Antennas operating at high frequency bands are sought after for applications in 5G, satellite, radar, and other communication systems. Graphene, a two-dimensional material known for its exceptional ...conductivity, mechanical strength, and chemical stability, is anticipated to serve as a viable substitute for copper in antenna applications. However, researches on graphene antennas at millimeter-wave and higher frequencies are mainly limited to theory and simulation, due to the fabrication challenges of achieving high-precision graphene patterns. Herein, we present the design and fabrication of a graphene folded reflectarray antenna (FRA) operating at millimeter-wave. The FRA is fabricated using screen-printing of graphene ink on an RT5880 substrate, followed by laser engraving for precise patterning. The main reflector has 918 patch units, and the polarizing grids have line widths and spacings of 100 μm. Measurements demonstrate that the antenna has a realized peak gain of 21.37 dBi at 37.5 GHz. The radiation patterns show a 3 dB beamwidth of 6° and 4° in the E-plane and H-plane respectively, with cross-polarization more than −18 dB. The laser-assisted screen-printing method provides a feasible strategy for the precision manufacture of graphene communication devices.
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Abstract
The fabrication of fully printable, flexible micro‐supercapacitors (MSCs) with high energy and power density remains a significant technological hurdle. To overcome this grand challenge, the ...2D material MXene has garnered significant attention for its application, among others, as a printable electrode material for high performing electrochemical energy storage devices. Herein, a facile and in situ process is proposed to homogeneously anchor hydrous ruthenium oxide (RuO
2
) nanoparticles on Ti
3
C
2
T
x
MXene nanosheets. The resulting RuO
2
@MXene nanosheets can associate with silver nanowires (AgNWs) to serve as a printable electrode with micrometer‐scale resolution for high performing, fully printed MSCs. In this printed nanocomposite electrode, the RuO
2
nanoparticles contribute high pseudocapacitance while preventing the MXene nanosheets from restacking, ensuring an effective ion highway for electrolyte ions. The AgNWs coordinate with the RuO
2
@MXene to guarantee the rheological property of the electrode ink, and provide a highly conductive network architecture for rapid charge transport. As a result, MSCs printed from the nanocomposite inks demonstrate volumetric capacitances of 864.2 F cm
−3
at 1 mV s
−1
, long‐term cycling performance (90% retention after 10 000 cycles), good rate capability (304.0 F cm
−3
at 2000 mV s
−1
), outstanding flexibility, remarkable energy (13.5 mWh cm
−3
) and power density (48.5 W cm
−3
).
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The industrial scale production and application of liquid conductive nanomaterials with well-defined conductive properties, printing adaptability and mechanical properties are crucial ...for the flexible electronic devices. Although graphene can be used as an attractive liquid nanoink platform for electronic devices, it is still a major challenge to prepare graphene conductive inks with high concentration, conductivity and stability with graphene powders as raw materials and improve the post-treatment process for printed patterns. Here, a novel graphene-based screen printing conductive ink employing liquid-exfoliated graphene powders produced by jet cavitation and carbon black jointly as conductive filler is presented. The inks with graphene powders containing thicker smaller-area flakes and carbon black fraction of 15% in the total conductive fillers exhibit printability down to lines of 90 μm in width and printed pattern electrical conductivity of 2.15 × 104 S/m at 7 μm thickness along with outstanding mechanical properties. Also, special post-treatment, i.e. heating-compression rolling-heating, makes the conductive ink formulation compatible with a wide range of substrates and suitable for Roll-to-Roll applications. Overall, this paper provides a new solution to high-efficiency, low-cost, large-scale production of printed flexible electronics.
In this study, we report a facile chemical synthesis of a novel MnCo2S4/halloysite (HNTs) nanoflakes decorated on nanotubes which coated on Ni foam via a screen-printing technique. The MnCo2S4 thin ...films were prepared using a coprecipitation method which demonstrate battery kind of behavior. The MnCo2S4/HNTs-based electrode shows a specific capacity of 359 mAh g−1 at 5 mV s−1 with excellent cycling stability. Furthermore, the symmetric system exhibits an outstanding energy density and power density of 6.98 Wh kg−1 and 1976.0 W kg−1, respectively. The results obtained with the MnCo2S4/HNTs composite in a symmetric system indicate that this composite material can potentially be used as an alternative electrode material for electrochemical energy storage.
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•Innovative halloysite nanotubes (HNTs) like nanostructures covered on MnCo2S4 nanoflakes.•MnCo2S4/HNTs prepared hybrid composite using a simple screen-printing technique.•The MnCo2S4/HNTs offering excellent specific capacities and cycling stability.•Hybrid MnCo2S4/HNTs electrode provided higher surface area for supercapacitor.
