Polyester Substrate Research Articles

Flexible polyester-embedded thermoelectric device with Bi2Te3 and Te legs for wearable power generation

This study presents an approach for powering wearable sensors by integrating nanostructured bismuth telluride (Bi2Te3 and Te legs) into flexible polyester substrates. The choice of polyester as the substrate is because it is widely used in clothing, especially in items such as shirts, blouses, dresses, and sportswear. This enables seamless integration with wearable devices. By capturing wasted body heat, our small and flexible thermoelectric generators (TEGs) offer long-term operation without the need to plug the batteries. We demonstrate the feasibility of using commercially available polyester for reproducible electrochemical deposition of highly oriented Bi2Te3 and Te material. Through electrodeposition, we embed Bi2Te3 and Te legs within the flexible polyester, creating a cost-effective and easily scalable hybrid system for wearable energy harvesting.Our optimized TEG design, which can be worn on the arm or forehead, achieves impressive power density compared to existing state-of-the-art solutions. With a mere 3.5 °C temperature difference, only two pairs of p- and n-type legs, and a thickness of approximately 15 µm, our TEG generates a maximum open circuit voltage of ∼0.1 mV and a maximum power density of ∼0.04 mW·K-1·cm−2. With 250 pairs, 10 mV can be reached. This cost-effective design also integrates electrical contacts, surpassing previous flexible TEG performances. These advancements make our TEGs suitable for driving microwatt-level electronic sensors and open new avenues for efficient energy harvesting in wearable applications.

Conductive graphene-based coagulated composites for electronic printing applications

Graphene is gaining significance in applications such as sensors, antennas, photonics and spintronics. In particular, it is suitable for printing components and circuits affording the properties of high conductivity alongside flexibility, elasticity and wearability. For this application, graphene is typically customised into a fluidic form—ink or paint. This paper reports a novel, economical, scalable methodology for synthesising electrically conductive graphene-based coagulated composite that could be utilised in the above-mentioned applications. Composites are prepared from graphene powder/ink and screen-printing ink (GP–SPI and GI–SPI, respectively) at different mass ratios, and the optimal composition is identified by brush coating on paper in the form of rectangular strips. As a proof of concept, at optimum mass ratios, the GP–SPI and GI–SPI composites exhibit electrical conductivities ranging 0.068–0.702 mS m−1 and 0.0303–0.1746 μS m−1, in order. The as-prepared conductive composites are then screen-printed onto a square with an area of 1 cm2 on ceramic, FR4, glass, paper, polyester and wood substrates. The coagulated GP–SPI and GI–SPI composites are compatible with all these substrates and yield a conductive coating, demonstrating their suitability in multifaceted applications. Furthermore, the method proposed herein eliminates the need for rare/precious expensive materials, state-of-the art equipment, highly skilled personnel and costs associated with the same, thereby broadening the avenues for low-cost, fluidic graphene-based functional composites.

Color Biomimetics in Textile Design: Reproduction of Natural Plant Colors through Instrumental Colorant Formulation.

This paper explores the intersection of colorimetry and biomimetics in textile design, focusing on mimicking natural plant colors in dyed textiles via instrumental colorant formulation. The experimental work was conducted with two polyester substrates dyed with disperse dyes using the exhaustion process. Textiles dyed with different dye colors and concentrations were measured in a spectrophotometer and a database was created in Datacolor Match Textile software version 2.4.1 (0) with the samples' colorimetric properties. Colorant recipe formulation encompassed the definition and measurement of the pattern colors (along four defined natural plants), the selection of the colorants, and the software calculation of the recipes. After textile dyeing with the lowest expected CIELAB color difference (ΔE*) value recipe for each pattern color, a comparative analysis was conducted by spectral reflectance and visual assessment. Scanning electron microscopy and white light interferometry were also used to characterize the surface of the natural elements. Samples dyed with the formulated recipe attained good chromatic similarity with the respective natural plants' colors, and the majority of the samples presented ΔE* between 1.5 and 4.0. Additionally, recipe optimization can also be conducted based on the colorimetric evaluation. This research contributes a design framework for biomimicking colors in textile design, establishing a systematic method based on colorimetry and color theory that enables the reproduction of nature's color palette through the effective use of colorants.

