Combination Of Spin-coating Research Articles

Fabrication of Silver-Nanowire/PVDF Self-Supporting Thin Flexible Electrode Membranes

Flexible electrodes play an increasing role for medical applications, such as ECG (electrocardiography) or TENS (Transcutaneous electrical nerve stimulation) due to comfort in use and thus their suitability for health monitoring under movement and during sport. Polymers, such as polyvinylidene fluoride (PVDF), are promising for the development of fabrication methods and materials for such application cases, as stable flexible thin polymer membranes can be produced at large scale. We have compared different up-scalable fabrication techniques of thin electrode membranes based on PVDF as a function of silver nanowire concentration, using electrospinning, spincoating, and drop-casting techniques. The produced thin films and membranes and thin films were investigated by electrical four-point probing, optical microscopy, atomic force microscopy, as well as by stability tests under bending, and water exposure. We show, that a combination of electrospinning and spin-coating presents a reliable method for the fabrication of AgNW-PVDF based flexible nanofiber membrane electrodes (NMEs). Our nanofiber membrane electrodes (NMEs) exhibit a 10 times lower sheet resistance than AgNW-PVDF thin film electrodes (TFEs) produced for comparisons by a combination of spincoating and drop-casting using the same amounts of AgNWs. Upon immersion in water for up to 48 hours, we do not detect any nanowire release or decomposition of the fabricated electrodes, which is promising in view of application of the AgNW-PVDF composite electrodes in humid environment.

Improved coverage of rGO film on Si inverted pyramidal microstructures for enhancing the photovoltaic of rGO/Si heterojunction solar cell

Solar cell fabricated by reduced graphene oxide (rGO)/textured silicon (T-Si) structure is feasible due to the capability to form a continuous film of graphene oxide (GO) on Si surface by direct drop-casting or spin coating. In this article, we have fabricated a uniform array of Si inverted pyramidal microstructures by anisotropic etching using a mixture of tetramethyl-ammonium hydroxide and isopropyl alcohol. Low average reflectance of 10.4% is obtained by T-Si structure as compared to that of 53.5% obtained by flat Si (F-Si) structure in UV–visible range. As a result, the front surface area of solar cell has been increased up to 43.2%. The dispersion of GO on Si surface textured with inverted pyramidal microstructures is performed by direct drop-casting of GO droplet or a combination of spin-coating and drop-casting on. The reduction of GO to form rGO is achieved by annealing in N2 at 400 °C. Direct drop-casting of GO droplet on T-Si results to the formation of suspended GO film, covering only the top of Si inverted pyramidal array. Due to the minimum contact area of rGO and T-Si after the reduction, higher diode ideality factor, η = 4.02 is obtained as compared to the reference rGO/F-Si diode with η = 3.99. A combination of spin-coating and drop-casting of GO droplet on T-Si helps in filling the GO sheets into the pyramidal structures, thus creating a large contact area with sidewalls of Si inverted pyramidal structures. As a result, the η value has been significantly reduced to 3.50. The power conversion efficiency also shows an increment due to the improvement of both short circuit current (Jsc) and open circuit voltage (Voc). Jsc and Voc have been increased from 0.010 mA/cm2 up to 0.081 mA/cm2, and from 96 mV up to 304 mV, respectively. Hence, the power conversion efficiency has been improved in several orders due to the improvement in both Jsc and Voc, which is from 2.0 × 10−4% up to 5.2 × 10−3%.

