Multifunctional Electronics Research Articles

Flexible MXene-Decorated Fabric with Interwoven Conductive Networks for Integrated Joule Heating, Electromagnetic Interference Shielding, and Strain Sensing Performances

Although flexible and multifunctional textile-based electronics are promising for wearable devices, it is still a challenge to seamlessly integrate excellent conductivity into textiles without sacrificing their intrinsic flexibility and breathability. Herein, the vertically interconnected conductive networks are constructed based on a meshy template of weave cotton fabrics with interwoven warp and weft yarns. The two-dimensional early transition metal carbides/nitrides (MXenes), with unique metallic conductivity and hydrophilic surfaces, are uniformly and intimately attached to the preformed fabric via a spray-drying coating approach. Through adjusting the spray-drying cycles, the degree of conductive interconnectivity for the fabrics is precisely tuned, thereby affording highly conductive and breathable fabrics with integrated Joule heating, electromagnetic interference (EMI) shielding and strain sensing performances. Interestingly, triggered by the interwoven conductive architecture, the MXene-decorated fabrics with a low loading of 6 wt % (0.78 mg cm-2) offer an outstanding electrical conductivity of 5 Ω sq-1. The promising electrical conductivity further endows the fabrics with superior Joule heating performance with a heating temperature up to 150 °C at a supply voltage of 6 V, excellent EMI shielding performance, and highly sensitive strain responses to human motion. Consequently, this work offers a novel strategy for the versatile design of multifunctional textile-based wearable devices.

Tl2O/WTe2 van der Waals heterostructure with tunable multiple band alignments

Two-dimensional van der Waals heterostructures (vdWHs) with tunable band alignment can be very useful for developing minimized multifunctional and controllable devices, but so far they are scarcely reported. Here, using first-principles calculations, we systematically investigate the electronic properties of Tl2O/WTe2 vdWH. Our results indicate that it is a direct bandgap semiconductor harboring a straddling type-I band alignment, with the conduction band minimum (CBM) and valence band maximum (VBM) both from two-dimensional WTe2. Interestingly, upon introducing feasible external strain or electric field, its band alignment can be easily transformed into staggered type-II, with CBM and VBM separated in different layers, achieving the long-sought tunable multiple band alignments. Along with this, the intriguing direct-to-indirect bandgap transition is also achieved in Tl2O/WTe2 vdWH. Our work thus provides a promising candidate in the field of two-dimensional multifunctional and controllable electronics.

Carbon nanotube dual-material gate devices for flexible configurable multifunctional electronics

Electronic devices with configurability to providing multiple functions are of great interests for their superior adaptability to the ever-changing and multifarious application scenarios. Here, we report flexible integrated circuits (ICs) possessing configurable functions constructed with dual-material gate (DMG) devices based on carbon nanotube thin films, which can serve as either transistors or diodes, on a 2-μm-thick parylene substrate. When configured as a transistor, the DMG device has great advantages over the normal-gated (NG) devices regarding the current on/off ratio (Ion/Ioff), the subthreshold swing (SS) and the drain-induced barrier lowering (DIBL) due to the regulated energy band distribution in channel area. When operating as a diode, a typical DMG device demonstrates a sufficient rectification ratio of 8×104 and a diode-on-current of over 26 μA. Scalable manufacturing of DMG devices was also demonstrated with great uniformity both in diode and transistor configurations. Finally, multifunctional integrated circuits, which can dynamically switch their function from rectifier to follower or from OR gate to voltage adder by changing controlling signals, were constructed. The functional-configurability, together with scalable manufacturing and the realization on ultrathin flexible substrates, will open up great opportunity for the future environmentally-adaptive system in the field of flexible electronics.

Toward Multifunctional Electronics: Flexible NBT-Based Film with a Large Electrocaloric Effect and High Energy Storage Property.

