Marcin Sloma

Flexible Temperature Sensors on Fibers

The aim of this paper is to present research dedicated to the elaboration of novel, miniaturized flexible temperature sensors for textronic applications. Examined sensors were manufactured on a single yarn, which ensures their high flexibility and good compatibility with textiles. Stable and linear characteristics were obtained by special technological process and applied temperature profiles. As a thermo-sensitive materials the innovative polymer compositions filled with multiwalled carbon nanotubes were used. Elaborated material was adapted to printing and dip-coating techniques to produce NTC composites. Nanotube sensors were free from tensometric effect typical for other carbon-polymer sensor, and demonstrated TCR of 0.13%/K. Obtained temperature sensors, compatible with textile structure, can be applied in rapidly developing smart textiles and be used for health and protections purposes.

Electroluminescent structures printed on paper and textile elastic substrates

Purpose – New types of substrates were used for fabrication of printed electroluminescent structures. Polymer foils mainly used as substrates for such optoelectronic elements were replaced with paper and textiles. Printing on non-transparent substrate requires elaboration of printed transparent electrode, while usually polyester foils with sputtered ITO transparent electrodes are used. The paper aims to discuss these issues. Design/methodology/approach – Electroluminescent structures were fabricated with elaborated polymer compositions filled with nanomaterials, such as carbon nanotubes and graphene platelets, dielectric and luminophore nanopowders. Structures were printed as “reverse stack”, where transparent electrode is printed on top of the last luminophore layer. For that carbon nanotubes and graphene platelets filled composition was used, deposited with spray-coating technique. Findings – Main issue with new substrates is proper wetting with the use of screen-printing pastes, and much higher roughne...

Transparent electrodes with nanotubes and graphene for printed optoelectronic applications

We report here on printed electroluminescent structures containing transparent electrodes made of carbon nanotubes and graphene nanoplatelets. Screen-printing and spray-coating techniques were employed. Electrodes and structures were examined towards optical parameters using spectrophotometer and irradiation meter. Electromechanical properties of transparent electrodes are exterminated with cyclical bending test. Accelerated aging process was conducted according to EN 62137 standard for reliability tests of electronics. We observed significant negative influence of mechanical bending on sheet resistivity of ITO, while resistivity of nanotube and graphene based electrodes remained stable. Aging process has also negative influence on ITO based structures resulting in delamination of printed layers, while those based on carbon nanomaterials remained intact. We observe negligible changes in irradiation for structures with carbon nanotube electrodes after accelerated aging process. Such materials demonstrate a high application potential in general purpose electroluminescent devices.

Electrical performance of carbon nanotube-polymer composites at frequencies up to 220 GHz

We have measured the sub-THz electrical response of screen printed carbon nanotube-poly(methyl methacrylate) polymer composites up to 220 GHz. The measured electrical losses using mm long coplanar waveguide geometries averaged as low as 0.15 dB/mm in the frequency range 40 GHz–110 GHz and showed a reduction in signal loss with increasing frequency; a behaviour opposite to that found in conventional metallic conductors. Between 140 and 220 GHz, the electrical losses averaged 0.28 dB/mm. We show that the low electrical losses are associated with the capacitive coupling between the nanotubes and discuss potential high frequency applications.

Graphene-Based Dipole Antenna for a UHF RFID Tag

This paper describes design and measurements of RFID tag built of a graphene-based dipole antenna and a chip operating in the UHF band in accordance with the EPC Global Class 1 Gen. 2 standard. Several tags have been constructed and tested with a standard RFID reader to reveal that each one is fully operational, but the interrogation range for the graphene-based circuits has been limited in comparison to copper antennae. This can be attributed to increased sheet resistance of a graphene layer. However, it seems that for applications were the read range is not crucial the novel antenna can be an alternative to more expensive circuits printed with silver-based inks.

Thick Film Polymer Composites with Graphene Nanoplatelets for Use in Printed Electronics

The paper presents the results of the investigation into layers based on graphene nanoplatelets in polymer resin. Several types of polymer composition with different amount of GNP’s were prepared by modified mixing process used in thick film material preparation. The composite structure was observed under a scanning electron microscope and atomic force microscope. Electoral and mechanical properties of screen printed layers on flexible PET foil were checked. Banding tests show good adhesion to polymer substrate and proved that GNP’s are good for reinforcing or as a conductive additive in composite materials.

Multiwalled carbon nanotubes deposition in thick film silver conductor

New method of fabrication conductive paste for screen printing in thick film technology was investigated. Fabrication of electronic paste with addition of multiwalled carbon nanotubes and nanoscale silver powder leads to many technological problems in the stir process of nanosized particles. A specialist ultrasonic method was applied to obtain homogeneous mixture. To obtain paste with proper reological properties and usable in thick film technology a selection process of suitable organic resin was conducted. Obtained mixtures with optimal parameters will be used for further experiments.

Graphene-based dipole antenna for a UHF RFID tag

This paper describes the design and measurements of a remote frequency identification (RFID) tag built of a graphene-based dipole antenna and a chip operating in the ultrahigh-frequency (UHF) band in accordance with the EPC Global Class 1 Gen. 2 standard. A custom-designed antenna has been designed first. Then, it was used to construct several tags that have been tested with a standard RFID reader to reveal that each one is fully operational, although the interrogation range for the graphene-based circuits has been limited in comparison to copper antennas. This can be attributed to increased sheet resistance of a graphene layer and-in the case of tags fabricated on paper-also to significant dielectric losses of the substrate material. However, it seems that for applications where the interrogation range is not crucial the novel antenna can be an alternative to much more expensive circuits printed with silver-based inks.

Polymer composites based on carbon nanotubes for printed electronics

Nanomaterials are known for their superior properties, and for that are the most investigated group of materials these days. These properties were utilized by the authors in new type of polymer thick film composition. Polymer compositions filled with carbon nanotubes are topic of interest in fabrication of new type printed electronics circuits, dedicated for production of elastic displays, transparent electrodes, EM shields, and various types of sensors such as pressure, temperature or biochemical sensors. Investigated materials were poly(methyl methacrylate) filled with multiwalled carbon nanotubes. Several polymer compositions were prepared with different concentration of polymer in solvent. Different amount of carbon nanotubes were added to each resin. Compositions were homogenized, screen printed on polyester substrate and cured. Resistance changes in function of polymer concentration were elaborated. Different concentration of polymer in solvent has significant influence on film thickness. As the result, fabricated thick film electrodes have less polymer concentration. In such composites more nanotube interconnections are present and more conductive paths are created.

Electric Properties of Graphene-Based Conductive Layers from DC Up To Terahertz Range

This paper describes results obtained using a hybrid measurement methodology employed to investigate electric properties of thin conductive layers based on graphene nanoplatelets in the frequency band spanning from dc up to terahertz range. As many as four different measurement methods were employed to cover the band of interest, including the terahertz time-domain spectroscopy and the Fourier-transform infrared spectroscopy besides resonator techniques applicable in the microwave band and the four-point dc technique. Raw measurement data obtained using these approaches were processed and based on the results a relationship between frequency and sheet resistance for various types of new graphene-based conductive layers was extracted. Eventually, several models that help to explain the observed behavior of each of the analyzed conductive inks were proposed.