Polyethylene Terephthalate Substrate Research Articles

Programming Motion into Materials Using Electricity-Driven Liquid Crystal Elastomer Actuators.

As thermally driven smart materials capable of large reversible deformations, liquid crystal elastomers (LCEs) have great potential for applications in bionic soft robots, artificial muscles, controllable actuators, and flexible sensors due to their ability to program controllable motion into materials. In this article, we introduce conductive LCE actuators using a liquid metal electrothermal layer and a polyethylene terephthalate substrate. Our LCE actuators can be stimulated at low currents from 2 to 4 A and produce a maximum work density of 9.4 . We illustrate the potential applications of this system by designing a palm-activated artificial muscle gripper, which can be used to grasp soft objects ranging from 5 to 55 mm in size, and even ring-shaped workpieces with precise external or internal support. Furthermore, inspired by the movement of fruit fly larvae, we designed a new soft robot capable of bioinspired crawling and turning by inducing anisotropic friction with an asymmetric design. Finally, we illustrate advanced motional control by designing an autonomously rotating wheel based on the asymmetric contraction of its spokes. To assist in the production of autonomously moving robots, we provide a thorough characterization of its motion dynamics.

Highly efficient polyaniline based flexible electrochemical sensor for bisphenol a detection

We report herein a novel label-free polyaniline (PANI) based bisphenol A (BPA) electrochemical sensor fabricated on a flexible polyethylene terephthalate (PET) substrate. The PANI layer was electrochemically deposited on a gold-coated PET substrate using the facile amperometric (current–time transient) technique. A thorough investigation of the PANI sensing layer was done using Raman spectroscopy and field emission scanning electron microscopy (FESEM) characterization techniques. The sensing properties of the implanted matrix for BPA detection were investigated through cyclic voltammetry (CV). The fabricated electrochemical sensor showed linearity in the concentration range of 0.05–––5.0 µM, a higher sensitivity of ∼ 56.69 A/M and a lower limit of detection (LOD) of ∼ 1.06 nM. The sensor exhibited excellent flexibility and a better shelf life of 20 weeks. The results highlight the importance of PANI thin film as an attractive matrix for the realization of electrochemical sensor for BPA detection.

Fabrication of highly conductive phosphorous-doped nc-SiCx:H thin film on PET

Plasma enhanced chemical vapor deposition (PECVD) method has been utilized to fabricate phosphorous-doped hydrogenated nanocrystalline silicon carbide (P-doped nc-SiCx:H) thin films on polyethylene terephthalate (PET) substrate. With the aim at obtaining highly conductive thin films, H2/Ar mixed dilution has been applied for creating plasma during deposition, and the variation of structural, electrical and optical properties with H2/Ar flow ratio RH have been systemically investigated through a series of characterizations. Results show that the highly crystallized P-doped nc-SiCx:H thin film can be prepared while the properties are controllable through adjusting RH. In the case of RH = 0.75, the maximum dark conductivity (6.42 S cm−1) and a wide optical bandgap (1.93 eV) are attained. Finally, detail discussion has been made to illustrate the growth mechanism of the flexible P-doped nc-SiCx:H thin films.

Stability of Silver-Nanowire-Based Flexible Transparent Electrodes under Mechanical Stress

Flexible transparent electrodes are integral to the advancement of flexible optoelectronic devices such as flexible displays and solar cells. However, indium tin oxide (ITO), a traditional material used in transparent electrodes, exhibits a significant increase in resistance under mechanical stress, which limits the long-term stability of flexible devices. Here, we prepare various types of silver nanowire (AgNW)-based transparent electrodes and investigate their stability in terms of electrical resistance and optical transmittance under compressive and tensile stresses. Under compressive stress, ITO on a polyethylene terephthalate (PET) substrate exhibits a significantly high electrical resistance of >3000 Ω after 1000 stress cycles, while the AgNW-coated electrode on a PET film exhibits a relatively smaller resistance of <1200 Ω. The AgNW-embedded electrode in a UV-curable polymer matrix (NOA63 or NOA71) exhibits an even lower electrical resistance of <450 Ω because AgNWs can easily maintain their network. A similar trend is observed under tensile stress. The AgNW-embedded electrode shows the highest resistance stability, whereas the ITO on the PET substrate shows the poorest stability. The optical transmittance is comparable regardless of the type of stress or electrode used. This superior stability of the AgNW-based electrodes, realized by integrating it with a polymer matrix, is promising for the development of durable and high-performance flexible optoelectronic devices.