Advances in smart and wearable devices are driving innovations in multifunctional flexible materials at a tremendous pace. Here, drawing support from the unique flexible fluorophlogopite mica platform, we present a promising all-inorganic bendable Mn-modified 0.65(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-0.35SrTiO3 (NBBST) film with dual use in electrocaloric (EC) refrigeration and energy storage via a cost-effective transfer-free process. An appreciable room-temperature EC effect with adiabatic temperature change of 12 K and isothermal entropy of 18 J K-1 kg-1 was realized in the NBBST film, which benefits from the large change in dipolar ordering near depolarization temperature. Also, the film exhibits a broad operating temperature span over 25 °C because of its relaxor feature. Most importantly, the film can maintain a high EC performance either under bending deformation at 5 mm radius or after undergoing 104 bending-unbending cycles. Meanwhile, the flexible NBBST film possesses good energy storage property with a recoverable energy density of 56 J cm-3 and an efficiency of 66%. This is the first example of a lead-free all-inorganic multifunctional film capacitor toward the flexible EC refrigeration and energy storage devices. This work shows bright prospects in the emerging flexible e-market.

Hierarchical elastomer tuned self-powered pressure sensor for wearable multifunctional cardiovascular electronics

Wearable pressure sensors, as essential components of flexible wearable electronics, may play important roles in early diagnosis and mortality prevention for cardiovascular healthcare. However, traditional self-powered pressure sensors can hardly obtain both high sensitivity and wide pressure range, which makes perceiving both cardiac and vascular signals in a wearable self-powered way challenging as these physiological signals not only have imperceptible changes but also span a broad pressure range. Here, we develop a flexible hierarchical elastomer tuned self-powered pressure sensor, which achieves both high-sensitivity and wide pressure range, showing a high sensitivity of 7.989 V kPa−1 and wide pressure range of 0.1–60 kPa simultaneously. Fast response (40 ms) and high signal noise ratio (38 db) with good stability are also achieved. We demonstrate that the self-powered pressure sensor can not only sensitively monitor pulse, artery and heart condition but also monitor the wide range blood pressure, which satisfies the diverse needs of wearable cardiovascular healthcare. As most of the pressure related to human interface is less than 50 kPa, we envision the sensor holds great potential in wearable electronics, mobile healthcare and human-machine interaction.

Spatially controlled lateral heterostructures of graphene and transition metal dichalcogenides toward atomically thin and multi-functional electronics.

Edge contacts between two-dimensional (2D) materials in the in-plane direction can achieve minimal contact area and low contact resistance, producing atomically thin devices with improved performance. Particularly, lateral heterojunctions of metallic graphene and semiconducting transition metal dichalcogenides (TMDs) exhibit small Schottky barrier heights due to graphene's low work-function. However, issues exist with the fabrication of highly transparent and flexible multi-functional devices utilizing lateral heterostructures (HSs) of graphene and TMDs via spatially controlled growth. This review demonstrates the growth and electronic applications of lateral HSs of graphene and TMDs, highlighting key technologies controlling the wafer-scale growth of continuous films for practical applications. It deepens the understanding of the spatially controlled growth of lateral HSs using chemical vapor deposition methods, and also contributes to the applications that depend on the scale-up of all-2D electronics with ultra-high electrical performance.

Integrated multifunctional flexible electronics based on tough supramolecular hydrogels with patterned silver nanowires

A hybrid conductive hydrogel system was facilely integrated with complex circuits. The obtained hydrogel electronics show excellent mechanical and electrical performances, enable monitoring tensile strain, pressure, and temperature.

Multiscale porous elastomer substrates for multifunctional on-skin electronics with passive-cooling capabilities.

In addition to mechanical compliance, achieving the full potential of on-skin electronics needs the introduction of other features. For example, substantial progress has been achieved in creating biodegradable, self-healing, or breathable, on-skin electronics. However, the research of making on-skin electronics with passive-cooling capabilities, which can reduce energy consumption and improve user comfort, is still rare. Herein, we report the development of multifunctional on-skin electronics, which can passively cool human bodies without needing any energy consumption. This property is inherited from multiscale porous polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) supporting substrates. The multiscale pores of SEBS substrates, with characteristic sizes ranging from around 0.2 to 7 µm, can effectively backscatter sunlight to minimize heat absorption but are too small to reflect human-body midinfrared radiation to retain heat dissipation, thereby delivering around 6 °C cooling effects under a solar intensity of 840 W⋅m-2 Other desired properties, rooted in multiscale porous SEBS substrates, include high breathability and outstanding waterproofing. The proof-of-concept bioelectronic devices include electrophysiological sensors, temperature sensors, hydration sensors, pressure sensors, and electrical stimulators, which are made via spray printing of silver nanowires on multiscale porous SEBS substrates. The devices show comparable electrical performances with conventional, rigid, nonporous ones. Also, their applications in cuffless blood pressure measurement, interactive virtual reality, and human-machine interface are demonstrated. Notably, the enabled on-skin devices are dissolvable in several organic solvents and can be recycled to reduce electronic waste and manufacturing cost. Such on-skin electronics can serve as the basis for future multifunctional smart textiles with passive-cooling functionalities.

