent and child. Here we present a wireless, non-invasive technology that not only offers measurement equivalency to existing clinical standards for heart rate, respiration rate, temperature and blood oxygenation, but also provides a range of important additional features, as supported by data from pilot clinical studies in both the NICU and PICU. These new modalities include tracking movements and body orientation, quantifying the physiological benefits of skin-to-skin care, capturing acoustic signatures of cardiac activity, recording vocal biomarkers associated with tonality and temporal characteristics of crying and monitoring a reliable surrogate for systolic blood pressure. These platforms have the potential to substantially enhance the quality of neonatal and pediatric critical care.

Binodal, wireless epidermal electronic systems with in-sensor analytics for neonatal intensive care.

Existing vital sign monitoring systems in the neonatal intensive care unit (NICU) require multiple wires connected to rigid sensors with strongly adherent interfaces to the skin. We introduce a pair of ultrathin, soft, skin-like electronic devices whose coordinated, wireless operation reproduces the functionality of these traditional technologies but bypasses their intrinsic limitations. The enabling advances in engineering science include designs that support wireless, battery-free operation; real-time, in-sensor data analytics; time-synchronized, continuous data streaming; soft mechanics and gentle adhesive interfaces to the skin; and compatibility with visual inspection and with medical imaging techniques used in the NICU. Preliminary studies on neonates admitted to operating NICUs demonstrate performance comparable to the most advanced clinical-standard monitoring systems.