Conformal ultra‐miniaturized frequency selective surface for medical shielding applications

SummaryThis article presents a novel wearable frequency selective surface (FSS) for shielding the communication link of implantable devices with the external environment. The proposed shield blocks a dual‐band frequency operating at 404 MHz and 2.45 GHz in the medical implant communication service (MICS) and industrial, scientific, and medical (ISM) bands. The two distinct stop bands provide a high‐frequency band ratio of 6.02 in an ultra‐miniaturized physical form factor of 0.024λo × 0.024λo, with at least 76.96% miniaturization when compared to the existing art. Each of the unit cells is imprinted on a conformal 50 μm polyester substrate in a symmetrical configuration. The polyester adheres with jean to realize its compatibility with wearable applications. The designed shield system offers a low profile of only 0.00146λo. By suppressing the grating lobe, the proposed shield achieves a high angular stability of 80° and polarization insensitivity of 90° in both transverse electric (TE) and transverse magnetic (TM) modes. The FSS is fabricated and measured results validate its performance. To evaluate the physical insight, an equivalent circuit model (ECM) analysis is done. To ensure durability, the proposed shield system is tested with Amitech SDR04.

Influence of selected parameters of the substrate of a microstrip textile antenna on changes in its resonance frequency under the influence of humidity

Textile antennas are one of the more essential parts of an electronic system incorporated in modern smart garments, used, for instance, for monitoring physiological signals. The article presents the study of the influence of selected parameters of the substrate of a textile microstrip antenna on the changes in its resonant frequency under the influence of changes in humidity. The impact of moisture was investigated for antennas with two different substrates: polyester and cotton. These materials differ significantly in their ability to absorb and release water. The article shows the construction of a measuring stand, measurement results for short and long-term exposure to moisture, and its statistical analysis. The obtained results indicate that textile antennas with a polyester substrate show more stability of the resonance frequency of the antenna compared to the antenna with a cotton substrate, regardless of changes in humidity. It has also been demonstrated that antennas exposed to prolonged, multi-day humidity variations exhibit higher changes in their resonant frequency than antennas subjected to short-term, 1-day variations.

The Influence of Titanium Dioxide (TiO2) Particle Size and Crystalline Form on the Microstructure and UV Protection Factor of Polyester Substrates.

The inclusion of particles in a polymeric substrate to achieve certain properties is a well-known practice. In the case of textile substrates, this practice may deeply affect the structure of the produced yarns, as even a filament with no textile applications can be obtained. In this manuscript, titanium dioxide (TiO2) particles were incorporated into polyester (PET) chips and the influence of these fillers on the properties of yarn and fabric, and the ultraviolet protection factor (UPF) was assessed. For this purpose, rutile and anatase crystalline forms of TiO2, as well as the size of the particles, were evaluated. Moreover, parameters such as mechanical properties, orientation of the macromolecules and thermal behavior were analyzed to ensure that the textile grade is maintained throughout the production process. The results showed that the inclusion of micro- and nanoparticles of TiO2 decreases the molecular weight and tenacity of PET. Also, although orientation and crystallinity varied during the textile process, the resulting heatset fabrics did not present important differences in those parameters. Finally, the attainment of textile-grade PET-TiO2 fabrics with UPF indexes of 50+ with both rutile and anatase and micro- and nano-sized TiO2 forms was demonstrated.

