Foot deformity and quality of life among independently ambulating children with spina bifida in South Korea.

BACKGROUND: Children with spina bifida (SB) may have congenital or acquired foot deformities due to neurological defects in the spinal cord. As the musculoskeletal system keeps growing, foot deformities can develop or become aggravated. Thus, healthcare providers should provide constant monitoring and proper orthopedic management. Since foot deformities can affect not only the gait but also the daily life of children with SB, it is necessary to investigate the impact of foot deformities on everyday life. The purpose of this study was to examine the relationship between foot deformity and health-related quality of life (HRQoL) among independently ambulating children with SB. METHODS: This cross-sectional study examined the associations between foot deformity and HRQoL using two patient-reported outcome measures (Oxford Ankle Foot Questionnaire, Pediatric Outcomes Data Collection Instrument) in 93 children with SB aged 7-18 years between January 2020 and July 2021. RESULTS: Children with foot deformity (n = 54) reported lower scores in all subscales (physical, school and play, emotional, and footwear) of the Oxford Ankle Foot Questionnaire for children than those without foot deformity (n = 39; p < 0.001). Additionally, in terms of the Pediatric Outcomes Data Collection Instrument, children with foot deformity also reported poorer scores in four subscales (transfer and basic mobility, sports and physical functioning, comfort and pain, happiness with physical functioning; p < 0.001) than those without foot deformity, whereas upper extremity functioning was not significantly affected. Children with foot deformities, particularly those with bilateral foot deformities, equinus deformities, or mixed deformities, which are different types of right and left foot deformities, have a lower perceived HRQoL (p < 0.05). CONCLUSIONS: Among independently ambulating children with SB, those with foot deformities showed lower HRQoL. Moreover, children with foot deformities tend to have other clinical problems, including bladder and bowel dysfunction. Therefore, orthopedic management should consider the multifaceted factors that affect children's daily life and HRQoL.

Stretchable, Skin-Attachable Electronics with Integrated Energy Storage Devices for Biosignal Monitoring.

The demand for novel electronics that can monitor human health, for example, the physical conditions of individuals, during daily life using different techniques from those used in traditional clinic diagnostic facilities is increasing. These novel electronics include stretchable sensor devices that allow various biosignals to be directly measured on human skin without restricting routine activity. The thin, skin-like characteristics of these devices enable stable operation under various deformations, such as stretching, pressing, and rubbing, experienced while attached to skin. The mechanically engineered design of these devices also minimizes the inconvenience caused by long-term wear owing to conformal lamination on the skin. The final form of a skin-attachable device must be an integrated platform with an independent and complete system containing all components on a single, thin, lightweight, stretchable substrate. To fabricate fully integrated devices, various aspects, such as material design for deformable interconnection, fabrication of high-performance active devices, miniaturization, and dense arrangement of component devices, should be considered. In particular, a power supply system is critical and must be combined in an electromechanically stable and efficient manner with all devices, including sensors. Additionally, the biosignals obtained by these sensors should be wirelessly transmitted to external electronic devices for free daily activity. This Account covers recent progress in developing fully integrated, stretchable, skin-attachable devices by presenting our strategies to achieve this goal. First, we introduce several integration methods used in this field to build stretchable systems with a special focus on the utilization of liquid gallium alloy. The unique characteristics and patterning process of liquid metal are summarized. Second, various skin-attachable sensors, including strain, pressure, with enhanced sensitivity and mechanical properties are discussed along with their applications for biosignal monitoring. Dual mode sensors that simultaneously detect temperature and pressure signals without interference are also introduced. Third, we emphasize supercapacitors as promising, efficient energy storage devices for power management systems in wearable devices. Supercapacitors for skin-attachable applications should have a high performance, such as high operation voltage, high energy and power densities, cyclic and air stability and water resistance. For this, strategies to select novel materials for electrode, electrolyte, and encapsulation are suggested. Several approaches to fabricate stretchable supercapacitor systems are also presented. Finally, we introduce recent examples of skin-attachable, stretchable electronics that integrate sensors, power management devices, and wireless data transfer functions on a single elastomer substrate. Conventional wireless technologies, such as near-field communications (NFC) and Bluetooth, are incorporated in miniaturized features on the devices. To date, much research has been performed in this field, but there are still many technologies to develop. The performance of individual devices and mass fabrication techniques should be enhanced. We expect that future electronic devices with fully integrated functions will include advanced human-machine interaction capabilities and expand the overall abilities of the human body.

