Implantable medical devices (IMDs) have become indispensable medical tools for improving the quality of life and prolonging the patient's lifespan. The minimization and extension of lifetime are main challenges for the development of IMDs. Current innovative research on this topic is focused on internal charging using the energy generated by the physiological environment or natural body activity. To harvest biomechanical energy efficiently, piezoelectric and triboelectric energy harvesters with sophisticated structural and material design have been developed. Energy from body movement, muscle contraction/relaxation, cardiac/lung motions, and blood circulation is captured and used for powering medical devices. Other recent progress in this field includes using PENGs and TENGs for our cognition of the biological processes by biological pressure/strain sensing, or direct intervention of them for some special self-powered treatments. Future opportunities lie in the fabrication of intelligent, flexible, stretchable, and/or fully biodegradable self-powered medical systems for monitoring biological signals and treatment of various diseases in vitro and in vivo.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201700029

Recent Progress on Piezoelectric and Triboelectric Energy Harvesters in Biomedical Systems.

Perovskite photodetectors (PPDs), which combine the advantages of perovskite semiconductor materials with superior optical and electronic properties and solution-processed manufacturing, have emerged as a new class of revolutionary optoelectronic devices with potential for various practical applications. Encouraged by the development of various solution-synthesis and film-deposition techniques for controlling the morphology and composition of perovskite materials with interesting optoelectronic properties, increasing research attention is focused on the development of high performance PPDs. In this review, the recent progress on emerging PPDs is comprehensively summarized from the perspective of device physics and materials science. The strategies for extending the spectral response range of PPDs and improving the performance of devices are investigated. Furthermore, the methods for realizing narrowband photodetectors are also discussed, where filter-free and self-filter narrowband PPDs are achieved based on the concept of charge collection narrowing. Meanwhile, the promising future directions in this research field are proposed and discussed, including multifunctional PPDs, perovskite–organic hybrid photodetectors, flexible and transparent PPDs, self-powered PPDs, and photodetector systems and arrays. This review provides valuable insights into the current status of highly sensitive PPDs and will spur the design of new structures and devices to further enhance their photo-detection performances and meet the need of versatility in practical application.

Recent progress on highly sensitive perovskite photodetectors

Flexible and self-powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self-powered and flexible PD based on the methylammonium lead iodide (CH3 NH3 PBI3 ) perovskite is demonstrated. Such a self-powered PD can operate even with irregular motion such as human finger tapping, which enables it to work without a bulky external power source. In addition, with high-quality CH3 NH3 PBI3 perovskite thin film fabricated with solvent engineering, the PD exhibits an impressive detectivity of 1.22 × 1013 Jones. In the self-powered voltage detection mode, it achieves a large responsivity of up to 79.4 V mW-1 cm-2 and a voltage response of up to ≈90%. Moreover, as the PD is made of flexible and transparent polymer films, it can operate under bending and functions at 360 Â° of illumination. As a result, the self-powered, flexible, 360 Â° omnidirectional perovskite PD, featuring high detectivity and responsivity along with real-world sensing capability, suggests a new direction for next-generation optical communications, sensing, and imaging applications.

/pdf/a-self-powered-and-flexible-organometallic-halide-perovskite-4tknqlhtkb.pdf

A Self-Powered and Flexible Organometallic Halide Perovskite Photodetector with Very High Detectivity.

Hybrid organic-inorganic perovskite materials garner enormous attention for a wide range of optoelectronic devices. Due to their attractive optical and electrical properties including high optical absorption coefficient, high carrier mobility, and long carrier diffusion length, perovskites have opened up a great opportunity for high performance photodetectors. This review aims to give a comprehensive summary of the significant results on perovskite-based photodetectors, focusing on the relationship among the perovskite structures, device configurations, and photodetecting performances. An introduction of recent progress in various perovskite structure-based photodetectors is provided. The emphasis is placed on the correlation between the perovskite structure and the device performance. Next, recent developments of bandgap-tunable perovskite and hybrid photodetectors built from perovskite heterostructures are highlighted. Then, effective approaches to enhance the stability of perovskite photodetector are presented, followed by the introduction of flexible and self-powered perovskite photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. A comprehensive summary of the research status on perovskite photodetectors is hoped to push forward the development of this field.

Hybrid Organic-Inorganic Perovskite Photodetectors.