Screen‐printed dual‐band wearable textile antenna incorporated with EBG structure for WBAN communications

SummaryA dual‐band, wearable coplanar microstrip patch antenna (CPW) integrated with electromagnetic bandgap structure (EBG) to operate dual wireless bands at 2.48 GHz industrial, scientific, and medical band (ISM) and 5.2 GHz WLAN. The proposed textile wearable antenna and EBG structure are screen‐printed using silver conductive ink on the cotton polyester substrate (εr = 1.6) for flexible wearable applications. A 3 × 3 EBG array is realized by a concentric square patch surrounded by the annular square ring to reduce back radiation and increase the forward gain and front‐back ratio. The proposed EBG‐backed antenna, compared with the conventional CPW‐fed antenna, improves forward gain from 2.18 to 6.59 dB at 2.48 GHz and 3.5 to 7.03 dB at 5.2 GHz. Moreover, the EBG array is used to isolate the human body from the antenna and reduces the specific absorption rate (SAR). The antenna is performed with a human phantom tissue model, which exhibits a specific absorption rate of 0.12 W/kg, and 0.260 W/kg for 1 g tissue at 2.48 GHz and 5.2 GHz, respectively.

Vapor-phase zeolitic imidazolate framework-8 growth on fibrous polymer substrates

The use of metal-organic frameworks (MOFs) in practical applications is often hindered by synthesis related challenges. Conventional solution-based approaches rely on hazardous solvents and often form powders that are difficult to integrate into practical devices. On the other hand, vapor-phase approaches generally result in MOF films on silicon substrates that make it difficult to characterize the MOF surface area, which is an important quality indicator. We address these challenges by introducing a solvent-free synthesis method to form MOF–fiber composites, which can be more easily integrated into devices. Additionally, these vapor-phase-formed MOF–fiber composites are compatible with Brunauer–Emmett–Teller surface area analysis to characterize MOF quality. Atomic layer deposition is used to form a ZnO film on polypropylene, polyester, and nylon fibrous substrates, which is subsequently converted to zeolitic imidazolate framework-8 (ZIF-8) using 2-methylimidazole vapor. We describe the effects of the ZnO film thickness and MOF conversion conditions on MOF crystallinity and surface area. We report a ZIF-8 surface area of ∼1300 m2/gMOF, which is comparable to reported surface areas of ∼1250–1600 m2/gMOF from conventional synthesis techniques, demonstrating good quality of the solvent-free MOF–fiber composites. We expect these results to extend vapor-phase MOF formation to new, practical substrates for advanced sensing and catalytic applications.

Impact of a precise pH value change on the characteristics of deposited tin monosulphide films onto a flexible substrate

The chemical bath deposition technique (CBD) is considered the cheapest and easiest compared with other deposition techniques. However, it is highly sensitive to effective parameter deposition values such as pH, temperature, and so on. The pH value of the reaction solution has a direct impact on both the nucleation and growth rate of the film. Consequently, this study presents a novel investigation into the effect of a precise change in the pH reaction solution value on the structural, morphological, and photoresponse characteristics of tin monosulphide (SnS) films. The films were grown on a flexible polyester substrate with pH values of 7.1, 7.4, and 7.7. The X-ray diffraction patterns of the grown films at pH 7.1 and 7.4 confirmed their polycrystalline nature. Additionally, an observed alteration in the crystal structure occurred as the pH value increased from 7.1 to 7.4, resulting in a transition from an orthorhombic crystal structure to a cubic crystal structure. In contrast, the XRD pattern of the grown film at pH 7.7 revealed that it was amorphous. The field-emission scanning electron microscopy images revealed a flower-like morphology for the grown film at 7.1, whereas the grown films at 7.4 and 7.7 revealed a grain morphology. The results also showed that the pH values were also having an important effect on the energy gap value (Eg) of films; the Eg values were 1.46, 1.57, and 1.65 eV for pH 7.1, 7.4, and 7.7, respectively. The photodetectors fabricated using grown films exhibited excellent photoresponse characteristics when subjected to near-infrared (750 nm) illumination. It was also demonstrated that the photodetector using the cubic structure film possessed faster response times and greater sensitivity than the photodetector using the orthorhombic structure film.