Effect of He diluted plasma on the deposition of flexible low-temperature polycrystalline silicon thin film

The growth of a low-temperature polycrystalline silicon (LTPS) thin film on a flexible polyethylene terephthalate (PET) substrate under the assistance of helium plasma has been examined in detail in this study. By utilizing the plasma enhanced chemical vapor deposition method, LTPS thin films are directly deposited on a PET substrate at a relatively low temperature (80 °C), and the variations in the morphology, structure, and electrical property of the samples with He flow are systematically characterized by performing a series of tests. The results show that the purely helium-diluted silane plasma has the function of inducing crystallization and fabricating the c-Si network. After optimizing the He flow rate to 600 SCCM, the LTPS thin film with the largest average grain size of ∼204.7 nm can be obtained, while the maximum dark conductivity (4.16 × 10−5 S/cm) is also achieved. Finally, a detailed discussion is presented to illustrate the growth mechanism of the LTPS thin film in He plasma.

Highly Efficient and Reliable Organic Light–Emitting Diodes Enabled by a Multifunctional Hazy Substrate for Extreme Environments

AbstractAs transparent, flexible, and wearable organic electronics degrade under normal outdoor environmental conditions (e.g., water vapor, oxygen, and UV light) and extreme environments, including washing or rain, a customized encapsulation technology is required to improve device reliability. Herein, a simple process is presented for fabricating multifunctional hazy substrates (MFHSs) with excellent gas diffusion barrier (GDB), flexibility, UV reflectance, light scattering, and waterproof properties. First, a spiky polyethylene terephthalate (PET) surface is produced with 76.0% optical haze through ion‐beam treatment followed by the formation of a hydrophobic layer to achieve a waterproof effect (contact angle: 153.3°). Then, a multifunctional multibarrier film is fabricated based on a nano‐laminated distributed Bragg reflector and functional polymer on the functional PET substrate to serve as a GDB and UV filter. This multibarrier film has excellent mechanical and chemical stabilities, in addition to having a water vapor transmission rate of 10−6 g m−2 day−1 and UV transmittance of <3%. The so‐fabricated MFHS not only increases the device efficiency by 73% but also enables a highly flexible and environmentally stable organic light–emitting diode. The surface treatment and encapsulation technologies developed in this study are expected to increase the lifetime of organic devices and facilitate high outdoor usability.

3-oxetanylmethanol as additive to PEDOT:PSS for improved conductivity and water-resistance and applications in ink-jet printed electrochemical transistors

3-oxetanylmethanol is used as additive to poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) water dispersions and the properties of thin films, prepared by spin-coating and ink-jet printing, either on glass or flexible polyethylene terephthalate (PET) substrates, are investigated. 1H NMR studies revealed that 3-oxetanylmethanol is reactive within the PEDOT:PSS medium during the film drying step at 120 °C, to form polyether compounds. Chemical cross-linking established through the esterification reaction of pendant hydroxyl groups in polyether chains, resulting from the 3-oxetanylmethanol in situ polymerization, and sulfonate groups from PSS, is also identified by the 1H NMR studies. Spin-cast films prepared from this formulation on either glass or PET exhibited electrical conductivity enhanced by more than two orders of magnitude, when compared to films obtained with the pristine PEDOT:PSS dispersion, reaching maximum values of around 596 and 682 Scm−1 for films on glass and PET, respectively, together with improved water-resistance. Atomic force microscopy and Raman spectroscopic studies, indicating that PEDOT chains are organized in more ordered domains in the films of the oxetane-based formulations, suggest that the polyether compounds modify the PEDOT:PSS phase segregation and promote charge transport across conducting PEDOT segments. Subsequently, improved conductivities and stability were also found for films prepared by high-resolution ink-jet printing of the formulations that led to the most conductive spin coated films. The potential application of the new ink formulations in printed electrodes interfacing aqueous media was assessed by ink-jet printing PEDOT-based electrochemical transistors operating with aqueous KCl electrolyte.

