Transduction Properties Research Articles

Model of cochlear microphonic explores the tuning and magnitude of hair cell transduction current

The mammalian cochlea relies on the active forcing of sensory outer hair cells (OHCs) to amplify traveling wave responses along the basilar membrane. These forces are the result of electromotility, wherein current through the OHCs leads to conformational changes in the cells that provide stresses on surrounding structures. OHC transducer current can be detected via the voltage in the scala tympani (the cochlear microphonic, CM), and the CM can be used as an indicator of healthy cochlear operation. The CM represents a summation of OHC currents (the inner hair cell contribution is known to be small) and to use CM to probe the properties of OHC transduction requires a model that simulates that summation. We developed a finite element model for that purpose. The pattern of current generators (the model input) was initially based on basilar membrane displacement, with the current size based on in vitro data. The model was able to reproduce the amplitude of experimental CM results reasonably well when the input tuning was enhanced slightly (peak increased by ∼6 dB), which can be regarded as additional hair bundle tuning, and with a current/input value of 200–260 pA/nm, which is ∼4 times greater than the largest in vitro measures.

LDL receptor-related protein 1 and its interacting partners in tissue homeostasis.

LDL receptor-related protein 1 (LRP1) is a multifunctional protein with endocytic and signal transduction properties due to its interaction with numerous extracellular ligands and intracellular proteins. This brief review highlights key developments in identifying novel functions of LRP1 in liver, lung, and the central nervous system in disease pathogenesis. In hepatocytes, LRP1 complexes with phosphatidylinositol 4-phosphate 5-kinase-1 and its related protein to maintain intracellular levels of phosphatidylinositol (4,5) bisphosphate and preserve lysosome and mitochondria integrity. In contrast, in smooth muscle cells, macrophages, and endothelial cells, LRP1 interacts with various different extracellular ligands and intracellular proteins in a tissue-dependent and microenvironment-dependent manner to either enhance or suppress inflammation, disease progression or resolution. Similarly, LRP1 expression in astrocytes and oligodendrocyte progenitor cells regulates cell differentiation and maturation in a developmental-dependent manner to modulate neurogenesis, gliogenesis, and white matter repair after injury. LRP1 modulates metabolic disease manifestation, inflammation, and differentiation in a cell-dependent, time-dependent, and tissue-dependent manner. Whether LRP1 expression is protective or pathogenic is dependent on its interaction with specific ligands and intracellular proteins, which in turn is dependent on the cell type and the microenvironment where these cells reside.

Regulatory interplay between Vav1, Syk and β-catenin occurs in lung cancer cells

Vav1 exhibits two signal transducing properties as an adaptor protein and a regulator of cytoskeleton organization through its Guanine nucleotide Exchange Factor module. Although the expression of Vav1 is restricted to the hematopoietic lineage, its ectopic expression has been unraveled in a number of solid tumors. In this study, we show that in lung cancer cells, as such in hematopoietic cells, Vav1 interacts with the Spleen Tyrosine Kinase, Syk. Likewise, Syk interacts with β-catenin and, together with Vav1, regulates the phosphorylation status of β-catenin. Depletion of Vav1, Syk or β-catenin inhibits Rac1 activity and decreases cell migration suggesting the interplay of the three effectors to a common signaling pathway. This model is further supported by the finding that in turn, β-catenin regulates the transcription of Syk gene expression. This study highlights the elaborated connection between Vav1, Syk and β-catenin and the contribution of the trio to cell migration.

Numerical study of bulk acoustofluidic devices driven by thin-film transducers and whole-system resonance modes.

In bulk acoustofluidic devices, acoustic resonance modes for fluid and microparticle handling are traditionally excited by bulk piezoelectric (PZE) transducers. In this work, it is demonstrated by numerical simulations in three dimensions that integrated PZE thin-film transducers, constituting less than 0.1% of the bulk device, work equally well. The simulations are performed using a well-tested and experimentally validated numerical model. A water-filled straight channel embedded in a mm-sized bulk glass chip with a 1- μm-thick thin-film transducer made of Al0.6Sc0.4N is presented as a proof-of-concept example. The acoustic energy, radiation force, and microparticle focusing times are computed and shown to be comparable to those of a conventional bulk silicon-glass device actuated by a bulk lead-zirconate-titanate transducer. The ability of thin-film transducers to create the desired acoustofluidic effects in bulk acoustofluidic devices relies on three physical aspects: the in-plane-expansion of the thin-film transducer under the applied orthogonal electric field, the acoustic whole-system resonance of the device, and the high Q-factor of the elastic solid, constituting the bulk part of the device. Consequently, the thin-film device is remarkably insensitive to the Q-factor and resonance properties of the thin-film transducer.

