Transparent Film Heaters Research Articles

Transparent flexible heater based on hybrid of carbon nanotubes and silver nanowires

Transparent film heaters have attracted increasing attention due to their usefulness in a wide range of applications, such as outdoor panel displays, avionic displays, and periscope and vehicle window defrosters. So far, transparent films made of only one kind of conductive nanomaterial have been tried in the fabrication of transparent film heaters. However, since each nanomaterial has its own advantages and disadvantages, satisfying various requirements from industry has so far been almost impossible. Here, we present a high-performance transparent film heater based on a hybrid of carbon nanotubes and silver nanowires. The new hybrid film shows a marked advance in haze reduction and an improvement in the flexibility of the silver nanowire film while maintaining excellent electrical conductivity. We demonstrate sufficient temperature rise even at low voltages and long-term stability of the new film heater. The present work sheds light on the feasibility of a more advanced film heater that will satisfy growing demands for better optoelectrical properties with excellent mechanical flexibility.

Uniformly Interconnected Silver‐Nanowire Networks for Transparent Film Heaters

AbstractThe fabrication and design principles for using silver‐nanowire (AgNW) networks as transparent electrodes for flexible film heaters are described. For best practice, AgNWs are synthesized with a small diameter and network structures of the AgNW films are optimized, demonstrating a favorably low surface resistivity in transparent layouts with a high figure‐of‐merit value. To explore their potential in transparent electrodes, a transparent film heater is constructed based on uniformly interconnected AgNW networks, which yields an effective and rapid heating of the film at low input voltages. In addition, the AgNW‐based film heater is capable of accommodating a large amount of compressive or tensile strains in a completely reversible fashion, thereby yielding an excellent mechanical flexibility. The AgNW networks demonstrated here possess attractive features for both conventional and emerging applications of transparent flexible electrodes.

Highly flexible transparent film heaters based on random networks of silver nanowires

We demonstrate a new concept for the fabrication of flexible transparent thin film heaters based on silver nanowires. Thanks to the intrinsic properties of random networks of metallic nanowires, it is possible to combine bendability, transparency and high heating performances at low voltage, typically below 12 V which is of interest for many applications. This is currently not possible with transparent conductive oxide technologies, and it compares well with similar devices fabricated with carbon nanotubes or graphene. We present experiments on glass and poly(ethylene naphthalate) (PEN) substrates (with thicknesses of 125 μm and extremely thin 1.3 μm) with excellent heating performances. We point out that the amount of silver necessary to realize the transparent heaters is very low and we also present preliminary results showing that this material can be efficiently used to fabricate photochromic displays. To our knowledge, this is the first report of metallic nanowire-based transparent thin film heaters. We think these results could be a useful approach for the engineering of highly flexible and transparent heaters which are not attainable by existing processes. Open image in new window

Thermal and structural dependence of the band gap of quantum dots measured by a transparent film heater

We report the temperature dependence of the optical absorption and emission spectra of quantum dots (QDs) for three different nanocrystal (NC) structures (CdSe core, CdSe/CdS core/shell, and CdSe/CdS/ZnS core/multishell) in the solid film state. For this, a transparent single-walled carbon nanotube (SWCNT) film attached to a QD thin layer was tested as a heater. The temperature dependence of spectral shifts in both absorption and emission of QDs was measured in the range 300–450 K, and the Stokes shift was calculated by measuring the energy difference between the absorption and emission peaks. We found that the Stokes shift decreased as QD shells were added and the temperature was increased, indicating a weaker electron–phonon coupling in the QDs with additional shells at higher temperature. Finally, the band gap of the QDs was measured as a function of temperature. The Debye temperature was obtained by empirically fitting the energy band gap.

Transparent Film Heaters based on Silver Nanowire Random Networks

ABSTRACTWe present the fabrication and characterization of transparent thin film heaters (TTFHs) based on silver nanowires. The goal is to develop a simple process for the production of transparent heating elements by large area printing techniques. The TTFHs are based on recently developed random networks of silver nanowires. Thanks to the very low sheet resistance achievable with silver nanowires, we show that it is possible to obtain high heating rates and good steady state temperatures at low voltages, typically below 12 V.

