Foreword Special Section on Flexible Electronics From the Selected Extended Papers Presented at 2018 IFETC

This Special Section is devoted to the research and development activities of all areas of flexible electronics science and technology. We have a selected number of high impact technical papers presented at the first IEEE International Flexible Electronics Technology Conference (IFETC) in 2018 for publication in J-EDS. The first IFETC was held in Ottawa, Ontario, Canada from the 7th to 9th August, 2018. The conference was financially sponsored by the IEEE Council on RFID, and technically sponsored by the National Research Council Canada, IEEE Electron Device Society, and the IEEE Instrumentation and Measurement Society. The conference was dedicated to the advances in flexible electronics in all areas of science and technology, and provided an opportunity for scientists, researchers, engineers, developers, and users in the field to share, discuss, and witness new concepts and ideas. A wide spectrum of academic research results was presented, with potential applications in current industrial technology and new application driven domains

Fiber Optic Sensors for Structural Health Monitoring of Air Platforms

Aircraft operators are faced with increasing requirements to extend the service life of air platforms beyond their designed life cycles, resulting in heavy maintenance and inspection burdens as well as economic pressure. Structural health monitoring (SHM) based on advanced sensor technology is potentially a cost-effective approach to meet operational requirements, and to reduce maintenance costs. Fiber optic sensor technology is being developed to provide existing and future aircrafts with SHM capability due to its unique superior characteristics. This review paper covers the aerospace SHM requirements and an overview of the fiber optic sensor technologies. In particular, fiber Bragg grating (FBG) sensor technology is evaluated as the most promising tool for load monitoring and damage detection, the two critical SHM aspects of air platforms. At last, recommendations on the implementation and integration of FBG sensors into an SHM system are provided

Plasma and corona discharge pretreatment of polyetheretherketone for adhesive bonding

To enhance the bondability of polyetheretherketone (PEEK), surface treatment techniques of plasma and corona discharge have been evaluated. The results have shown that these two methods are effective and practical. The treated materials not only reach their highest possible joint strength, but also show very promising joint durability. In addition, the various environments, e. g. atmosphere, heat, water, and solvent, have little effects on the enhanced bondability of the treated materials. By using Contact Angle Measurement, Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondaty Ion Mass Spectrometry (TOF-SIMS) to characterise the PEEK surfaces before and after treatment, it was established that the lack of active chemical groups, which if present can form strong interatomic and intermolecular forces across the adhesive/PEEK interface, is the main cause for the poor bondability of the untreated PEEK. Both plasma and corona discharge treatment introduce such active functional groups, for instance, hydroxyl, carboxylic acid, amine and etc., onto the surface of PEEK film and so greatly enhance the intrinsic adhesion at the interface between treated PEEK surfaces and epoxy adhesive, as confirmed by the TOF-SIMS interfacial analysis. It is deduced that low molecular weight molecules (LMWM) are formed on treated surfaces, which contain high concentration of oxygen and/or nitrogen, and can be removed by solvent washing. The removal of LMWM will drastically reduce the wettability of the treated surfaces, but does not impair the enhanced bondability. It has been found that both plasma and corona discharge treated surfaces are in a thermodynamically unstable state. When exposed to the atmosphere, the treated surfaces tend to lose their improved wettability and decrease their surface polarity. Increasing temperature can not only accelerate these processes but also change the surface chemical structures of the treated materials back to that of the untreated films to some extent, as revealed by the TOF-SIMS analysis. Water immersion, on the contrary, tend to reverse the above processes

Measurement of microwave frequency using a monolithically integrated scannable echelle diffractive grating

NRC publication: Ye

Highly conductive and transparent carbon nanotube composite thin films deposited on polyethylene terephthalate solution dipping

In this letter we present highly conductive and transparent thin films of single-walled carbon nanotubes (SWCNT) and conductive polymer composite deposited on polyethylene terephthalate film substrates by solution dipping. The initial results show that 66 \u3a9/\u25a1 sheet resistance can be achieved with 80% transmission at the wavelength of 550 nm. This result is much superior to the performances of the pure SWCNT thin films deposited using the same technique. The improvement is attributed to the increase of effective electric conductive tube\u2013tube junctions in the CNT network.Peer reviewed: YesNRC publication: Ye

Highly transparent and conductive carbon nanotube coatings deposited on flexible polymer substrate by solution method

Transparent single-walled carbon nanotubes (SWCNT) based flexible conductive coatings have found great application potentials in flexible displays and solar cells. In this paper we report a simple method for the fabrication of this type conductive coatings. By using plasma treatment of the flexible polymer substrates, the fabrication of SWCNT flexible coating can be easily achieved through a simple dip coating process. Initial results show that one-dip yields a sheet resistance of 128 \u3a9/ and film transmission of more than 90% at the wavelength of 550 nm, while two-dip produces a coating with a sheet resistance of 75 \u3a9/ and transmission of more than 80% at the wavelength of 550 nm. The performances achieved are comparable to those of the ITO coatings and significantly better than those reported in the literature for the SWCNT coatings produced by using similar methods.Peer reviewed: YesNRC publication: Ye

Towards the simultaneous monitoring of load and damage in aircraft structures using fiber Bragg grating sensors

Load monitoring and damage detection are the two critical aspects of aircraft structural health monitoring (SHM). The load monitoring is achieved by detecting the local strain changes while the damage detection is generally accomplished by the monitoring of acoustic signal changes. It would be ideal that a single sensor can perform both tasks simultaneously. This paper reports the demonstration of using fiber Bragg gratings to monitor load and acoustic signal applied on a simulated aircraft structure. The results clearly show that a single fiber Bragg grating sensor with short grating length has the potential to perform both tasks simultaneously.Peer reviewed: YesNRC publication: Ye

Optical manipulation of microparticles in an SU-8/PDMS hybrid microfluidic chip incorporating a monolithically integrated on-chip lens set

An SU-8/PDMS microfluidic chip incorporating a monolithically integrated on-chip lens set for transport and manipulation of microparticles is developed. The components, including the on-chip lens set, the microfluidic channel, and the fiber grooves, are defined in a single layer of SU-8 by one-step photolithography. The design of the on-chip lens set and the fabrication of the microfluidic chip are fully described. The influence of the beam-waist radius on the manipulation performance is theoretically analyzed and experimentally verified for the first time. In the cross-type optofluidic architecture, the evaluation is performed by measuring the particle displacement with different beam-waist radii under different fluid-flow rates. The on-chip lens set is designed to have a specific dimension to achieve the required beam-waist radius. It is revealed that the particle displacement is counter-proportional to the beam-waist radius. An experiment is performed. The results show that the particle displacement is increased by reducing the beam-waist radius. The optical manipulation of microparticles is also demonstrated by using two counter-propagating light beams that are perpendicular to the fluid-flow direction with the beamwaist radius determined by two on-chip lens sets placed on the two sides of the microfluidic channel. The proposed architecture could be used to enhance the performance in particle transport, separation, and concentration.Peer reviewed: YesNRC publication: Ye