Naphthyl end-capped bithiophene film on plant-based polyamide-4,10

We report on a vacuum deposited 5,5’-bis(naphth-2-yl)-2,2’-bithiophene (NaT2) film on bio-based polyamide-4,10 (PA410) substrate. The substrate is moderately hydrophobic with dominant dispersive interactions. Nominally 25 nm thick NaT2 films on PA410 adopt lying-down (face-on) crystals that follow island type growth mode. They show charge carrier mobilities 3⋅10−5 cm2/Vs as well as the area normalized photoresponsitivities up to 20 μA/W at 100 V and a light intensity of 78 W/m2. Full coverage is achieved for 50 nm film thickness. This performance matches that of identically prepared films on polyester substrates that are commonly employed in organic electronics. This study shows how photosensitive bithiophenes can be grown on low carbon footprint polyamides, ultimately lowering the carbon footprint of the entire device.

Innovative flexible thermal storage textile using nanocomposite shape-stabilized phase change materials

A novel flexible thermal storage system based on organic phase change materials (PCMs) deposited on a non-woven polyester (PET) substrate is described in this article. Thermally regulating effects were created via encapsulation of polyethylene glycol (PEG) in carbon nanofibers (CNFs) to manufacture a shape-stable phase change material (SSPCM). Improvement in the thermal conductivity (TC) of the system was obtained by incorporating reduced graphite oxide nanoparticles (rGONP) into the CNFs. A new method was applied to load and secure the manufactured SSPCMs on the fibrous substrate so that an acceptable level of flexibility was preserved (change in bending length less than 30%). The sample performance was evaluated by measuring its thermal properties. The physical properties, wash fastness, abrasion resistance, morphology, and PCM leakage of the samples were also assessed. The results point to a good thermal storage ability of the samples with characteristic phase change temperature ranges of 30.1–31.4 °C and 19.2–24.3 °C for melting and freezing, respectively, and a latent heat of 8.9–22.9 J g−1 for meting and 11.2–21.4 J g−1 for freezing. The use of the CNF-rGONP for PEG enhanced the TC of the system by 454%, thus providing a rapid thermal response, and efficiently prevented the leakage of PEG. Finally, the loading and fixation method on the non-woven substrate allowed an acceptable level of durability with less than 4% of weight loss during washing and abrasion tests. This system provides a promising solution for rapid response, flexible thermal storage wearables.

Knittle Pressure Sensor Based on Graphene/Polyvinylidene Fluoride Nanocomposite Coated on Polyester Fabric.

In this paper, a knittle pressure sensor was designed and fabricated by coating graphene/Polyvinylidene Fluoride nanocomposite on the knitted polyester substrate. The coating was carried out by a dip-coating method in a nanocomposite solution. The microstructure, surface properties and electrical properties of coated layers were investigated. The sensors were tested under the application of different pressures, and the corresponding sensor signals were analyzed in terms of resistance change. It was observed that the change in resistance was 55% kPa-1 with a sensitivity limit of 0.25 kPa. The sensor model was created and simulated using COMSOL Multiphysics software, and the model data were favorably compared with the experimental results. This investigation suggests that graphene-based nanocomposites can be used in knittle pressure sensor applications.

Investigation of cyanine-based infrared dyes as calibrants in radiochromic films.

