Low-Power and Tunable-Performance Biomemristor Based on Silk Fibroin

Resistive Switching Layer-Modulated Volatile and Nonvolatile Memristors with Flexible and Controlled Transient Properties

A growing concern for sustainable electronics to support a more eco-friendly future has significantly increased the demand for flexible and biodegradable electronics. This work explores the effect of using entirely biocompatible materials in the memristor device to achieve volatile and nonvolatile resistive switching operations by modulating the switching layer (SL) materials. The physically transient memristors (PTMs), based on an Mg electrode, a polytrimethylene carbonate (PTMC)/polyvinylpyrrolidone (PVP) switching layer, and a chitosan/PVP substrate, exhibited both volatile and nonvolatile memory characteristics, as well as quantized conductance (G0) states. The PTM device has a low set/reset voltage (<1 V), a large memory (ROFF/RON) window (>106), and long-term HRS/LRS retention (>103 s) characteristics during its nonvolatile operation. The I-V and pulse response revealed that switching occurs due to the constriction of the Mg metallic filament to the atomic scale, with a resistance ≤ 12.9 kΩ. The LRS and HRS are controlled within the range of quantized conductance (G0 = 2e2/h) to bulk conductance (G) states. The three different concentrations (1:0.5, 1:1, and 1:1.5) of blended film (PTMC:PVP) exhibit volatile resistive switching operation. The blended polymer films display a unique dual-phase surface morphology, facilitating ionic transportation. The device was encapsulated using an ALD-deposited Al2O3 layer to enable a controllable biodegradation process, allowing control over its lifespan. The tunable volatile/nonvolatile electrical characteristics and controllable biodegradation demonstrate the potential of this device for implantable biomedical memory, secure hardware systems, and flexible wearable electronics.

Biodegradable silk fibroin-based triboelectric nanogenerator with enhanced output regulated by interfacial and ionic polarization

Bio-based triboelectric nanogenerators (TENGs) are expected to power medical device and detect real-time human motion behavior due to eco-friendliness and biocompatibility. However, the output performance of the TENGs needs to be boosted. In this study, a biodegradable silk fibroin-based TENG with enhanced output performance regulated by interfacial and ionic polarization is proposed. The friction layers, regenerated silk fibroin (RSF) film and silk nanoribbon (SNR) film, are functionalized through the induction of histidine with imidazolyl and lithium chloride, respectively, thus increasing the dielectric constant and triboelectric properties of friction layers. The enhancement is attributed to the enlarged difference of electron-absorbing ability and electron-donating ability of the two friction layers. The total silk fibroin-based TENG shows a maximum voltage of 63.0 V, and a current of 2.4 μA. Moreover, the obtained maximum power density of 828.8 mW m-2 is 9.5 times higher than that of the counterpart without functionalization. And the output power density is much higher than that of existing fully degradable bio-based TENGs reported previously. The components of the silk fibroin-based TENG can gradually degrade in vitro. As a wearable device, the silk fibroin-based TENG can precisely monitor real-time human motion due to its high sensitivity, which can realize self-powered supply and simultaneous sensing. Moreover, the unencapsulated TENG is successfully used as a self-powered humidity sensor. The bio-based TENGs with enhanced performance highlight their application potential in wearable and implantable fields.

Enhanced Resistive Switching and Conduction Mechanisms in Silk Fibroin-Based Memristors with Ag Nanoparticles for Bio-Neuromorphic Applications

This study explores the resistive switching (RS) behavior and conduction mechanisms of Ag/SF-Ag NP/Si memristors with varying Ag NP concentrations. I-V measurements confirm stable RS characteristics across 100 cycles, with consistent set and reset voltages. Increasing Ag NP concentration enhances conductive filament formation, leading to sharper switching transitions and a higher HRS/LRS ratio, w-hich increases from 43 (0 wt% Ag NP) to 4.6 × 104 (10 wt% Ag NP). Log(I)-log(V) analysis reveals a conduction transition from Ohmic to Poole-Frenkel mechanisms, indicating improved charge percolation. Reliability tests show stable LRS values, while HRS exhibits greater variation at higher Ag NP concentrations. These results demonstrate that Ag NPs play a crucial role in optimizing memristor performance, improving switching characteristics, and enhancing reliability. The findings suggest that Ag/SF-Ag NP/Si memristors are promising for high-performance resistive memory and neuromorphic computing applications.

