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Climbing-inspired twining electrodes using shape memory for peripheral nerve stimulation and recording

Authors:Yingchao Zhang1,2, and Xue Feng1,2*

Peripheral neuromodulation has been widely used throughout clinical practices and basic neuroscience research. However, the mechanical and geometrical mismatches at current electrode-nerve interfaces and complicated surgical implantation often induce irreversible neural damage, such as axonal degradation. Here, compatible with traditional 2D planar processing, we propose a 3D twining electrode by integrating stretchable mesh-serpentine wires onto a flexible shape memory substrate, which has permanent shape reconfigurability (from 2D to 3D), distinct elastic modulus controllability (from ~100 MPa to ~300 kPa) and shape memory recoverability at body temperature. Similar to the climbing process of twining plants, the temporarily flattened 2D stiff twining electrode can naturally self-climb onto nerves driven by 37 oC normal saline, and form 3D flexible neural interfaces with minimal constraint on the deforming nerves. In vivo animal experiments, including right vagus nerve stimulation for reducing the heart rate and action potential recording of the sciatic nerve, demonstrate the potential clinical utility.

A Synapse-inspired Structural System for Highly Stretchable Electronic Skin

Authors:Jinsheng Zhao, Mingxing Shi

The pressure sensation is the core of haptics, which can be achieved by pressure sensor in an electronic skin. Although varieties of multifunctional sensors can be fabricated by adopting diverse microstructures and functional materials, achieving an electronic skin with superior sensing capabilities under large-scale deformations is rarely reported previously. Herein, inspired by the microstructure of synapse in the nervous system, a highly stretchable electronic skin comprising of synapse-inspired structural system is designed and fabricated. The electronic skin possesses stable response and long-term durability in sensing pressure due to the improved strain isolation and restrained interfacial failure, no matter what deformations the electronic skin may undergo, such as stretching, bending, or even twisting. Experimental studies and finite element analyses show that the mechanical properties allow this electronic skin to apply in large motions including bending states of fingers and wrists. This advanced development of electronic skin demonstrates potential applications in intelligent robots, bionic prostheses, health monitoring, human-machine interface and other fields.

Melt Processing Complementary Semiconducting Polymer Blends for Organic Field-Effect Transistors

Authors:Yan Zhao*

Complementary semiconducting polymer blends (c-SPBs), composed of a matrix polymer with conjugation-break spacers along the polymer backbone and a fully conjugated polymer that functions as a tie chain, was recently proposed and established by our group. Compared with traditional fully conjugated polymer, c-SPBs have low and tunable melting points, enhanced solubility and decent electronic performance. These properties make melt processing—a proven technology in the plastic thin film industry—applicable for c-SPBs based devices. Here we introduce melt-processable c-SPB and develop a solvent-free process for fabricating organic field-effect transistors (OFETs, Figure 1). The melt-processed devices exhibited an average mobility of 0.4 cm2V−1s−1 and current on/off ratios higher than 105. In-situ temperature- dependent grazing incidence X-ray diffraction (GIXRD) and charge transport measurements provide the evidence that the c-SPB has a reversible morphology and device performance. Based on the reversible feature of melt processing, thermally healable OFETs were further demonstrated. This study opens up a new venue to melt-processable semiconducting polymers and bodes well for melt-processed organic electronics.

A Multifunctional Stretchable Sensor for Continuous Monitoring Long-term Leaf Physiology and Microclimate

Authors:Yicong Zhao*, Shenghan Gao*, Jia Zhu#, Jiameng Li*, Hang Xu*, Kexin Xu†, Huanyu Cheng#, Xian Huang*

