Fiber-based structures are highly desirable for wearable electronics that are expected to be light-weight, long-lasting, flexible, and conformable Many fibrous structures have been manufactured by well-established lost-effective textile processing technologies, normally at ambient conditions The advancement of nanotechnology has made it feasible to build electronic devices directly on the surface or inside of single fibers, which have typical thickness of several to tens microns However, imparting electronic functions to porous, highly deformable and three-dimensional fiber assemblies and maintaining them during wear represent great challenges from both views of fundamental understanding and practical implementation This article attempts to critically review the current state-of-arts with respect to materials, fabrication techniques, and structural design of devices as well as applications of the fiber-based wearable electronic products In addition, this review elaborates the performance requirements of the fiber-based wearable electronic products, especially regarding the correlation among materials, fiber/textile structures and electronic as well as mechanical functionalities of fiber-based electronic devices Finally, discussions will be presented regarding to limitations of current materials, fabrication techniques, devices concerning manufacturability and performance as well as scientific understanding that must be improved prior to their wide adoption

Fiber‐Based Wearable Electronics: A Review of Materials, Fabrication, Devices, and Applications

WITH the ever-widening scope of modern mathematical analysis and its many ramifications, it is quite impossible to include, in a single volume of reasonable size, an adequate and exhaustive discussion of the calculus in its more advanced stages. It therefore becomes necessary, in planning a thoroughly sound course in the subject, to consider several important aspects of the vast field confronting a modern writer. The limitation of space renders the selection of subject-matter fundamentally dependent upon the aim of the course, which may or may not be related to the content of specific examination syllabuses. Logical development, too, may lead to the inclusion of many topics which, at present, may only be of academic interest, while others, of greater practical value, may have to be omitted. The experience and training of the writer may also have, more or less, a bearing on both these considerations.Advanced CalculusBy Dr. C. A. Stewart. Pp. xviii + 523. (London: Methuen and Co., Ltd., 1940.) 25s.

Advanced Calculus I

Radio-frequency identification technology, based on the reader/tag paradigm, is quickly permeating several aspects of everyday life. The electromagnetic research mainly concerns the design of tag antennas having high efficiency and small size, and suited to complex impedance matching to the embedded electronics. Starting from the available but fragmented open literature, this paper presents a homogeneous survey of relevant methodologies for the design of UHF passive tag antennas. Particular care is taken to illustrate, within a common framework, the basic concepts of the most-used design layouts. The design techniques are illustrated by means of many noncommercial examples.

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The art of UHF RFID antenna design: impedance-matching and size-reduction techniques

Antenna Theory And Design

RFID research: An academic literature review (1995–2005) and future research directions

We present RFID (radio frequency identification)-based passive UHF (ultra-high frequency) wristbands fabricated with a 3D printing pen. The used 3D printing material is flexible and biodegradable, and thus suitable for fabrication of such inexpensive and widely useful wearable wireless platforms. The tag antenna (that is fabricated from conductive thread) and the RFID IC (integrated circuit) are embedded into the platform by using 3D-printed fasteners. This paper presents the wristband fabrication, ensures their reliability, and carries out practical testing in normal use environments. Based on the achieved results, the studied combination of conductive thread and 3D printing pen is a suitable fabrication solution for intelligent wearable platforms. The fabricated wristbands show high moisture reliability and excellent wireless performance in practical testing situations.

Intelligent Wristbands - Fabrication of Wearable RFID Solutions by 3D Printing Pen

Wireless body-centric sensing systems require light-weight and wearable sensor nodes for remote health monitoring of people. This imposes the need for wearable antennas which are comfortable to the users. In this article we demonstrate the capability of conductive fabrics and embroidered structures in the fabrication of such antennas and sensors. We also outline their measured performance in several prominent applications.

Electro-textiles — The enabling technology for wearable antennas in wireless body-centric systems

A novel field collapse event ESD test method is presented in this paper. The device under test is continuously grounded in an electrostatic field and when the field is removed it drives current through the device. We show with measurements and simulations how to use this method to test ESD immunity of electronic products.

http://ieeexplore.ieee.org/iel7/6959874/6968791/06968810.pdf

Field collapse event ESD test method

We present the comparison of wearable passive UHF RFID tags based on dipole and patch antennas made of textile materials. The tags' wireless performance was evaluated when attached to the upper back of a test subject. Despite the fundamentally different structures and electromagnetic operation mechanisms of the antennas, both tags attained read ranges of several meters. In the optimized configuration, the patch tag achieved slightly higher performance, but was found to be more sensitive toward variable antenna-body separation.

Comparison of wearable passive UHF RFID tags based on electro-textile dipole and patch antennas in body-worn configurations

In this paper the performance of passive UHF RFID bow tie tag with different impedance matching was analyzed by simulation and measurement. Tag antenna design differs from conventional antennas. In tag design, when the PRC of tag is up to -7 dB or -8dB, it can be considered as good tag and even as low as -5 dB PRC is sufficient for several application. However, Co-Design is recommended for the application specific solutions to ensure proper operation of RFID tags and avoid unnecessary lost of performance.

Leena Ukkonen

Papers

Intelligent Wristbands - Fabrication of Wearable RFID Solutions by 3D Printing Pen

Electro-textiles — The enabling technology for wearable antennas in wireless body-centric systems

Field collapse event ESD test method

Comparison of wearable passive UHF RFID tags based on electro-textile dipole and patch antennas in body-worn configurations

Performance of RFID bowtie tag antenna with different impedance matching