A novel capacitive pressure sensor based on micro-structured polydimethylsiloxane (PDMS) dielectric layer was developed for wearable E-skin and touch sensing applications. The pressure sensor was ...fabricated on a flexible polyethylene terephthalate (PET) substrate, using PDMS and silver (Ag) as the dielectric and electrode layers, respectively. A set of PDMS films with pyramid shaped micro-structures were fabricated using a laser engraved acrylic mold. The electrodes (top and bottom) were fabricated by depositing Ag on PET films using additive screen-printing process. The pressure sensor was assembled by attaching the top and bottom Ag electrodes to the smooth side of pyramid shaped micro-structured PDMS (PM-PDMS) films. The top PM-PDMS was then placed on the bottom PM-PDMS. The capability of the fabricated pressure sensor was investigated by subjecting the sensor to pressures ranging from 0 to 10 kPa. A sensitivity of 0.221% Pa<inline-formula> <tex-math notation="LaTeX">^{\mathbf {-1}} </tex-math></inline-formula>, 0.033% Pa<inline-formula> <tex-math notation="LaTeX">^{\mathbf {-1}} </tex-math></inline-formula> and 0.011% Pa<inline-formula> <tex-math notation="LaTeX">^{\mathbf {-1}} </tex-math></inline-formula> along with a correlation coefficient of 0.9536, 0.9586 and 0.9826 was obtained for the pressure sensor in the pressure range of 0 Pa to 100 Pa, 100 Pa to 1000 Pa, and 1 kPa to 10 kPa, respectively. The pressure sensor also possesses a fast response time of 50 ms, low hysteresis of 0.7%, recovery time of 150 ms and excellent cycling stability over 1000 cycles. The results demonstrated the efficient detection of pressure generated from various activities such as hand gesture and carotid pulse measurement. The PM-PDMS based pressure sensor offers a simple and cost-effective approach to monitor pressure in E-skin applications.
Expanding the practical application range of self‐healing materials has become an important challenge for developing smart materials. Herein, the synthesis of printable, triple‐mode fluorescence ...responsive, and colorless self‐healing elastomers, formed by the combination of disulfide cross‐linked polyurethane (PU) polymers, carbon dots (CDs) down‐conversion fluorescence materials, and lanthanide ions doped upconversion fluorescence materials. The PU elastomers with optimal mechanical properties and good restorability (recover large strain of 500% after relaxation at room temperature (R.T.) for 2 h) are selected to incorporate CDs for fabricating fluorescence responsive elastomers (denoted as PU‐CDs). Significantly, the prepared PU‐CDs exhibit not only superior tensile strength and toughness (20.95 MPa and 85.13MJ m–3, respectively) than the previously reported R.T. self‐healing elastomers but also show good self‐healing properties and achieve blue fluorescence emissions under the ultraviolet excitation. Furthermore, a series of dual‐mode fluorescence patterns based on formulated core@shell structural upconversion inks are prepared on the transparent PU‐CDs elastomers by a directly screen‐printing method. Self‐healing and integrating a series of fluorescence patterns and damaged electrical patterns can also be accomplished successfully. The designed self‐healing materials provide new ideas and important guidance for developing and applying the next generation of smart materials.
This study designs a novel printable triple‐mode down/up‐conversion fluorescence responsive, colorless, and transparent room temperature self‐healing elastomer. The elastomer can exhibit blue emissions under UV excitation and dual‐mode designable fluorescence patterns under 980 and 808 nm irradiation. This study can provide new and important guidance for the development and application of the next generation of self‐healing materials.
Li-ion batteries are life-saving energy storage technology. However, the battery manufacturing process still needs complicated and expensive production lines because of the sensitive nature of active ...materials towards the open atmosphere. Additionally, employing hazardous N-Metil-2-Pirrolidon (NMP) solvents, which are also restricted by the World Health Organization for electrode preparation, contributes to unsafe working conditions. In this study, water-based LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode inks were produced and printed by the screen-printing method, which is widely used in sensors and electronics fabrication due to its potential practical applications and low-cost production possibilities. Despite their suitability for operation at high voltage ranges, NMC811 cathodes typically exhibit rapid capacity drops over time because of side reactions and Cathode-Electrolyte Interphase (CEI) thickening. In this study, to overcome the capacity drop issue and make it possible to produce water-based cathode inks, NMC811 particles were encapsulated with reduced graphene oxide (rGO) via a hydrothermal method. Water-based Carboxymethyl cellulose (CMC) - Polyethylene oxide (PEO) binders are compared with conventional Polyvinylidene fluoride (PVDF)-NMP binders and exhibited promising electrochemical stability of 75 % after 50 cycles within a high voltage range of 2.8–4.6 V. Therefore, the water-based novel cathode ink presented in this study is not only well-suited for advancing the development of printed batteries but also stride towards more eco-friendly processes thanks to replacing the toxic NMP with water. Moreover, battery printing technologies have also a strategic importance by reducing the investment cost of battery-producing.
