Piezoelectric Microfibers Research Articles

Ultrasound-responsive microfibers promoted infected wound healing with neuro-vascularization by segmented sonodynamic therapy and electrical stimulation

Bacteria-infected wounds pose challenges to healing due to persistent infection and associated damage to nerves and vessels. Although sonodynamic therapy can help kill bacteria, it is limited by the residual oxidative stress, resulting in prolonged inflammation. To tackle these barriers, novel 4 octyl itaconate-coated Li-doped ZnO/PLLA piezoelectric composite microfibers are developed, offering a whole-course "targeted" treatment under ultrasound therapy. The inclusion of Li atoms causes the ZnO lattice distortion and increases the band gap, enhancing the piezoelectric and sonocatalytic properties of the composite microfibers, collaborated by an aligned PLLA conformation design. During the infection and inflammation stages, the piezoelectric microfibers exhibit spatiotemporal-dependent therapeutic effects, swiftly eliminating over 94.2 % of S. aureus within 15 min under sonodynamic therapy. Following this phase, the microfibers capture reactive oxygen species and aid macrophage reprogramming, restoring mitochondrial function, achieving homeostasis, and shortening inflammation cycles. As the wound progresses through the healing stages, bioactive Zn2+ and Li + ions are continuously released, improving cell recruitment, and the piezoelectrical stimulation enhances wound recovery with neuro-vascularization. Compared to commercially available dressings, our microfibers accelerate the closure of rat wounds (Φ = 15 mm) without scarring in 12 days. Overall, this "one stone, four birds" wound management strategy presents a promising avenue for infected wound therapy.

Near‐field electrospinning fabrication of piezoelectric polymer microfiber sensors for detection of weak mechanical excitation

AbstractCollection and conversion of widespread mechanical energy is one promising way to alleviate environmental pollution and energy crisis. Piezoelectric materials can effectively realise this conversion between mechanical and electrical energies. Here, via near‐field electrospinning, piezoelectric poly(vinylidene fluoride) microfibers were fabricated on flexible polyethylene terephthalate substrate. Bending measurement indicated that open‐circuit voltage response from piezoelectric microfibers was strain dependent but insensitive to bending frequency. The microfiber sensor could detect acoustic signals with sound pressure level between 70 and 120 dB and the recorded acoustic frequency was well consistent with the nominal frequency. Light wind from a low‐power hand fan was also detected by this microfiber sensor. This simply structured and highly flexible piezoelectric microfiber sensor provided a promising and low‐cost fabrication measure for weak mechanical excitation sensing.

Electrical current visualization sensor based on magneto-electrochromic effect

Electrical safety is a major threat to public safety worldwide, with fires and explosions causing damage to property and loss of life. Detection and monitoring of the occurrence of destructive current spikes can provide valuable insights into system health and inform preventative maintenance. Current sensors based on the Magnetoelectric (ME) effect have been regarded as optimal solutions because of the low power consumption and high sensitivity of ME devices compared to conventional current sensors (current transformers, Hall-effect current sensors, etc.). However, none of the conventional sensing techniques can provide ex-situ recording or a means for a human-readable signal output. Development of a current sensor that can sense, visualize, and record a current level remains a challenge. Here, we report an electric current visualization sensor that uses a coupled magnetoelectric/electrochromic effect to transform environmental current energy into electrical signals, and subsequently to a color change readily interpreted by a human observer. The current visualization sensor uses a PZT piezoelectric microfiber composite (MFC) / FeSiB alloy (Metglas) laminate combined with a Prussian blue-based electrochromic device (ECD). Such a current sensor demonstrates high efficiency self-powered current sensing and non-volatile signal recording.

