Simultaneous Roll Transfer and Interconnection of Flexible Silicon NAND Flash Memory

Deeply Implantable, Shape-Morphing, 3D MicroLEDs for Pancreatic Cancer Therapy

Controlled photooxidation-mediated disruption of collagens in the tumor microenvironment can reduce desmoplasia and enhance immune responsiveness. However, achieving effective light delivery to solid tumors, particularly those with dynamic volumetric changes like pancreatic ductal adenocarcinoma (PDAC), remains challenging and limits the repeated and sustained photoactivation of drugs. Here, 3D, shape-morphing, implantable photonic devices (IPDs) are introduced that enable tumor-specific and continuous light irradiation for effective metronomic photodynamic therapy (mPDT). This IPD adheres seamlessly to the surface of orthotopic PDAC tumors, mitigating issues related to mechanical mismatch, delamination, and internal lesions. In freely moving mouse models, mPDT using the IPD with close adhesion significantly reduces desmoplastic tumor volume without causing cytotoxic effects in healthy tissues. These promising in vivo results underscore the potential of an adaptable and unidirectional IPD design in precisely targeting cancerous organs, suggesting a meaningful advance in light-based therapeutic technologies.

Printing nanoparticle-based isotropic/anisotropic networks for directional electrical circuits

With the demand for integrated nanodevices, anisotropic conductive films are one type of interconnection structure for electronic components, which have been widely used for improving the integration of the system in printed circuit boards. This work presents a template-assisted printing strategy for the fabrication of nanoparticle-based networks with multi electrical properties. By manipulating the microfluid behavior under the guidance of the grid-shaped template, the continuity of liquid bridges can be precisely controlled in two directions. The isotropous circuits with crossbar paths, discrete paths as well as unidirectional paths are obtained, which achieve the switching of on/off states in the circuits. This work demonstrates a new type of directional circuits by the template-assisted printing method, which provides an effective fabrication strategy for electrical components and integrated systems.

An epidermal electronic system for physiological information acquisition, processing, and storage with an integrated flash memory array

Epidermal electronic systems that simultaneously provide physiological information acquisition, processing, and storage are in high demand for health care/clinical applications. However, these system-level demonstrations using flexible devices are still challenging because of obstacles in device performance, functional module construction, or integration scale. Here, on the basis of carbon nanotubes, we present an epidermal system that incorporates flexible sensors, sensor interface circuits, and an integrated flash memory array to collect physiological information from the human body surface; amplify weak biosignals by high-performance differential amplifiers (voltage gain of 27 decibels, common-mode rejection ratio of >43 decibels, and gain bandwidth product of >22 kilohertz); and store the processed information in the memory array with performance on par with industrial standards (retention time of 10⁸ seconds, program/erase voltages of ±2 volts, and endurance of 10⁶ cycles). The results shed light on the great application potential of epidermal electronic systems in personalized diagnostic and physiological monitoring.

A Flash-Induced Robust Cu Electrode on Glass Substrates and Its Application for Thin-Film μLEDs

A robust Cu conductor on a glass substrate for thin-film μLEDs using the flash-induced chemical/physical interlocking between Cu and glass is reported. During millisecond light irradiation, CuO nanoparticles (NPs) on the display substrate are transformed into a conductive Cu film by reduction and sintering. At the same time, intensive heating at the boundary of CuO NPs and glass chemically induces the formation of an ultrathin Cu₂ O interlayer within the Cu/glass interface for strong adhesion. Cu nanointerlocking occurs by transient glass softening and interface fluctuation to increase the contact area. Owing to these flash-induced interfacial interactions, the flash-activated Cu electrode exhibits an adhesion energy of 10 J m^-2 , which is five times higher than that of vacuum-deposited Cu. An AlGaInP thin-film vertical μLED (VLED) forms an electrical interconnection with the flash-induced Cu electrode via an ACF bonding process, resulting in a high optical power density of 41 mW mm^-2 . The Cu conductor enables reliable VLED operation regardless of harsh thermal stress and moisture infiltration under a high-temperature storage test, temperature humidity test, and thermal shock test. 50 × 50 VLED arrays transferred onto the flash-induced robust Cu electrode show high illumination yield and uniform distribution of forward voltage, peak wavelength, and device temperature.

Recent Process of Flexible Transistor-Structured Memory

Flexible transistor-structured memory (FTSM) has attracted great attention for its important role in flexible electronics. For nonvolatile information storage, FTSMs with floating-gate, charge-trap, and ferroelectric mechanisms have been developed. By introducing an optical sensory module, FTSM can be operated by optical inputs to function as an optical memory transistor. As a special type of FTSM, transistor-structured artificial synapse emulates important functions of a biological synapse to mimic brain-inspired memory behaviors and nervous signal transmissions. This work reviews the recent development of the above mentioned FTSMs, with a focus on working mechanism and materials, and flexibility.