Non-woven fabric electrodes based on graphene-based fibers for areal-energy-dense flexible solid-state supercapacitors

Abstract Nowadays, lightweight, flexible, and wearable sustainable electric-power sources have attracted increasing attention due to the rapid development of portable electronics. Graphene fiber fabrics, as newly discovered carbon textiles, have exhibited attractive properties for wearable power devices. How to realize scalable construction of non-woven graphene-based fabric electrodes with high areal capacitance is challenging for portable electronics. Here, a novel coagulation bath fabrication technique was firstly reported to prepare reduced graphene oxide fiber fabrics (rGOFFs) for areal-energy-dense supercapacitors. The as-prepared rGOFFs showed high flexibility and conductivity. The symmetric supercapacitors (SCs) assembled with rGOFFs (95 μm) based fabric electrodes performed a high specific gravimetric capacitance (Cm) of 285 F/g at 0.1 A/g and 220 F/g at 1 A/g. The areal capacitance (Ca) of rGOFFs (220 μm) based electrode reached up to 2812 mF/cm2 at 1 mA/cm2. After electrochemical deposition of polyaniline (PANI) on rGOFFs (220 μm) substrate, the Ca of rGOFF@PANI – 220 μm based electrode was intensified to 3828 mF/cm2 at 1 mA/cm2 (172 F/cm3). The symmetric all-solid-state SCs showed an energy density from 28 μWh/cm2 (254 μW/cm2) to 11 μWh/cm2 (4950 μW/cm2). Overall, the as-designed rGOFFs based fabric electrodes and their fabrication techniques are of great potential for the next-generation multi-functional textile electronics.

Intrinsic Dipole Coupling in 2D van der Waals Ferroelectrics for Gate‐Controlled Switchable Rectifier

AbstractMiniaturization of device elements, such as ferroelectric diodes, depends on the downscaling of ferroelectric film, which is also crucial for developing high‐density information storage technologies of ferroelectric random access memories (FeRAMs). Recently emerged ferroelectric two‐dimensional (2D) van der Waals (vdWs) layered materials bring an additional opportunity to further increase the density of FeRAMs. A lateral, switchable rectifier is designed and fabricated based on atomically thin 2D α‐In2Se3 ferroelectric diodes, thus breaking the thickness limitation of conventional ferroelectric films and achieving an unprecedented level of miniaturization. This is realized through the interrelated coupling between out‐of‐plane and in‐plane dipoles at room temperature; that is, horizontal polarization reversal can be effectively controlled through a vertical electric field. Being further explored as a switchable rectifier, the obtained maximum value of rectification ratio for the α‐In2Se3 based ferroelectric diode can reach up to 2.5 × 103. These results indicate that 2D ferroelectric semiconductors can offer a pathway to develop next‐generation multifunctional electronics.

Multifunctional Ultrastretchable Printed Soft Electronic Devices for Wearable Applications

AbstractMultifunctionality is a major development trend in flexible stretchable wearable electronics, requiring integration of electrical conductivity, sensing performance, and heating management on a portable electronic device. Herein, the silver fractal dendrites (Ag FDs) conductive ink is formulated and deposited into the polystyrene–block–polyisoprene–block–polystyrene (SIS) thin films by a simple and cost‐effective transfer‐printing method for preparing the patterned multifunctional wearable electronics (MWEs). The MWEs based on Ag FDs ink‐38 wt% exhibit high electrical conductivity (4.86 × 105 S m−1), excellent sensing property (highly stretchability of 500% with a maximum gauge factor (GF) of 659.5), low‐voltage driving Joule heating performance (heated to 52.3 °C at 1 V), and good mechanical stability. As strain sensors, the MWEs have been successfully used to monitor the bending motion of the six major joints in the human body. As Joule heaters, the MWEs have been successfully used for thermochromism and hyperthermia. The developed MWEs prepared by a simple and low‐cost transfer‐printing possess highly promising application for next‐generation multifunctional and smart wearable electronics.

