E. Grant

Flexible, durable printed electrical circuits

This study investigates the screen printing of transmission lines into a variety of nonwoven substrates using different conductive inks for durable and wearable electronic textile applications. The viscosity of the ink dictated the performance of the printed media during washing trials. The printed inks begin to degrade and display lower conductivity after 25 wash cycles. A method to control the durability of the printed circuits, which includes coating of the printed lines with a meltblown layer, has been developed.

Nonwoven Fabric Active Electrodes for Biopotential Measurement During Normal Daily Activity

Body movement is responsible for most of the interference during physiological data acquisition during normal daily activities. In this paper, we introduce nonwoven fabric active electrodes that provide the comfort required for clothing while robustly recording physiological data in the presence of body movement. The nonwoven fabric active electrodes were designed and fabricated using both hand- and screen-printing thick-film techniques. Nonstretchable nonwoven (Evolon 100) was chosen as the flexible fabric substrate and a silver filled polymer ink (Creative Materials CMI 112-15) was used to form a transducer layer and conductive lines on the nonwoven fabrics. These nonwoven fabric active electrodes can be easily integrated into clothing for wearable health monitoring applications. Test results indicate that nonwoven textile-based sensors show considerable promise for physiological data acquisition in wearable healthcare monitoring applications.

Utility of nonwovens in the production of integrated electrical circuits via printing conductive inks

Abstract This study reports on the printing of conductive inks directly onto nonwovens to produce circuits and embedded systems. The approach adopted applies polymer thick film (PTF) processing technologies directly onto compliant, flexible, nonwoven substrates. The paper reports on the characterization of various PTF conductive inks and printed transmission lines. The performance metrics related to the circuits are impacted by the ink viscosity and by the contact angle of the ink on the surface of the nonwoven structure. These parameters dictate the manner in which the ink is distributed onto and into the substrate. The manner in which ink droplets interact with the surface of the substrate determines the mechanisms responsible for both in-plane flow and through-the-plane flow of the ink.

Warp Break Detection in Jacquard Weaving Using Micro-Electro-Mechanical Systems: Effect of Yarn Type

This paper reports a study aimed at detecting warp breaks in terms of yarn type using a Micro-Electro-Mechanical Systems (MEMS) accelerometer based detection system, which has been described in earlier publications. The MEMS accelerometers were mounted on harness cords of a Jacquard tie. MEMS output acceleration signals were analyzed. The signals were acquired while warp ends were up and at the moment of intentional break with a pair of sharp scissors simulating missing warp ends. The results indicated that MEMS acceleration signals at intentional breaks for continuous filament from standard and high strength fibers could be detected. The break signals of cotton and cotton/polyester spun yarns were undetectable.

Meltblown structures formed by a robotic and meltblowing integrated system: Impact of process parameters on fiber orientation and diameter distribution

In a previous publication, we described a novel system that forms three-dimensional (3D) structures on 3D molds and two-dimensional (2D) structures on a rotating drum through proper integration of a laboratory scale meltblown unit with a small die and a six-axis robot. In this paper, we investigate the impact of take-up speed. die-to-collector distance (DCD). polymer throughput rate. and attenuating air pressure on the fiber orien tation and diameter distribution of 2D structures formed by the system. We introduce a new parameter, the fiber stream approach angle, which can be precisely controlled by the robot, and discuss its impact on the meltblown structure. In the experimental range studied, fiber orientation and diameter distribution are significantly impacted by the parameters. Among these parameters. the fiber stream approach angle shows the highest effect on fiber orientation distribution.

