Flexible Hybrid Electronics Nanofiber Electrodes with Excellent Stretchability and Highly Stable Electrical Conductivity for Smart Clothing

In this paper, a side-by-side, dual-nozzle electrospinning process was used to prepare a flexible hybrid electronics (FHE) material with excellent stretchable properties. A highly stable electrical conductivity was also imparted to the resulting membrane electrodes using silver nanoparticles (AgNPs) and carbon-based nanomaterials of different structures. The AgNP/carbon-based nanomaterials were coated onto bicomponent polymer nanofibers (composed of polyurethane (PU) and polyvinylidene difluoride (PVDF)) on the nanofiber membrane. The FHE nanofiber electrodes were finally integrated into clothing designed to accurately measure human body sensing signals (e.g., electrocardiography (ECG) and electromyography (EMG) signals). To effectively increase the high electrical conductivity, a polymer-type dispersant (polyisobutylene-b-poly­(oxyethylene)-b-polyisobutylene, a triblock copolymer) was used to effectively and stably disperse AgNPs with different particle sizes and carbon-based nanomaterials with different geometric dimensions (e.g., zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional graphene) through non-covalent adsorption. Moreover, the bicomponent PVDF–PU nanofibers were immersed in a mixed dispersant of AgNPs and carbon-based nanomaterials at low concentrations, and thermal post-treatment was conducted to improve the electrical conductivity. The AgNP/graphene oxide (GO) nanofiber electrode exhibited a continuous phase with a stable material microstructure after 5000 repetitions of 50% tension–tension fatigue testing. The waveform pattern obtained from the proposed AgNP/GO nanofiber electrode was compared with those of traditional ECG and EMG electrodes. The nanofiber web electrode treated with organic/inorganic mixed dispersants and verified via tests of its electrical and fatigue properties was found to be suitable for long-term ECG and EMG monitoring, and it has excellent potential in wearable smart sensors

Flexible Hybrid Electronics Nanofiber Electrodes with Excellent Stretchability and Highly Stable Electrical Conductivity for Smart Clothing

In this paper, a side-by-side, dual-nozzle electrospinning process was used to prepare a flexible hybrid electronics (FHE) material with excellent stretchable properties. A highly stable electrical conductivity was also imparted to the resulting membrane electrodes using silver nanoparticles (AgNPs) and carbon-based nanomaterials of different structures. The AgNP/carbon-based nanomaterials were coated onto bicomponent polymer nanofibers (composed of polyurethane (PU) and polyvinylidene difluoride (PVDF)) on the nanofiber membrane. The FHE nanofiber electrodes were finally integrated into clothing designed to accurately measure human body sensing signals (e.g., electrocardiography (ECG) and electromyography (EMG) signals). To effectively increase the high electrical conductivity, a polymer-type dispersant (polyisobutylene-b-poly­(oxyethylene)-b-polyisobutylene, a triblock copolymer) was used to effectively and stably disperse AgNPs with different particle sizes and carbon-based nanomaterials with different geometric dimensions (e.g., zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional graphene) through non-covalent adsorption. Moreover, the bicomponent PVDF–PU nanofibers were immersed in a mixed dispersant of AgNPs and carbon-based nanomaterials at low concentrations, and thermal post-treatment was conducted to improve the electrical conductivity. The AgNP/graphene oxide (GO) nanofiber electrode exhibited a continuous phase with a stable material microstructure after 5000 repetitions of 50% tension–tension fatigue testing. The waveform pattern obtained from the proposed AgNP/GO nanofiber electrode was compared with those of traditional ECG and EMG electrodes. The nanofiber web electrode treated with organic/inorganic mixed dispersants and verified via tests of its electrical and fatigue properties was found to be suitable for long-term ECG and EMG monitoring, and it has excellent potential in wearable smart sensors

Piezoelectric Property Enhancement of PZT/Poly(vinylidenefluoride-<i>co</i>-trifluoroethylene) Hybrid Films for Flexible Piezoelectric Energy Harvesters