Recent Advances in Flexible and Stretchable Sensing Systems: From the Perspective of System Integration

Biological signals generated during various biological processes are critically important for providing insight into the human physiological status. Recently, there have been many great efforts in developing flexible and stretchable sensing systems to provide biological signal monitoring platforms with intimate integration with biological surfaces. Here, this review summarizes the recent advances in flexible and stretchable sensing systems from the perspective of electronic system integration. A comprehensive general sensing system architecture is described, which consists of sensors, sensor interface circuits, memories, and digital processing units. The subsequent content focuses on the integration requirements and highlights some advanced progress for each component. Next, representative examples of flexible and stretchable sensing systems for electrophysiological, physical, and chemical information monitoring are introduced. This review concludes with an outlook on the remaining challenges and opportunities for future fully flexible or stretchable sensing systems.

Influence of Flexibility of the Interconnects on the Dynamic Bending Reliability of Flexible Hybrid Electronics

The growing interest towards thinner and conformable electronic systems has attracted significant attention towards flexible hybrid electronics (FHE). Thin chip-foil packages fabricated by integrating ultra-thin monocrystalline silicon integrated circuits (ICs) on/in flexible foils have the potential to deliver high performance electrical functionalities at very low power requirements while being mechanically flexible. However, only very limited information is available regarding the fatigue or dynamic bending reliability of such chip-foil packages. This paper reports a series of experiments where the influence of the type of metal constituting the interconnects on the foil substrates on their dynamic bending reliability has been analyzed. The test results show that chip-foil packages with interconnects fabricated from a highly flexible metal like gold endure the repeated bending tests better than chip-foil packages with stiffer interconnects fabricated from copper or aluminum. We conclude that further analysis work in this field will lead to new technical concepts and designs for reliable foil based electronics.

Transparent, Flexible, Fatigue-Free, Optical-Read, and Nonvolatile Ferroelectric Memories

Perovskite oxide films are widely used in various commercial industries. However, they are usually prepared at high temperature and in oxygen ambience, detrimental to most transparent and flexible substrates and bottom conductive electrodes such as indium tin oxide (ITO). It remains challenging to integrate perovskite oxides into transparent and flexible electronics. Here, the 1.2 wt % Ag-doped ITO (Ag-ITO) grown on a mica substrate is employed as the bottom electrode, which can withstand high temperature and repeated bending, and then we achieve the transparent, flexible, fatigue-free, and optical-read ferroelectric nonvolatile memories based on the mica/Ag-ITO/Bi_3.25La_0.75Ti₃O₁₂/ITO structures. The as-prepared memories show ∼80% transmittance for visible lights and fatigue-free performance after more than 10⁸ writing/erasing cycles. These performances are stable after repeated bending down to 3 mm in a curvature radius. More importantly, the "1/0" state of the memory can be read out by the photovoltaic current rather than destructive polarization switching, an emergent functionality for many applications. This work substantially promotes the applications of perovskite oxide films in transparent and flexible electronics, including wearable devices.

Fabrication of Simultaneously Implementing "Wired Face-Up and Face-Down Ultrathin Piezoresistive Si Chips" on a Film Substrate by Screen-Offset Printing

We realized the implementation of an ultrathin piezoresistive Si chip and stretchable printed wires on a flexible film substrate using simple screen-offset printing technology. This process does not require a special MEMS fabrication equipment and is applicable to face-up chips where electrodes are formed on the top surface of the chip, as well as to face-down chips where electrodes are formed on the bottom surface of the chip. This fabrication process is quite useful in the field of flexible hybrid electronics (FHE) as a method for mounting and wiring electronic components on a flexible substrate. In this study, we confirmed that face-up and face-down chips could be mounted on polyimide film tape. Furthermore, it was confirmed that the two types of chips could be simultaneously mounted even if they exist on the same substrate. Five-μm-thick piezoresistive Si chips were transferred and wired on a polyimide film tape using screen-offset printing, and a band-plaster type blood pulse sensor was fabricated. Moreover, we successfully demonstrated that the blood pulse could be measured with neck, inner elbow, wrist, and ankle.

Variations of the elastic modulus perpendicular to the surface of rubrene bilayer films

We propose a structural bilayer model successfully explaining the layered nature or characteristics of rubrene films.

Roll-to-roll fabrication of touch-responsive cellulose photonic laminates

Hydroxypropyl-cellulose (HPC), a derivative of naturally abundant cellulose, can self-assemble into helical nanostructures that lead to striking colouration from Bragg reflections. The helical periodicity is very sensitive to pressure, rendering HPC a responsive photonic material. Recent advances in elucidating these HPC mechano-chromic properties have so-far delivered few real-world applications, which require both up-scaling fabrication and digital translation of their colour changes. Here we present roll-to-roll manufactured metre-scale HPC laminates using continuous coating and encapsulation. We quantify the pressure response of the encapsulated HPC using optical analyses of the pressure-induced hue change as perceived by the human eye and digital imaging. Finally, we show the ability to capture real-time pressure distributions and temporal evolution of a human foot-print on our HPC laminates. This is the first demonstration of a large area and cost-effective method for fabricating HPC stimuli-responsive photonic films, which can generate pressure maps that can be read out with standard cameras.

