The human skin, because of its ability to receive stimuli from the outside world, plays a huge role in human life. It is a structure that is responsible for one of the human body senses - the sense of touch, at the same time characterized by resistance to external factors, ensuring thermoregulation and protection against water loss. Recently, attempts have been made to create artificial leather that fulfills the same functions as human skin. The research related to this area attracts a lot of attention. To produce this artificial material, with reproducing as accurately as possible, the functions of human skin, it is necessary to use a range of sensors, such pressure, temperature and humidity sensors. Moreover, all structure and sensor should be printed on flexible, similar to the skin, substrates, which is possible using various methods of printed electronics, such screen printing. This paper presents an overview of available, flexible pressure sensors produced using printed electronics methods, which potential application is the artificial skin structure.
Aerosol jet printing is a new technology which is able to form a micrometer size patterns directly on the substrate. It is possible due to the special ink treatment - first, the ink is formulated to form a mist or fog with a very small droplets (average size about 1 μm). Then the atomized ink is transported to the printing head. In the printing head, a special shear gas flow focuses the mist into several micrometer size stream. This technology is an additive method which allows printing even on the 3D substrates. The achievement of 10 μm line wide makes it comparable with conventional flat, many stages photolithography. In this article, authors present the self-made printing head for the aerosol jet method and the results of the printing process. The printing process was performed with ultrasonic atomizer and the nanosilver ink. As a result, authors have obtained conductive, 40 μm wide silver lines.
In a wildly spreading research on carbon nanotube fibers as a potential material for the future, one of the most promising fields are electrical and electronic engineering. As it was mentioned repeatedly the main thing that need to be dealt with for a serious consideration of carbon nanotube structures in application as good conducting wires is a necessity of improvement their electrical conductivity values. In the many possibilities of such electrical properties improve, one of the best is chemical doping. In this work we present a oxidative doping treatment on carbon nanotube fibers via Fenton reaction. However the first assumptions on introduction hydroxide ion doping has changed after performing experiments. The reaction resulted in iron doping on carbon nanotube fibers. Such a result most probably is associated with a great reactivity of carbon nanotube with iron particles. This reactivity is being used in carbon nanotube structures production procedure, due to catalytic action of iron in the issue of carbon nanotube synthesis. This result, however differs from intentions gave us new carbon nanotube-iron composite, which seems to have a great potential for further research.
In the world of constant facilities of human life, as well as improving the comfort of patients, there are more and more reports on non-invasive methods of testing and health related procedures. One of the most common invasive procedures performed by patients is the procedure of taking blood from the fingertip to the glucose test. It is not surprising, therefore, that the attention of researchers around the world is focused on eliminating the need for invasiveness of these tests. The tendency to facilitate and minimize interference in body coherence concerns all tests with which diabetic patients come in contact. In the light of this trend, a promising idea seems to be the possibility of non-invasive measurements of one of the conditions associated with diabetes - ketoacidosis. Such novel and non-invasive procedure is for example monitoring the amount of acetone exhaled with air by a diabetics suffering from ketoacidosis. In this work we present the sensors of acetone vapors based on titanium oxide and graphene nano-flakes or carbon nanotubes fabricated using a screen printing technology on the ceramic substrate. We have also performed test of sensitivity of fabricated sensors into the acetone gases presence in both room temperature and 150° degrees.
Printing electronics even though the printing techniques are known for a long time, are gaining in importance. The possibility of making the electronic circuits on flexible, big-area substrates with efficient and cheap technology make it attractive for the electronic industry. Spray coating, as a one of printing methods, additionally provide the chance to print on the non-flat, complicated shaped substrates. Despite the spray coating is mostly used to print a big pads, it is reachable to spray the separate conductive lines both as a quickly-produced prototype and as a fully manufactured circuit. Our work presents the directly printed lines with spray coating technique. For the printing process self-made ink was used. We tested three different approaches to line formation and compare them in the terms of line edge, resistivity and thickness. Line profiles provide the information about the roughness and the line size. In the end we showed the aerosol jet printed meander to give an overview of this similar to spray coating but more sophisticated technique.
In the last few years there has been a growing interest in wearable electronic products, which are generating considerable interest especially in sport and medical industries. But rigid electronics is not comfortable to wear, so things like stretchable substrates, interconnects and electronic devices might help. Flexible electronics could adjust to the curves of a human body and allow the users to move freely. The objective of this paper is to study possibilities of polymer composites with conductive nanomaterials application in wearable electronics. Pastes with graphene, silver nanoplates and carbon nanotubes were manufactured and then interconnects were screen-printed on the surfaces of polyethylene terephthalate (PET) and fabric. Afterwards, the resistance and mechanical properties of samples were examined, also after washing them in a washing machine. It has been found that the best material for the conductive phase is silver. Traces printed directly on the fabric using conductive composites with one functional phase (silver nanoplates or graphene or carbon nanotubes) are too fragile to use them as a common solution in wearable electronics. Mechanical properties can be improved not only by adding carbon nanotubes or graphene to the silver paste, but also by printing additional layer of graphene paste or carbon nanotube paste onto silver layer. In fact, these solutions are not sufficient enough to solve a problem of using these composites in wearable electronics.
Films and fibers made of carbon nanotubes were found to be promising materials for future electrical and electronic engineering. Despite of many advantages provided by these materials, they are not without problems. The biggest issue is that the macroscopic CNT structures, such as films or fibers, have much lower electrical conductivity values than it is for individual carbon nanotubes. And therefore researchers worldwide try to increase electrical properties of those macroscopic structures. One of the approaches scientists are currently investigating is chemical doping. Despite chemical doping has been already reported there is still a huge list of compounds that are capable to increase the conductivity values and has not been tested yet. In this work one of such compounds has been examined. It is a strong p-dopant 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). The solution of F4TCNQ in three different solvents (chloroform, acetic acid and dimethylsulfoxide) has been prepared and applied on purified CNT films. Both electrical conductivity and specific conductivity was measured. The best electrical conductivity value achieved is 5,24·106 S·m-1. Samples were also observed under SEM.
Carbon nanotube (CNT) yarns and sheets due to their biocompatibility, very good mechanical strength and flexibility can find wide range of applications in nanomedicine, inter alia as mechanical actuators for artificial muscles or electrodes used for deep brain stimulation. However, because of CNT film behavior in liquid environment, before their using in biological applications, they should be coated with a special protective layer. The purpose of created coatings is not only to protect the films, but also to increase their conductivity. The aim of the research was to test various methods of achieving such coatings on CNT films and to evaluate quality and flexibility of coated CNT films. The coatings were made using various suspensions containing polymer materials such methyl polymethacrylate and conductive silver flakes. The methods tested in this study were: dipping, painting and flooding of the CNT yarns.
Carbon nanomaterials: graphene, fullerenes and in particular carbon nanotubes (CNTs) are extremely interesting and extraordinary materials. It is mostly thanks to theirs unusual electrical and mechanical properties. Carbon nanotubes are increasingly examined to enable its usage in many fields of science and technology. It has been reported that there is a high possibility to use CNTs in electronics, optics, material engineering, biology or medicine. However, this material still interests and inspire scientists around the world and the list of different CNTs applications is constantly expanding. In this paper we are presenting a study on the possibility of application carbon nanotubes as a textile fiber coating for smart clothing applications. Various suspensions and pastes containing CNTs have been prepared as a possible coating onto textile fibers. Different application techniques have also been tested. Those techniques included painting with nanotube suspension, spray coating of suspensions and immersion. Following textile fibers were subject to tests: cotton, silk, polyester, polyamide and wool. Obtained composites materials were then characterized electrically by measuring the electrical resistance.