Search

Three new methods for accurate electronic component positioning for thermoformed electronics are presented in this paper. To maintain the mechanical and electrical properties of printed-ink tracks, prevent deformation and stretching during thermoforming, and ensure reproducibility, the component positioning principle for all three proposed methods is based on keeping the temperature of some regions in the thermoplastic substrate less than the glass transition temperature of the thermoplastic carrier, to keep those regions resistant to plastic deformation. We have verified the accuracy of the different approaches by implementing these methods in a semi-sphere mold for positioning seven LEDs and one printed capacitive touch sensor. We compared the result of our fabrication processes with the typical fabrication process of in-mold electronics (direct printing on a thermoplastic foil and followed by a thermoforming step) and noticed that the sample produced by the typical process had tracks that were randomly stretched, tracks were not in a straight path after thermoforming and they were not electrically conductive. Furthermore, the final 3D position of the components was not reproducible sample by sample. However, with our proposed fabrication methods, the tracks and pads do not deform or expand during thermoforming and are electrically conductive after. Moreover, the round shape of the touch sensor remains the same as in the 2D design. Based on the results of the experiments, it appears that the proposed methods are capable of positioning electronic components with high precision in thermoformed electronics. [ABSTRACT FROM AUTHOR]

The integration of assembled foils in injection-molded parts is a challenging step. Such assembled foils typically comprise a plastic foil on which a circuit board is printed and electronic components are mounted. Those components can detach during overmolding when high pressures and shear stresses prevail due to the injected viscous thermoplastic melt. Hence, the molding settings significantly impact such parts' successful, damage-free manufacturing. In this paper, a virtual parameter study was performed using injection molding software in which 1206-sized components were overmolded in a plate mold using polycarbonate (PC). In addition, experimental injection molding tests of that design and shear and peel tests were made. The simulated forces increased with decreasing mold thickness and melt temperature and increasing injection speed. The calculated tangential forces in the initial stage of overmolding ranged from 1.3 N to 7.3 N, depending on the setting used. However, the experimental at room temperature-obtained shear forces at break were at least 22 N. Yet, detached components were present in most of the experimentally overmolded foils. Hence, the shear tests performed at room temperature can only provide limited information. In addition, there might be a peel-like load case during overmolding where the flexible foil might bend during overmolding. [ABSTRACT FROM AUTHOR]

Due to constant advancements in materials research, conductive textile-based materials have been used increasingly in textile-based wearables. However, due to the rigidity of electronics or the need for their encapsulation, conductive textile materials, such as conductive yarns, tend to break faster around transition areas than other parts of e-textile systems. Thus, the current work aims to find the limits of two conductive yarns woven into a narrow fabric at the electronics encapsulation transition point. The tests consisted of repeated bending and mechanical stress, and were conducted using a testing machine built from off-the-shelf components. The electronics were encapsulated with an injection-moulded potting compound. In addition to identifying the most reliable conductive yarn and soft–rigid transition materials, the results examined the failure process during the bending tests, including continuous electrical measurements. [ABSTRACT FROM AUTHOR]

Digital microfluidics (DMF) holds great potential for the alleviation of laboratory procedures in assisted reproductive technologies (ARTs). The electrowetting on dielectric (EWOD) technology provides dynamic culture conditions in vitro that may better mimic the natural embryo microenvironment. Thus far, EWOD microdevices have been proposed for in vitro gamete and embryo handling in mice and for analyzing the human embryo secretome. This article presents the development of the first microfluidic chip utilizing EWOD technology designed for the manipulation of bovine embryos in vitro. The prototype sustains the cell cycles of embryos manipulated individually on the chips during in vitro culture (IVC). Challenges related to the chip fabrication as well as to its application during bovine embryo IVC in accordance with the adapted on-chip protocol are thoroughly discussed, and future directions for DMF in ARTs are indicated. [ABSTRACT FROM AUTHOR]