Communication with plants to understand their growth mechanisms and interaction with surrounding environment may improve production yield in agriculture and facilitate prevention of plant diseases and negative influence of environmental stress[1]. Typical sensing technologies in plant biology and precision agriculture largely rely on techniques with low spatial and temporal resolutions, unable to determine localized variation in leaf physiology and microenvironments[2, 3]. Here, techniques to develop multifunctional stretchable leaf-mounted sensor have been developed to offer optimized adaptability to plant growth and monitor leaf physiological and environmental conditions in continuous and highly sensitive manners. The multifunctional leaf sensor contains multiple heterogeneous sensing elements made of metal, carbon nanotube matrix and silicon (Figure 1a), leading to temperature, hydration, light illuminance, and strain sensing capabilities on a leaf (Figure 1b). The entire sensor can withstand different deformations and grow together with the host leaf in a measurement period of 7 days (Figure 1c).
The sensor can be connected to a miniaturized multifunctional sensing circuit equipped with wireless transfer capability to conduct remote data transmission(Figure 2a). Indoor experiments are conducted to demonstrate the multifunctional monitoring ability of the sensor in real situations (Figure 2b-e). As shown in temperature measurement result (Figure 2b), the sensor can timely respond to four different external conditions that induce rapid temperature changes as large as 4.9 °C in local environment. The sensor is also able to monitor temperature changes that caused by natural conditions, resulting in a slow room temperature change of 5.4 °C in a day. It can be observed that the sensor has very sensitive responses to in-door lighting as well as external sunlight (Figure 2c). Its responses closely follow the variation of sunlight during the day and instantly adapt to the change in in-door lighting after the light has been switched off. The hydration sensing element has also demonstrated stable responses to slow hydration changes on the leaf as well as rapid environmental humidity changes caused by fog generation and water spraying (Figure 2d). The result of strain sensing indicates that the leaf grew steadily during the test (Figure 2e). It is noticeable that growth of the leaf is mainly in the width (y-direction), causing large deformation (15.5%) of the sensor in length as compared with 2.4% strain in width. These experimental results indicate that the multifunctional stretchable sensor holds the promise to advance monitoring techniques in plant biology and precision agriculture, resulting in improved capability to record slow and subtle physiological changes in plants and plant/environment interaction.

ECG Signal Analysis Based on Flexible ECG Detectors

Authors:Kunwei Zheng, Xue Feng*

Diseases of the human are usually accompanied by abnormal changes in certain physiological parameters, such as a cold usually accompanied by an increase in body temperature, and cardiovascular disease is usually accompanied by changes in blood pressure.
Electrocardiogram (ECG) is a physiological parameter produced by the electrical activity of the heart transmitted to the surface of the skin. Since the heart is the most important organ in the human body, it is responsible for transporting blood to the body and regulating the body's internal environment. Changes of the body should also be reflected in the activity of the heart and on the ECG signal.
As their advantages, flexible electronic devices can detect human physiological signals for days, including ECG signals. This has great research value for the analysis of some intermittent diseases, such as atrial fibrillation and ventricular fibrillation caused by various diseases.
In this work, the ECG signals obtained based on flexible electronic devices are restored, analyzed and processed, and various types of valuable eigenvalues are extracted, and combined with various primary diseases and physiological fatigues of the human body through various algorithms. Connection between them is established and a basis for the diagnosis of primary disease and fatigue based on ECG signals is given.

Full Printed Flexible Capacitive Sensor for Non-contact Respiratory Monitoring

Authors:Yanan Zheng*#†, Zhe Yu*#†, Yiwei Liu*#, Shang Jie*#, Run-Wei Li*#

Respiration is an important indicator of human health. Unusual respiratory patterns are a critical symptom of many diseases, such as sleep apnea hypopnea syndrome (SAHS), asthma, chronic obstructive pulmonary disease (CODP) and anemia.[1] At present, the detection of respiration mainly uses a resistive strain sensor. The sensor senses respiration through deformation, so it must be closely attached to the human skin, which is not only uncomfortable to wear, but also prone to skin irritation.[2, 3] In this paper, a highly sensitive capacitive sensor is prepared by full printed method. The sensor can be directly printed on the clothes, and the non-contact detection of respiratory can be realized by detecting small changes of the bioelectric field generated by the human body. [4] The maximum detection distance is 10 cm, and the relative change rate of capacitance caused by respiratory exceeds 0.2% when the detection distance is 5 cm. In short, this paper reports a new and promising sensor device for long real-time detection of respiratory.