Microfluidic fabrication of β‐phase enriched poly(vinylidene fluoride) microfibers toward flexible piezoelectric sensor

Abstractβ‐phase enriched piezoelectric poly(vinylidene fluoride) (PVDF) films/fibers are often prepared by high‐energy costing methods, including mechanical stretching, high‐electric field or electrospinning. In this study, PVDF piezoelectric microfibers, for the first time, were prepared by microfluidic spinning technology. The β‐phase enriched PVDF microfibers with various diameters could be easily obtained inside the microfluidic channel due to the mass transfer induced phase inversion of the inner PVDF solution. The influence of diameter of the fibers, PVDF concentration of the inner phase and water content of the outer phase on the β‐phase content and crystallinity degree of the obtained fibers was studied in detail. The obtained β‐phase enriched fiber was weaved into meshes. Flexible piezoelectric fabrics were then developed based on these meshes, and further used as in‐situ and real time human motion monitoring. This simple and effective strategy provides a promising microfluidic spinning technique toward the development of functional microfibers and wearable piezoelectric sensors, which may also give some implies for the industrial wet‐spinning of piezoelectric PVDF fibers in the future.

Electrospinning core-sheath piezoelectric microfibers for self-powered stitchable sensor

Abstract Owing to the limitations of two-dimensional devices such as easily damaged and airtight characteristics in practical applications, flexible fiber electronics which can narrow the gap between devices and wearable applications due to their unique stitchable function have been attracting tremendous attention nowadays. Here, this paper introduced a simple strategy for fabricating the piezoelectric microfiber with a novel core-sheath structure by directly electrospinning the poly(vinydene fluoride-trifluoroethylene) (P(VDF-TrFE)) onto the flexible conductive wire. Precise control of the fiber diameter and thickness of P(VDF-TrFE) functional layer can be achieved. Specifically, this stitchable fiber exhibits high sensitivity of 60.82 mV/N and excellent durability of 15000 cycles under positive compression, and finite element method (FEM) was carried out cooperating with practical experiment to analyze the stress and electric field distribution of piezoelectric fibers under both positive compression and bending modes through COMSOL software. The flexible stitchable fiber can bear various complex, even severe deformations such as bending and knotting, enabling itself to be woven into textile and further generate power and response when subjected to external deformation, which is of significance for the portable and wearable electronics that are expected to be breathable and comfortable. This work also offers a general and effective solution for the flexible and wearable electronic devices.

Orthogonal Anisotropic Sensing and Actuating Characteristics of a 1-3 PZT Piezoelectric Microfiber Composite

Orthogonal anisotropic sensing plays an important role in determining driver and sensor properties, while the fiber diameter directly affects the sensitivity of piezoelectric fiber composites. However, few studies have been carried out on fibers at the micron level. Here, well-aligned piezoelectric fiber arrays approximately 10 μm in diameter were prepared using an activated carbon template. A 1-3 lead zirconate titanate (PZT) piezoelectric microfiber composite was obtained by infiltrating epoxy resin into fibers. The microfibers were embedded orderly and well distributed in the epoxy matrix. The orthogonal anisotropy of the sensing and actuating performance was investigated and evaluated. The 1-3 PZT piezoelectric microfiber composite was clearly anisotropic with a much better piezoelectric sensitivity along the longitudinal direction of the fibers. The highest output voltage in the longitudinal direction was twice as large as that in the transverse direction. The highest strain in the longitudinal sensitivity direction was about four times the strain of the transverse direction.

Electrospinning of poly(γ‐benzyl–α,L‐glutamate) microfibers for piezoelectric polymer applications

ABSTRACTOne of the latest developments in the field of piezoelectric polymers is the use of poly(γ‐benzyl‐α,L‐glutamate) (PBLG), a poly(amino acid) that can be poled along its α‐helical axis and fabricated into thermally stable piezoelectric microfibers via electrospinning. This study demonstrates a method for improving the piezoelectricity of electrospun PBLG microfibers by controlling the orientation of fibers using a method based on a concentrated electric field. The piezoelectricity is verified via customized quasi‐static and dynamic measurement methods, while the correlation between fiber alignment and the piezoelectric constant, d33, in the longitudinal mode of the electrospun PBLG fibers is investigated. When the level of alignment was varied from 50% to 90%, the piezoelectric constant increased linearly, showing a maximum d33 of 27 pC N−1 and a maximum force sensitivity of 65 mV N−1 at peak alignment. A fabricated flexible prototype based on electrospun PBLG fibers provides a new solution for the use of PBLG fibers in wearable energy harvesters or composites based on piezoelectric polymer fibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46440.