A Flexible Loudspeaker Using the Movement of Liquid Metal Induced by Electrochemically Controlled Interfacial Tension.

A flexible liquid metal loudspeaker (LML) is demonstrated consisting of a gallium-based eutectic liquid metal (Galinstan) and basic aqueous electrolyte (NaOH(aq) ). The LML is driven by liquid metal motion induced by the electrochemically controlled interfacial tension of the Galinstan in NaOH(aq) electrolyte under an applied alternating current (AC) voltage. The fabricated LML produces sound waves in the human audible frequency band with a sound pressure level of ≈40-50 dB at 1 cm from the device and exhibits mechanical stability under bending deformation with a bending radius of 3 mm. Various sounds can be generated with the LML from a single tone to piano notes and human voices. To understand the underlying mechanism of sound generation by the LML, motion analyses, sound measurements, and electrical characterization are conducted at various frequencies. For the first time, this work suggests a new type of liquid metal-based electrochemically driven sound generator in the field of flexible acoustic devices that can be applied to future wearable electronics.

Super-Absorbent Polymer Valves and Colorimetric Chemistries for Time-Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin-Mounted Soft Microfluidics.

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.

Sub-5 nm nanostructures fabricated by atomic layer deposition using a carbon nanotube template.

The fabrication of nanostructures having diameters of sub-5 nm is very a important issue for bottom-up nanofabrication of nanoscale devices. In this work, we report a highly controllable method to create sub-5 nm nano-trenches and nanowires by combining area-selective atomic layer deposition (ALD) with single-walled carbon nanotubes (SWNTs) as templates. Alumina nano-trenches having a depth of 2.6 âˆ¼ 3.0 nm and SiO2 nano-trenches having a depth of 1.9 âˆ¼ 2.2 nm fully guided by the SWNTs have been formed on SiO2/Si substrate. Through infilling ZnO material by ALD in alumina nano-trenches, well-defined ZnO nanowires having a thickness of 3.1 âˆ¼ 3.3 nm have been fabricated. In order to improve the electrical properties of ZnO nanowires, as-fabricated ZnO nanowires by ALD were annealed at 350 °C in air for 60 min. As a result, we successfully demonstrated that as-synthesized ZnO nanowire using a specific template can be made for various high-density resistive components in the nanoelectronics industry.

Topcoat-Assisted Perpendicular and Straightly Parallel Coexisting Orientations of Block Copolymer Films.

Highly ordered perpendicular orientation and straightly parallel orientation coexisting polystyrene-block-polydimethylsiloxane (PS-b-PDMS) cylindrical microdomains with 10 nm width can be realized by using polyvinyl acetate as a partially dewetted topcoat and solvent annealing with acetone vapor. During solvent annealing, the swelled topcoat begins to dewet and the dewetting rim sweeps the surface of the block copolymer films to align the cylindrical microdomains with the direction of dewetting propagation. However, the wetted region of the topcoat/PS-b-PDMS film forms with a perpendicular orientation due to reduced surface tension and sufficient concentration gradient in the solvent evaporation step. The orientational changes (perpendicular/straightly parallel orientation) in the dewetted/wetted area are also investigated according to the vapor pressure of solvent annealing. The degree of directionality of the swept PS-b-PDMS films according to the distance from the dewetting front, which is equivalent with time after sweeping, is examined. To control the direction of dewetting and complex structures within a specific area, an imprinting process is introduced to form topographical line-space patterns in the topcoat and perpendicular/parallel orientation of BCP patterns in the line-space patterns, respectively.

Fabrication of stretchable single-walled carbon nanotube logic devices.

