Highly Conductive Carbon Nanotube-Thermoplastic Polyurethane Nanocomposite for Smart Clothing Applications and Beyond

Nanomaterials 2019, 9(9), 1287

The following paper presents a simple, inexpensive and scalable method of production of carbon nanotube-polyurethane elastomer composite. The new method enables the formation of fibers with 40% w/w of nanotubes in a polymer. Thanks to the 8 times higher content of nanotubes than previously reported for such composites, over an order of magnitude higher electrical conductivity is also observed. The composite fibers are highly elastic and both their electrical and mechanical properties may be easily controlled by changing the nanotubes content in the composite. It is shown that these composite fibers may be easily integrated with traditional textiles by sewing or ironing. However, taking into account their light-weight, high conductivity, flexibility and easiness of molding it may be expected that their potential applications are not limited to the smart textiles industry.

Electrical and rheological percolation threshold of graphene pastes for screen-printing

Circuit World, vol. 45, no. 1, pp. 26–30, 2019

A comparison of electric and viscosity percolation threshold is crucial from the scientific and technical points of view to understand the features and capabilities of heterogeneous graphene composite materials and properly select the functional phase volume. Therefore, the purpose of this paper is to present the analysis of the electrical and rheological percolation thresholds in the polymer–graphene screen printing pastes and the analysis of the relation between these two parameters.

In the paper, the properties of polymer-based pastes with graphene nanoplatelets were tested: paste viscosity and printed layers conductivity. The tests of pastes with different filler content allowed to determine both the electrical and rheological percolation thresholds using power law, according to Kirkpatrick’s percolation model.

The electrical percolation threshold for graphene nanoplatelets (GNPs) in the composite was 0.74 Vol.% when the rheological percolation threshold is observed to be at 1.00 Vol.% of nanoplatelets. The percolation threshold values calculated using the Kirkpatrick’s percolation model were 0.87 and 0.5 Vol.% of GNPs in the paste for electrical and rheological percolation thresholds, respectively.

Recently, GNPs are becoming more popular as the material of the functional phase in screen printing heterophase materials, because of their unique mechanical and electrical properties. However, till date no research presented in the literature is related to the direct comparison of both the electrical and rheological percolation thresholds. Such analysis is important for the optimization of the printing process toward the highest quality of printed conductive paths, and finally the best electrical properties.

Photonic curing of silver paths on 3D printed polymer substrate

Circuit World, Vol. 45 Issue: 1, pp.26-30, 2019

Despite almost limitless possibilities of rapid prototyping, the idea of 3D printed fully functional electronic device still has not been fulfilled – the missing point is a highly conductive material suitable for this technique. The purpose of this paper is to present the usage of the photonic curing process for sintering highly conductive paths printed on the polymer substrate.

This paper evaluates two photonic curing processes for the conductive network formulation during the additive manufacturing process. Along with the xenon flash sintering for aerosol jet-printed paths, this paper examines rapid infrared sintering for thick-film and direct write techniques.

This paper proves that the combination of fused deposition modeling, aerosol jet printing or paste deposition, along with photonic sintering, is suitable to obtain elements with low resistivity of 3,75·10−8 Ωm. Presented outcomes suggest the solution for fabrication of the structural electronics systems for daily-use applications.

The combination of fused deposition modelling (FDM) and aerosol jet printing or paste deposition used with photonic sintering process can fill the missing point for highly conductive materials for structural electronics.

Heterophase materials for fused filament fabrication of structural electronics

Journal of Materials Science: Materials in Electronics, vol. 30, no. 2, pp. 1236–1245, 2018

In this work, new electrically conductive composite filaments are developed for the fabrication of conductive paths, 3D printed with FDM technology. These composite materials consist of electrically conductive copper powder and a polymer matrix. The influence of three different polymers (ABS, PLA, PS) on the electrical properties of the composites was examined. Electrical measurements of the composite filaments with the increasing copper powder concentrations, allow identifying the percolation threshold for elaborated composites. Results show that the lowest resistivity (0.156 × 10−5 Ωm) was achieved for the ABS/Cu composite at the 84.6 wt% Cu concentration. The obtained resistivity values are much lower than for other conductive composites and nanocomposites filaments reported in the literature. Voltage-current characteristics determined for each composite material showed that composites have Ohmic characteristics in low voltage regime. At high voltage regime, the electrical power dissipated in the composites caused a rapid increase in temperature. It was discovered that a polymer matrix influences the maximum value of the electrical power that can be dissipated in the filament before losing electrical conductivity. Examples of conductive 3D printed structures made from elaborated composites are also presented.