Radiochromic material such as lithium pentacosa-10,12-diynoate (LiPCDA) has been suggested as the radiation-sensitive material for real-time in vivo fiber-optic dosimetry. In this configuration, micron-thick radiochromic coating would measure the absorbed dose, where a major challenge is the uncertainty in the active material thickness, necessitating calibration. A homogeneously incorporated inert infrared (IR) dye, which must also be stable in ambient conditions and against radiolysis, can be added to the radiochromic film to enable optical calibration. This study investigates four commercial cyanine-based dyes (IR-783, IR-806, IR-868, and IR-880) for use as an optical calibrant in fiber-optic radiochromic dosimeters. All dyes were dissolved in water to confirm solubility. IR-783 and IR-806 were dissolved in 10% w/w gelatin solution and coated onto a polyester substrate, which were then sandwiched between two layers of adhesives forming IR-783 and IR-806 films. A second batch of IR dyes in gelatin incorporated the LiPCDA, and was coated onto substrate and sandwiched between adhesive to form IR dye+LiPCDA films. The absorbance spectra of the films were measured periodically (176 and 102 days for IR-dye films, and IR dye+LiPCDA, respectively). The average percentage absorbance, normalized to day 1, was fit to either a single or a double exponential decay model to calculate the spectral stability lifetime (τ1 , τ2 ). Films were irradiated using a 6 MV LINAC beam with a standard setup of 100 source to axis distance (SAD), 10cm×10cm field size and 1.5cm depth. The change in absorbance of the IR-dye+LiPCDA films were measured after they were irradiated to 1, 2, 5, 10, and 20Gy at 3Gy/min. Only IR-783 and IR-806 were sufficiently water soluble. In gelatin matrix, these dyes demonstrated a decrease in absorbance with time for IR-783 and IR-806 dyes, with IR-783 films having an average τ1 =73±7 days and IR-806 films τ1 =7±3 days. When combined with LiPCDA, IR-806 degraded, losing its original peak at ∼820nm. Similarly, IR-783, combined with LiPCDA, showed signs of degradation; however, its original absorbance peak was still observed at ∼800nm. In the IR-783+LiPCDA films, the IR-783 dye had a τ=4±1 days, an order of magnitude faster than the IR-783 with no LiPCDA films. When exposed to x-ray irradiation, the IR-783 dye in the IR-783+LiPCDA films showed no change in absorbance with increasing absorbed dose. In contrast, the LiPCDA in the films responded as expected, increasing in optical density with increased absorbed dose. IR-783 and IR-806 dyes were observed to degrade over time following exponential decay curves. IR-806 could not be combined with the LiPCDA without degrading. The combination of IR-783 with LiPCDA demonstrated single exponential decay behavior at a comparatively faster rate than films that did not have LiPCDA. IR-783 was insensitive to ionizing radiation and thus may be suitable for thickness correction, but an alternative manufacturing procedure may need to be developed.

Evaluation of enzymatic depolymerization of PET, PTT, and PBT polyesters

Millions of tons of waste polyester plastics, including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT), end up in the environment as soil and water contaminants. Recent advances in enzymatic polyester degradation have motivated researchers toward the biorecycling of plastic wastes. Leaf-branch compost cutinase (LCC) enzymes have been proven to be effective in the biodegradation of PET. This study focuses on enzymatic depolymerization of waste PET, PTT, and PBT materials by using an ICCG variant of LCC (LCCICCG) produced from Escherichia coli BL21(DE3). The degradation efficiency of the polyesters was determined by the monomer terephthalic acid (TPA) released from the depolymerization reaction. It was found that the most efficient depolymerization was achieved for PET, followed by PTT and PBT. A kinetic model based on Langmuir adsorption and the Michaelis-Menten equation was developed to describe the enzymatic depolymerization of PET, PTT, and PBT with various enzyme and substrate loadings. The model simulation results revealed that the LCCICCG enzyme loading should be linearly increased as the work capacity of the polyester substrate increases. A specific enzyme loading of 0.91 mg/g PET is suggested to achieve 90% depolymerization of PET within three days. The experimental data and model simulation results can be used to help further engineer the enzyme and process to achieve a complete biodegradation of polyester wastes at a large scale.