Batteryless NFC Based Flexible Smart Packaging for Meat Quality and Open Status Inspection

Authors:Haoyu Zhou, Siying Li, Sujie Chen, Xiaojun Guo *

In this work, a batteryless near field communication (NFC) based flexible smart packaging patch was implemented for inspecting the freshness of the meat and the open status of the packaging. The system consists of an NFC chip, a flexible ammonia sensor and a flexible anti-open sensor as shown in Fig. 1. The designed NFC chip consists of analog front-end as sensor interfaces, wireless transmission module for data exchage with smart phone and an EEPROM for data storage. The wireless communication is compatible with ISO14443 protocol and the chip communicates in passive mode of NFC. The NH3 sensor was fabricated on polyethylene terephthalate (PET) using dimethyl sulfoxide (DMSO) doped poly(3,4-ethylene dioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) film as sensitive material [1,2]. The anti-open sensor was fabricated on fragile paper using PEDOT:PSS to form the memory code circuit [3]. Ultra-low power consumption of the sensors allow the whole system to be operated under batteryless conditions. Fig. 2(a) shows that the measured response of the NH3 sensor agrees well with the that obtained via the Keithley source meter 6430. The anti-open sensor readout results at ‘open’ and ‘unopen’ status via NFC also remain very stable under thermal endurance test for one week.

Controlled buckling and postbuckling behaviors of thin film devices suspended on an elastomeric substrate with trapezoidal surface relief structures

Authors:Honglei Zhou*, Weiyang Qin*, Qingmin Yu*#, Furong Chen*, Xudong Yu*, Huanyu Cheng†, Huaping Wu&

The wavy structure is a simple, practical, and promising structural design scheme widely used in the field of flexible and stretchable electronics. In the development of the strategies to enable stretchable characteristics in the device, buckling of thin film devices suspended on an elastomeric substrate with surface relief structures provides an alternative tactic for applications that require both high areal coverage and large stretchability without compromising electric performance (e.g., flexible photovoltaics, batteries, supercapacitors, etc.). In this study, we utilize the energy method to reveal the mechanical mechanisms of controlled buckling and postbuckling behaviors of the stiff thin film devices suspended on the elastomeric substrate with trapezoidal surface relief structures (Figure 1). Both two- and three-dimensional models are explored to simulate the buckling behaviors of the thin film devices in the finite element analysis (FEA). Theoretical predictions of the buckling profile and the maximum strain in the thin film devices are compared reasonably well with those obtained from the FEA. The influences of thin film width and the contact width (between the thin film and the structured substrate) on the amplitude and the maximum strain of the buckled thin film devices are discussed. Results show that the amplitude of the buckled thin film device decreases as the contact width increases, whereas the maximum strain in the buckled thin film devices increases with the increasing contact width. The elastic stretchability of the buckled film/substrate system is also discussed. The validated analytic tool provides a powerful basis for further experimental designs.

Investigation on the Electrical Breakdown Strength of Soft Dielectrics

Authors:J. Zhou, L. Jiang

Soft dielectrics, as one category of electroactive materials, are capable of producing exceptionally large deformation under electrical stimuli [1]. Due to this unique property, soft dielectrics have extensive applications, such as artificial muscles, soft robots, actuators, oscillators and energy harvesters [2]. In these applications, soft dielectrics are subjected to an electric field, which can be realized by applying direct voltage or spraying charges on their surfaces. For safety reasons, one critical issue of using soft dielectrics lies in determining their electrical breakdown strength. However, as discussed in the literature, the electrical breakdown strength of soft dielectrics can be affected by various factors, such as elstic properties, deformation and original thickness of the material [3]. On the other hand, robust methods accounting for all these effects to predict the electrical breakdown strength of soft dielectrics are still lacking. Therefore, this work aims to develop a novel method to determine the electrical breakdown strength of various types of soft dielectrics. Among the existing studies on the cause of the electrical breakdown, the theories that attribute it to the evolution of instrinsic defects in the material have attracted much attention. When considering that the electrical breakdown of soft dielectrics is linked to the evolution of the intrinsic defects, configurational mechanics appears to be a suitable tool to determine the electrical breakdown strength. First proposed by Eshelby [4], configurational mechanics focuses on the evolution of the defects within the material. Based on the theory of configurational mechanics, this work presents a novel and universal method to predict the electrical breakdown strength of soft dielectrics. With the developed method, electrical breakdown data measured from different experiment set-ups can be well captured. Moreover, the developed method can be implemented in finite element simulation for soft dielectrics with different configurations. This work is expected to provide helpful solutions to the long-standing issue of using soft dielectrics and insights into imrpoving the electrical breakdown strength of soft dielectrics, which is also a significant topic for their applications.