Investigation of water vapor barrier performances of diamond-like carbon coatings on flexible PET fabricated at room temperature

Polyethylene terephthalate (PET) emerges as the predominant packaging material for food and electronics. To prevent water vapor from penetrating the polymer, an effective method is to deposit a coating on it that does not damage it. Diamond-like carbon (DLC), which can be deposited at low temperatures, offers a promising protective coating. In this research, DLC coatings were chemical vapor deposited (CVD) on PET substrates using an anode layer linear ion source method. The findings indicate that the water vapor transmission rate (WVTR) of PET substrates coated with DLC coating was significantly reduced to as low as 0.12 g/(m2·24 h), which represents a 30 times reduction compared to the uncoated PET substrates. To further understand the mechanism of water vapor barrier capabilities, molecular dynamics (MD) simulation and first-principles density functional theory (DFT) calculation were carried out to verify the capability and active site of the adsorption and dispersion of water molecules on carbon coating and PET. In addition, the DLC coated PET exhibited exceptional flexibility, and even after subjecting it to 2160 bending cycles, it showed no signs of cracking, indicating its mechanical robustness and durability. This research serves as a strong reference for utilizing DLC to address water vapor permeation challenges.

Analysis of Antibacterial and Antiviral Properties of ZnO and Cu Coatings Deposited by Magnetron Sputtering: Evaluation of Cell Viability and ROS Production

The development and testing of antimicrobial coatings continues to be a crucial approach, considering the ongoing emergence of antibiotic-resistant bacteria and the rapid transmission of highly pathogenic viruses. In this study, three types of coatings—pure metallic copper (Cu), zinc oxide (ZnO), and a three-layer zinc oxide and copper mixed coating (ZnO/Cu/ZnO)—were deposited by magnetron sputtering on polyethylene terephthalate substrates to evaluate their antimicrobial potential using various microorganisms, including viruses. Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria were used for the assessment of antibacterial properties. Antiviral testing was performed using MS2 bacteriophage and replication-deficient Semliki Forest virus, both representing single-stranded RNA-containing viruses. The samples’ ability to cause reactive oxygen species formation was measured, and the effect on bacterial metabolic activity was evaluated. Cu-coated samples showed high inhibitory activity (>95%) against E. coli and S. aureus bacteria, as well as against tested viruses (SFV and MS2). The antibacterial and antiviral properties of ZnO/Cu/ZnO and ZnO coatings were not significant. Although ZnO/Cu/ZnO and ZnO caused inhibition of the metabolic activity of the bacteria, it was insufficient for complete bacteria eradication. Furthermore, significant reactive oxygen species (ROS) production was detected only for single Cu-coated samples, correlating with the strong bacteria-killing ability. We suppose that the ZnO layer exhibited a low release of Zn ions and prevented contact of the Cu layer with bacteria and viruses in the ZnO/Cu/ZnO coating. We conclude that current ZnO and Cu-ZnO-layered coatings do not possess antibacterial and antiviral activity.

