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

In this paper we present and analyze the Albano-patch antenna, a folded microstrip patch-type tag antenna mounted on a box corner. The radiation properties of the antenna design are analyzed with finite element method (FEM) simulations and the tag's performance is evaluated with read range measurements

Folded Microstrip Patch-Type RFID Tag Antenna Mounted on a Box Corner

In passive ultra-high frequency (UHF) radio frequency identification (RFID) there is a need for tag antennas that can be used in the vicinity of metal. In this paper we study the performance of bow tie type tag antenna in the vicinity of metal by simulations and measurements, including detailed signal analysis such as measuring the threshold power levels and backscatter performance. Effects of different air gaps and packing materials such as plastic foam and cardboard are studied.

RFID signal analysis of bow tie tag antenna in the vicinity of metal

This paper studies a novel RFID-enabled strain sensing approach using the radar cross-section measurement technique and taking advantage of the nonlinearity properties of the RFID chip. As a proof of concept, we applied the method for the measurement of an RFID-enabled strain sensor that was realized on fabric using electro-textiles in order to observe large variations of peak-power frequencies and corresponding strain levels. We carried out the radar measurements first applying the three-target calibration technique and then using the novel double-power-detection method, which relies upon the detection of the backscattered response for two distinct transmitting power levels and then calculating the difference of these two responses. The nonlinearity of the chip causes a large variation of its impedance value and thus a large difference of RCS values for carefully chosen power levels, allowing for the elimination of the need for calibration. Practical measurements have validated the method and the reliability of the technique.

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A novel RFID-enabled strain sensor using the double power measurement technique

This paper discusses the fabrication and wireless performance evaluation of textile-integrated passive ultra-high frequency (UHF) radiofrequency identification (RFID) tags, which are embedded inside flexible additively manufactured wireless platforms. Two different methods are utilized to fabricate the tag antenna, including embroidery with conductive thread and conductive e-textiles. After antenna fabrication, RFID ICs (integrated circuits) are attached to the antenna patterns, to achieve fully functional RFID tags. These two types of tags are embedded inside flexible 3D-printed platforms, which can protect the tags from mechanical stresses and moisture. Our preliminary results show that the peak read ranges of both types of platforms are higher than 6 meters, which are suitable for versatile wireless applications.

Embroidered and e-textile Conductors Embedded inside 3D-printed Structures

We present an inductively coupled split-ring resonator based small passive RFID pressure sensor for wireless intracranial pressure measurement. The proposed sensor has a volume as small as $\pi \times (4\ \text{mm})^{2} \times 1\ \text{mm}$ . In the simulation, the proposed sensor can provide nearly 1 m operation distance when implanted in the intracranial environment. In our preliminary measurement in the air, the sensor has a resolution of 3 cmH2O.

Leena Ukkonen

Papers

Folded Microstrip Patch-Type RFID Tag Antenna Mounted on a Box Corner

RFID signal analysis of bow tie tag antenna in the vicinity of metal

A novel RFID-enabled strain sensor using the double power measurement technique

Embroidered and e-textile Conductors Embedded inside 3D-printed Structures

Inductively Coupled Split Ring Resonator as Small RFID Pressure Sensor for Biomedical Applications