The Flexible and Multifunctional PANI Electrochemical Device based on highly stable Ag@Pt AHNW Transparent Electrode

Authors:Kailing Zhou, Hao Wang, Qianqian Zhang, and Hui Yan

In industry development, as a common sense, the stability of stainless steels and active metal against chemical and electrochemical corrosion have been successfully solved by introducing alloying elements with high thermodynamic stability to form solid solution[1, 2]. This inspires us to solve the critical issue with the weak stability of Ag NW based transparent electrodes by alloy method. Sun et al. have found that Ag based alloy can be prepared by a galvanic displacement reaction between Ag nanowires and precursors of more noble metals (e.g. Au, Pt, Pd)[3]. For the Ag based transparent electrode, the long nanowires can form an effective electron percolation network with superior optical transmittance and electrical conductivity compared to the shorter ones[4]. However, it still exists a challenge to synthesize large-area and long Ag NW based alloy nanowires with intact one-dimensional structure through conventional solution approaches[5] since the reaction process is complex and impacted by many factors [6- 8]. Here, long, complete and uniform Ag@Pt alloy-walled hollow nanowire (Ag@Pt AHNW) is facilely obtained by combining electrochemical reaction technique and galvanic replacing mechanism. The electrode based on Ag@Pt AHNW owns high conductivity with satisfactory transparency, high thermal stability, remarkable mechanical flexibility and high resistance to chemical corrosion and electrochemical oxidation. The efficacy of the Ag@Pt AHNW based transparent electrode is demonstrated by applying it into PANI device for multifunctional electrochemical applications.

Balloon with integrated flexible electronics for electrical stimulation and bioelectrical signal detection in pelvic floor dysfunction therapy

Authors:Tao Zhou1*, Haoran Fu1, Ying Chen1, Shurong Dong2, Shengming Wang2

In clinical treatment for pelvic floor dysfunction (PFD), electrical stimulation and biofeedback associated treatment are widely used for pelvic floor muscle dysfunctions (PFMDs), which is considered as a main reason for stress urinary incontinence (SUI) in female patients[1,2]. Utilize electrode design on the medical inflatable balloon is an effective way to realize the biofeedback combined with electrical stimulation therapy for PFD patients. To make electrical stimulate therapy more effective and obtain the human physiological electrical signal at the same time during the treatment and recovery of PFD patients, present work take advantage of flexible electrode and circuit design on the surface of medical inflatable balloon: referring to some reported works[3,4], the inflating and deflating behavior of the balloon is numerically simulated by finite element method firstly in present study. According to the simulation results, deformation at latitudinal direction is larger than that at longitudinal direction, so the longitudinal direction layout of serpentine interconnects is considered to improve the stretchable ability of balloon electrode system. In order to make the deformation of electrode match the deformation of balloon when the balloon interacts with body, avoid the separation and relative displacement of electrode from the balloon, and consider the feasibility of device fabrication, a reasonable paper-cut design is chosen for electrode. The mechanical feasibility of the paper-cut designed electrode is verified by FEM simulations and experiments.

Supersensitive All-Fabric Pressure Sensors Using Printed Textile Electrode Arrays for Human Motion Monitoring and Human-Machine Interaction

Authors:Ziqiang Zhou, Ying Li, and Lu Li

Integrating the advantages of ultrahigh sensitivity, good breathability, low-cost and large-area fabrication process, and facile integration with other functional devices is full of challenges for wearable pressure sensors. Here, a novel all-fabric piezoresistive pressure sensor is designed with a bottom interdigitated textile electrode screen-printed by silver paste and a top bridge of AgNWs-coated cotton fabric. The entire fabrication process is facile, economical and suitable for large-scale integrated production. Benefiting from the high porous microstructure , large surface roughness and ultra-low resistance of the conductive fabric, our piezoresistive pressure sensors show excellent detection performance, including extra-high sensitivity of 2.46 ×104 kPa-1 to 5.65×105 kPa-1 over a wide pressure regime (0-30 kPa), giant on/off ratio of ≈106, fast response time (6 ms), and low detection limit (0.76 Pa). Thanks to these merits, the devices not only have the ability to detect various tiny signals of the human body, but also can be widely applied for human-computer interactive system as a real-wearable sensor platform, which was demonstrated by playing the piano and computer games.

