Recently, textile machine manufacturers introduced to the market significant technological advances. Examples of such advances are higher speeds, higher level of automation, new concept of jacquard weaving that enables control of individual warp threads, CAD systems, and wider machines than seen before. This paper reviews the new development of formation systems of textile structures with emphasis on technologies that enables the production of giant-area fabrics. The review includes broad range of technologies (weaving, knitting, needlepunching, hydroentanglement, meltblowing, etc.). Additionally, the paper sheds the light on the potential of the textile technologies to manufacture electrotextile fabric structures.

Thin fluorescent organic fibers are used to collect short wavelength sunlight, convert it to longer wavelengths and illuminate photovoltaic (PV) arrays. Using this approach, miniature and lightweight PV arrays have been fabricated. The incoming light is collected by many fibers and mixed before reaching the PV array. Thus homogenous illumination is provided even with partially shadowed fibers, which can cover a large area and can be arranged in a form of a fabric. The PV array itself can be located in any (even dark) place.

In this work we developed and tested high-performance miniature 21 mm2 AlGaAs/GaAs monolithic arrays consisting of 6 cells connected in series. Output electric power density of 75 mW/cm2 and an open-circuit voltage about 6 V was measured outdoors for the arrays integrated with a bundle of 0.25 – 1.00 mm thick polystyrene fibers. The influence of PV array output parameters on the fluorescent fiber diameter, length, as well as on bandgap and design of solar cells is discussed.

We studied the features of the newly developed Top and Bottom Contact Field Effect Transistor (TBCFET) with organic semiconductor layers. TBCFETs with ca.0.5μm channel length (L) were fabricated and their transistor properties were measured. The output drain-source currents (IDS) of TBCFET were 1 to 2 orders of magnitude higher than those of ordinary planar type FETs with 100μm channel length. On the other hand, because of the TBC structure, off current tends to become larger in the TBCFET. Therefore, in order to solve this off-current problem, we intentionally formed the Schottky junction at the top electrode/semiconductor interface. As a result, the off current became about 2 orders of magnitude smaller than before the formation of the Schottky junction.

The increasing desire to internet the soldier on the battlefield requires a new approach to outfit the soldier with communications systems capable of operating in multiple frequency domains as shown in Table 1. Outfitting the soldier with multiple unwieldy antennas often results in the equipment being left behind, used improperly or broken. The ultimate in unobtrusive antennas is one that conforms to the body and does not interfere with the normal degrees of freedom of the soldier's uniform. Conformal antennas mounted on the body must take into account the electrical properties of the body, particularly at frequencies above 30 MHz. In addition, integration into the textile structure requires that the antenna be isolated from effects of clothing usage including clothing movement, wet operation, washing, and mechanical abrasion.

Wide bandgap semiconductors have been sputter deposited onto non-crystalline substrates, low melting point materials, including polymer fibers, textiles and glasses. The semiconductors are amorphous and can be deposited over large (square meter) areas economically. The electro-optical properties of these materials are not defect limited, and do not require thermal processing. Alternating current electroluminescent device structures/coatings composed of rare-earth ion doped nitrides have been deposited onto point-bonded fabrics, polymer membranes, and polymer sheets. Light emission is detected from the coated fabrics over the entire visible range, UV and IR. A notable feature of fabric-based structures is the inclusion of ambient air in the fabric voids. Increased light emission intensity is obtained by extracting electrons from the plasma discharge during device operation. These fabrics do not require weaving, which could be difficult with semi-crystalline or brittle semiconductor materials. Multilayer assembly and bonding with continuous sheets, cladding, filling and or contact bonding are all available at any point in the fabric assembly. Non-woven, pin-bonded, materials may still function after some damage, e.g. rips or punctures, due to redundant connections at each pad. Further advantages are the simple incorporation of optically active ions, such as rare earths, high thermal conductivity, high breakdown voltage, and complete miscibility of the group III-A and -B nitrides, allowing bandgap engineering. The deposition process is scalable and may be applied to the fibers or yarns before or after fabric formation.

Thiophene-phenylene oligomer semiconductors (structures below) have many favorable attributes for electronics on flexible and rounded substrates. They are synthesized in 2–3 steps from readily available starting materials and are chemically stable. Their mobilities are typically above 0.01 cm2/Vs and their threshold voltages can be tuned by altering the thiophene-phenylene ratio. Deposition from solution is facile, and cast films with usable mobilities are repeatedly obtained on a variety of surfaces. Higher-order function such as nonvolatile memory and chemical sensitivity have been demonstrated.