Cost-effective synthesis of copper sulfide nanoparticles and flexible films for photocatalytic and antibiotic applications

Herein, we investigate the effects of temperature and thiourea addition rate on the synthesis of copper sulfide nanoparticles (CuS NPs) via a chemical co-precipitation method, exploring their impact on the size and morphology of CuS NPs. Our systematic approach resulted in the successful synthesis of CuS NPs with significantly smaller nanoflower sizes than previously reported in the literature, providing insights into the nucleation and growth mechanisms under various synthesis conditions. Furthermore, the photocatalytic activity of the synthesized CuS NPs with three types of distinctive morphologies, namely, nanoflowers with 50 nm diameter (F-50), nanoflowers with 200 nm diameter, and nanogravels with 50 nm diameter, is comparatively analyzed. Notably, the F-50 exhibits a superior photocatalytic performance compared to the other samples, demonstrating the considerable influence of the NP size and morphology on their functional properties. Furthermore, the antibacterial property of the small CuS nanoflowers is examined using an antibacterial film fabricated by coating the NPs on a polyethylene terephthalate substrate, which is widely used as a protective or packaging film in various industries because of its transparency and flexibility. The antibacterial film can be used to kill both gram-positive and -negative bacteria effectively. This research contributes significantly to the understanding and optimization of CuS NP synthesis and application, emphasizing the potential of small-sized nanoflower CuS NPs in photocatalysis and antibacterial applications.

Effects of copper metal organic decomposition ink on properties of single-walled carbon nanotube based flexible transparent electrodes

The effects of copper metal organic decomposition (Cu MOD) ink on the electrical and mechanical properties of SWCNT-based flexible transparent electrodes were investigated. In particular, we designed and demonstrated Cu MOD ink as bonding agents between oxidized SWCNT (Ox-SWCNT) and the polyethylene terephthalate (PET) substrate. PET substrates were surface-treated via plasma etching, and ultraviolet/ozone (UV/O3) treatment was conducted for enhancing the dispersion of SWCNTs. Subsequently, spray coating of numerous times with Ox-SWCNT dispersion and once with Cu MOD ink was applied to the PET substrates at low temperatures. In this way, a robust, flexible, and transparent Ox-SWCNT/Cu@PET composite electrode was fabricated. The as-prepared Ox-SWCNT/Cu@PET composite electrode exhibited good properties, with a sheet resistance of 483.9 Ω/sq and transmittance of 82.1%. Even after 10000 bending cycles and 100 peel-off times, the resistance was only increased by factors of 1.07 and 1.12, respectively, confirming good mechanical robustness. In addition, the electrode exhibited excellent environmental stability; its electrical resistance was only increased by a factor of 1.35 after subjected to harsh environmental conditions (85 °C, 85% relative humidity) for 48 h. These results indicate that the Ox-SWCNT/Cu@PET composite electrodes are promising for wide application as FTCEs.

Morphological, electrical, and electromagnetic characterization of nanometric films of Cu and Ni and their combination in bilayers

Modern developments in telecommunication and microelectronics have resulted in spurious radiation, which can promote electromagnetic interference and environmental pollution. To minimize this problem, this work studied nanometric metallic films (65 nm/layer) based on Cu and Ni and their combinations in bilayers deposited on a polyethylene terephthalate substrate by magnetron sputtering. Field emission gun scanning electron microscopy analyses showed that the films have different morphological textures, due to the processing parameters and the free energy of the metals. Electrical measurements by the 4-point method and dielectric spectroscopy showed that the films have low conductivity values, due to oxides formed on the surfaces of the films and defects. X-ray diffraction confirmed the formation of metallic oxides in the films. Electromagnetic characterization (8.2-12.4 GHz) of the monolayer films showed poor performance. Meanwhile, the bilayer films (Ni/Cu and Cu/Ni) showed different behaviors with reflection and absorption contributions. Attenuation values close to 95 % for the Cu/Ni film were obtained.