In this study, lead zirconate titanate (PZT) ceramic particles were added for further improvement. PZT belongs to the perovskite family and exhibits good piezoelectricity. Thus, it was added in this experiment to enhance the piezoelectric response of the poly­(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) copolymer, which produced a voltage output of 1.958 V under a cyclic pressure of 290 N. In addition, to further disperse the PZT particles in the PVDF-TrFE matrix, tetradecylphosphonic acid (TDPA) was synthesized and employed to modify the PZT surface, after which the surface-modified PZT (m-PZT) particles were added to the PVDF-TrFE matrix. The TDPA on the PZT surface made it difficult for the particles to aggregate, allowing them to disperse in the polymer solution more stably. In this way, the PZT particles with piezoelectric responses could be uniformly dispersed in the PVDF-TrFE film, thereby further enhancing its overall piezoelectric response. The test results showed that upon the addition of 10 wt % m-PZT, the piezoelectric coefficient of m-PZT/PVDF-TrFE 10 wt % was 27 pC/N; and under a cyclic pressure of 290 N, the output voltage reached 3.426 V, which demonstrated a better piezoelectric response than the polymer film with the original PZT particles. Furthermore, the piezoelectric coefficient of m-PZT/PVDF-TrFE 10 wt % was 27.1 pC/N. This was exhibited by maintaining a piezoelectric coefficient of 26.8 pC/N after 2000 cycles. Overall, a flexible piezoelectric film with a high piezoelectric coefficient was prepared by following a simple fabrication process, which showed that this film possesses great commercial potential

Piezoelectric Property Enhancement of PZT/Poly(vinylidenefluoride-<i>co</i>-trifluoroethylene) Hybrid Films for Flexible Piezoelectric Energy Harvesters

In this study, lead zirconate titanate (PZT) ceramic particles were added for further improvement. PZT belongs to the perovskite family and exhibits good piezoelectricity. Thus, it was added in this experiment to enhance the piezoelectric response of the poly­(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) copolymer, which produced a voltage output of 1.958 V under a cyclic pressure of 290 N. In addition, to further disperse the PZT particles in the PVDF-TrFE matrix, tetradecylphosphonic acid (TDPA) was synthesized and employed to modify the PZT surface, after which the surface-modified PZT (m-PZT) particles were added to the PVDF-TrFE matrix. The TDPA on the PZT surface made it difficult for the particles to aggregate, allowing them to disperse in the polymer solution more stably. In this way, the PZT particles with piezoelectric responses could be uniformly dispersed in the PVDF-TrFE film, thereby further enhancing its overall piezoelectric response. The test results showed that upon the addition of 10 wt % m-PZT, the piezoelectric coefficient of m-PZT/PVDF-TrFE 10 wt % was 27 pC/N; and under a cyclic pressure of 290 N, the output voltage reached 3.426 V, which demonstrated a better piezoelectric response than the polymer film with the original PZT particles. Furthermore, the piezoelectric coefficient of m-PZT/PVDF-TrFE 10 wt % was 27.1 pC/N. This was exhibited by maintaining a piezoelectric coefficient of 26.8 pC/N after 2000 cycles. Overall, a flexible piezoelectric film with a high piezoelectric coefficient was prepared by following a simple fabrication process, which showed that this film possesses great commercial potential

Graphene Nanoplatelet/Multiwalled Carbon Nanotube/Polypyrrole Hybrid Fillers in Polyurethane Nanohybrids with 3D Conductive Networks for EMI Shielding

This work reports the preparation of graphene nanoplatelet (GNP)/multiwalled carbon nanotube (MWCNT)/polypyrrole (PPy) hybrid fillers via in situ chemical oxidative polymerization with the addition of a cationic surfactant, hexadecyltrimethylammonium bromide. These hybrid fillers were incorporated into polyurethane (PU) to prepare GNP/MWCNT/PPy/PU nanohybrids. The electrical conductivity of the nanohybrids was synergistically enhanced by the high conductivity of the hybrid fillers. Furthermore, the electromagnetic interference (EMI) shielding effectiveness (SE) was greatly increased by interfacial polarization between the GNPs, MWCNTs, PPy, and PU. The optimal formulation for the preparation of GNP/MWCNT/PPy three-dimensional (3D) nanostructures was determined by optimization experiments. Using this formulation, we successfully prepared GNP/PPy nanolayers (two-dimensional) that are extensively covered by MWCNT/PPy nanowires (one-dimensional), which interconnect to form GNP/MWCNT/PPy 3D nanostructures. When incorporated into a PU matrix to form a nanohybrid, these 3D nanostructures form a continuous network of conductive GNP–PPy–CNT–PPy–GNP paths. The EMI SE of the nanohybrid is 35–40 dB at 30–1800 MHz, which is sufficient to shield over 99.9% of electromagnetic waves. Therefore, this EMI shielding material has excellent prospects for commercial use. In summary, a nanohybrid with excellent EMI SE performance was prepared using a facile and scalable method and was shown to have great commercial potential