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•Thermochromic poly(L-lactic acid) based materials have been produced and their printability on different substrates evaluated.•The materials morphology, physical–chemical, mechanical ...and electrical properties were determined.•The highest optical thermochromic response was observed for PLLA/Bmim2NiCl4 incorporating 40% wt.•Good ink printability, adhesion and thermochromic response was demonstrated on different substrates: paper, PET, wood and textile.
Ionic liquids (ILs) have been combined with different polymer matrixes to develop smart and functional materials. Due to their versatility, hybrid materials with specific tailor made properties can be obtained, including printable thermochromic materials, with a strong potential for sensing applications.
In this context, the thermochromic IL bis(1-butyl-3-methylimidazolium) tetrachloronickelate (Bmim2NiCl4) was incorporated into a biopolymer derived matrix, poly(L-lactic acid) (PLLA) in distinct concentrations up to 40% wt. aiming to develop environmentally friendly screen-printable printable thermochromic materials.
The addition of IL does not induce changes on the thermal properties of the material. On the other hand, the incorporation of the IL leads to the development of a porous structure in the films, a mechanical plasticizing effect in the polymer matrix, revealed by the decrease of the Young’s Modulus from 1110 ± 66 MPa to 572 ± 41 MPa and a increase in the electrical conductivity from 2.89x10-14 S·cm−1 to 2.66x10-8 S·cm−1, for PLLA and the samples with 40 % wt. of IL, respectively.
Finally, the thermochromic material was screen-printed on various substrates, including paper, polyethylene terephthalate (PET), textile and wood, opening the way for a wide range of applications.
Zn0·80Cd0·20O (ZnCdO) alloy coated screen-printed films on glass substrates were sintered in muffle furnace at different temperatures (500 °C, 550 °C & 600 °C) for 10 min duration and probed by ...different analytical techniques to reveal the effect of sintering on their structure, optical and electrical characteristics. X-ray diffraction (XRD) patterns exhibit polycrystalline phases of both hexagonal ZnO and cubic (CdO) crystal structures with a maximum intensity along (101) diffraction plane. UV-VIS and photoluminescence (PL) absorbance peaks exhibit red shift in their respective spectra. Zn–O, Cd–O stretching modes were observed in infrared transmission spectra of the raw and sintered films in 4000–400 cm−1 region, respectively. EPR studies exhibit the formation of oxygen vacancies and inherent defect in the Cd alloyed ZnO composite developed during synthesis process. All the parameters such as particle size, optical constants, activation energies and paramagnetic oxygen vacancies have been affected by sintering temperature.
•A facile screen-printing route has been used to develop Zn0·80Cd0·20O thick film.•Sintering temperature effect on physical properties of Zn0·80Cd0·20O film has been studied.•Optical Eg has been reduced from 3.21 eV to 2.82 eV when sintered at 600 °C.•Detailed photoluminescence study has been done.•Sintering temperature effect on EPR spectra of Zn0·80Cd0·20O film has been studied.
In order to improve the luminous properties of high-power white light-emitting diodes (WLEDs), we proposed a facile preparation of patterned phosphor-in-glass (PiG) in which yellow Y3Al5O12:Ce3+ ...(YAG:Ce3+) and red CaAlSiN3:Eu2+ (CASN:Eu2+) phosphor parts are separated. The patterned PiGs with sector piece and concentric ring phosphor geometries were prepared by screen-printing and low-temperature sintering. Experimental results indicated that LED modules packaged by the patterned PiGs yield high luminous efficacy and excellent color quality owing to the reducing reabsorption of yellow emission by red phosphor. In addition, the angular color uniformity (ACU) of LED modules with the ring patterned PiGs are better than those of LED modules with the piece patterned PiGs. It is also discovered that the luminous efficacy and corresponding correlated color temperature (CCT) of LED module packaged by the piece/ring patterned PiG are decreased with the increasing of piece/ring number.
•The PiG with excellent luminous properties is achieved by patterned structure.•The patterned PiG was prepared by screen-printing and low-temperature sintering.•The effects of various pattern geometries were systematically investigated.•The patterned structure provides a way to tune the optical properties of WLEDs.
