Electrically conductive yarns have attracted consider- able attention because of their desirable properties including electrical conductivity, flexibility, electrostatic discharge, electromagnetic interference protection and radio frequency interference protection. The development of conductive yarns is also critical for various applications in wearable electronics such as wearable displays, solar cells, actuators, data managing devices, and biomedical sensors. Conductive yarns directly spun from conductive materials including metals, metal oxides, carbon nanotubes (CNTs), and conducting polymers were first demonstrated as prototype materials for wearable electronics, yet they are expensive and difficult to be produced on a large scale A more economic and productive way of making conductive yarns is coating conventional fibers with a layer of metals, CNTs, or conducting polymers, followed by spinning into yarns. Cotton, cellulose in nature, is the most widely used natural fiber in the world. It is low-cost and clean to produce, and has a wide variety of applications in textile clothe, upholstery, daily care, and medicine To address the challenge, this group of scientist reported a novel, facile, and versatile approach for preparing highly durable, electrically conductive cotton yarns by electroless deposition (ELD) of metal particles onto cotton yarns modified with polyelectrolyte brushes as adhesion layer. The process is really interesting, and can be seen in the following figure. The resulting yarns were tested as wires to power LEDs, it can be seen that they don’t need more cables or conducting glue, just a DC power (battery) and put the LED into the fabric. It turns on as it was connected with normal wires. This yarn can help to produce electronic textiles because of its great conductive properties.

Xuqing Liu, Haixin Chang

Electrically conductive yarns have attracted consider- able attention because of their desirable properties including electrical conductivity, flexibility, electrostatic discharge, electromagnetic interference protection and radio frequency interference protection.

The development of conductive yarns is also critical for various applications in wearable electronics such as wearable displays, solar cells, actuators, data managing devices, and biomedical sensors.

Conductive yarns directly spun from conductive materials including metals, metal oxides, carbon nanotubes (CNTs), and conducting polymers were first demonstrated as prototype materials for wearable electronics, yet they are expensive and difficult to be produced on a large scale

A more economic and productive way of making conductive yarns is coating conventional fibers with a layer of metals, CNTs, or conducting polymers, followed by spinning into yarns.

Cotton, cellulose in nature, is the most widely used natural fiber in the world. It is low-cost and clean to produce, and has a wide variety of applications in textile clothe, upholstery, daily care, and medicine

To address the challenge, this group of scientist reported a novel, facile, and versatile approach for preparing highly durable, electrically conductive cotton yarns by electroless deposition (ELD) of metal particles onto cotton yarns modified with polyelectrolyte brushes as adhesion layer. The process is really interesting, and can be seen in the following figure.

The resulting yarns were tested as wires to power LEDs, it can be seen that they don’t need more cables or conducting glue, just a DC power (battery) and put the LED into the fabric. It turns on as it was connected with normal wires.

This yarn can help to produce electronic textiles because of its great conductive properties. 

Toward All-Carbon Electronics: Fabrication of Graphene-Based Flexible Electronic Circuits and Memory Cards Using Maskless Laser Direct Writing

Jiajie Liang, Yongsheng Chen 

Graphene is emerging as a novel 2D material in the field of materials science because of its intrinsic electronic, thermal, mechanical, structural and chemical properties. How ever, to fully realize its potential for all the proposed devices, once key is to develop an easy method to fabricate patterned graphene films.

Lately, the advanced technique of laser direct cutting, which has the advantages of maskless, rapid prototyping, reliability, amenability, upward scalability, and low cost, is of increasing importance in device fabrication and has been used to construct microstructures on various films of semiconductor, metal, and dielectric polymer

However, it is still a big step away using this technique to meet the need for fabricating the real-world micro/nano- electronic circuits and devices. To date, two key issues remain for this technique. First, the silicon-based semiconducting microstructures fabricated with the laser-writing technique make it rather difficult to have a clean structure and thus are unusable because of the nonvolatile remains. Second, as to the fabrication of organic or polymer films using this technique, their relatively poor chemical stability and resistance likewise extremely handicap their further use in this field. In this paper, the researchers describe a maskless process to fabricate all-carbon electronic circuits using a continuous graphene film prepared from a graphene solution spin-coating process followed by maskless laser writing.

Of great significance is that this writing process could be operated directly in air at ambient conditions, and various patterns used for electrical circuits and devices can be easily achieved.

On this basis, a novel prototype of write-once-read-many-times (WORM) memory cards along with a data-retrieving system has been demonstrated, the WORM were made on different substrates: flexible polyimide, quartz, and glass substrates. Then and graphene oxide solutions were spin coated to get uniform thin layers. Finally they were reduced to have graphene, over them small thin-film gold squares were deposited to act as the electrodes.

Remarkably, owing to the extraordinary chemical stability of graphene, these graphene-based WORM memory cards possess almost infinite data retention time and extreme reliability, which are crucial in the practical use of some memory devices, such as identification cards, radio- frequency tags, passports, e-tickets, and military applications.

“Double Exposure Method”: a Novel Photolithographic Process to Fabricate Flexible Organic Field-Effect Transistors and Circuits

Organic electronic devices are the expectation of future electronics due to its great potential mainly flexible electronics. But there are some limitations in the development of practical applications. It’s urgent to develop effective high-resolution patterning techniques. Photolithography show overwhelming advantages in reducing the minimal feature dimensions over other conventional printing techniques, with which high resolution highly integrated organic transistors could be fabricated.

Before getting into fully organic electronic devices there is the promise of making hybrid systems that have both Si electronic components and organic components. One of the applications of organic polymers that has been studied is to use them as dielectric material, replacing SiO₂ in conventional transistors. How ever, the use of organic polymers has the problem that many of them cannot endure conventional photolithography.

To solve these problems the researchers developed a novel photolithographic method called “double exposure method”. They starter with a Polysterine thin film spin coated over ITO/PET and annealed at 80º C. Then a photoresist was spin coated over the PS film and UV irradiated, patterned for the electrodes and irradiated again. Then a thin gold film was deposited and washed with a solvent and exposed again to the method. And finally deposited organic semiconductors of 50 nm (pentacene). This process was also used for other logic circuits.

Characteristic curves showing the performance of the OFET

In summary, they developed and tested a method to fabricate flexible organic field effect transistors and circuits. The performance obtained  was comparable to the ones from traditional Si techniques. 

3-Dimensional Graphene Carbon Nanotube Carpet-Based Microsupercapacitors with High Electrochemical Performance

James M. Tour, Jian Lin.

The development of nanostructured-capacitive structures has been an active area of research because they would allow us to have smaller and flexible electronics, breaking the limit of actual technics.

In this paper it’s shown how 3D grapheme/CNT carpets can work has supercapacitors at good frequencies and altern current, mainly used for line filtering applications. With a frecuency response comparable to the aluminum electrolytic capacitors but with higher current density.

The microcapacitor was fabricated first with photolithography over silicon, then nickel was added to the marked substrate, it acts as both the current collector and the catalyst to grow the graphene.

The graphene was synthesized over the Ni electrodes by CVD at 800º C.After, the CNT carpets were synthesized from the patterned Fe/Al₂O₃/at was first deposited by CVD over the graphene layer. 

The capacitor propierties were teasted with a potensiostat in a two-electrode cell configuration. They used 1M Na₂SO₄ aqueous electrolyte to measure.

They tested the frecuency response specific areal capacitances and found an excellent response in frequencies over 120Hz.

The potential application of this capacitors can go from smaller chargers, noise filters of different electronic circuits and  even signal filtering in sensors mounted over mobile electronics.