Cell delivery system using injectable polymeric films

Event Abstract Back to Event Cell delivery system using injectable polymeric films Hirokazu Kaji1, Taro Kondo1, Jin Suzuki1, Nobuhiro Nagai2 and Toshiaki Abe2 1 Tohoku University, Bioengineering and Robotics, Japan 2 Tohoku University, Clinical Cell Therapy, Japan Introduction: There have been ongoing efforts for the development of cell delivery system to overcome the intractable diseases. Age-related macular degeneration (AMD) is the leading cause of visual impairment and blindness in the elderly population, whose main complication is the development of subretinal choroidal neovascularization and degeneration of retinal pigment epithelial (RPE) cells[1]. In this regard, subretinal transplantation of RPE cells to the degenerated site has attracted a great deal of attention as an innovative therapeutics for the treatment of AMD. However, poor viability, distribution and integration of the transplanted cells in suspension to the narrow subretinal space have limited this approach. Therefore, development of cell delivery system would bring significant benefits for the AMD treatment. Recently, we developed micropatterned ultrathin polymeric films (nanosheets), which can direct growth and morphogenesis of RPE cells toward local delivery of RPE cells[2]. Here, we examined whether micropatterned nanosheets can be delivered to the subretinal space of rat eyes using a syringe needle. Materials and Methods: Micropatterned nanosheets consisting of biodegradable poly(lactic-co-glycolic acid) (PLGA) and nile red were prepared on a poly(vinyl alcohol) (PVA) coated glass substrate by a combination of spincoating and microcontact printing technique. A typical diameter of circular nanosheets was 300 μm. The freestanding nanosheets were obtained by dissolving the PVA layer with PBS. Sprague-Dawley rats (SLC) weighing 250-300 g were used in this study. All animals were handled in accordance with the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research after receiving approval from the Institutional Animal Care and Use Committee of the Tohoku University Environmental & Safety Committee. After the rats were anesthetized with ketamine hydrochloride and xylazine hydrochloride, micropatterned nanosheets were injected into the subretinal space using a 27G syringe needle (Fig. 1a). Results and Discussion: Micropatterned nanosheets were injected with 2 μL of saline to the subretinal space through the sclera. Figure 1b shows optical coherence tomography (OCT) images of the retina taken one week after the injection of the micropatterned nanosheets. A shadow of the sheet like structure was observed in the subretinal space while there was not such shadow in the OCT image of a control. Also, a shadow of the circular nanosheet was observed at the posterior segment of the isolated eye (Fig. 1c). These results indicate that the nanosheets were successfully injected and spread into the subretinal space of rat eyes. Conclusions: We developed micropatterned nanosheets consisting of biodegradable polymers, which can be delivered to the subretinal space using a syringe needle. The injection of micropatterned nanosheets through a syringe needle could be a minimal invasive way to reduce the incision size of the sclera and subsequent inflammatory response. The flexible micropatterned nanosheets injectable by the syringe needle hold great promise to transplant organized RPE cells. Figure 1. (a) Schematic representation of the injection of micropatterned nanosheets into the subretinal space. (b) OCT images of (upper) the retina one week after the injection of the maicropatterned nanosheets and (lower) a control. Arrow in the upper image indicates the injected nanosheets. c) Photo of an isolated eyeball. Arrow indicates the injected nanosheets. JSPS KAKENHI Grant-in-Aid for Scientific Research (B) (26286031); JSPS KAKENHI Grant-in-Aid for Challenging Exploratory Research (26560233); Japan National Society for the Prevention of Blindness

Fabrication of Stacked Organic Electroluminescence Devices with a Combination of Spin Coating and Electrospray Deposition

A combination of spin coating and electrospray deposition (ESD) was applied for the fabrication of an organic light-emitting diode (OLED) with a stacked structure. Two kinds of polymer materials were used to fabricate a multilayered structure. One was poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV; Sigma-Aldrich) and the other was poly[2,5-di(hexyloxy)cyanoterephthalylidene] (CN-PPV; Sigma-Aldrich). With the addition of acetone to polymer material (MEH-PPV and CN-PPV) solution, smaller droplets were produced at the emitter resulting in thin-film fabrication under a dry condition. This condition was adopted for CN-PPV film deposition on MEH-PPV surface made by the spin coating method. The double-layered OLED obtained successfully emitted light at a bias voltage of 15 V. Layer-by-layer stacking of CN-PPV and MEH-PPV was confirmed by the UV-induced fluorescence spectrum. In case of the layer-by-layer structure, the obtained spectrum showed a linear combination of spectrum from MEH-PPV and CN-PPV.

Fabrication of Stacked Organic Electroluminescence Devices with a Combination of Spin Coating and Electrospray Deposition

Fabrication of Stacked Organic Electroluminescence Devices with a Combination of Spin Coating and Electrospray Deposition

Characterisation of the surface composition in electrospun nanowebs with static secondary ion mass spectrometry (S-SIMS)

Electrospinning is a recently rediscovered method to produce non-woven nanowebs of which the individual polymer fibres have diameters of 50–500 nm. Applications require specific functionalities to be present at the surface. The use of additives in the electrospun solution provides an elegant alternative to functionalised polymers. This study has focused on the use of the static secondary ion mass spectrometry (S-SIMS) to characterise the surface composition of nanofibres electrospun from acetone solutions containing 15% (w/w) of poly(ɛ-caprolactone) (PCL, molecular weight 40,000) and 0–15 mol% (relative to PCL) cetyltrimethylammonium bromide (CTAB). Specifically, the calibration of the relative signal intensities of structural ions from PCL and CTAB as a function of the local concentrations requires adequate reference samples to be prepared. In general, this step becomes a major bottleneck in nanoscale analysis. A relatively simple method using a combination of spincoating and hand barcoating of solutions has been developed. Its applicability and limitations for monitoring the surface enrichment of CTAB in PCL nanowebs are discussed.

Crosslinkable hole-transport materials for preparation of multilayer organic light emitting devices by spin-coating

Our approach to prepare multilayer light emitting devices (LEDs) by low-cost spin-coating techniques is the combination of spin-coating and photo-crosslinking. The oxetane functionality was used as the polymerizable moiety, which was crosslinked in bulk by a cationic mechanism. The resulting films were resistant against solvents used in subsequent spin-coating steps. The synthesis of bis-functionalized hole transporting triarylamines by palladium catalyzed C—N-coupling reaction, their polymerization, characterization, and first application in two-layer blue light emitting OLEDs are presented.