Efficient metallization based on nondestructive modification of catechol-tetraethylenepentamine composites and electroless deposition applied to polyethylene terephthalate for flexible electronics

An improved metallized polyethylene terephthalate (PET) substrate prepared by catechol (CA) and tetraethylenepentamine (TEPA) composites modification with electroless deposition (ELD) copper layer is presented. Through the polymerization of CA with TEPA, amino and imino groups were generated to adsorb the activated particles required for metallization. To achieve the practical application of this method, different catalytic approaches were validated. Under different catalytic conditions, the catalytic effect of UV light was most pronounced, reaching almost four times than that in darkness. The resulting solid copper layers exhibited highly reliable electrical properties, including a low resistivity of 2.73 μΩ cm, tightly spaced crystalline particles and excellent mechanical properties. The fabricated metallized PET substrates were verified for use in flexible circuit boards, demonstrating the compatibility of the proposed CA-TEPA composites modification method with the PET substrates. This method provides an effective approach to the metallization of the PET substrates, which has a widespread application in manufacturing of flexible electronics such as film capacitors.

Angle-Independent Color Change in Thermoresponsive Gel-Immobilized Colloidal Amorphous Film Attached to PET Substrate.

Gel-immobilized colloidal amorphous structures comprise short-range-ordered monodisperse submicrometer particles embedded into a soft polymer gel. They exhibit an angle-independent structural color that is tunable in response to external stimuli via a volume change in the gel, which has significant potential for the development of sensors that respond to stimuli via angle-independent color changes. In this study, the amorphous structure of a charged colloidal suspension in water was immobilized in a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) gel film and simultaneously attached to a polyethylene terephthalate (PET) substrate. The gel film exhibited a uniform angle-independent color that changed in response to changes in temperature (i.e., thermosensitivity). Attachment to the PET substrate suppressed changes in the gel film area and film distortion, despite significant volume changes in the gel. Consequently, the degree of thermosensitivity was enhanced. The PET-attached gel-immobilized colloidal amorphous film was easy to handle and had excellent flexibility, allowing it to wrap around the surfaces of curved objects. These features are advantageous for sensor applications.

Interfacial mechanical properties of graphene on randomly rough PET substrate surface: A molecular dynamics study

In this work, molecular dynamics (MD) simulations are performed to create a series of polyethylene terephthalate (PET) substrates with random roughness, and the morphological characteristics and interfacial bonding of graphene on the real rough PET surface are first simulated. The results show that the interfacial mechanical behavior of graphene freely adhered to the PET roughness is influenced by the surface profile. Besides causing the non-conformal contact, the rough surface hinders the propagation of bending waves from the graphene corner regions during the adhesion and weakens their overlap. The increased surface roughness weakens interfacial adhesion and inhibits interfacial sliding, leading to the formation of larger morphological defects such as wrinkles. Furthermore, the measurement of the interfacial adhesion energy of graphene/PET substrate is achieved by the shaft loaded blister test (SLBT), which for the first time is used to simulate the interfacial debonding of graphene on rough PET surfaces. For low surface roughness, interfacial adhesion dominates the debonding behavior and the blister boundary preferentially extends along the interfacial defect area. For high surface roughness, the increasingly serious non-conformal contact makes the blister more likely to instability and enter the stage where normal and shear interactions are coupled.

Thermal Stress Impact on Electrical Conductivity and Microstructure of Thin Aluminum Films Deposited on Polyethylene Terephthalate Substrates

Thermal Stress Impact on Electrical Conductivity and Microstructure of Thin Aluminum Films Deposited on Polyethylene Terephthalate Substrates