Multicolor electrochromic fabric with a simple structure of PEDOT:PSS/DMSO

Smart textiles with highly controllable and tunable color changes have attracted considerable attention because of their promising practical application functionality, such as military clothes, sensors, decorations, and protective purposes like information encryption and alert, including thermochromism, photochromism, electrochromism, etc. Among them, the color variation of stimulus-responsive fabric triggered by electricity is more conveniently and effectively controlled than the color change that relies on stimuli like temperature and ultraviolet radiation. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfo-nate) (PEDOT:PSS) are one kind of the most promising electrochromic materials. Currently, electrochromic fabrics (ECFs) based on PEDOT:PSS is still hindered by relatively poor conductive efficiency and complex structure. Here, we developed a multicolor ECFs with a simplified structure using polyester (PET) fabric, PEDOT:PSS/dimethy sulfoxide (DMSO), ionic liquids as an electrochromic container, a conductive color-changing layer and ion transfer medium, respectively. Therein, PEDOT:PSS enhanced conductivity by changing the conformation with DMSO. The conductive solution PEDOT:PSS/DMSO was coated on the flexible PET substrates and then treated with ionic liquids as a conductive layer and redox reactions functional layer to realize the color-changing. These ECFs exhibited impressive electrochromic behavior with color-changing between light blue and dark blue. Moreover, the device was endowed with hydrophobicity and self-cleaning by spraying commercially available hydrophobic agents. To overcome the monochromatic color-changing capacity of traditional ECFs, subtractive principle was introduced to design multicolor electrochromic fabric. Multicolor electrochromic along with excellent flexibility, stability, and lightweight features, are practical for camouflage applications, such as the reversible yellow-green conversion that can adapt to land and grass fighting scenes. We believe the simple-structured multicolor electrochromic fabric would be promising for flexible display in any textile-based markets, such as adaptive camouflage.

Polyester‐based wearable bandpass microstrip filter

AbstractIn this research paper, a polyester‐based bandpass microstrip filer is proposed. Split ring resonator, stepped‐impedance resonator structure, and coupled microstrip lines are used to design the proposed filter circuit in the pass band of 4.35 to 4.60 GHz for NATO frequency band military applications. The filter is fabricated using polyester substrate and self‐adhesive copper tape. The Agilent vector network analyzer is used to test the fabricated polyester wearable filter. There is good agreement between the simulated as well as measured insertion loss and return loss of the proposed wearable filter.

Graphene/PET-based temperature-sensitive conductor with enhanced responsiveness via magnetic induction for resistance-temperature sensors

Graphene/textile stretchable devices have garnered significant attention in the field of flexible wearable smart devices due to their inherent softness, flexibility, scalability, and breathability. In particular, the development of heat dissipation and sensing materials that exhibit efficient heat and electrical transfer properties presents a considerable challenge that requires the creation of a highly continuous graphene network within textile substrates. This study seeks to address this challenge through the oriented of graphene structure via magnetic fields. By inducing a magnetic field and employing a simple impregnation method, graphene is adsorbed in an orderly fashion onto a polyester (PET) substrate. The resulting magnetic reduced graphene oxide-polyester (MrGO-PET) composite material exhibits thermal conductivity values of 5.53 W/mK, 4.1 W/mK and 8.02 W/mK along the XYZ axes respectively and demonstrates stability under 10 heating-cooling cycles. When applied to LED chips for heat dissipation purposes, MrGO-PET achieves lower surface temperatures and broader temperature distribution ranges. Following integration, MrGO-PET serves as a temperature sensor with high sensitivity (TCR = −0.594 ℃-1) and precision (0.1 ℃) within the 25–50 ℃ range while exhibiting fast response times (42 s) within the 36.5–40 ℃ range alongside good heating-cooling cycle stability. Our research represents a valuable attempt to establish enhanced functionality at macroscopic scales for two-dimensional nanomaterials.

Purification and biochemical characterization of SM14est, a PET-hydrolyzing enzyme from the marine sponge-derived Streptomyces sp. SM14.