Flexible and Transparent Electrothermal Film Heaters Based on Graphene Materials

High-performance and novel graphene-based electrothermal films are fabricated through a simple yet versatile solution process. Their electrothermal performances are studied in terms of applied voltage, heating rate, and input power density. The electrothermal films annealed at high temperature show high transmittance and display good heating performance. For example, the graphene-based film annealed at 800 °C, which shows transmittance of over 80% at 550 nm, can reach a saturated temperature of up to 42 °C when 60 V is applied for 2 min. Graphene-based films annealed at 900 and 1000 °C can exhibit high steady-state temperatures of 150 and 206 °C under an applied voltage of 60 V with a maximum heating rate of over 7 °C s(-1) . For flexible heating films patterned on polyimide, a steady-state temperature of 72 °C could be reached in less than 10 s with a maximum heating rate exceeding 16 °C s(-1) at 60 V. These excellent results, combined with the high chemical stability and mechanical flexibility of graphene, indicate that graphene-based electrothermal elements hold great promise for many practical applications, such as defrosting and antifogging devices.

The manufacture of a transparent film heater by spinning multi-walled carbon nanotubes

A flexible, transparent heater was manufactured by spinning multi-walled carbon nanotubes (MWCNTs). MWCNT sheets were produced by continuously pulling on well-aligned MWCNTs, and films were produced by directly coating a flexible film. Single and double sheets were produced with sheet resistances of ∼699 Ω/sq and ∼349 Ω/sq and transmittances of 81% to 85% and 67% to 72%, respectively. Both films were heated by applying a direct current, and showed rapid thermal responses and uniform temperature distribution. The rate of temperature change was found to depend on the power applied. Frost on the surface of these films was rapidly removed so that they may have applications as automatic defrosters in vehicles of goggles.

Thermal Behavior of Transparent Film Heaters Made of Single-Walled Carbon Nanotubes

We investigate thermal behavior of transparent film heaters (TFH) made of single-walled carbon nanotubes. We fabricate the TFH by using the spray coating method. We studied the temperature dependence of the electrical resistance of the TFH in terms of Joule and external heating in various gas environments. Test results show that the effect of the electrical current through the TFH on the temperature dependence of the electrical resistance is not important and that the humidity and the degree of vacuum significantly affect the shape of the resistance−temperature curve. We discuss the physical meanings underlying the experimental results and how to make use of these findings. This study improves the understanding of the heating effect on electrical conductance of the TFH made of single-walled carbon nanotubes which could be a good candidate for the heater in many applications requiring both transparency and heating function.

Transparent Film Heater Using Single‐Walled Carbon Nanotubes

A transparent heater is produced from single-walled carbon nanotubes (SWCNTs) with a high thermal conductivity. A transparent conducting SWCNT film is fabricated on glass or polymer substrates by using a vacuum infiltration method. SWCNT films with a transparency of 65–97 % and a sheet resistance of 230–3500 Ω square–1 are demonstated. These films are good candidates for many applications that require transparent film heaters.

Тепловізійний неруйнівний метод дослідження прозорих тонкоплівкових нагрівачів

Тепловізійний неруйнівний метод дослідження прозорих тонкоплівкових нагрівачів

Premature Transition to Film Boiling during Stepwise Heat Generation. 3rd Report. Observation of Contact Area of Bubbles on a Heating Surface.

Premature transition to film boiling of R113 subjected to stepwise heating at atmospheric pressure is investigated using a transparent ITO film heater made by evaporation onto a glass substrate. The film simultaneously provides surface temperature measurement and permits viewing of the contact area of boiling bubbles from the underside of the heating surface. The ratio of the contact area of bubbles to the area of the heating surface increases to 100% just after boiling incipience, since an initial bubble appearing at a high wall superheat of around 90 K grows quickly along the heating surface and covers it. The contact area ratio is much higher than that in steady-state nucleate boiling throughout the boling duration from the departure of the initial bubble to the transition to film boiling. A dry area appears during the growth of the initial bubble. The occurrence of the dry area, which can be observed even at a low heat generation rate, may be mainly due to the self-evaporation of highly superheated liquid.

Novel integrated thermo-optic switches

We have demonstrated novel integrated optical switches based on the thermo- optic (TO) effect. The TO switches are input grating couplers. A temperature change causes a change Δ N in the effective refractive index of the guided mode in the grating region of the waveguide. This index change, in turn, induces a detuning away from or towards the resonance maximum of the in-coupling efficiency and thus actuates ON-OFF switching of the guided mode. We used transparent thin film heaters separated from the waveguiding film F(SiO 2 /TiO 2 ) by a buffer layer F′ (SiO 2 ). We fabricated films F and F′ using a dip-coating method (sol-gel process), and the surface relief gratings (1200 lines mm -1 ) were produced by means of an embossing technique. The temporal response of the switches was investigated and was compared with a solution of the heat conduction problem.