Hydrophilic–Hydrophobic Nanohybrids of AuNP-Immobilized Two-Dimensional Nanomica Platelets as Flexible Substrates for High-Efficiency and High-Selectivity Surface-Enhanced Raman Scattering Microbe Detection

A flexible hybrid substrate was developed by affixing gold nanoparticles (AuNPs) onto the surface of two-dimensional nanomica platelets (NMPs). The substrate was successfully used in biosensors with high efficiency and high selectivity through surface-enhanced Raman scattering (SERS). By controlling the amphiphilicity of the hybrid substrate, the flexible substrate was made highly selective toward biomolecules. Four different SERS substrate systems were constructed, including intercalated mica, exfoliated NMPs, hydrophilic exfoliated NMPs, and hydrophobic exfoliated NMPs. NMPs were only 1 nm thick. AuNPs adsorbed on both sides of NMPs and thus created excellent three-dimensional hot junction effects in the z-axis direction. For the detection of adenine in DNA, a satisfactory Raman enhancement factor (EF) of up to 8.9 × 106 was achieved with the detection limit as low as 10–8 M. Subsequently, the AuNP/NMP hybrids were adopted to rapidly detect hydrophilic Staphylococcus hominis and hydrophobic Escherichia coli. The AuNP/PIB–POE–PIB/NMP nanohybrid was concurrently hydrophilic and hydrophobic. This amphiphilic property greatly enhanced the detection selectivity and signal intensity for hydrophilic or hydrophobic bacteria. Overall, AuNPs/PIB–POE–PIB/NMPs developed as SERS substrates enable rapid, sensitive biodetection

Hydrophilic–Hydrophobic Nanohybrids of AuNP-Immobilized Two-Dimensional Nanomica Platelets as Flexible Substrates for High-Efficiency and High-Selectivity Surface-Enhanced Raman Scattering Microbe Detection

A flexible hybrid substrate was developed by affixing gold nanoparticles (AuNPs) onto the surface of two-dimensional nanomica platelets (NMPs). The substrate was successfully used in biosensors with high efficiency and high selectivity through surface-enhanced Raman scattering (SERS). By controlling the amphiphilicity of the hybrid substrate, the flexible substrate was made highly selective toward biomolecules. Four different SERS substrate systems were constructed, including intercalated mica, exfoliated NMPs, hydrophilic exfoliated NMPs, and hydrophobic exfoliated NMPs. NMPs were only 1 nm thick. AuNPs adsorbed on both sides of NMPs and thus created excellent three-dimensional hot junction effects in the z-axis direction. For the detection of adenine in DNA, a satisfactory Raman enhancement factor (EF) of up to 8.9 × 106 was achieved with the detection limit as low as 10–8 M. Subsequently, the AuNP/NMP hybrids were adopted to rapidly detect hydrophilic Staphylococcus hominis and hydrophobic Escherichia coli. The AuNP/PIB–POE–PIB/NMP nanohybrid was concurrently hydrophilic and hydrophobic. This amphiphilic property greatly enhanced the detection selectivity and signal intensity for hydrophilic or hydrophobic bacteria. Overall, AuNPs/PIB–POE–PIB/NMPs developed as SERS substrates enable rapid, sensitive biodetection

Facile Fabrication and Analysis of Highly Sensitive PtTFPP/Carbon Black/Polystyrene Oxygen-Sensitive Composite Films for Optical Dissolved-Oxygen Sensor