Optimized Adeno-Associated Virus Vectors for Efficient Transduction of Human Retinal Organoids.

The most widely used vectors for gene delivery in the retina are recombinant adeno-associated virus (rAAV) vectors. They have proven to be safe and effective in retinal gene therapy studies aimed to treat inherited retinal dystrophies, although with various limitations in transduction efficiency. Novel variants with modified capsid sequences have been engineered to improve transduction and overcome limitations of naturally occurring variants. Although preclinical evaluation of rAAV vectors based on such novel capsids is mostly done in animal models, the use of human induced pluripotent stem cell (hiPSC)-derived organoids offers an accessible and abundant human testing platform for rAAV evaluation. In this study, we tested the novel capsids, AAV9.GL and AAV9.NN, for their tropism and transduction efficiency in hiPSC-derived human retinal organoids (HROs) with all major neuronal and glial cell types in a laminated structure. These variants are based on the AAV9 capsid and were engineered to display specific surface-exposed peptide sequences, previously shown to improve the retinal transduction properties in the context of AAV2. To this end, HROs were transduced with increasing concentrations of rAAV9, rAAV9.GL, or rAAV9.NN carrying a self-complementary genome with a cytomegalovirus-enhanced green fluorescent protein (eGFP) cassette and were monitored for eGFP expression. The rAAV vectors transduced HROs in a dose-dependent manner, with rAAV9.NN achieving the highest efficiency and fastest onset kinetics, leading to detectable eGFP signals in photoreceptors, some interneurons, and Müller glia already at 2 days post-transduction. The potency-enhancing effect of the NN peptide insert was replicated when using the corresponding AAV2-based version (rAAV2.NN). Taken together, we report the application of an HRO system for screening novel AAV vectors and introduce novel vector candidates with enhanced transduction efficiency for human retinal cells.

Design criteria to fabricate plasmonic gold nanomaterials for surface-enhanced Raman scattering (SERS)-based biosensing

The discovery of noble metal plasmonic nanoparticles (PNPs) has introduced surface-enhanced Raman scattering (SERS) as a highly sensitive and specific bioanalytical technique with greater potential in point-of-need disease diagnosis. This Tutorial provides an overview of the principles governing a gold PNP-based biosensor design for sensitive and reliable SERS-based detection of disease biomarkers. First, we will highlight the optical transducer properties of PNPs, the principles of SERS, the benefits of SERS detection, and the modes of SERS for biomarker detection. The analytical performance (sensitivity and specificity) and the reliability (accuracy and reproducibility) of a SERS biosensor are mainly dictated by (i) the chemical and optical transducer properties of PNPs, (ii) the functional nano interface, where the interaction(s) between PNPs and target biomolecules take place, and (iii) SERS data acquisition and evaluation metrics. Maintaining a balance between SERS signal enhancement and reproducibility is critical for advancing the field deployment of SERS technologies. However, the reproducibility of SERS biosensors is often overlooked in lieu of the assay sensitivity. Consequently, next, we will discuss the systematic optimization strategies for fabricating gold PNPs as SERS substrates and designing their functional interface to design SERS biosensors with sufficient sensitivity, specificity, and reproducibility. We will highlight the choice of PNPs and their integration into biosensing platforms depending on the mode of SERS detection. Last, we will discuss the SERS data acquisition and performance evaluation as an integral part of the SERS biosensors development workflow.