Flexible nanofilms coated with aligned piezoelectric microfibers preserve the contractility of cardiomyocytes.

The use of engineered cardiac tissue for high-throughput drug screening/toxicology assessment remains largely unexplored. Here we propose a scaffold that mimics aspects of cardiac extracellular matrix while preserving the contractility of cardiomyocytes. The scaffold is based on a poly(caprolactone) (PCL) nanofilm with magnetic properties (MNF, standing for magnetic nanofilm) coated with a layer of piezoelectric (PIEZO) microfibers of poly(vinylidene fluoride-trifluoroethylene) (MNF+PIEZO). The nanofilm creates a flexible support for cell contraction and the aligned PIEZO microfibers deposited on top of the nanofilm creates conditions for cell alignment and electrical stimulation of the seeded cells. Our results indicate that MNF+PIEZO scaffold promotes rat and human cardiac cell attachment and alignment, maintains the ratio of cell populations overtime, promotes cell-cell communication and metabolic maturation, and preserves cardiomyocyte (CM) contractility for at least 12 days. The engineered cardiac construct showed high toxicity against doxorubicin, a cardiotoxic molecule, and responded to compounds that modulate CM contraction such as epinephrine, propranolol and heptanol.

Bio-inspired directional sensor with piezoelectric microfiber and helical electrodes

Inspired by the hair cells of vertebrates and aquatics, we proposed a hair sensor design that mimics the directionality and linearity of hair cells. The sensor promotes a novel use of piezoelectric microfiber with unique helical electrodes. The sensing mechanism was modeled both analytically and numerically. The analytical model explicitly illustrates the effects of the various design parameters on the performance of the sensor; the numerical model took into account the complex geometry of the sensor and elucidated the importance of the orientation of piezoelectric polarization on the piezoelectric effects. Both models provide valuable insight to optimize the sensor performance. Hair sensor prototypes were fabricated and characterized in the laboratory. The sensor output was found to be linearly dependent on the magnitude of applied displacements. Besides, at the same magnitude of deflection, the sensor responses followed a cosine function with the loading direction, which is similar to what is observed on the directionality of biological hair cells. These experimental observations were consistent with the results of model simulations. An algorithm was proposed to determine the magnitude and direction of acoustic stimuli by utilizing just a pair of orthogonally polarized and closely spaced hair cell sensors.

Rhombohedral PLZT piezoelectric microfibers: a combined Raman and X-ray diffraction study

A combination of micro- and macro-scale structural characterization methods was implemented for clarification of the influence of different sintering atmospheres on the structural properties of Pb1−xLax(ZryTi1−y)O3 (PLZT) fibers. Three powders, PbZrO3 and ZrO2 (PZ + Z), PbZrO3 (PZ), and PbZrO3 + PbO (PZ + P), were used for the generation of protective atmospheres. Vibrations corresponding to the rhombohedral phase in (Pb0.93La0.07)(Zr0.65Ti0.35)O3 fibers were measured and mapped along the section of the fibers by micro-Raman spectroscopy. Comparison of the Raman data with the evolution of the unit cell parameters indicates that the PZ + Z protective atmosphere ensures the best properties during the PLZT sintering at the temperature of 1250 °C for 6 hours.