Self-assembled structures are typically demonstrated on small scales under well-controlled lab environments. Here, the authors present a roll-to-roll process for the continuous manufacturing of square-meters of self-assembled cellulose-based mechano-chromic films and demonstrate the recording of pressure profiles generated by foot-imprints in real time.

Flexible, Fatigue-Free, and Large-Scale Bi3.25La0.75Ti3O12 Ferroelectric Memories

Flexible, fatigue-free, large-scale, and nonvolatile memory is an emerging technological goal in a variety of fields, including electronic skins, wearable devices, and other flexible electronics. Perovskite oxide films deposited on rigid substrates (e.g., Si and SrTiO₃) at 500-700 °C and >1.0 Pa oxygen ambience have been widely used in electronic industries. However, their applications in flexible electronics are challenging, if not impossible. Here, the Bi_3.25La_0.75Ti₃O₁₂ ferroelectric films with SrRuO₃ or Pt electrodes were prepared on the two-dimensional mica substrates, and then the flexible Pt/SrRuO₃/Bi_3.25La_0.75Ti₃O₁₂/Pt memories have been achieved through reducing the mica to ∼10 μm thickness. These memories show the saturated polarization of P_s ∼ 20 μC/cm², and either the <1% bending strain or a normal light illumination hardly overcomes the potential barrier among different polarizations which originate from the noncentral symmetry of the atomic structure. As a result, they can undergo 10⁹ write/erase cycles and/or 10000 times bending with 1.4 mm in radius without any fatigue or damage. Furthermore, they can withstand the operation at 20-200 °C or under light illumination. In short, these flexible oxide memories provide comprehensive performance for industrial applications.

Recent Advances in Tactile Sensing Technology

Research on tactile sensing technology has been actively conducted in recent years to pave the way for the next generation of highly intelligent devices. Sophisticated tactile sensing technology has a broad range of potential applications in various fields including: (1) robotic systems with tactile sensors that are capable of situation recognition for high-risk tasks in hazardous environments; (2) tactile quality evaluation of consumer products in the cosmetic, automobile, and fabric industries that are used in everyday life; (3) robot-assisted surgery (RAS) to facilitate tactile interaction with the surgeon; and (4) artificial skin that features a sense of touch to help people with disabilities who suffer from loss of tactile sense. This review provides an overview of recent advances in tactile sensing technology, which is divided into three aspects: basic physiology associated with human tactile sensing, the requirements for the realization of viable tactile sensors, and new materials for tactile devices. In addition, the potential, hurdles, and major challenges of tactile sensing technology applications including artificial skin, medical devices, and analysis tools for human tactile perception are presented in detail. Finally, the review highlights possible routes, rapid trends, and new opportunities related to tactile devices in the foreseeable future.

Organic Ferroelectric-Based 1T1T Random Access Memory Cell Employing a Common Dielectric Layer Overcoming the Half-Selection Problem

Organic electronics based on poly(vinylidenefluoride/trifluoroethylene) (P(VDF-TrFE)) dielectric is facing great challenges in flexible circuits. As one indispensable part of integrated circuits, there is an urgent demand for low-cost and easy-fabrication nonvolatile memory devices. A breakthrough is made on a novel ferroelectric random access memory cell (1T1T FeRAM cell) consisting of one selection transistor and one ferroelectric memory transistor in order to overcome the half-selection problem. Unlike complicated manufacturing using multiple dielectrics, this system simplifies 1T1T FeRAM cell fabrication using one common dielectric. To achieve this goal, a strategy for semiconductor/insulator (S/I) interface modulation is put forward and applied to nonhysteretic selection transistors with high performances for driving or addressing purposes. As a result, high hole mobility of 3.81 cm² V^-1 s^-1 (average) for 2,6-diphenylanthracene (DPA) and electron mobility of 0.124 cm² V^-1 s^-1 (average) for N,N'-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDI-FCN₂ ) are obtained in selection transistors. In this work, we demonstrate this technology's potential for organic ferroelectric-based pixelated memory module fabrication.

Laser-Material Interactions for Flexible Applications

The use of lasers for industrial, scientific, and medical applications has received an enormous amount of attention due to the advantageous ability of precise parameter control for heat transfer. Laser-beam-induced photothermal heating and reactions can modify nanomaterials such as nanoparticles, nanowires, and two-dimensional materials including graphene, in a controlled manner. There have been numerous efforts to incorporate lasers into advanced electronic processing, especially for inorganic-based flexible electronics. In order to resolve temperature issues with plastic substrates, laser-material processing has been adopted for various applications in flexible electronics including energy devices, processors, displays, and other peripheral electronic components. Here, recent advances in laser-material interactions for inorganic-based flexible applications with regard to both materials and processes are presented.