Spurious-mode vibrations caused by alternating current poling and their solution process for Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

The effects of alternating current poling (ACP) at 80 °C on electrical properties of [001]-oriented 0.72 Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-28PT) single crystals (SCs) have been investigated. The square-wave ACP SCs poled at high voltage (HV, 5 kVrms/cm) occasionally showed large fluctuations and low opposite values of piezoelectric coefficient (d33 = ± 1370 pC/N) in one plate. This revealed spurious-mode vibrations (SMV) of impedance spectrum. However, after depolarizing and repolarizing the sample with a sine-wave ACP at low voltage (LV, 3.5 kVrms/cm), the d33 enhanced to be 1720 pC/N (+26%) and did not exhibit large fluctuation or opposite values in one plate any more. The impedance spectrum became clean and the abnormal SMV disappeared. We proposed four possible mechanisms of the SMV, and speculate that the main cause maybe by macro-scale sub-domain structure and/or phase change in the main domain structure and/or phase in the SC plate due to the specific poling conditions not eternal mechanical damage of PMN-PT SCs. This study will be useful to realize a high d33 and improve other properties of PMN-PT ACP SC ultrasonic transducers without any SMV for high-frequency medical imaging equipment.

Two-Dimensional Nanostructures for Electrochemical Biosensor.

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials—e.g., the electronic properties, performance, and mechanical flexibility—and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

Metal-Free Multilayer Hybrid PENG Based on Soft Electrospun/-Sprayed Membranes with Cardanol Additive for Harvesting Energy from Surgical Face Masks.

Disposable surgical face masks are usually used by medical/nurse staff but the current Covid-19 pandemic has caused their massive use by many people. Being worn closely attached to the people's face, they are continuously subjected to routine movements, i.e., facial expressions, breathing, and talking. These motional forces represent an unusual source of wasted mechanical energy that can be rather harvested by electromechanical transducers and exploited to power mask-integrated sensors. Typically, piezoelectric and triboelectric nanogenerators are exploited to this aim; however, most of the current devices are too thick or wide, not really conformable, and affected by humidity, which make them hardly embeddable in a mask, in contact with skin. Different from recent attempts to fabricate smart energy-harvesting cloth masks, in this work, a wearable energy harvester is rather enclosed in the mask and can be reused and not disposed. The device is a metal-free hybrid piezoelectric nanogenerator (hPENG) based on soft biocompatible materials. In particular, poly(vinylidene fluoride) (PVDF) membranes in the pure form and with a biobased plasticizer (cardanol oil, CA) are electrospun onto a laser-ablated polyimide flexible substrate attached on a skin-conformable elastomeric blend of poly(dimethylsiloxane) (PDMS) and Ecoflex. The multilayer structure of the device harnesses the piezoelectricity of the PVDF nanofibers and the friction triboelectric effects. The ultrasensitive mechanoelectrical transduction properties of the composite device are determined by the strong electrostatic behavior of the membranes and the plasticization effect of cardanol. In addition, encapsulation based on PVDF, PDMS, CA, and parylene C is used, allowing the hPENG to exhibit optimal reliability and resistance against the wet and warm atmosphere around the face mask. The proposed device reveals potential applications for the future development of smart masks with coupled energy-harvesting devices, allowing to use them not only for anti-infective protection but also to supply sensors or active antibacterial/viral devices.

Investigation on the Role of Ionic Liquids in the Output Signal Produced by Bacterial Cellulose-Based Mechanoelectrical Transducers.

Green sensors are required for the realization of a sustainable economy. Biopolymer-derived composites are a meaningful solution to such a needing. Bacterial Cellulose (BC) is a green biopolymer, with significant mechanical and electrical properties. BC-based composites have been proposed to realize generating mechanoelectrical transductors. The transductors consist of a sheet of BC, impregnated of Ionic Liquids (ILs), and covered with two layers of Conducting Polymer (CP) as the electrodes. Charges accumulate at the electrodes when the transductor is bent. Generating sensors can produce either Open Circuit (OC) voltage or Short Circuit (SC) current. In the paper, the OC voltage and SC current, generated from BC-based composites, in a cantilever configuration and subjected to dynamic deformation are compared. The influence of ILs in the transduction performance, both in the case of OC voltage and SC current is investigated. Experimental investigations of structural, chemical, and mechanoelectrical transduction properties, when the composite is dynamically bent, are performed. The mechanoelectrical investigation has been carried on both in the time and in the frequency domains. Reported results show that no relevant changes can be obtained because of the use of IL when the OC voltage is considered. On the contrary, dramatic changes are observed for the case of SC current, whose value increases by about two orders of magnitude.