The integration of structural electronics in injection-molded parts is a challenging step. The films—comprising of laminated stacks with electronics—are exposed to shear stresses and elevated temperatures by the molten thermoplastic. Hence, molding settings have a significant impact on the successful, damage-free manufacturing of such parts. In this paper, test films with polycarbonate (PC) sheets as outer and two different thermoplastic polyurethanes (TPUs) as middle layers incorporating conductive tracks on a flexible printed circuit board (flexPCB) are manufactured and overmolded with PC. Parameter studies investigating the influence of the melt temperature, mold temperature, injection speed and used TPU layer were performed. The molded parts were inspected visually and compared with a numerical simulation using injection molding software. A shear distortion factor for the TPU layer was derived based on the simulations that linked the shear stresses with the injection time and the softening (melting) of the TPU. The distortion of the films was found to reduce with higher melt temperature, lower mold temperature and faster injection speed. Films using the TPU with the higher melting temperature yielded significantly better results. Moreover, distortion on the films reduced with the increasing distance to the gate and a larger cavity thickness was found to be beneficial. All those relations could be correlated with the shear distortion factor. [ABSTRACT FROM AUTHOR]

Over-molding has been proposed in recent years as an integrated functional flexible circuit board in a plastic part. This method uses the conventional process for film insert technology. Over-molding has attracted significant attention across many industries due to its potential to deliver different electrical functions in a variety of different part geometries, especially in automotive interiors and home appliances. While it has great application potential, manufacturing challenges continue throughout foil fabrication and injection molding. This raises challenges for designers and researchers responsible for maintaining the reliability of such electronic flexible circuits. Therefore, the purpose of this research paper is to improve some of the over-molding process parameters. On 0805 and 1206 over-molded zero-ohm resistors, electrical, mechanical, and failure characterization was performed. Those components were mounted in parallel, perpendicular, and 45° angled arrangements on two different polymer substrates, polyimide (PI) and polyethylene terephthalate (PET) using lead-free solder, low-melt solder, and conductive adhesive paste. Moreover, as an over-molding material, polycarbonate (PC) with medium viscosity was used. The effect of using different mold shapes (corner mold, 2 mm flat mold, and 3 mm flat mold) and injection molding process parameters (injection speeds and melt temperature) was studied. [ABSTRACT FROM AUTHOR]

Electrical stimulation of gametes and embryos and on-chip manipulation of microdroplets of culture medium serve as promising tools for assisted reproductive technologies (ARTs). Thus far, dielectrophoresis (DEP), electrorotation (ER) and electrowetting on dielectric (EWOD) proved compatible with most laboratory procedures offered by ARTs. Positioning, entrapment and selection of reproductive cells can be achieved with DEP and ER, while EWOD provides the dynamic microenvironment of a developing embryo to better mimic the functions of the oviduct. Furthermore, these techniques are applicable for the assessment of the developmental competence of a mammalian embryo in vitro. Such research paves the way towards the amelioration and full automation of the assisted reproduction methods. This article aims to provide a summary on the recent developments regarding electrically stimulated lab-on-chip devices and their application for the manipulation of gametes and embryos in vitro. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for removing out-of-plane deformation in stretched metal interconnects by adding a fractal structure to the original meander shape and using an optimized fabrication stack. In thermoformed electronics, in cases where copper is used as conductor, the twisting of meander-shaped structures caused by excessive mechanical stress can cause a non-uniform surface, delamination of the metal interconnect from the substrate, and in some cases, a short circuit to the adjacent tracks. Typically, designers of stretchable electronics use various shapes and widths of the copper interconnect to tackle this issue. Using conventional meander shapes such as horseshoes and U-shapes is not universally practical, especially when stretching is higher than 30 percent leading to significant out-of-plane buckling. Limiting this out-of-plane buckling by reducing the track width is not always applicable, as a minimum width is needed from a technology and conductivity perspective. The presented approach is inspired by computational and experimental studies of multiple meander shapes and fabrication methods. A geometry- and fabrication-based approach is presented, reducing the mechanical stress of almost all possible meander shapes by increasing the meander's path length to accommodate the metal track's produced torque during stretching. An analytical approach is provided for calculating the optimal meander parameters and the optimal fabrication stack is achieved based on simulation results. Experiments and finite element modeling for a case study show the improvement in the stress distribution and reduction of out-of-plane buckling. [ABSTRACT FROM AUTHOR]

