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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]

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 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]

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]

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]