Seeking to increase the triboelectric charge density on a friction layer is one of the most basic approaches to improve the output performance of triboelectric nanogenerators (TENGs). Here, we studied the storage mechanism of triboelectric charge in the friction layer and discussed the function of carrier mobility and concentration in the charge-storing process. As guided by these results, a kind of composite structure is constructed in the friction layer to adjust the depth distribution of the triboelectric charges and improve the output performance of TENGs. To further elucidate this theory, a simple TENG, whose negative friction layer is a composite structure by integrating polystyrene (PS) and carbon nanotubes (CNTs) into polyvinylidene fluoride (PVDF), was fabricated, and its performance test was also carried out. Comparing with a pure PVDF friction layer, the composite friction layer can raise the triboelectric charge density by a factor of 11.2. The extended residence time of electrons in the frict...

Dynamic Behavior of the Triboelectric Charges and Structural Optimization of the Friction Layer for a Triboelectric Nanogenerator.

We report a MAPbI3-based self-powered photodetector (SPPD). It has a dual sensing mechanism that relies on the joint properties of a photoelectric effect and a triboelectric effect of the perovskite material. Both the photoconductivity and the surface triboelectric density of the MAPbI3-based composite thin film are significantly altered upon solar illumination, which results in considerable reduction of the output voltage. The SPPD exhibits excellent responsivity (7.5 V W–1), rapid response time (<80 ms), great repeatability, and broad detection range that extends from UV to visible regions. This work presents a route to designing high-performance self-powered photodetectors from the aspect of materials.

High-Performance Organolead Halide Perovskite-Based Self-Powered Triboelectric Photodetector.

In the long pursuit of smart robotics, it has been envisioned to empower robots with human-like senses, especially vision and touch. While tremendous progress has been made in image sensors and computer vision over the past decades, tactile sense abilities are lagging behind due to the lack of large-scale flexible tactile sensor array with high sensitivity, high spatial resolution, and fast response. In this work, we have demonstrated a 64 × 64 flexible tactile sensor array with a record-high spatial resolution of 0.9 mm (equivalently 28.2 pixels per inch) by integrating a high-performance piezoresistive film (PRF) with a large-area active matrix of carbon nanotube thin-film transistors. PRF with self-formed microstructures exhibited high pressure-sensitivity of ∼385 kPa-1 for multi-walled carbon nanotubes concentration of 6%, while the 14% one exhibited fast response time of ∼3 ms, good linearity, broad detection range beyond 1400 kPa, and excellent cyclability over 3000 cycles. Using this fully integrated tactile sensor array, the footprint maps of an artificial honeybee were clearly identified. Furthermore, we hardware-implemented a smart tactile system by integrating the PRF-based sensor array with a memristor-based computing-in-memory chip to record and recognize handwritten digits and Chinese calligraphy, achieving high classification accuracies of 98.8% and 97.3% in hardware, respectively. The integration of sensor networks with deep learning hardware may enable edge or near-sensor computing with significantly reduced power consumption and latency. Our work could empower the building of large-scale intelligent sensor networks for next-generation smart robotics.

Large-Scale Integrated Flexible Tactile Sensor Array for Sensitive Smart Robotic Touch

We report a halide perovskite based flexible threshold-switched memristor with ultra-high speed as an artificial neuron that exhibits excellent leaky integrate-and-fire dynamics and strength-modulated spike frequency response performance.

Halide perovskite memristor with ultra-high-speed and robust flexibility for artificial neuron applications

Ultra-high Switching Times Flexible and high-performance selectors as critical parts has begun to attract increasing attention for suppressing the interferent current and enabling precise addressing in high-density array integration of memories and sensors. In article number 2100771, Chen Wang, Zhenxuan Zhao, and colleagues present a flexible threshold switching selector based on halide perovskites, which performs ultra-high switching times (ON/OFF) represented by the Mobius ring. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aelm.202270009

Zhen Xuan Zhao

Papers

High-Performance Organolead Halide Perovskite-Based Self-Powered Triboelectric Photodetector.

Large-Scale Integrated Flexible Tactile Sensor Array for Sensitive Smart Robotic Touch

Halide perovskite memristor with ultra-high-speed and robust flexibility for artificial neuron applications

Flexible Threshold Switching Selectors with Ultrahigh Endurance Based on Halide Perovskites (Adv. Electron. Mater. 2/2022)