Forming Shaped/Molded Structures by Integrating Meltblowing and Robotic Technologies

A novel system is described that forms three-dimensional (3D) molded nonwoven structures through proper integration of a laboratory scale meltblown unit with a small die and a six-axis robot. The 3D fiberweb structures can be formed by deposition of fibers from the die of the meltblown unit, which is manipulated by the robot, on any desired 3D mold. The mold rotational and surface speeds can be controlled by an additional external axis. The die is connected by two flexible hoses to the melt extruder of the meltblown unit and a hot air supply system. This system directly sprays fibers onto a 3D mannequin mold to produce structures from polypropylene polymers. With varying degrees of success. several robot manipulation algorithms of fiber deposition on the mold are developed to accurately control the basis weight uniformity the fiberwebs. A rule-based control algorithm using a linear variable differential transducer to map the mold contour results in the greatest fiberweb basis weight uniformity.

Developing portable acoustic arrays on a large‐scale e‐textile substrate

This research deals with the production of electronic textiles (e‐textiles) demonstrators. Initially, the research dealt with the creation of 4×5 microphone array on a large area conformal textile substrate. Once the interface electronics were connected to the 4×5 microphone array, this system became an effective acoustic array. Here, a new acoustic eight microphone array design has been designed, fabricated and tested. Changes were made to improve microphone array performance, and to optimize the associated software for data capture and analysis. This new design was based on UC‐Berkeley mote microcomputer technology. The mote‐based system addresses the issue of scaling acoustic arrays, to allow for distributing microphones over large‐areas, and to allow performance comparisons to be made with the original 4×5 microphone acoustic array.

Warp breaks detection in Jacquard weaving using MEMS: System development

Abstract Research related to warp breaks has been limited to monitoring break frequency and the reason associated with breaks in order to improve warp yarn quality. While this approach led to improvement in weaving efficiency, warp breaks still represent a major problem, especially for todays high-speed weaving machines. Researchers have been trying to develop commercial automated systems to repair warp breaks with no success. The goal of this study is to explore inexpensive methods to detect warp breaks using nontraditional technique that would pave the way to automate warp break repair. To achieve the goal, a system that can detect warp breaks using MEMS accelerometers as sensors was developed for Jacquard weaving. The MEMS accelerometers were mounted on harness cords of a Jacquard tie. MEMS output acceleration signals components in the vertical and horizontal directions were analysed using time and frequency domains. The signals were acquired while warp ends are running and at the moment of intentional breaks. The analysis led to a successful detection of warp breaks, especially using the horizontal acceleration component that is mainly due to harness cord vibration.

Signal Propagation and Multiplexing Challenges in Electronic Textiles

Weaving, knitting or placing electronic circuits within a textile matrix offer exciting possibilities for large-scale conformal circuits where the circuit dimensions can be measured on the scale of yards instead of inches. However, compared with conventional printed circuit board circuits, the textile manufacturing process and the electrical/mechanical properties of the fibers used in making the textile place unusual constraints on the electrical performance of textile circuits. In the case of distributed sensors connected via an electronic fabric, signal attenuation and the ability to form reliable interconnections are major challenges. To explore these challenges we have woven and knitted a variety of electrical transmission lines and optical fibers in fabrics to analyze their performance. The formation of interconnects and disconnects between conductors woven in textiles is also discussed, and a passive acoustic array is described as a possible electronic textile application.

High-Frequency Characterization of Printed CPW Lines on Textiles using a Custom Test Fixture

A screen printer is used to print conductive inks, loaded with silver particles, on nonwoven textiles substrates. To evaluate this technology for use as flexible interconnects; a custom test fixture was designed to assist in the high frequency characterization of CPW transmission lines. Due to the flexible nature of textile substrates it is necessary to have mechanical support at the points of electrical contact. However, the test fixture must not alter the electrical characteristics of the CPW lines. This test fixture removes the electrical effects of the mechanical support, and provides a simple and repeatable methodology for evaluating various types of textiles substrates, conductive inks, geometrical variations, and other parameters. Time-domain reflectometry (TDR) is used to measure the characteristic impedance of samples across geometrical variations in the 10 cm long CPW lines. A comparison showing the effects of the measuring the samples using the test fixture to measuring the samples on a solid acrylic substrate, and a metal plate are presented