The fabrication of a stretchable single-walled carbon nanotube (SWCNT) complementary metal oxide semiconductor (CMOS) inverter array and ring oscillators is reported. The SWCNT CMOS inverter exhibits static voltage transfer characteristics with a maximum gain of 8.9 at a supply voltage of 5 V. The fabricated devices show stable electrical performance under the maximum strain of 30% via forming wavy configurations. In addition, the 3-stage ring oscillator demonstrates a stable oscillator frequency of ∼3.5 kHz at a supply voltage of 10 V and the oscillating waveforms are maintained without any distortion under cycles of pre-strain and release. The strains applied to the device upon deformation are also analyzed by using the classical lamination theory, estimating the local strain of less than 0.6% in the SWCNT channel and Pd electrode regions which is small enough to keep the device performance stable under the pre-strain up to 30%. This work demonstrates the potential application of stretchable SWCNT logic circuit devices in future wearable electronics.

Self-Assembled Tamoxifen-Selective Fluorescent Nanomaterials Driven by Molecular Structural Similarity.

Most supramolecular systems were discovered by using a trial-and-error approach, leading to numerous synthetic efforts to obtain optimal supramolecular building blocks for selective guest encapsulation. Here, we report a simple coassembly strategy for preparing tamoxifen-selective supramolecular nanomaterials in an aqueous solution. The synthetic amphiphile molecule, 1,1,2,2-tetraphenylethylene (TPE), promotes large tamoxifen aggregate disassembly into smaller, discrete aggregates such as ribbon-like and micellar assemblies in coassembled solutions, enhancing the solubility and dispersion. The TPE moiety exhibits enhanced emission upon tamoxifen interaction, enabling the observation of the coassembled species in an aqueous solution for cell imaging. The tamoxifen-selective fluorescent micelles in the presence of a 1:1 molar ratio of TPE derivative with tamoxifen show enhanced tamoxifen absorption and anticancer effects against MCF-7 breast cancer cells. These supramolecular approaches, based on the coassembly of building blocks with molecular structural similarity, can provide a novel strategy for the efficient development of selective molecular carriers with enhanced biological activities.

Controlling the electronic properties of SWCNT FETs via modification of the substrate surface prior to atomic layer deposition of 10 nm thick Al2O3 film.

We demonstrate the controllability of the electronic transport properties of single-walled carbon nanotube (SWCNT) field effect transistors (FETs) via the use of 10 nm thick atomic-layer-deposited aluminum oxide (Al2O3) gate dielectric films, where the substrate surfaces were modified with differently functionalized self-assembled monolayers (SAMs) prior to their growth, namely SAMs with hydrophobic (-CH3) or hydrophilic (-OH) groups. Al2O3 grown on a hydrophilic surface causes the SWCNT FETs to keep their intrinsic p-type transfer characteristics by alleviating the electron-doping effect originating from defects in the Al2O3 film. However, the SAM with methyl groups increases the defect density of the Al2O3 film, enhancing the n-type transfer characteristics and inducing ambipolar to n-type behavior in the SWCNT FETs. In this work, we find clues about the distribution of charged defects in the Al2O3 film, which strongly influences the transfer characteristics of the SWCNT FETs, by measuring the thickness-dependent flat band voltages.

High performance stretchable UV sensor arrays of SnO2 nanowires.

A high performance, stretchable UV sensor array was fabricated based on an active matrix (AM) device that combined field effect transistors of SWCNTs and SnO2 nanowires. The AM devices provided spatial UV sensing via the individual sensors in the array. SnO2 NW UV sensors showed an average photosensitivity of ∼10(5) and a photoconductive gain of ∼10(6) under very low UV (λ = 254 nm) power intensities of 0.02-0.04 mW cm(-2). The UV sensing performance was not deteriorated by a prestrain of up to 23% induced by radial deformation, consistent with the mechanical analysis.

p-n hetero-junction diode arrays of p-type single walled carbon nanotubes and aligned n-type SnO2 nanowires.

p-n hetero-junction diode arrays were fabricated using specific direct techniques for the transfer of p-type single walled carbon nanotubes (SWCNTs) and aligned n-type SnO2 nanowires (NWs) onto a patterned substrate surface. Their electronic and optoelectronic properties were characterized. Perpendicular crossings of the p- and the n-channels with each other were confirmed by transfer characteristics with respect to the bottom gate. The resulting diode showed a good rectifying behavior with a rectification ratio of over 10² at ±5 V, where the equivalent circuit model of a serially connected diode and resistor was used for analysis of the electrical properties. Both the forward and the reverse currents were observed to increase with the application of a positive gate bias, indicating an n-type gate dependence. Under a forward bias, the dominant contribution of the SnO2 NW channel to the total resistance of the equivalent model is attributed to the n-type gate dependence since the resistance of the n-channel increased with a negative gate bias, resulting in the decrease of the forward current. Under a reverse bias, positive gate increased the concentration of valence electrons in the SWCNTs, enhancing direct tunneling to the conduction band of the SnO2 NWs. High sensitivity to UV irradiation under the reverse bias was also demonstrated with a photosensitivity over 10², suggesting potential applicability of the hetero-junction diodes in optoelectronic devices.