Bioinspired Artificial Intelligent Nociceptive Alarm System Based on Fibrous Biomemristors

With the advancement of modern medical and brain-computer interface devices, flexible artificial nociceptors with tactile perception hold significant scientific importance and exhibit great potential in the fields of wearable electronic devices and biomimetic robots. Here, a bioinspired artificial intelligent nociceptive alarm system integrating sensing monitoring and transmission functions is constructed using a silk fibroin (SF) fibrous memristor. This memristor demonstrates high stability, low operating power, and the capability to simulate synaptic plasticity. As a result, an artificial pressure nociceptor based on the SF fibrous memristor can detect both fast and chronic pain and provide a timely alarm in the event of a fall or prolonged immobility of the carrier. Further, an array of artificial pressure nociceptors not only monitors the pressure distribution across various parts of the carrier but also provides direct feedback on the extent of long-term pressure to the carrier. This work holds significant implications for medical support in biological carriers or targeted maintenance of electronic carriers.

Emerging Robust Polymer Materials for High-Performance Two-Terminal Resistive Switching Memory

Facing the era of information explosion and the advent of artificial intelligence, there is a growing demand for information technologies with huge storage capacity and efficient computer processing. However, traditional silicon-based storage and computing technology will reach their limits and cannot meet the post-Moore information storage requirements of ultrasmall size, ultrahigh density, flexibility, biocompatibility, and recyclability. As a response to these concerns, polymer-based resistive memory materials have emerged as promising candidates for next-generation information storage and neuromorphic computing applications, with the advantages of easy molecular design, volatile and non-volatile storage, flexibility, and facile fabrication. Herein, we first summarize the memory device structures, memory effects, and memory mechanisms of polymers. Then, the recent advances in polymer resistive switching materials, including single-component polymers, polymer mixtures, 2D covalent polymers, and biomacromolecules for resistive memory devices, are highlighted. Finally, the challenges and future prospects of polymer memory materials and devices are discussed. Advances in polymer-based memristors will open new avenues in the design and integration of high-performance switching devices and facilitate their application in future information technology.

Applications of biomemristors in next generation wearable electronics

With the rapid development of mobile internet and artificial intelligence, wearable electronic devices have a great market prospect. In particular, information storage and processing of real-time collected data are an indispensable part of wearable electronic devices. Biomaterial-based memristive systems are suitable for storage and processing of the obtained information in wearable electronics due to the accompanying merits, i.e. sustainability, lightweight, degradability, low power consumption, flexibility and biocompatibility. So far, many biomaterial-based flexible and wearable memristive devices were prepared by spin coating or other technologies on a flexible substrate at room temperature. However, mechanical deformation caused by mechanical mismatch between devices and soft tissues leads to the instability of device performance. From the current research and practical application, the device will face great challenges when adapting to different working environments. In fact, some interesting studies have been performed to address the above issues while they were not intensively highlighted and overviewed. Herein, the progress in wearable biomemristive devices is reviewed, and the outlook and perspectives are provided in consideration of the existing challenges during the development of wearable biomemristive systems.

Enzymatic Crosslinked Silk Fibroin Hydrogel for Biodegradable Electronic Skin and Pulse Waveform Measurements

The development of a portable, controllable, and environmentally friendly electronic skin (e-skin) is highly desirable; however, it presents a major challenge. Herein, a biocompatible, biodegradable, and easily usable hydrogel was designed and fabricated as e-skin to enable the transmission of information regarding the spatial pressure distribution. Silk fibroin (SF) was used as the hydrogel skeleton, which endowed the hydrogel with intelligent mechanical sensitivity. During its conditioning in weakly acidic media, the density of the enzymatic crosslink increased and a dense network was formed due to the formation of covalent/hydrogen bonds. Additionally, a conductive SF/polyvinyl alcohol (PVA) hybrid film was molded as a flexible electrode after graphite deposition. The above SF sensing unit based on SF hydrogels and SF/PVA hybrid films showed high strain sensitivity (4.78), fast responsiveness (<0.1 s), good cycling stability (≥10,000), excellent biocompatibility, and biodegradability. Importantly, a coplanar 8 × 8 pixel SF-based e-skin array was successfully fabricated and applied for 3D signal transmission of the object. The SF-based e-skin was capable of precisely tracking the changes in the pulse pressure, the movement of the finger joint, and the vibrations of the vocal cord. Therefore, the current findings provide a solid foundation for future studies exploring the next generation of electronic devices.