Uncooled Infrared Detector Based on an Aluminum Nitride Piezoelectric Fishnet Metasurface

This article reports on the first demonstration of a high resolution (~1.9 nW/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> measured in 200 Hz bandwidth) and fast (~5.3 ms) uncooled Infrared (IR) detector based on a high frequency (172 MHz) aluminum nitride nano-plate piezoelectric fishnet-like metasurface (PFM). For the first time, an ultrathin (650 nm) piezoelectric fishnet-like metasurface is employed to form the vibrating body of a nanoelectromechanical resonator with a unique combination of optical, thermal and electromechanical properties. Sensing and actuation of a high frequency and high electromechanical performance (quality factor, Q ~2254 and electromechanical coupling coefficient, k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ~1.4%) bulk acoustic mode of vibration in the free-standing ultrathin structure is achieved thanks to the superior piezoelectric transduction properties of the proposed metasurface. Strong absorption (60%) of mid wavelength infrared (MWIR) radiation in the ultra-low volume resonant device is obtained thanks to the properly engineered optical properties of the fishnet-like metasurface which provide multiple plasmonic resonances at 3-5 μm to the structure. The demonstrated resonant PFM detector technology marks a milestone towards the implementation of a new class of high performance, miniaturized and low power MWIR imaging systems.

The GTPase-activating protein-related domain of neurofibromin interacts with MC1R and regulates pigmentation-mediated signaling in human melanocytes

The melanocortin 1 receptor (MC1R) is a G-protein coupled receptor (GPCR) which plays a major role in controlling melanogenesis. A large body of evidence indicates that GPCRs are part of large protein complexes that are critical for their signal transduction properties. Among proteins which may affect MC1R signaling, neurofibromin (Nf1), a GTPase activating protein (GAP) for Ras, is of special interest as it regulates adenylyl cyclase activity and ERK signaling, two pathways involved in MC1R signaling. Moreover, mutations in this gene encoding Nf1 are responsible for neurofibromatosis type I, a disease inducing hyperpigmented flat skin lesions. Using co-immunoprecipitation and Bioluminescence Resonance Energy Transfer experiments we demonstrated a physical interaction of Nf1 with MC1R. In particular, the GAP domain of Nf1 directly and constitutively interacts with MC1R in melanocytes. Pharmacologic and genetic approaches revealed that the GAP activity of Nf1 is important to regulate intracellular signaling pathways involved in melanogenesis and, consequently, melanogenic enzyme expression and melanin production. These finding shed new light on the understanding and cure of skin pigmentation disorders.

Recording the Frequency Spectrum of Near-Wall Turbulent Pressures on an Acoustic Noise Background

The paper considers the problem of recording the spectral components of the frequency spectrum of near-wall turbulent pressures under the effect of acoustic noise. The previously proposed method for measuring pressure fluctuations on an acoustic noise background uses a two-element pressure transducer that wave-filters the measured turbulent fluctuation field. Here, we analytically investigate the wave properties of a two-element transducer in the turbulent pressures field. With proper selection of the characteristics, the proposed pressure fluctuation receiver, due to its wave properties, can cut off the acoustic noise contribution to the measurement results. The parameters and relations determining the conditions for efficient acoustic noise suppression are established.

Time reversibility of Lamb waves in thin plates with surface-bonded piezoelectric transducers is temperature invariant at the best reconstruction frequency

The Lamb wave time-reversal method has been widely proposed as a baseline-free method for damage detection in thin-walled structures. Under varying thermal environments, it would require that the time reversibility of Lamb waves is temperature invariant. In this study, we examine the temperature dependence of Lamb waves and its time reversibility using experiments and finite element simulations on isotropic plates with surface-bonded piezoelectric wafer transducers for actuation and sensing. The study is conducted at three different temperatures of the system from 25°C to 75°C for a wide range of excitation frequency. The results indicate that the time reversibility can undergo significant changes due to temperature variations depending on the excitation frequency. However, at the best reconstruction frequency corresponding to the maximum similarity of the reconstructed signal with the original input signal (proposed recently as the probing frequency), the change in the percent similarity with temperature is insignificant. The results also demonstrate that changes in the physical properties of both adhesive layers and piezoelectric transducers with temperature play a dominant role in influencing Lamb wave amplitudes. However, only the change in the characteristics of the adhesive layers is responsible for the temperature dependence of the time reversibility of Lamb waves.