Droplets as Carriers for Flexible Electronic Devices.

Coupling soft bodies and dynamic motions with multifunctional flexible electronics is challenging, but is essential in satisfying the urgent and soaring demands of fully soft and comprehensive robotic systems that can perform tasks in spite of rigorous spatial constraints. Here, the mobility and adaptability of liquid droplets with the functionality of flexible electronics, and techniques to use droplets as carriers for flexible devices are combined. The resulting active droplets (ADs) with volumes ranging from 150 to 600 µL can conduct programmable functions, such as sensing, actuation, and energy harvesting defined by the carried flexible devices and move under the excitation of gravitational force or magnetic force. They work in both dry and wet environments, and adapt to the surrounding environment through reversible shape shifting. These ADs can achieve controllable motions at a maximum velocity of 226 cm min−1 on a dry surface and 32 cm min−1 in a liquid environment. The conceptual system may eventually lead to individually addressable ADs that offer sophisticated functions for high‐throughput molecule analysis, drug assessment, chemical synthesis, and information collection.

Tailor-Made Engineering of Bioinspired Inks for Writing Barcode-like Multifunctional Sensory Electronics

This letter reports on a novel cost-efficient and multifunctional barcode-like sensors array (BLSA) printed with a conductive bioinspired smart ink. The conductive ink (P@G ink), which can be further chemically engineered with different organic ligands, was generated via facile one-pot hydrothermal reduction of graphene oxide (GO) in dopamine (DA) as coreductan Usingvarious chemical derivatives of the P@G inks on a flexible substrate (e.g., Kapton), a highly integrated BLSA as well as smart nose/tongue mimic array were generated for simultaneous sensing and distinguishing of complex physical and chemical stimuli, including temperature, light, air pressure, relative humidity, and volatile organic compounds (VOCs). Due to these very attractive features, the reported P@G ink-based BLSA would have the potential for unique opportunities regarding “all-in-one”—yet cost-effective—disposable electronics and sensors.

Realizing efficiency improvement of polymer solar cells by using multi-functional cascade electron transport layers

Abstract Contact property between metal oxide electron transport layer (ETL) and active layer is one of the key factors to the performance of polymer solar cells (PSCs). To achieve better lattice matching and fewer defects, indium trioxide (In2O3) and zinc oxide (ZnO) (In2O3/ZnO) were used as the inorganic composite ETL, combining with an organic material PCBM as interface layer to obtain homogeneous phase separation of the active layer. The resulting device demonstrates a high fill factor of 69.83% and power conversion efficiency of 9.036% for PTB7:PC71BM based PSCs. Moreover, the acceptor material of PCBM serving as interface layer can interact with donor material of active layer to promote the exciton dissociation. This study provides a new method to improve the performance of PSCs by using multi-functional cascade electron transport layers.

Electronics system thermal management optimization using finite element and Nelder-Mead method

The demand for high-performance, smaller-sized, and multi-functional electronics component poses a great challenge to the thermal management issues in a printed circuit board (PCB) design. Moreover, this thermal problem can affect the lifespan, performance, and the reliability of the electronic system. This project presents the simulation of an optimal thermal distribution for various samples of electronics components arrangement on PCB. The objectives are to find the optimum components arrangement with minimal heat dissipation and cover small PCB area. Nelder-Mead Optimization (NMO) with Finite Element method has been used to solve these multi-objective problems. The results show that with the proper arrangement of electronics components, the area of PCB has been reduced by 26% while the temperature of components is able to reduce up to 40%. Therefore, this study significantly benefits for the case of thermal management and performance improvement onto the electronic product and system.