Flexible dielectric sensors received significant interest for real-time in situ cure monitoring of polymeric composites over the past decade. Currently, the state-of-the-art dielectric sensors mainly focus on detecting the distinct stages of the polymeric composite curing process. While low-cost and quantitative monitoring of the thermal, mechanical, and chemical properties of the materials during the cure is of great interest, to date, such a sensor system has not been realized because the existing devices excessively depend on external instrumentations, combined with a lack of an embedded reliable data processing module. Here, a fully integrated dielectric monitoring sensor system (DMS) incorporating dielectric and temperature sensors is developed, capable of monitoring in real-time the temperature, the degree of cure, and the glass transition temperature ($T_{g}$) of polymeric composites. An independent characterization of the cure kinetics was performed using differential scanning calorimetry and Raman spectroscopy. These data enabled associating the main physical and chemical transformations in the polymeric materials with particular features observed in the dielectric measurements. We demonstrate the accurate estimation of the degree of cure and $T_{g}$ of an epoxy resin. The proposed system shows the potential for a new generation of intelligent manufacturing technology of composite materials. [ABSTRACT FROM AUTHOR]

The smart textiles and wearable technology markets are expanding tirelessly, looking for efficient solutions to create long-lasting products. The research towards novel integration methods and increasing reliability of wearables and electronic textiles (e-textiles) is expanding. One obstacle to be tackled is the washability and the endurance to mechanical stresses in the washing machine. In this article, different layering of thermoplastic polyurethane (TPU) films and knit fabrics are used to integrate three different designs of stretchable copper-based meander tracks with printed circuit boards. The various combinations are washed according to the ISO 6330-2012 standard to analyze their endurance. Results suggest that one meander design withstands more washing cycles and indicate that the well-selected layer compositions increase the reliability. Higher stretchability together with greater durability is accomplished by adding an extra meander-shaped TPU film layer. [ABSTRACT FROM AUTHOR]

Many of today’s stretchable interconnection technologies make extensive use of meandered interconnections, these provide 2-D in-plane springs capable of extending and compressing as the need arises. While a significant quantity of research work exists on these interconnects, few generic methodologies exist to design circuits in a consistent manner. This shortfall leads to questionable design practices, which can negatively affect reliability and performance. Presented within this paper is a method to quickly determine which meander fits within a given area based on common geometric boundary conditions. [ABSTRACT FROM AUTHOR]

Objectives: In this paper, the effect of the position of the inlet and outlet microchannels on the flow profile and the geometry of the recognition chamber for sample pre-treatment in an electrochemical biosensor to be used in osteoporosis management were investigated. Methods: All numerical computation presented in this work were performed using COMSOL Multiphysics and Fluent. Simulation was performed for a three-dimensional, incompressible Navier–Stokes flow and so explicit biphasic volume of fluid (VOF) equations were used. Results: In the designed microfluidic system, a pressure-driven laminar flow with no-slip boundary condition was responsible for fluid actuation through microchannels in a reproducible approach. Based on the simulation results, the number of outlets was increased and the angel through which the inlets and outlets were attached to the microchamber was changed so that the dead volume would be eliminated and the fluid flow trajectory, the velocity field and pressure were evenly distributed across the chamber. The Re number in the inlets was equal to 4.41, suggesting a laminar flow at this site. Conclusion: The simulation results along with the fact that the design change was tested using laser ablated tape and a color dye at different steps provided the researchers with the opportunity to study the changes in a fast and accurate but cheap method. The absence of backflow helps with the cross-talk concern in the channels and the lack of bubbles and complete coverage of the chamber helps with a better surface modification and thus better sensing performance. [ABSTRACT FROM AUTHOR]

The primary bottleneck of the stretchable mold interconnect (SMI) technology is its reliance on carrier boards. These are necessary to handle the meandered circuit during production and to ensure dimensional stability of the flexible circuit board before encapsulation. However, for all the problems it solves, it also introduces a new major problem by requiring a peeling step—which is difficult to automate. This paper aims to present some of the work that went into eliminating this problem, discussing both unsuccessful and functioning methods to tackle this conundrum and some of the experimental work that went into verifying these techniques. First, alterations to the design to simplify peeling are considered, followed by adhesive-based peeling processes and mechanical pin-based systems. Next, masking and structuring of the carrier board adhesive are considered. Finally, two carrierless methods that circumvent the problems are discussed, a two-step process—which cuts temporary support structures after partial encapsulation—and a technique whereby the frame is designed to fail in a controlled manner during the first use of the circuit, creating a carrierless process feasible for high-volume production. [ABSTRACT FROM AUTHOR]