Parametric Study of Environmental Conditions on The Energy Harvesting Efficiency for The Multifunctional Composite Structures

This paper presents a parametric study of the efficacy of an integrated vibration energy harvesting device under the environmental condition representative of an offshore wind turbine. A multifunctional glass fibre composite with an integrated Micro Fibre Composite (MFC) energy harvesting device was tested by swept sine vibration under environmental conditions that ranged from −40 °C to 70 °C in temperature and 10%RH to 90%RH in humidity in order to characterise the sensitivity and dependence of energy harvesting on environmental conditions. Experimental vibration testing was complemented with theoretical analysis to investigate the relative contributions to the temperature dependence of energy harvesting. This included mechanical properties of the stiffness and strength of the cantilever structure and the electrical properties of the MFC transducer, including its dielectric constants and charge coefficients. An inverse proportionality was observed between the magnitude of harvested energy and the climatic temperature. The efficiency of energy harvesting was dominated by the stiffness of the cantilever, which displayed viscoelastic temperature dependence. The sample was also tested with a vibration profile obtained from a wind turbine in order to validate the temperature influence under typical service conditions. Numerical modal analysis was used to determine the shapes of resonance modes, the frequencies of which were temperature dependent. Humidity was observed to have a secondary influence on energy harvesting, with no significant short-term effect on the structural properties of the samples within the limits of the experimental method.

Selective mode excitation of Lamb wave in composite laminates for a circular and two ring‐shaped piezoelectric actuators

AbstractIn the current research the effect of the radius of a transducer, vibration frequency and anisotropic properties of the host structure on the occuring wave fields is analyzed. Semi‐analytical approach based on the Green's matrix representations and the Fourier transform is applied for calculation of dispersion curves and wave fields in two types of composite layups in a wide frequency‐thickness product range. The contribution of each wave mode in the excited wave field is analyzed. A method for decomposition of the Lamb waves is proposed and examined for the example of a combination of two ring‐shaped actuators.

Polymeric cantilevered piezotronic strain microsensors processed by Atomic Layer Deposition

We propose an original and reliable method for processing cantilevered piezotronic strain microsensors based on diode junctions made of dominant wurtzite zinc oxide (ZnO) polycrystalline thin film by atomic layer deposition (ALD). These strain sensitive microsensors are integrated into millimetre-sized polyimide cantilevers by means of maskless laser lithography on the polymer foil, where the zinc oxide thin film is microstructured on top of patterned interdigitated platinum microelectrodes. We show how the structural and transducing properties are strongly influenced by the ALD deposition parameters, leading to the expected Schottky barrier modulation by electromechanical coupling. The linearity, sensitivity, frequency response and noise figure of the created piezotronic strain sensors are reported, leading to measured gauge factors as high as 150. Electrical power consumption inferior to 50 μW is reported.

Abstract 5484: Influence of the thermal and electric properties of biological tissues on the maximum temperature during TTFields therapy