A comparative study of two graphene based elastomeric composite sensors

Flexible and stretchable multifunctional electronics is expected to be one of the most active research areas in the next decade. In this work, we fabricate graphene based flexible film sensors using two different matrices; polydimethylsiloxane (PDMS) and epoxy. A graphene platelet (GnP) refers to a nanosheet that consists of a few stacked graphene layers, mostly below ~10 nm in thickness. The mechanical, electrical and thermal properties of the fabricated composite films were evaluated. The morphology showed a good dispersibility of GnPs into the PDMS and epoxy matrices. The percolation threshold for GnP/PDMS and GnP/epoxy composite film was achieved at 3.19 vol% and 1.08 vol%, respectively. The fabricated composite films showed improvements in thermal conductivity for GnP/PDMS and GnP/epoxy composite film by 147% and 444%, respectively. The Young's modulus for GnP/epoxy system showed a significant increase by 1344% as compared to GnP/PDMS system, whose increment was by 144%. Upon pressure implication, bending and torsional deformation, GnP/PDMS system demonstrated a better electrical response and flexibility and simultaneously, showed a good stretchability by producing maximum strain up to 25%. The GnP/PDMS system is sensitive to temperature in a wide temperature range (−25 °C–163 °C), and is more suitable as a temperature sensor in cryogenic and high temperature environment than GnP/epoxy system. On the other hand, the GnP/epoxy produced higher repeatability during fatigue testing, emphasizing that GnP/epoxy composite films are highly durable as a strain sensor. This research has enlightened on the importance of selecting the optimum matrix, which is a key factor that determines the overall superior functionality of a flexible sensor.

Noninvasive Urea Monitoring Using a Flexible Electrochemical Sweat Based Sensor

With the development of technology in healthcare systems, interest in a wearable, portable, and even implantable device is growing, allowing health indicators to be read by direct skin contact [1], [2]. The non-invasive sensing platform overcomes the inconvenience of the conventional monitoring system and enabling easy and quick medical diagnosis in real time [3]. Urea is a major metabolite of the human body in a form of nitrogen, a key biomarker above the renal failure, dehydration, and hepatic issues [4], [5]. Urea detection is conceivable from serum, urine, and sweat in the body. The concentration of urea in the sweat is higher than that of serum so sweat based urea sensor can substitute the current pricking test method [6]. Higher levels of urea in sweat are also essential notices because they are correlated with uremia [7]. To sense the non-electric active of urea, the present method uses an enzyme in electrochemical sensors. The enzyme-based sensor consists of an enzyme (urease) and a mediator, which distinguishes the urease-catalyzed hydrolysis products [8]. However, the enzymatic sensor is complex, unstable, and costly, so non-enzyme sensors are better suited for wearable sensor devices. Nickel-based catalysts with nanostructures, large surface area, good electrical conductivity, and low cost are the best nominees for urea detection as they oxidize urea without enzymes [9]. Recently, a polymer-type substrate has been utilized for the flexible and wearable sensor device which requires porous and conductive polymers. Herein, we investigated a facile approach to form nickel oxyhydroxide with metal (metal-NiOOH) based flexible electrochemical sensor by electrospinning method. The morphology and the structure of the metal-NiOOH catalysts were observed using transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. The metal-NiOOH catalysts with polymer showed excellent flexibility and competent linear sensitivity to urea electrooxidation in the physiological concentration area. A comprehensive investigation of the performances regarding metal-NiOOH as a catalyst in a sweat-based sensor will be presented. References Feiner, Ron, et al. "Engineered hybrid cardiac patches with multifunctional electronics for online monitoring and regulation of tissue function." Nature materials 15.6 (2016): 679. Liu, Yuhao, Matt Pharr, and Giovanni Antonio Salvatore. "Lab-on-skin: a review of flexible and stretchable electronics for wearable health monitoring." ACS nano 11.10 (2017): 9614-9635. Pickup, John C., et al. "In vivo glucose monitoring: the clinical reality and the promise." Biosensors and Bioelectronics 20.10 (2005): 1897-1902. D'Apolito, Maria, et al. "Urea-induced ROS cause endothelial dysfunction in chronic renal failure." Atherosclerosis 239.2 (2015): 393-400. Thudichum, J. L. W. "On the analysis of urea in urine for clinical purposes." British medical journal 1.38 (1857): 788 Stefaniak, Aleksandr B., and Christopher J. Harvey. "Dissolution of materials in artificial skin surface film liquids." Toxicology in Vitro 20.8 (2006): 1265-1283. Kazory, Amir. "Emergence of blood urea nitrogen as a biomarker of neurohormonal activation in heart failure." The American journal of cardiology 106.5 (2010): 694-700. Liu, Yan-Ling, et al. "Flexible electrochemical urea sensor based on surface molecularly imprinted nanotubes for detection of human sweat." Analytical chemistry 90.21 (2018): 13081-13087. Mahshid, Sahar Sadat, et al. "Template-based electrodeposition of Pt/Ni nanowires and its catalytic activity towards glucose oxidation." Electrochimica Acta 58 (2011): 551-555. Acknowledgement This work was supported by Agency for Defense Development (ADD) as global cooperative research for high performance and light weight bio-urine based fuel cell (UD160050BD) and the Ocean University of China-Auburn University (OUC-AU) Grants program.