This research has designed and fabricated an oxygen-sensitive composite film, based on fluorescence quenching by oxygen, which can be applied in optical dissolved-oxygen sensor probes. The composite film is prepared by mixing polystyrene (PS) and indicator dye (platinum tetrakis pentrafluorophenyl porphine, PtTFPP). Tributyl phosphate (TBP) and common black pigment (i.e., carbon black, CB) are then added to enhance the oxygen permeability and specific surface area of the film and to increase its oxygen sensitivity. A nonionic surfactant (i.e., Triton X-100) is used to facilitate the uniform dispersion of carbon black within the PtTFPP/PS composite film, producing a highly oxygen-sensitive film. This research shows that the highest sensitivity (I0/I100) is achieved at a weight ratio of 150:1 (PS/PtTFPP), with a linear correlation coefficient (R2) of 0.9955. With the addition of 3 wt % TBP to PS, the sensitivity increases to 16.51, with an R2 value of 0.9939. The addition of CB to this film increases the sensitivity further to 19.12 (R2 = 0.9916). The above results show that the addition of TBP and CB can effectively enhance the oxygen sensitivity of the film. This study successfully fabricates an oxygen-sensitive compound film with high oxygen sensitivity and detection accuracy in a simple and cost-effective manner. The methods used in this study can be used for developing other highly sensitive sensors, which can be used in professional water-quality assessments for commercial purposes

Facile Fabrication and Analysis of Highly Sensitive PtTFPP/Carbon Black/Polystyrene Oxygen-Sensitive Composite Films for Optical Dissolved-Oxygen Sensor

This research has designed and fabricated an oxygen-sensitive composite film, based on fluorescence quenching by oxygen, which can be applied in optical dissolved-oxygen sensor probes. The composite film is prepared by mixing polystyrene (PS) and indicator dye (platinum tetrakis pentrafluorophenyl porphine, PtTFPP). Tributyl phosphate (TBP) and common black pigment (i.e., carbon black, CB) are then added to enhance the oxygen permeability and specific surface area of the film and to increase its oxygen sensitivity. A nonionic surfactant (i.e., Triton X-100) is used to facilitate the uniform dispersion of carbon black within the PtTFPP/PS composite film, producing a highly oxygen-sensitive film. This research shows that the highest sensitivity (I0/I100) is achieved at a weight ratio of 150:1 (PS/PtTFPP), with a linear correlation coefficient (R2) of 0.9955. With the addition of 3 wt % TBP to PS, the sensitivity increases to 16.51, with an R2 value of 0.9939. The addition of CB to this film increases the sensitivity further to 19.12 (R2 = 0.9916). The above results show that the addition of TBP and CB can effectively enhance the oxygen sensitivity of the film. This study successfully fabricates an oxygen-sensitive compound film with high oxygen sensitivity and detection accuracy in a simple and cost-effective manner. The methods used in this study can be used for developing other highly sensitive sensors, which can be used in professional water-quality assessments for commercial purposes

Polymer-Assisted Dispersion of Boron Nitride/Graphene in a Thermoplastic Polyurethane Hybrid for Cooled Smart Clothes

The avoidance and mitigation of energy wastage have attracted increasing attention in the context of global warming and climate change. With advances in materials science, diverse multifunctional materials with high thermal conductivity have shown excellent energy-saving potential. In this study, a hybrid film exhibiting high thermal conductivity with excellent stretchability and washability was prepared. First, a simple surface modification of boron nitride (BN) was performed to realize a modified boron nitride (BNOH) filler. Next, an organic dispersant was synthesized to enhance the dispersion of BNOH and graphene nanoplatelets (GNPs) in the proposed composite. Subsequently, a simple procedure was used to combine the dispersed GNPs and BNOH fillers with thermoplastic polyurethane (TPU) to fabricate a hybrid structure. The hybrid films composed of BNOH–GNP/TPU with a dispersant exhibited a high thermal conductivity of 12.62 W m–1 K–1 at a low filler loading of 20 wt.%. This hybrid film afforded excellent stretchability and washability, as indicated by the very small thermal-conductivity reduction to only 12.23 W m–1 K–1 after 100 cycles of fatigue testing and to 12.01 W m–1 K–1 after 10 washing cycles. Furthermore, the cooling and hydrophobicity properties of the hybrid film were enhanced when compared with neat TPU. Overall, our approach demonstrates a simple and novel strategy to break the passive effect of traditional commercial cooling clothing by combining a high-thermal-conductivity film with an active cooling source to amplify the cooling effect and develop wearable cooled smart clothes with great commercial potential