Abstract Tumor Treating Fields (TTFields) is a non-invasive technique used in the treatment of glioblastoma. It consists in applying an electric field with a frequency of 200 kHz in two perpendicular directions alternately. This technique has an anti-mitotic effect if the induced field is at least 1 V/cm at the tumor bed. The Optune device, used to deliver these fields in real subjects, controls the injected current to keep scalp's temperature below potentially harmful values by controlling the temperature of the transducers. The thermal impact of this technique was recently predicted by our group. In this work we aim to investigate how the uncertainties regarding both the electric and thermal properties of tissues, transducers and gel affect the maximum temperature reached by each tissue and might affect the time that the device is applying the fields due to its thermal restrictions. We used a realistic head model created from MR images to perform our studies and run the simulations in COMSOL Multiphysics. After an extensive literature review, we selected a reasonable range of values for each property and performed a one-way sensitivity analysis. To obtain the temperature distribution we solved Pennes' equation in frequency domain studies. We observed that the most significant electric parameters are scalp, skull and gel's conductivity values. In general, an increase in the conductivity led to higher temperatures, as expected. In terms of changes in the temperature reached by the transducers it was seen that it can vary between +1.3°C (when scalp's conductivity is increased by a factor of 80% to 0.45 S/m) and -1.7°C (scalp's conductivity decreased to 0.14 S/m). The thermal parameters that are more critical are the ones that can directly change how quickly heat is transferred to the environment, namely scalp's properties. Transducer temperature varied between -0.6°C and +1.3°C when scalp's thermal conductivity was increased by 46% and decreased by 53%, respectively. Furthermore, the sweat rate and the convection factor and emissivity of the medical tape that covers the arrays also led to significant temperature variations. The latter analysis can be used to study new types of materials that can be more appropriate to apply these fields. The remaining electric (relative permittivity) and thermal (metabolic heat, blood perfusion, blood density and specific heat and thermal conductivity of skull, CSF and brain) parameters did not lead to significant temperature variations. These results show the importance of precisely knowing the most crucial physical properties in TTFields modelling studies. Due to the very strict current control injection mode of Optune based on the temperature of the transducers, it would be beneficial to experimentally measure the properties here discussed. Citation Format: Nichal Gentilal, Pedro Cavaleiro Miranda. Influence of the thermal and electric properties of biological tissues on the maximum temperature during TTFields therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5484.

Framework for analyzing the thermoreflectance spectra of metal thermal transducers with spectrally tunable time-domain thermoreflectance

The time-domain thermoreflectance (TDTR) technique has been widely used to measure thermal properties. The design and interpretation of the TDTR experiment rely on an in-depth understanding of the thermoreflectance signature for a given metal thermal transducer. Although the TDTR signals of several metal thermal transducers have been experimentally investigated, a practical framework bridging the electronic properties and the thermoreflectance characteristics of metal thermal transducers will be helpful for future studies. Compiling published results and our analysis and tests, in this work, we show a theoretical strategy to determine the thermallyinduced change of reflectance spectra with the electronic properties of metal transducers as the input. As a natural consequence of the proposed framework, we show that the optimal probe photon energy occurs near the interband transition threshold of the metal. To validate our approach, TDTR experiments are performed with Au and Cu as two representative metal thermal transducers in two temporal regimes when electrons and lattices have different temperatures (&amp;lt;10 ps) and reach thermal equilibrium (&amp;gt;10 ps), respectively. The experimental results show good agreement with the theory. The work fundamentally elucidates the thermally induced optical response of metal thermal transducers and also provides practical guidelines for choosing the appropriate probe photon energy to optimize the TDTR signal for a given metal thermal transducer, which is useful for broadening the adaptability of TDTR to various experimental conditions, materials, and new laser sources.

Bioinspired Multiresonant Acoustic Devices Based on Electrospun Piezoelectric Polymeric Nanofibers.

Cochlear hair cells are critical for the conversion of acoustic into electrical signals and their dysfunction is a primary cause of acquired hearing impairments, which worsen with aging. Piezoelectric materials can reproduce the acoustic-electrical transduction properties of the cochlea and represent promising candidates for future cochlear prostheses. The majority of piezoelectric hearing devices so far developed are based on thin films, which have not managed to simultaneously provide the desired flexibility, high sensitivity, wide frequency selectivity, and biocompatibility. To overcome these issues, we hypothesized that fibrous membranes made up of polymeric piezoelectric biocompatible nanofibers could be employed to mimic the function of the basilar membrane, by selectively vibrating in response to different frequencies of sound and transmitting the resulting electrical impulses to the vestibulocochlear nerve. In this study, poly(vinylidene fluoride-trifluoroethylene) piezoelectric nanofiber-based acoustic circular sensors were designed and fabricated using the electrospinning technique. The performance of the sensors was investigated with particular focus on the identification of the resonance frequencies and acoustic-electrical conversion in fibrous membrane with different size and fiber orientation. The voltage output (1–17 mV) varied in the range of low resonance frequency (100–400 Hz) depending on the diameter of the macroscale sensors and alignment of the fibers. The devices developed can be regarded as a proof-of-concept demonstrating the possibility of using piezoelectric fibers to convert acoustic waves into electrical signals, through possible synergistic effects of piezoelectricity and triboelectricity. The study has paved the way for the development of self-powered nanofibrous implantable auditory sensors.