C.K. Yen

Significant piezoelectric and energy harvesting enhancement of poly(vinylidene fluoride)/polypeptide fiber composites prepared through near-field electrospinning

In this study we applied near-field electrospinning (NFES) to prepare ordered poly(vinylidene fluoride) (PVDF)/poly(γ-methyl L-glutamate) (PMLG) composite fibers displaying enhanced piezoelectricity. Using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC), we analyzed the miscibility, specific interactions, and secondary structures of the PVDF/PMLG composites. The NFES process improved the piezoelectric properties of the PMLG/PVDF composites, resulting in better orientation of their dipoles, a high ultimate stress (27.47 MPa), and a high Youngs modulus (2.77 GPa), as determined through micro-tensile testing. After patterning PVDF/PMLG piezoelectric composite fibers onto a poly(ethylene terephthalate)-based structure with parallel electrodes, we obtained a flexible PVDF/PMLG energy harvester that could capture ambient energy with a maximum peak voltage of 0.08 V, a power of 637.81 pW, and the energy conversion efficiency is 3.3%. The electro-mechanical energy conversion efficiency of this PVDF/PMLG energy harvester was up to three times higher than those of pristine individual PVDF and PMLG energy harvesters. Such PMLG/PVDF piezoelectric composite fibers exhibiting good piezoelectricity and good mechanical properties might have applicability in several fields, including biomedical engineering, green energy, wearable sensors, and energy harvesting.

Near-field electrospinning enhances the energy harvesting of hollow PVDF piezoelectric fibers

In this study we used the near-field electrospinning (NFES) process with the metallic coaxial needle injector to fabricate piezoelectric poly(vinylidene fluoride) (PVDF) hollow fiber tubes. Using these tubes, we designed an energy capture device featuring parallel electrodes to harvest low-frequency energy. We examined the effects of several parameters on the properties of the piezoelectric PVDF fiber tubes (PPTs), including the core flow rate, shell flow rate, concentration of PVDF, rotating tangential speed, and electric field. The elongation of the PPTs was greater than that of solid PVDF fibers, with the tensile strength of the PPTs reaching 32.49 MPa (as determined through a micro-tensile measurement). The output voltage of the PPTs was considerably higher (71.66 mV) and, with an external load resistance of 6 MΩ, the output power was also significantly greater (856.07 pW) than the solid PVDF fiber (output voltage = 45.66 mV and the maximum output power = 347.61 pW). As a result, the power generation of the PPTs was 2.46 times higher than that of the solid fibers. Thus, the PPTs not only displayed mechanical stiffness but also produced a greater power output.

Energy harvesting with piezoelectric poly(γ-benzyl-L-glutamate) fibers prepared through cylindrical near-field electrospinning

In this study, we examined the electrical energy conversion and mechanical characteristics of piezoelectric fibers of the synthetic polypeptide poly(γ-benzyl-L-glutamate) (PBLG), prepared through cylindrical near-field electrospinning (CNFES) of a uniform macromolecular solution of PBLG in CH2Cl2. A high electric field (from 5 × 106 to 1.5 × 107 V m−1) provided the electrostatic force to pull the polymer solution into a Taylor cone, from which the PBLG fibers were electrospun, yielding piezoelectric PBLG fibers highly oriented in an α-helical conformation, as determined through Fourier transform infrared spectroscopic analysis. The orientation of the α-helical conformation of these polypeptide fibers was greater than those of other polymer piezoelectric materials; indeed, micro-tensile testing revealed that the Youngs modulus and tensile stress of the fibers were 3.64 GPa and 60.54 MPa, respectively, greater than those of the typical piezoelectric polymer poly(vinylidene difluoride). The voltage outputs of single piezoelectric fibers reached as high as 89.14 mV with 8 MΩ resistance, with a maximum power output of 138.42 pW. PBLG piezoelectric fibers directly patterned on a cicada wing, with an interdigitated electrode for energy harvesting and a vibrational frequency of approximately 10–30 Hz, produced voltages ranging from 7.64 to 14.25 mV; such systems have potential applications as sensors and harvesters.

Energy Harvester and Cell Proliferation from Biocompatible PMLG Nanofibers Prepared Using Near-Field Electrospinning and Electrospray Technology

This paper describes the application of piezoelectric fibers and films formed using near-field electrospinning (NFES) and electrospray (ESP) technology. Poly(γ-methyl L-glutamate) (PMLG), a biocompatible material, was mixed with poly(ethylene oxide) (PEO) and surfactant to obtain a solution of appropriate viscosity and conductance. Because the orientation of the dipoles in PMLG was enhanced upon applying an electric field, we could use the NFES and ESP processes to align dipoles and enhance the piezoelectric properties of the resulting fibrous materials. The maximum peak voltage of a fiber-based harvester prepared using this approach was 0.056 V. Because the fibers and films were non-toxic biological materials displaying excellent piezoelectric characteristics, we deposited them on glass substrates coated with indium tin oxide to observe their effects on the proliferation of cells. The negative charge of PMLG decreased the proliferation of mouse fibroblast cells (NIH3T3); indeed, decreasing the interspacing between the fibers slightly decreased the proliferation of these cells. Moreover, the migration of the cells was inhibited significantly, or even halted, when the coverage of the ESP films increased, implying a growth inhibition effect.