A fully printed sensor with optical readout for real-time flow monitoring

In recent years, there has been a growing interest in the development of flexible thermal flow sensing devices due to their wide-ranging applications. In this study, we present the fabrication of a screen-printed flow sensor with optical readout on a 125 μm polyethylene terephthalate substrate in a three-layer configuration. The device comprises electrodes made from a commercial silver (Ag) ink, a heating area using a commercial carbon ink, and a thermochromic (TC) layer employing a commercial ink with a standard activation temperature of 31 °C. We designed a specialized experimental setup to evaluate the performance of the optical flow sensor under static and dynamic conditions. To analyze the device’s thermal response and performance across various flow conditions, we utilized a combination of electrical measurements and infrared (IR)-optical imaging techniques. The all-printed device operates on the basis of a thermodynamic cycle frequency, which activates the TC ink, causing it to blink at a frequency related to the flow passing over the sensor. The results of our preliminary testing are highly promising, as the sensor successfully demonstrated a clear relationship between flow and optical duty cycle. This innovative device offers a contactless, low-cost, easy-to-use flow detection method and holds significant potential for various practical applications.

Evaluation of thermal stresses on thin Al and AZO films deposited on polyethylene terephthalate substrates for flexible electronics applications

Thin aluminum (Al) films are widely used in electronic devices and flexible photovoltaics. In a similar capacity, Aluminum Doped Zinc Oxide (AZO) serves the same purpose. This study examines the sensitivity of both films to thermal stresses when sputtered onto Polyethylene Terephthalate substrates. These stresses include a constant temperature of 100 °C and temperature fluctuations ranging from 0 °C to 100 °C. The resistance of the films was affected by isothermal aging, but not by thermal cycling. Interestingly, thermal cycling led to microcracks in the film, while isothermal aging resulted in a slight increase in bonding and oxygen content in the Al films. For AZO films, imaging did not reveal any noticeable changes in morphology. However, both thermal cycling and isothermal aging led to a minor increase in the resistance of AZO films. These findings highlight the pronounced impact of thermal stress on the performance and structural integrity of both thin films.

An Optically Transparent Metamaterial Absorber with Tunable Absorption Bandwidth and Low Infrared Emissivity

A transparent metamaterial absorber (MMA) with both tunable absorption bandwidth and low infrared (IR) emissivity is proposed in this paper. The MMA is hierarchical, which consists of an infrared shielding layer (IRSL), two radar-absorption layers (RALs), an air/water layer, and an indium–tin–oxide (ITO) backplane from the top downwards. The IRSL and the RALs are made of ITO patterns etched on polyethylene terephthalate (PET) substrates. By changing the thickness of the water, the 90% absorption bandwidth can be tuned from 6.4–11.3 GHz to 12.7–20.6 GHz, while retaining good polarization and angular stability. An equivalent circuit model (ECM) is present, to reveal the physical mechanism of absorption. The proposed MMA has a low theoretical IR emissivity of about 0.24. A sample was fabricated and measured, and the experimental results are consistent with the simulation results, showing its potential applications in stealth glass and multifunctional radome.

Synaptic memristors based on flexible organic pentacene thin films by the thermal evaporation method for neuromorphic computing

As the development of neuromorphic computing, it is meaningful to explore the synaptic memristors based on organic materials owing to their advantages in low cost, good mechanical flexibility and strong biocompatibility. In this work, organic pentacene thin films have been deposited on different substrates by the thermal evaporation method. The prepared thin films on SiO2/Si substrates demonstrate the co-existence of digital and analog resistive switching (RS) behaviors as well as a series of synaptic plasticity. To characterize the flexibility of the organic thin films, lateral memristors have been fabricated on polyethylene terephthalate (PET) substrates and demonstrate comparable RS behaviors when the bending radius is decreased to 1.26 cm or after 1000 bending. Furthermore, vertical memristors with Pt/pentacene/indium tin oxide (ITO) structure have been constructed when the organic thin films are deposited on ITO/PET substrates, exhibiting bipolar RS behaviors with low SET voltage of 0.65 V. The vertical synaptic memristors can be used to simulate the “learning-forgetting” experience of human brain. More importantly, an artificial neural network (ANN) can be simulated based on the vertical synaptic memristors, demonstrating 93.8 % recognition accuracy for hand-written digit image. This study suggests potential applications of the organic pentacene thin films for neuromorphic computing.