Flexible Thin-Film Speaker Integrated with an Array of Quantum-Dot Light-Emitting Diodes for the Interactive Audiovisual Display of Multi-functional Sensor Signals.

One of the core technologies for wearable electronics is the use of an interactive display device that is attached to the body or clothes to transmit various bio-signals and environmental stimuli to the user. In this study, we report a flexible audiovisual display device consisting of a polyvinylidene difluoride (PVDF) thin-film speaker stacked on an 8 × 8 array of quantum-dot light-emitting diodes (QD-LEDs) and a multi-functional sensor consisting of temperature and ultraviolet (UV) sensors connected to a pressure sensor, allowing the body temperature and UV exposure to be displayed both visually and acoustically. Polydimethylsiloxane is employed as an insulator between the carbon nanotube (CNT)/polyaniline temperature sensor and the ZnO/CNT UV sensor to form a capacitor-type pressure sensor. With the use of a stretchable polymer substrate, liquid metal Galinstan interconnections, and the flexible Au-grid electrodes, both the PVDF speaker and the QD-LED array are stable under repeated cycles of bending deformation with a bending radius of 7.5 mm. By connecting the audiovisual display device to the skin-attached multi-functional sensor, changes in the body temperature and UV exposure are displayed as LED patterns with accompanying acoustic alarms. This study demonstrates the significant potential of our proposed audiovisual monitoring device and multi-functional sensor for use in health-monitoring applications, especially for the elderly and infants requiring prompt care.

p-n homo-junction arrays of aligned single walled carbon nanotubes fabricated by selective patterning of polyethyleneimine film.

We describe the fabrication and electrical performance of p-n homo-junction diode arrays of horizontally aligned single walled carbon nanotubes (SWCNTs). Horizontally aligned SWCNTs grown on stable temperature-cut quartz with a density of ∼ 6 SWCNTs µm(-1) were transferred onto a SiO(2)/Si substrate. After the electrical breakdown, aligned SWCNT field effect transistors (FETs) showed unipolar p-type characteristics with a large current on/off ratio of 10(6) at 1 V and a hole mobility per tube of 1500 cm(2) V(-1) s(-1). Spin-coating of polyethyleneimine (PEI) onto p-type SWCNT FETs showed the n-type transfer characteristics. Patterning of spin-coated PEI film enabled the fabrication of p-n homo-junction arrays of aligned SWCNTs in an easy way, where the rectifying behavior was observed with a rectification ratio of ∼ 10(4) at ± 2 V. A comparative study with a p-n homo-junction of random networks of SWCNTs confirmed the advantage of aligned SWCNTs for applications in high performance electronic devices.

Micromechanics and advanced designs for curved photodetector arrays in hemispherical electronic-eye cameras.

The fabrication of a hemispherical electronic-eye camera with optimized designs based upon micromechanical analysis is reported. The photodetector arrays combine layouts with multidevice tiles and extended, non-coplanar interconnects to improve the fill factor and deformability, respectively. Quantitative comparison to micromechanics analysis reveals the key features of these designs. Color images collected with working cameras demonstrate the utility of these approaches.

Experimental and modeling studies of imaging with curvilinear electronic eye cameras.

Model calculations and the experimental measurements of the imaging properties of planar, hemispherical, and elliptic parabolic electronic eye cameras are compared. Numerical methods for comprehensive full field calculations of image formation are enabled by use computationally efficient modes. Quantitative agreement between these calculations and experimentally measured images of test patterns reveals advantages of curvilinear camera systems, and provides guidelines for future designs.

Degradation pattern of SnO(2) nanowire field effect transistors.