A highly shape-adaptive coaxial fiber based electronic skin for self-powered tactile sensing

Authors:Miaomiao Zhu*, Mengna Lou#, Zhaoling Li #

As the most promising candidate to emulate natural skin for reconstructing the tactile sensation of damaged skin or endowing the perception of prosthesis and robotics, electronic skin can mimic the functions of biological skin through converting external stimuli into electronic signals. Accompanied by the fast and massive development of wearable devices, electronic skin with a highly shape adaptive structure are required. In addition to the conformal materials such as fibrous membranes and fabrics, self-powered system is also an important emerging trend to achieve the flexible and deformable electronic skin due to it without bulky batteries. Here we design a coaxial fiber based piezoelectric electronic skin for imitating the human somatosensory system without external hard power supply. We prove that the coaxial structure can enhance the piezoelectric properties of the fibers by synergistic effect. The sensitivity of as-fabricated electronic skin is 11.04 mV•kPa-1, which can respond quickly to the stimulus of external force, and it also possess a superior durability. Furthermore, it has been demonstrated that such flexible electronic skin can detect and quantify various joint-related human motions. Additionally, when enlarging it into the desired pressure sensing matrix, it hold the capability for discriminating the different shape of the objects, which can applied in real-time tactile mapping. We envision that this fiber based electronic skin has substantial demand and application in the development of artificial systems, such as healthcare monitoring technologies advanced smart robotics, human-machine interfaces and next-generation prosthetics. And this emerging intelligent wearable electronics is expected to accelerated the intelligentialize process of our life.

Thin, Durable And High-Performance Flexible Batteries for Flexible Electronics

Authors:Minshen Zhu*, Oliver G. Schmidt* #

Flexible electronics have surged in the past several decades, which remarkably advance sustainability, health, security, and connectivity of humanity.1 Meanwhile, the rapid developments of flexible electronics demand high-performance flexible batteries that can deliver large and dynamically stable energy for flexible devices. In addition, it is desirable that the flexible batteries feature thin thickness and high durability under high-level mechanical deformations. Such requirements are difficult to achieve in conventional batteries because slight flexing can cause serious delamination and damage to the components inside. Therefore, novel materials and designs are crucial to render batteries flexible.
In this presentation, we present high-performance flexible batteries based on flexible electrodes constructed by interpenetrating novel materials with carbon nanotubes. Firstly, the layered MXene is functionalized by the KMnO4 and complexed with carbon nanotubes to form a parallel circuitry at nanoscale, which enables ultrahigh rate capability (50% capacity retention when the current density increases from 0.1 A/g to 10 A/g) of the aqueous zinc ion batteries (Figure 1). Meanwhile, carbon nanotubes serve as the matrix for the freestanding electrodes, thus rendering the flexibility for the batteries. The as-fabricated flexible batteries feature ultrathin thickness (0.1 mm for the entire battery) and durable output under high-level mechanical deformations.
In addition to the aqueous zinc ion batteries, a flexible lithium ion battery is designed by coupling two interpenetrating assemblies: rolled-up NiFe2O4 nanomembranes and commercial LiMn2O4 nanoparticles embedded in carbon nanotube matrix. Stabilized by the PAAm/gelatin based artificial interface, the freestanding anode (NiFe2O4-carbon nanotubes) shows high capacity of 612 mAh/g based on the entire mass of the freestanding electrode. Such high performance enables high energy output of 295 Wh/kg at the power density of 14000 W/kg for the flexible lithium ion battery. In addition, excellent stability of the full flexible battery is achieved as no capacity fade is observed in 1000 charge/discharge cycles (Figure 2). Moreover, the intrinsic flexibility of the freestanding electrodes enables the fabrication of a flexible lithium-ion battery, which shows high stability even under harsh mechanical deformations.

Current page 7, Total 7 pages, 134 records
  • Abstract submission
    May 1, 2019
    Extended to May 10, 2019
  • Notification of acceptance
    May 10, 2019
    Extended to May 15, 2019
  • Early registration
    May 20, 2019
  • Registration payment
    June 20, 2019
    Extended to June 30, 2019
  • Exhibition payment
    June 30, 2019
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Shaoxu He   Email: heshaoxu@gfeit.org

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