Carbonized Silk Nanofibers in Biodegradable, Flexible Temperature Sensors for Extracellular Environments

Temperature is one of the key parameters for activity of cells. The trade-off between sensitivity and biocompatibility of cell temperature measurement is a challenge for temperature sensor development. Herein, a highly sensitive, biocompatible, and degradable temperature sensor was proposed to detect the living cell extracellular environments. Biocompatible silk materials were applied as sensing and packing layers, which endow the device with biocompatibility, biodegradability, and flexibility. The silk-based temperature sensor presented a sensitivity of 1.75%/°C and a working range of 35-63 °C with the capability to measure the extracellular environments. At the bending state, this sensor worked at promising response of cells at different temperatures. The applications of this developed silk material-based temperature sensor include biological electronic devices for cell manipulation, cell culture, and cellular metabolism.

Bio-memristors based on silk fibroin

Bio-memristors constitute candidates for the next generation of non-volatile storage and bionic synapses due to their biocompatibility, environmental benignity, sustainability, flexibility, degradability, and impressive memristive performance. Silk fibroin (SF), a natural and abundant biomaterial with excellent mechanical, optical, electrical, and structure-adjustable properties as well as being easy to process, has been utilized and shown to have potential in the construction of bio-memristors. Here, we first summarize the fundamental mechanisms of bio-memristors based on SF. Then, the latest achievements and developments of pristine and composited SF-based memristors are highlighted, followed by the integration of memristive devices. Finally, the challenges and insights associated with SF-based bio-memristors are presented. Advances in SF-based bio-memristors will open new avenues in the design and integration of high-performance bio-integrated systems and facilitate their application in logic operations, complex circuits, and neural networks.

Nonmulberry silk proteins: multipurpose ingredient in bio-functional assembly

The emerging field of tissue engineering and regenerative medicines utilising artificial polymers is facing many problems. Despite having mechanical stability, non-toxicity and biodegradability, most of them lack cytocompatibility and biocompatibility. Natural polymers (such as collagen, hyaluronic acid, fibrin, fibroin, and others), including blends, are introduced to the field to solve some of the relevant issues. Another natural biopolymer: silkworm silk gained special attention primarily due to its specific biophysical, biochemical, and material properties, worldwide availability, and cost-effectiveness. Silk proteins, namely fibroin and sericin extracted from domesticated mulberry silkwormBombyx mori, are studied extensively in the last few decades for tissue engineering. Wild nonmulberry silkworm species, originated from India and other parts of the world, also produce silk proteins with variations in their nature and properties. Among the nonmulberry silkworm species,Antheraea mylitta(Indian Tropical Tasar),A. assamensis/A. assama(Indian Muga), andSamia ricini/Philosamia ricini(Indian Eri), along withA. pernyi(Chinese temperate Oak Tasar/Tussah) andA. yamamai(Japanese Oak Tasar) exhibit inherent tripeptide motifs of arginyl glycyl aspartic acid in their fibroin amino acid sequences, which support their candidacy as the potential biomaterials. Similarly, sericin isolated from such wild species delivers unique properties and is used as anti-apoptotic and growth-inducing factors in regenerative medicines. Other characteristics such as biodegradability, biocompatibility, and non-inflammatory nature make it suitable for tissue engineering and regenerative medicine based applications. A diverse range of matrices, including but not limited to nano-micro scale structures, nanofibres, thin films, hydrogels, and porous scaffolds, are prepared from the silk proteins (fibroins and sericins) for biomedical and tissue engineering research. This review aims to represent the progress made in medical and non-medical applications in the last couple of years and depict the present status of the investigations on Indian nonmulberry silk-based matrices as a particular reference due to its remarkable potentiality of regeneration of different types of tissues. It also discusses the future perspective in tissue engineering and regenerative medicines in the context of developing cutting-edge techniques such as 3D printing/bioprinting, microfluidics, organ-on-a-chip, and other electronics, optical and thermal property-based applications.