The degradation pattern of SnO(2) nanowire field effect transistors (FETs) was investigated by using an individual SnO(2) nanowire that was passivated in sections by either a PMMA (polymethylmethacrylate) or an Al(2)O(3) layer. The PMMA passivated section showed the best mobility performance with a significant positive shift in the threshold voltage. The distinctive two-dimensional R(s)-µ diagram based on a serial resistor connected FET model suggested that this would be a useful tool for evaluating the efficiency for post-treatments that would improve the device performance of a single nanowire transistor.

Flexible/Stretchable Supercapacitors with Novel Functionality for Wearable Electronics.

With the miniaturization of personal wearable electronics, considerable effort has been expended to develop high-performance flexible/stretchable energy storage devices for powering integrated active devices. Supercapacitors can fulfill this role owing to their simple structures, high power density, and cyclic stability. Moreover, a high electrochemical performance can be achieved with flexible/stretchable supercapacitors, whose applications can be expanded through the introduction of additional novel functionalities. Here, recent advances in and future prospects for flexible/stretchable supercapacitors with innate functionalities are covered, including biodegradability, self-healing, shape memory, energy harvesting, and electrochromic and temperature tolerance, which can contribute to reducing e-waste, ensuring device integrity and performance, enabling device self-charging following exposure to surrounding stimuli, displaying the charge status, and maintaining the performance under a wide range of temperatures. Finally, the challenges and perspectives of high-performance all-in-one wearable systems with integrated functional supercapacitors for future practical application are discussed.

Fabrication of nanowire channels with unidirectional alignment and controlled length by a simple, gas-blowing-assisted, selective-transfer-printing technique.

A printing-based lithographic technique for the patterning of V(2)O(5) nanowire channels with unidirectional orientation and controlled length is introduced. The simple, directional blowing of a patterned polymer stamp with N(2) gas, inked with randomly distributed V(2)O(5) nanowires, induces alignment of the nanowires perpendicular to the long axis of the line patterns. Subsequent stamping on the amine-terminated surface results in the selective transfer of the aligned nanowires with a controlled length corresponding to the width of the relief region of the polymer stamp. By employing such a gas-blowing-assisted, selective-transfer-printing technique, two kinds of device structures consisting of nanowire channels and two metal electrodes with top contact, whereby the nanowires were aligned either parallel (parallel device) or perpendicular (serial device) to the current flow in the conduction channel, are fabricated. The electrical properties demonstrate a noticeable difference between the two devices, with a large hysteresis in the parallel device but none in the serial device. Systematic analysis of the hysteresis and the electrical stability account for the observed hysteresis in terms of the proton diffusion in the water layer of the V(2)O(5) nanowires, induced by the application of an external bias voltage higher than a certain threshold voltage.

Curvilinear electronics formed using silicon membrane circuits and elastomeric transfer elements.

Materials and methods to achieve electronics intimately integrated on the surfaces of substrates with complex, curvilinear shapes are described. The approach exploits silicon membranes in circuit mesh structures that can be deformed in controlled ways using thin, elastomeric films. Experimental and theoretical studies of the micromechanics of such curvilinear electronics demonstrate the underlying concepts. Electrical measurements illustrate the high yields that can be obtained. The results represent significant experimental and theoretical advances over recently reported concepts for creating hemispherical photodetectors in electronic eye cameras and for using printable silicon nanoribbons/membranes in flexible electronics. The results might provide practical routes to the integration of high performance electronics with biological tissues and other systems of interest for new applications.

Co/Pt nanodot arrays fabricated via pulsed laser deposition using the phase-separated diblock copolymer film as a template.

We fabricated hexagonal arrays of Co/Pt nanodots on Si surfaces by pulsed laser deposition (PLD) using cylindrically phase-separated polystyrene-b-poly(methylmethacrylate) (PS-b-PMMA) diblock copolymer thin films as templates after the removal of PMMA. The size and the separation of the nanodots were 23 and 40 nm, respectively, and the density of the nanodots was 1.5 x 10(11)/cm2. The magnetic properties of nanodot arrays measured by vibrating sample magnetometer were compared with those of PLD grown film. The films showed magnetic anisotropy with an easy axis in the in-plane direction, whereas no noticeable anisotropy was observed for nanodot arrays. In addition, the saturation magnetization (Ms) of both the Co/Pt nanodots and the film increased with the Pt content.