Energy harvester made of Taiwan local Nephila pilipes spider silk

Many researches reveal that proteins have the property of piezoelectricity. Therefore, the study presents the concept of energy harvester made of natural spider silk. Moreover, with high density of protein, spider silk can produce more strong and stable piezoelectric property through the polarization technology. The major ampullate gland of native Nephila pilipes was chosen as the silk source in this study, and it was examined by Flourier transform infrared spectroscopy (FTIR), and electrical testing. FTIR reveals the polarized silk increases significantly at the peak of 1610 cm−1 to 1660 cm−1. It means that polarized silk has better α-helix and ß-sheet arrangement than non-polarized ones. The result of the electrical testing shows that the output voltage of polarized silk has 3.485 times higher than that of non-polarized silks. Thus, Taiwan local Nephila pilipes spider silks show great potential in energy harvester due to its piezoelectricity.

An ultra-wide angle module for optical performance enhancement of fixed-type Photovoltaic systems

This study presents an ultra-wide angle module on the fixed-type Photovoltaic (PV) panel to enhance the efficiency without a mechanical solar tracker. This ultra-wide angle module was composed of an array of light guiding unit, and each unit consisted of an asymmetrical compound parabolic curve (ACPC) and a free-form curve collimator. The ACPC was used to collect the misalignment and diffused light and the light was guided to the free-form curve collimator. The collimator provided the light for a smaller angle and better uniformity, and each light guiding unit was put in array for easily attaching to the PV panel. The simulation results show that this ultra-wide angle module had the optical efficiency above 80% when the misalignment angle was smaller than 20°. In addition, the commercial products are used for the experiment, and the results show that the CPC had 24% higher and the light guiding unit had 37% higher power generation than the naked PV panel.

Preparation of biodegradable polymer microcarriers by ultrasonic emulsification

The polymer material PCL (polycaprolactone) has good biodegradability and good performance on drug coating. For the long-term delivery drugs, the biodegradable polymers reduced drug side effects and enhanced the drug efficacy. This study combined emulsification and ultrasonic nozzle to prepare biodegradable polymer microspheres. The ultrasonic emulsification compared to other general emulsification methods had advantage of being stable and fast. In the process, the oil phase solution PCL flew through the ultrasonic nozzle at flow rate 0.5–5 ml/min. Through the standing wave energy on the nozzle surface, the PCL solution was sprayed into droplets. Then, the droplets were dripped into the aqueous phase solution PVA (Polyvinyl alcohol) to cure as the PCL microspheres. After the emulsification process was completed, the solution was poured into water to make the solvent of the emulsion solution volatilized. Finally, the solution was rinsed with water and the PCL microspheres were filtered by the filter. As a result, the PCL microspheres were able to be observed through an optical microscopy (OM) and a scanning electron microscopy (SEM). In order to measure the rate of degradation, the PCL microspheres were used for the experiment. The PCL microspheres at 2.8×1.2×1.4 cm3 volume were poured into an amano Lipase PS solution at a concentration of 0.005 mg/ml. Then, the solution was under a constant temperature (50 °C) and stable shaking situation, and the weight changes of the PCL microspheres were recorded per day. The result shows that the PCL microspheres particle size was 30–75 µm and the PCL microspheres at 2.8×1.2×1.4 cm3 volume were degraded fully in 7 days.

Study of the drug fiber for wound healing by direct-writing near field electrospinning with subdivision control

In this research, the mixed solution of polycaprolactone (PCL) and natural anti-inflammatory drugs (F101) in the direct writing system of near-field electrospinning (DWs-NFES) was used the uniform experimental design and controllable injection flow rate process to produce stable fibrous support structure. Finally, the mesh structure (60 × 60 mm2) of 0.89 µm drug fibers diameter was deposited. The result was confirmed the mesh structure to upgrade the fibers density in unit area. Therefore, the drug fibers of DWs-NFES were higher the gel and injured group about 3.67 times in the wound healing experiment.

Large-Area Piezoelectric PVDF Fibers Fabricated by Near-Field Electrospinning with Multi-Spinneret Structures

In the study, we improved the near-field electrospinning (NFES) by multi-spinnerets with a cylindrical collector to fabricate a large area permanent piezoelectric of polyvinylidene fluoride (PVDF) fibers array. We designed multi-spinnerets by using printed circuit board (PCB) and drilled spinnerets on the solder balls. With different process parameters, we can obtain different diameters of PVDF fibers. By using the Taguchi method analysis, we found that the optimum sample of PVDF fiber arrays were manufactured by an electrical field of 1.6 × 107 V/m. The cylindrical collector with high tangential velocity of 1779.9 mm/s and the heat treatment temperature of 65 °C for one hour. In addition, we used X-ray diffraction (XRD) and scanning electron microscopy (SEM) to analyze β-phase crystal quality and the surface character of PVDF fibers, respectively. From the observation of XRD, it revealed a high diffraction peak at 2θ = 20.6° of piezoelectric crystal β-phase structure. As PVDF solution with concentration of 18 wt % and the conductivity of 44.2 μS/cm was electrospun via NFES with multi-spinneret structure, we obtained a smooth manufacturing process. When the periodical tapping frequency was applied with 9 Hz, the maximum peak voltage of 86.9 mV was generated. In a cicada’s wing test, when the tapping frequency input was applied during 10–50 Hz, the maximum output voltage signals of 6.2 mV were generated.

Structural design of high efficient synchronous permanent magnet bike dynamotor

In the study, a new design of synchronous permanent magnet bike dynamotor (SPMBD) with interdigitated magnetic resistance route (IDTMR) structure was proposed to enhance the efficiency of generator by changing the magnetic route structure. The main design is through changing the distance between the poles, width, thickness and numbers of poles in the interdigitated structure to change the magnetic field. The power generation efficiency was studied under different circumstances using ANSYS MAXWELL electromagnetic simulation and actual measurement given speed to achieve the most appropriate geometry parameters.