Drug development is currently hampered by the inability of animal experiments to accurately predict human response. While emerging organ on chip technology offers to reduce risk using microfluidic models of human tissues, the technology still mostly relies on end-point assays and biomarker measurements to assess tissue damage resulting in limited mechanistic information and difficulties to detect adverse effects occurring below the threshold of cellular damage. Here we present a sensor-integrated liver on chip array in which oxygen is monitored using two-frequency phase modulation of tissue-embedded microprobes, while glucose, lactate and temperature are measured in real time using microfluidic electrochemical sensors. Our microphysiological platform permits the calculation of dynamic changes in metabolic fluxes around central carbon metabolism, producing a unique metabolic fingerprint of the liver's response to stimuli. Using our platform, we studied the dynamics of human liver response to the epilepsy drug Valproate (Depakine™) and the antiretroviral medication Stavudine (Zerit™). Using E6/E7LOW hepatocytes, we show TC50 of 2.5 and 0.8 mM, respectively, coupled with a significant induction of steatosis in 2D and 3D cultures. Time to onset analysis showed slow progressive damage starting only 15–20 hours post-exposure. However, flux analysis showed a rapid disruption of metabolic homeostasis occurring below the threshold of cellular damage. While Valproate exposure led to a sustained 15% increase in lipogenesis followed by mitochondrial stress, Stavudine exposure showed only a transient increase in lipogenesis suggesting disruption of β-oxidation. Our data demonstrates the importance of tracking metabolic stress as a predictor of clinical outcome. [ABSTRACT FROM AUTHOR]

Abstract: Fiber‐reinforced polymer composites with integrated intelligence, such as sensors, actuators, and communication capabilities, are desirable as infrastructures for the next generation of “internet of things.” However, the shape mismatch between the 3D composites and a planar electronic circuit causes difficulties in integrating electronic circuit‐based intelligences. Here, an easily scalable approach, by incorporating a large‐area stretchable circuit with thermoforming technology, to fabricate 3D multifunctional composites is reported. The stretchable circuit is first fabricated on a rigid and planar carrier board, then transferred and sandwiched between thermoplastic composites through lamination processes. A thermoforming step shapes the sandwiched and planar structure by heating up the encapsulating polymers beyond their glass transition temperature and pushing them and the circuit against a mold. Using the proposed process, large‐sized composites with integrated matrices of light‐emitting diodes (LEDs) and capacitive sensors are successfully fabricated. A giant (with a size of 0.5 m × 1 m) seven‐segment display is assembled using the fabricated composites with integrated LEDs and capacitive sensors to display 128 symbols. The results demonstrate the potential of the proposed approach as a facile, reproducible, and scalable process for creating 3D multifunctional composites. [ABSTRACT FROM AUTHOR]

An impulse-radio ultra-wideband (IR-UWB) cavity-backed slot antenna covering the [5.9803; 6.9989] GHz frequency band of the IEEE 802.15.4a-2011 standard is designed and implemented in an air-filled substrate integrated waveguide (AFSIW) technology for localization applications with an accuracy of at least 3 cm. By relying on both frequency- and time-domain optimization, the antenna achieves excellent IR-UWB characteristics. In free-space conditions, an impedance bandwidth of 1.92 GHz (or 29.4%), a total efficiency higher than 89%, a front-to-back ratio of at least 12.1 dB, and a gain higher than 6.3 dBi are measured in the frequency domain. Furthermore, a system fidelity factor larger than 98% and a relative group delay smaller than 100 ps are measured in the time domain within the 3 dB beamwidth of the antenna. As a result, the measured time-of-arrival of a transmitted Gaussian pulse, for different angles of arrival, exhibits variations smaller than 100 ps, corresponding to a maximum distance estimation error of 3 cm. Additionally, the antenna is validated in a real-life worst-case deployment scenario, showing that its characteristics remain stable in a large variety of deployment scenarios. Finally, the difference in frequency- and time-domain performance is studied between the antenna implemented in AFSIW and in dielectric filled substrate integrated waveguide (DFSIW) technology. We conclude that DFSIW technology is less suitable for the envisaged precision IR-UWB localization application. [ABSTRACT FROM PUBLISHER]