High performance poly (3-hexylthiophene) (P3HT) thin film transistors (TFTs) array was fabricated on a polycarbonate substrate by micro-contact printing method. A thin polyimide layer (40 nm) was applied before silicon oxide deposition to improve the electrical properties of the TFT device. Also, the effects of O2 plasma treatment on the field effect mobility and output current behaviors of the devices were investigated. By plasma treatment, the surface roughness of gate dielectric was improved which accounts for the increased field effect mobility and the hole Schottky barrier height in electrode/semiconductor interface was lowered resulting in large drain current in the device. Based on the experiments, we fabricated P3HT TFTs array with 0.025 cm2/V·s in saturation field effect mobility and on/off current ratio of 103 ∼ 104 on a polycarbonate substrate.

Today's complex geo-political climate has forced the U.S. armed services into new operational strategies. The prevalence of international terrorism, the threat from chemical and biological weapons, and the pressure to “do more with less” has placed increasing demands on the military. This new operational environment requires highly mobile troops having enhanced decision-making capability provided through the rapid transfer and dissemination of information to each member of the squad. What is missing is the ability to process and use this information via an Intranet at the level of the individual soldier. The purpose of our work has been to develop, evaluate and implement such a wearable conductive network for the dismounted soldier.

Organic thin film transistors (OTFTs) that operate at low voltage were fabricated using a tantalum oxide (Ta2O5) gate insulator on plastic substrates. The Ta2O5 insulator was prepared by anodizing a Ta gate electrode. The high dielectric constant of the Ta2O5 enabled the OTFTs to operate at a lower voltage than those of previous devices. The OTFTs exhibited a high field-effect mobility of 0.35 - 0.51 cm2/Vs, and a current on/off ratio of 105-106 at gate voltages of less than 5 V. The threshold voltage of -1.1 V and the subthreshold slope of 0.2 V/decade were the best among those reported to date. We also demonstrated operation of a phosphorescent organic light-emitting device (OLED) with the OTFT operating at a low voltage.

The ability to integrate electrical functionality into textile garments is becoming increasingly desired both on the battlefield and in the work environment. In order to accomplish this, the issue of compatibility of mechanical properties between dissimilar materials needs to be addressed. Textiles are typically selected for comfort while electrical materials are chosen for superior electrical properties with secondary consideration given to properties such as flexibility. As a result many attempts to integrate electrical functionality into textiles result in stiff, unwieldy garments that have difficulty gaining user acceptance.

Part of the electrotextile work done at Foster-Miller has focused on the integration of these dissimilar materials in a manner that does not degrade the wearability of the garment. Our work has included the development of textile cables that carry power and data using both electrical and optical media. In order to assess the wearability of these cables a method was needed of testing their stiffness. Several methods of measuring textile stiffness existed but did not address the many issues and material characteristics unique to conductive textiles.

Synthesis and functionalization of 3-bromothiophene afforded novel 2,5-bis[(3,4-ethylenedioxy)thien-2-yl]-)-3-substituted thiopehene monomers with blue emission characteristics and having a quantum yield of 3–5%. Cyclic voltammetry was employed to investigate the electrochemical behavior of the four monomers reported here. Polymer films were deposited by repeated potential cycling. These materials are considered for use in tailoring properties in opto-electronic device applications.

An all-printed organic smart pixel is achieved through the combination of an electrochemical transistor and an electrochromic display cell. Smart pixels of this kind are arranged into a cross-point matrix resulting in an active-addressed display. This type of display has been realized on coated fine paper, operates at voltages less than 2 Volts and exhibits good bistability properties. Here we report on the operation characteristics of electrochemical smart pixels in which the ion concentration of the electrolyte has been varied.

The process of electrostatic fiber formation, or electrospinning, was used to generate polymer filaments with diameters in the 50–200 nm range. We have shown that in addition to process parameters such as solution concentration, spinning voltage, and deposition distance, an oscillating electric field can also influence the morphology of the electrospun nanofibers. Specifically, effects of the oscillating field strength and frequency, spinning voltage, and deposition distance on fiber diameter as well as size and number density of the beaded structures in the fibrous thin films are examined.

The results of our study demonstrate that modulated field potential produces more uniform fibers. Increasing either the oscillating field strength or frequency yields more uniform average fiber diameter. Also, for systems with the “beads on a string” fiber morphology, increasing the oscillating field strength produces more uniform bead sizes.

The ability to tailor fiber morphology using an oscillating electric field has promising implications in a wide range of applications including controlled-release drug delivery systems and biocompatible implants. We show here the potential of using electrospun nanofibers as a porous template for growing fuzzy conductive polymers to modify the surface of a neural recording microelectrode device. These hairy nanostructures can increase signal transport and mediate the mechanical property differences between the device and the soft brain tissues.