Local Crack-Programmed Gold Nanowire Electronic Skin Tattoos for In-Plane Multisensor Integration.

Sensitive, specific, yet multifunctional tattoo-like electronics are ideal wearable systems for "any time, any where" health monitoring because they can virtually become parts of the human skin, offering a burdenless "unfeelable" wearing experience. A skin-like, multifunctional electronic tattoo made entirely from gold using a standing enokitake-mushroom-like vertically aligned nanowire membrane in conjunction with a programmable local cracking technology is reported. Unlike previous multifunctional systems, only a single material type is needed for the integrated gold circuits involved in interconnects and multiplexed specific sensors, thereby avoiding the use of complex multimaterials interfaces. This is possiblebecause the programmable local cracking technology allows for the arbitrary fine-tuning of the properties of elastic gold conductors from strain-insensitive to highly strain-sensitive simply by adjusting localized crack size, shape, and orientations-a capability impossible to achieve with previous bulk cracking technology. Furthermore, in-plane integration of strain/pressure sensors, anisotropic orientation-specific sensors, strain-insensitive stretchable interconnects, temperature sensors, glucose sensors, and lactate sensors without the need of soldering or gluing are demonstrated. This strategy opens a new general route for the design of next-generation wearable electronic tattoos.

Magnetic Liquid Metal (Fe-EGaIn) Based Multifunctional Electronics for Remote Self-Healing Materials, Degradable Electronics, and Thermal Transfer Printing.

Flexible materials with the ability to be bent, strained, or twisted play a critical role in soft robots and stretchable electronics. Although tremendous efforts are focused on developing new stretchable materials with excellent stability, inevitable mechanical damage due to long term deformation is still an urgent problem to be tackled. Here, a magnetic healing method based on Fe‐doped liquid metal (Fe‐GaIn) conductive ink via a noncontact way is proposed. Further, multifunctional flexible electronics are designed with combined performances of superior remote self‐healing under magnetic field, water‐degradable, and thermal transfer printing, which attribute to three parts of the materials including Fe‐GaIn conductive ink, degradable PVA substrate, and adhesive fructose. The as‐made light emitting diodes (LED) circuit is demonstrated with both structural and functional repairing after single or multipoint damage. The self‐healing time from multipoint damage is pretty fast within 10 s. Due to the water‐soluble PVA film, the recycling process is simple via immersing into water. Through heating, the electric circuit on fructose can be transferred to other flexible substrate with high efficiency, which broadens the practical applications of the present system. The novel and multifunctional electronics hold great promise for self‐healing electronics, transient electronics, and soft robots.

Mimicking Human and Biological Skins for Multifunctional Skin Electronics

AbstractElectronic skin (e‐skin) technology is an exciting frontier to drive the next generation of wearable electronics owing to its high level of wearability, enabling high accuracy to harvest information of users and their surroundings. Recently, biomimicry of human and biological skins has become a great inspiration for realizing novel wearable electronic systems with exceptional multifunctionality as well as advanced sensory functions. This review covers and highlights bioinspired e‐skins mimicking perceptive features of human and biological skins. In particular, five main components in tactile sensation processes of human skin are individually discussed with recent advances of e‐skins that mimic the unique sensing mechanisms of human skin. In addition, diverse functionalities in user‐interactive, skin‐attachable, and ultrasensitive e‐skins are introduced with the inspiration from unique architectures and functionalities, such as visual expression of stimuli, reversible adhesion, easy deformability, and camouflage, in biological skins of natural creatures. Furthermore, emerging wearable sensor systems using bioinspired e‐skins for body motion tracking, healthcare monitoring, and prosthesis are described. Finally, several challenges that should be considered for the realization of next‐generation skin electronics are discussed with recent outcomes for addressing these challenges.