Conventional electronic circuits are made up of electronic components assembled on either rigid substrates like FR4 and ceramic or on flexible substrates based on polymers such as polyimide, PET and PEN foils. The latter type of substrates offers considerable improvements in freedom of motion over its rigid complement although the deformations are still pretty limited due to the inability of common electronic materials, such as metals, to cope with the corresponding deformation. Moreover, the assembly of rigid electronic components can often reduce the circuit’s ability to bend. The current trend towards increased component density on substrates makes the final assembly even less flexible. However, electronic circuits which can fully conform and easily fit in the arbitrary curved surface topologies are of keen interest in various areas of applications. Aside from flexibility, a certain degree of stretching is required for the three-dimensional shaping of electronic systems. Hence, deformability will offer electronics a number of additional features like bendability, conformability shaping and lightweight. Three-dimensional shaped electronics can be obtained either by multi-time (dynamic or elastic) or one time (static, permanent) stretching. In this paper an introduction on deformable and conformable electronics is outlined highlighting the different existing approaches. Some examples of flexible and stretchable electronic applications will be provided in various fields. [ABSTRACT FROM AUTHOR]

Metal-elastomer interfacial systems, often encountered in stretchable electronics, demonstrate remarkably high interface fracture toughness values. Evidently, a large gap exists between the rather small adhesion energy levels at the microscopic scale (‘intrinsic adhesion’) and the large measured macroscopic work-of-separation. This energy gap is closed here by unravelling the underlying dissipative mechanisms through a systematic numerical/experimental multi-scale approach. This self-containing contribution collects and reviews previously published results and addresses the remaining open questions by providing new and independent results obtained from an alternative experimental set-up. In particular, the experimental studies on Cu-PDMS (Poly(dimethylsiloxane)) samples conclusively reveal the essential role of fibrillation mechanisms at the micro-meter scale during the metal-elastomer delamination process. The micro-scale numerical analyses on single and multiple fibrils show that the dynamic release of the stored elastic energy by multiple fibril fracture, including the interaction with the adjacent deforming bulk PDMS and its highly nonlinear behaviour, provide a mechanistic understanding of the highwork-of-separation. An experimentally validated quantitative relation between the macroscopic work-of-separation and peel front height is established from the simulation results. Finally, it is shown that a micro-mechanically motivated shape of the traction-separation law in cohesive zone models is essential to describe the delamination process in fibrillating metal-elastomer systems in a physically meaningful way. [ABSTRACT FROM AUTHOR]

A novel manufacturing procedure for the fabrication of ultra-wideband cavity-backed substrate integrated waveguide antennas on textile substrates is proposed. The antenna cavity is constructed using a single laser-cut electrotextile patch, which is folded around the substrate. Electrotextile slabs protruding from the laser-cut patch are then vertically folded and glued to form the antenna cavity instead of rigid metal tubelets to implement the vertical cavity walls. This approach drastically improves mechanical flexibility, decreases the antenna weight to slightly more than 1 g and significantly reduces alignment errors. As a proof of concept, a cavity-backed substrate integrated waveguide antenna is designed and realized for ultra-wideband operation in the [5.15–5.85] GHz band. Antenna performance is validated in free space as well as in two on body measurement scenarios. Furthermore, the antenna’s figures of merit are characterized when the prototype is bent at different curvature radii, as commonly encountered during deployment on the human body. Also the effect of humidity content on antenna performance is studied. In all scenarios, the realized antenna covers the entire operating frequency band, meanwhile retaining a stable radiation pattern with a broadside gain above 5 dBi, and a radiation efficiency of at least 70%. [ABSTRACT FROM AUTHOR]