The successful enzymatic degradation of polyester substrates has fueled worldwide investigation into the treatment of plastic waste using bio-based processes. Within this realm, marine-associated microorganisms have emerged as a promising source of polyester-degrading enzymes. In this work, we describe the hydrolysis of the synthetic polymer PET by SM14est, a polyesterase which was previously identified from Streptomyces sp. SM14, an isolate of the marine sponge Haliclona simulans. The PET hydrolase activity of purified SM14est was assessed using a suspension-based assay and subsequent analysis of reaction products by UV-spectrophotometry and RP-HPLC. SM14est displayed a preference for high salt conditions, with activity significantly increasing at sodium chloride concentrations from 100 mM up to 1,000 mM. The initial rate of PET hydrolysis by SM14est was determined to be 0.004 s-1 at 45°C, which was increased by 5-fold to 0.02 s-1 upon addition of 500 mM sodium chloride. Sequence alignment and structural comparison with known PET hydrolases, including the marine halophile PET6, and the highly efficient, thermophilic PHL7, revealed conserved features of interest. Based on this work, SM14est emerges as a useful enzyme that is more similar to key players in the area of PET hydrolysis, like PHL7 and IsPETase, than it is to its marine counterparts. Salt-tolerant polyesterases such as SM14est are potentially valuable in the biological degradation of plastic particles that readily contaminate marine ecosystems and industrial wastewaters.

Giant Magnetoimpedance Effect of Multilayered Thin Film Meanders Formed on Flexible Substrates.

The giant magnetoimpedance effect of multilayered thin films under stress has great application prospects in magnetic sensing, but related studies are rarely reported. Therefore, the giant magnetoimpedance effects in multilayered thin film meanders under different stresses were thoroughly investigated. Firstly, multilayered FeNi/Cu/FeNi thin film meanders with the same thickness were manufactured on polyimide (PI) and polyester (PET) substrates by DC magnetron sputtering and MEMS technology. The characterization of meanders was analyzed by SEM, AFM, XRD, and VSM. The results show that multilayered thin film meanders on flexible substrates also have the advantages of good density, high crystallinity, and excellent soft magnetic properties. Then, we observed the giant magnetoimpedance effect under tensile and compressive stresses. The results show that the application of longitudinal compressive stress increases the transverse anisotropy and enhances the GMI effect of multilayered thin film meanders, while the application of longitudinal tensile stress yields the opposite result. The results provide novel solutions for the fabrication of more stable and flexible giant magnetoimpedance sensors, as well as for the development of stress sensors.

Fabrication of PA-PEI-MOF303(Al) by Stepwise Impregnation Layer-by-Layer Growth for Highly Efficient Removal of Ammonia.

NH3 is a typical alkaline gaseous pollutant widely derived from industrial production and poses great risks to humans and other biota. Metal-organic frameworks (MOFs) have excellent adsorption capacities relative to materials traditionally used to adsorb NH3. However, in practice, applications of MOFs as adsorbents are restricted because of its powder form. We prepared a polyamide (PA) macroporous polyester substrate using an emulsion template method and modified the surface with polyethylenimine (PEI) to improve the MOF growth efficiency on the substrate. The difficulty of loading the MOF because of the fast nucleation rate inside the PA macroporous polyester substrate was solved using a stepwise impregnation layer-by-layer (LBL) growth method, and a PA-PEI-MOF303(Al) hierarchical pore composite that very efficiently adsorbed NH3 was successfully prepared. The PA-PEI-MOF303(Al) adsorption capacity for NH3 was 16.07 mmol·g-1 at 298 K and 100 kPa, and the PA-PEI-MOF303(Al) could be regenerated repeatedly under vacuum at 423 K. The NH3 adsorption mechanism was investigated by in situ Fourier transform infrared spectroscopy and by performing two-dimensional correlation analysis. Unlike for the MOF303(Al) powder, the formation of multi-site hydrogen bonds between Al-O-Al/C-OH, N-H, -OH, C=O, and NH3 in PA-PEI-MOF303(Al) was found to be an important reason for efficient NH3 adsorption. This study will provide a reference for the preparation of other MOF-polymer composites.