Efficient Inkjet Printing of Graphene-Based Elements: Influence of Dispersing Agent on Ink Viscosity

Nanomaterials 2018, 8(8), 602

Inkjet printing is an excellent printing technique and an attractive alternative to conventional technologies for the production of flexible, low-cost microelectronic devices. Among many parameters that have a significant impact on the correctness of the printing process, the most important is ink viscosity. During the printing process, the ink is influenced by different strains and forces, which significantly change the printing results. The authors present a model and calculations referring to the shear rate of ink in an inkjet printer nozzle. Supporting experiments were conducted, proving the model assumptions for two different ink formulations: initial ink and with the addition of a dispersing agent. The most important findings are summarized by the process window regime of parameters, which is much broader for the inks with a dispersing agent. Such inks exhibit preferable viscosity, better print-ability, and higher path quality with lower resistivity. Presented results allow stating that proper, stable graphene inks adjusted for inkjet technique rheology must contain modifiers such as dispersing agents to be effectively printed.

Microscale Hybrid Flexible Circuit Printed with Aerosol Jet Technique

IEEE Transactions on Nanotechnology, 2018, V: 17, I:5.

Today, a microprinted electronics circuits are gaining more and more importance, but still printed electronic devices such as transistors or OLEDs are unstable in air and shows a poor performance. Moreover, printed microelectronic elements do not meet quality and high-reliability requirements, essential in electronics applications. To fulfill these needs, hybrid electronic circuits, combining printed technology, and surface-mount technology, are recommended. This approach gets advantages from both methods:Surface-mount devices (SMD) elements provide a high device functionality whereas a printed pattern ensures the device flexibility and efficiency. In this work, silver nanoparticle-based aerosol jet ink (AgNP ink) is used to realize the approach of a hybrid circuit with aerosol jet printed pads and surface-mount devices. The ultrasonic atomization process ensures the high printing resolution and appropriate line formation. Electrical and mechanical characterization was performed to present the connection performance and quality. Cross section view and morphological inspection explain the joint high quality and good performance. Resistance characterization presents the high current conductance comparable with connections made by silver epoxy or ink-jet printing. Shear test results show an excellent connection strength complying with USA Military Standard. Finally, a flexible hybrid conductance touch sensor is manufactured, demonstrating the feasibility of the presented assembling solution.

First PRINTduino™ has arrived, and more will come.

One of the goals of 3WELES project is to fabricate fully functional microcontroller circuit, printed and 3D printed, with additional discrete components. An electronic circuit from silver paste was screen-printed on an elastic substrate, and elements were attached with electrically conductive adhesive. This allowed to fabricate a fully functional clone of Arduino™ microcontroller but based on a fully printed circuit, instead of PCB. We are currently working on 3D printed PRINTduino™, fabricated with elaborated materials, and with FDM and DW techniques.

This project was a part of a bachelor thesis „Applications of electrically conductive adhesives for assembly of printed electronics on a low temperature and elastic substrates” by Paweł Sawczuk.

3D Aerosol Jet Printed elements printed with 3D printed robot?

Phew! So much “3D printed”!

But it is coming. A group of two undergraduate students and one graduate student is preparing a new 3D printed 6 axis robot, being a compilation of several projects available online: BCN3D project, Andreas Hoelldorfer’s robot, and AR2 arm. If will be introduced to our newly built AJP laboratory equipment.

What about precision, what about functionality, what about durability? We do not know, but we are gonna build it, we will learn a lot from it, and it will work as we want!

Team members are Adrian Wawrzyn, Bartosz Szkoda, Kacper Krętowski, supervised by Jakub Krzemiński (MSc)

First demonstrator has arrived

Now we are getting somewhere!

First experiments towards the elaboration of conductive filament filled with Cu powders for fused filament fabrication technique gives positive results. We are now able to print conductive paths inside polymer casings – and by “we” I mean Barłomiej Podsiadły (PhD student). Next steps will cover other demonstrators i.e. keyboard, loudspeaker, inductor and transformer, 3D Printduino™ (2D is easy and done), … BFR components(?)