This article explains a step-wise protocol to develop an electrochemical sensor to quantify serum levels of C-telopeptide (CTX) crosslinks also known as crosslaps in a matter of minutes and with high level of accuracy. The technique needs only one-step (incubation) and can thus be used for point of care screening. Due to the excellent electrical properties of the as-prepared immunosensor, CTX levels were successfully measured from 1 to 1000 pg/mL. This is while the normal reference of the marker is 50-450 pg/mL, suggesting that the sensor can acceptably detect CTX. The results also showed a good correlation with ECLIA in measuring serum levels of CTX. [ABSTRACT FROM AUTHOR]

A method to fabricate thermoplastically deformable electronic circuits is presented, with the intent of achieving low-cost 2.5D free-form rigid smart objects. This by utilizing existing flexible circuit technology based stretchable circuits, in combination with thermoplastic materials. After fabricating the circuit in a flat state, a thermoforming step shapes the device by heating it beyond its glass transition temperature, and pushing it against a mold. Preliminary tests show the feasibility to fabricate simple circuits using off-the-shelf circuit components; showing a minimal decrease in conductivity of the polyimide supported copper-based interconnects. [ABSTRACT FROM AUTHOR]

This paper reports a step-wise protocol to immobilize corresponding antibody on gold electrodes for electrochemical measurement of Osteocalcin (Oc), a bone turnover marker, levels in human serum. To our knowledge this is the first such sensor developed for Oc measurement. The magnitude of electrochemical response current was linearly dependent on Oc concentration with an R square of 0.99. The detection limit was calculated to be 0.65 ng/mL. The sensor was capable to assess antigen levels of 2.5–90 ng/mL. The correlation between our sensor results and that of electrochemiluminescence (ECLIA), the current state-of-art, was also investigated and the results showed a high correlation (slope of 0.97 and R2 of 0.98) between the two systems. This is while the total assay time for the Oc sensor is about 5 min and ECLIA needs several hours to be performed. [ABSTRACT FROM PUBLISHER]

In this work, we report a microfluidic platform that can be easily translated into a biomarker diagnostic. This platform integrates microfluidic technology with electrochemical sensing and embodies a reaction/detection chamber to measure serum levels of different biomarkers. Microfabricated Au electrodes encased in a microfluidic chamber are functionalized to immobilize the antibodies, which can selectively capture the corresponding antigen. An oxidative peak is obtained using the chronoamperometry technique at room temperature. The magnitude of the response current varies linearly with the logarithmic concentration of the relative biomarker and, thus, is used to quantify the concentration of the relative biomarker in serum samples. We demonstrated the implementation, feasibility and specificity of this platform (Osteokit) in assaying serum levels of bone turnover markers (BTMs) using osteocalcin (limits of detection (LOD) = 1.94 ng/mL) and collagen type 1 cross-linked C-telopeptide (CTX) (LOD = 1.39 pg/mL). To our knowledge, this is the first such device fabricated to measure BTMs. Our results also showed that the sensitivity of Osteokit is comparable with the current states of art, electrochemiluminescence (ECLIA). [ABSTRACT FROM AUTHOR]

ABSTRACT Interdigital sensors (IDS) have received great attention for production monitoring of polymers over the past decade. However, conventional IDS are limited by high noise to environment due to the dual side access of the sensor, low nominal capacitance, and sensitivity. In this study, a shielded IDS fabricated by flexible circuit board (FCB) technology is presented to overcome these challenges. Compared to conventional sensors, the environmental dependence of the new sensor is minimized by the copper shield. Furthermore, nominal capacitance of at least 350% higher, and an increase of sensitivity per unit area are achieved. To demonstrate the capabilities of the new IDS, a FCB comprising the proposed sensor is fabricated, attached to a mould, and successfully applied for in situ real-time production monitoring of an epoxy resin. The resulting flexible sensor is noninvasive towards the fabricated parts, and measures the key stages along the production process. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2028-2037 [ABSTRACT FROM AUTHOR]