The combination of soluble polymers with printing and coating techniques enabled the fabrication of polymer field-effect transistors (PFETs) on flexible films. The devices were built in a top gate configuration, with four functional layers deposited. The electrodes were patterned by gravure offset printing, where source-drain were made from conducting polyanilin and carbon black filled conducting ink was used as gate material. The doctor blading technique was utilized for coating low viscosity solutions, where Poly(3-alkyllthiophene) served as active semiconductor material. Thus completely printed PFETs have been demonstrated. Further steps for printing integrated polymer circuits included the fabrication of inverters combined from two printed. Screen-printing could be used as an alternative to coating and has the potential to enable vertical electrical interconnects between top and bottom layer of circuits. To test the suitability insulating layers were screen-printed homogenously onto lithographically patterned electrodes made from gold. The PFETs' yield was sufficient enough to let a 7-stage ring oscillator work with a clock frequency of 4 Hz.

An organic light emitting device (OLED) has been successfully fabricated on a thin paper-like polyimide substrate (about 10 μm-thick), which is sandwiched between silicone oxide and silicone nitride films. The emission characteristics of the OLEDs, which consist of diamine derivative (α-NPD) and 8-hydroxyquinoline aluminum (Alq3), are similar to those fabricated on a conventional glass substrate. Since the substrates and the OLEDs are very thin like a paper, the devices can be applicable for paper-like displays.

Electrospinning is a superior process compared to other conventional spinning methods for the production of fibers in the sub-micron to nanometer scales. Such fiber membranes have exceptionally large surface areas and small pore sizes. The process requires an electrostatic force, which induces charges on the liquid droplet of the polymer solution or melts and therefore overcomes the surface tension and viscoelasticity forces to create an electrically charged jet. When the jet dries or solidifies, an electrically charged fiber remains, which can be directed or accelerated by the electrical forces and then collected in non-woven fiber membrane or other useful shapes. The present research work demonstrates the electrospinning of polycarbonate solution with solvent mixtures THF (Tetrahydrofuran) and DMF (Di-methyl formamide) to produce nanometer scale polycarbonate fibers. The solvent mixture of THF and DMF was the major parameter for producing nano-polycarbonate fibers along with the formation of byproducts beads. The electrostatic voltage, viscosity and surface tension also showed significant effect on bead formation and bead density. The microstructures of the polycarbonate beads were quantitvely investigated by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM).

The design, synthesis, and properties of two mixed perfluorophenyl-thiophene oligomers 5,5″′-diperfluorophenyl-2,2′:5′,2″:5″,2″′:5″′,2″″:5″″,2″″′-quaterthiophene (2) and 5,5′-bis{1-[4-(thien-2-yl)-2,3,5,6-tetrafluorophenyl)] }-2,2′-dithiophene (3) are presented. Molecular characterization included the following techniques: multinuclear NMR, DSC and TGA, optical UV-Vis and photoluminescence spectroscopy, and cyclic voltammetry. Thin films can be easily grown by vacuum evaporation and have been characterized by optical UV-Vis and photoluminescence, XRD, and field-effect transistor measurements. Electron and hole mobilities of 0.06–0.08 cm2/(V s) and 0.001–0.003 cm2/(V s) were found for 2 and 3, respectively.

Organic electroluminescent diode (OELD) has been investigated for use as a light source of polymeric optical integrated devices. The OLED was fabricated by organic molecular beam deposition (OMBD) technique. The OLEDs were fabricated on both glass and polymeric substrates. The device fabricated on a polymeric substrate shows similar device characteristics to those on a glass substrate. Optical signals of faster than 100 MHz has been created by applying pulsed voltages directly to the rubrene doped OLED. Optical photo detectors (OPDs) utilizing superlattice structure phthalocyanines provide increased pulse response with input optical signals and the response was faster than 1 MHz.

Poly(3,4-ethlyenedioxythiophene), PEDOT, has found wide use in applications such as electrostatic coatings, antistatic layers and electrode materials in electronic devices. Electrochemical deposition of PEDOT is a prominent means of obtaining thin, uniform films. However, the relationship of these films' properties to their morphological structure is still poorly understood. We have prepared PEDOT films by electrochemical oxidation of monomer (3,4-ethylenedioxythiophene), EDOT, under constant current conditions, employing a variety of electrolytes, and processing conditions. We report the effect of using different dopants, deposition time, deposition temperature and current density on the observed conductivity of PEDOT films. Atomic force microscopy studies were carried out to determine the possible effect of the process variables on the resulting film morphology. Also, the effect of residual solvent on the conductivity of the films was studied by thermogravimetric analysis (TGA).

Electrically conducting organic polymers are a novel class of ‘synthetic metals’ that combine the chemical and mechanical properties of polymers with the electronic properties of metals and semiconductors. Electronically conducting polymers have been studied extensively owing to their applications in energy conversion devices, sensors, electro chromic devices, electromagnetic interference shielding (EMI), electronic circuits etc. Polyaniline - an organic conducting polymer - has been blended with poly methyl methacrylate and the blends have been electrospun to produce conducting nanofibers. The electrospun blends have been characterized to study fiber morphology and formulate conditions for nanofiber formation.