Emulating the directional sensitivity of fish hair cell sensor

This article describes the sensor development efforts that are inspired by the unique acoustic source tracking capability of aquatics such as fish. The physiological basis in the natural system has been attributed to the unique directional responses of hair cell sensor in the otolith. To emulate such directional transduction behaviors, a hair sensor based on piezoelectric microfiber is attempted. The sensor employs piezoelectric fiber both as the hair shaft and as the transduction element. A pair of electrodes was deposited on the fiber surface both for sensor signal collection and for polarizing the piezoelectric materials. Both computational modeling analysis and experimental study were conducted to validate the sensor performance. The hair sensor was found to possess directional responses that change in the pattern of a cosine function of the loading direction, resembling that observed in the hair cell sensor in the biological system. Such transduction behaviors pave the technical basis to emulate the unique acoustic tracking strategy by aquatics. PACS 07.07.Df, 07.10.Pz, 77.84.Cg, 87.19.lt

Piezoelectrochemical Effect: A New Mechanism for Azo Dye Decolorization in Aqueous Solution through Vibrating Piezoelectric Microfibers

A newly discovered piezoelectrochemical (PZEC) effect for the direct conversion of mechanical energy to chemical energy is applied for the mechanically induced degradation of a dye of C.I. Acid Orange (AO7) from aqueous solution in the presence of BaTiO3 microdendrites. The mechanism of the PZEC degradation of the dye depends on the ultrasonic vibration used, in which the formation of the strain-induced electric charges on the dendrite surface is due to the deformation and local charge accumulation on the BaTiO3. With sufficient applied electric potential, strained piezoelectric dendrites in AO7 aqueous solution triggered the decomposition reaction. The process is monitored by following the decolorization rate of AO7. The effects of pH, catalyst loading, and initial dye concentration on dye degradation were also studied. Kinetic analyses reveal that the PZEC degradation rates of AO7 can be approximated in terms of the Langmuir–Hinshelwood model. The value of the adsorption equilibrium constant, KAO7, was 0.149 (mgl–1)−1, and the value of the kinetic rate constant of the surface reaction, kc, was 0.50 mgl–1 min–1. These new strain-induced chemical reactions can provide a simple and cost-effective technology for decomposing organic pollutants in aqueous solution by scavenging waste energy such as noise or stray environmental vibrations.

Poly (ã‐Benzy; á,L glutamic acid)‐based piezoelectric film microfibers.

Composite films and microfibers based on the biopolymer poly(ã‐benzyl á,L‐glutamate) (PBLG) and their fabrication and piezoelectric properties are presented. By simultaneous poling and curing of PBLG/methylmethacrylate, we fabricated a flexible composite film with approximately 20% of the PBLG molecules oriented normal to the film surface exhibiting (d33 = 20 pC/N), and its Young’s modulus was 1 GPa. In an effort to optimize net dipole orientation in PBLG, we produced piezoelectric microfibers (diameter: 100 nm) with nearly all of the PBLG dipoles oriented along the fiber axis, evidenced by x‐ray diffraction. The PBLG fibers showed high piezoelectricity (d33 = 32 pC/N) and an elastic modulus of 570 MPa. Both the piezoelectric film and fiber systems can be fabricated directly from solution in a mold or on a substrate. Due to the versatility in the fabrication process and the high piezoelectricity, these materials show great promise as transducer materials.

Direct Water Splitting Through Vibrating Piezoelectric Microfibers in Water

We propose a mechanism, a piezoelectrochemical effect for the direct conversion of mechanical energy to chemical energy. This phenomenon is further applied for generating hydrogen and oxygen via direct water decomposition by means of as-synthesized piezoelectric ZnO microfibers and BaTiO3 microdendrites. Fibers and dendrites are vibrated with ultrasonic waves leading to a strain-induced electric charge development on their surface. With sufficient electric potential, strained piezoelectric fibers (and dendrites) in water triggered the redox reaction of water to produce hydrogen and oxygen gases. ZnO fibers under ultrasonic vibrations showed a stoichiometric ratio of H2/O2 (2:1) initial gas production from pure water. This study provides a simple and cost-effective technology for direct water splitting that may generate hydrogen fuels by scavenging energy wastes such as noise or stray vibrations from the environment. This new discovery may have potential implications in solving the challenging energy and environmental issues that we are facing today and in the future.