A novel wearable radio frequency identification (RFID) tag with sensing, processing, and decision-taking capability is presented for operation in the 2.45-GHz RFID superhigh frequency (SHF) band. The tag is powered by an integrated light harvester, with a flexible battery serving as an energy buffer. The proposed active tag features excellent wearability, very high read range, enhanced functionality, flexible interfacing with diverse low-power sensors, and extended system autonomy through an innovative holistic microwave system design paradigm that takes antenna design into consideration from the very early stages. Specifically, a dedicated textile shorted circular patch antenna with monopolar radiation pattern is designed and optimized for highly efficient and stable operation within the frequency band of operation. In this process, the textile antenna’s functionality is augmented by reusing its surface as an integration platform for light-energy-harvesting, sensing, processing, and transceiver hardware, without sacrificing antenna performance or the wearer’s comfort. The RFID tag is validated by measuring its stand-alone and on-body characteristics in free-space conditions. Moreover, measurements in a real-world scenario demonstrate an indoor read range up to 23 m in nonline-of-sight indoor propagation conditions, enabling interrogation by a reader situated in another room. In addition, the RFID platform only consumes 168.3 \mu \textW , when sensing and processing are performed every 60 s. [ABSTRACT FROM PUBLISHER]

This research presents a case study of production monitoring on an aerospace composite component: the hinge arm of the droop nose mechanism on the Airbus A380 wing leading edge. A sensor network composed of Fibre Bragg Gratings, capacitive sensors for cure monitoring and thermocouples was embedded in its fibre reinforced lay-up and measurements were acquired throughout its Resin Transfer Moulding production process. Two main challenges had to be overcome: first, the integration of the sensor lines in the existing Resin Transfer Moulding mould without modifying it; second, the demoulding of the component without damaging the sensor lines. The proposed embedding solution has proved successful. The wavelength shifts of the Fibre Bragg Gratings were observed from the initial production stages, over the resin injection, the complete curing of the resin and the cooling-down prior to demoulding. The sensors proved to be sensitive to detecting the resin flow front, vacuum and pressure increase into the mould and the temperature increase caused by the resin curing. Measurements were also acquired during the post-curing cycle. Residual strains during all steps of the process were derived from the sensors' wavelength shift, showing values up to 0.2% in compression. Moreover, the capacitive sensors were able to follow-up the curing degree during the production process. The sensors proved able to detect the resin flow front, whereas thermocouples could not measure an appreciable increase of temperature due to the fact that the resin had the same temperature as the mould. [ABSTRACT FROM AUTHOR]

In this contribution, a conformable 64x45 RGB light-emitting diode (LED) matrix is presented. A design concept of stretchable electronics is used: non-stretchable polymer islands host rigid LEDs and are interconnected by horseshoe shaped metallic conductors, which are able to deform together with an elastomeric substrate. Thin-film metallization is used to enable a pixel pitch of 1 mm, while polyimide is used to realize the non-stretchable islands, but also to support the meandering conductors. The design of the stretchable interconnections has been optimized with respect to their mechanical and electrical performance. Thermoplastic polyurethane is introduced at a final stage of the fabrication process to ensure its compatibility with conventional thin-film processing. A passive matrix addressing scheme is used to drive the LED matrix. At a supply voltage of 10 V, the brightness of the display reaches up to 700 cd/m2. [ABSTRACT FROM AUTHOR]

A high-performance, three-element substrate-integrated-waveguide (SIW) cavity-backed slot antenna array that covers the (5.15–5.85) GHz band is designed for integration inside or underneath the worktop of a desk, to set up a stable, high data-rate ultra-short-range $3 \times 3$ multiple-input multiple-output (MIMO) wireless communication link with a mobile user (MU) positioned on top of that worktop. The antenna topology and array geometry are carefully selected to maximally exploit the multiplexing capabilities of the ultra-short-range $3 \times 3$ MIMO channel over a wide bandwidth, yielding an increased channel capacity and/or reduced power consumption. In addition, special care was taken to guarantee a channel capacity that is less dependent on the relative orientation of the MU. Furthermore, the SIW implementation technology is combined with innovative antenna materials to guarantee a low-profile, low-cost, stable, and high-performance broadband array design that maintains its excellent performance after integration. A prototype of the antenna array was fabricated, integrated according to two different integration scenarios, and validated. Measurements prove that the antenna array allows integration into a worktop with only a minor influence on its return loss and mutual coupling, guaranteeing a bandwidth of at least 1.078 GHz and a minimum isolation between antenna elements of 30 dB within the entire (5.15–5.85) GHz band. [ABSTRACT FROM PUBLISHER]

Microfluidic organ-on-a-chip technology aims to replace animal toxicity testing, but thus far has demonstrated few advantages over traditional methods. Mitochondrial dysfunction plays a critical role in the development of chemical and pharmaceutical toxicity, as well as pluripotency and disease processes. However, current methods to evaluate mitochondrial activity still rely on end-point assays, resulting in limited kinetic and prognostic information. Here, we present a liver-on-chip device capable of maintaining human tissue for over a month in vitro under physiological conditions. Mitochondrial respiration was monitored in real time using two-frequency phase modulation of tissue-embedded phosphorescent microprobes. A computer-controlled microfluidic switchboard allowed contiguous electrochemical measurements of glucose and lactate, providing real-time analysis of minute shifts from oxidative phosphorylation to anaerobic glycolysis, an early indication of mitochondrial stress. We quantify the dynamics of cellular adaptation to mitochondrial damage and the resulting redistribution of ATP production during rotenone-induced mitochondrial dysfunction and troglitazone (Rezulin)-induced mitochondrial stress.We show troglitazone shifts metabolic fluxes at concentrations previously regarded as safe, suggesting a mechanism for its observed idiosyncratic effect. Our microfluidic platform reveals the dynamics and strategies of cellular adaptation to mitochondrial damage, a unique advantage of organ-on-chip technology. [ABSTRACT FROM AUTHOR]

In this paper, we present the developments of a new technology to realize 2.5-/3-D electronic circuits. The starting point is an electronic circuit embedded in a hard thermoplastic material, which is transformed into a 2.5-/3-D shape using a thermoforming process. The electronic circuit consists of stretchable copper interconnections in combination with electronic components. The circuit is produced using conventional printed circuit board process steps: a copper sheet is laminated on a thermoplastic material, such as Polycarbonate (PC) or Polyethylene Terephthalate Glycol (PET-G). The copper is structured using lithography and wet etching, and the electronic components are assembled using conductive adhesives. We investigated the use of different designs for stretchable interconnects to overcome the stretching of the electronic circuit by thermoforming it. A semispherical-shaped mold was used for this purpose where the local strain of the substrate can reach 100% with a sharp bending. It was shown that meander-shaped interconnects could accommodate the gradual deformation during the forming of the substrate either for PC and PET-G. However, at the mold’s edge, the copper-meandered tracks showed a delamination of the copper from the substrate. In the meanwhile, the electrical conductivity of the copper tracks did not show any significant variation. Another meander design based on an elliptical shape (in order to increase the length of the track) is proposed and compared with the first design. [ABSTRACT FROM PUBLISHER]

Silver nanowires (AgNWs) have emerged as a promising nanomaterial for next generation stretchable electronics. However, until now, the fabrication of AgNWbased components has been hampered by complex and time-consuming steps. Here, we introduce a facile, fast, and one-step methodology for the fabrication of highly conductive and stretchable AgNW/polyurethane (PU) composite electrodes based on a high-intensity pulsed light (HIPL) technique. HIPL simultaneously improved wire-wire junction conductivity and wire-substrate adhesion at room temperature and in air within 50 μs, omitting the complex transfer-curing-implanting process. Owing to the localized deformation of PU at interfaces with AgNWs, embedding of the nanowires was rapidly carried out without substantial substrate damage. The resulting electrode retained a low sheet resistance (high electrical conductivity) of <10 Ω/sq even under 100% strain, or after 1,000 continuous stretching-relaxation cycles, with a peak strain of 60%. The fabricated electrode has found immediate application as a sensor for motion detection. Furthermore, based on our electrode, a light emitting diode (LED) driven by integrated stretchable AgNW conductors has been fabricated. In conclusion, our present fabrication approach is fast, simple, scalable, and costefficient, making it a good candidate for a future roll-to-roll process. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We present a str etchable and foldable passive matrix driven display using 45 by 80 RGB LED's mounted on a meandering printed circuitry embedded in a polyurethane film. The meander interconnections have been optimized with respect to their electrical and mechanical properties to provide a display with a 3 mm pitch between the pixels and a stretchability of up to 10%. At an operating supply voltage of 5 V, the brightness of the display exceeds 30 cd/m2. [ABSTRACT FROM AUTHOR]