Background/Objectives: Neonatal hypothermia remains a significant contributor to neonatal mortality and morbidity mainly in low and middle-income countries, such as those in sub-Saharan Africa. The objective of this systematic review and meta-analysis is to assess the prevalence of neonatal hypothermia and its risk factors in sub-Saharan Africa. Methods: The Preferred Reporting Items for Systematic Review and Meta-Analysis statement (PRISMA) guideline was used to search databases (PubMed, Scopus, Cocrane library and Google Scholar) for studies reporting both the prevalence and factors associated with neonatal hypothermia in sub-Saharan Africa. We have included cross-sectional, cohort and descriptive studies published between 1 June 2014 and 31 May 2024. The Joanna Briggs Institute (JBI) quality appraisal checklist was used for the appraisal of studies. Subgroup analysis was conducted by country, study design and population. A total of 21 articles with 12,803 participants from 9 countries were included in the analysis. Results: The pooled prevalence of neonatal hypothermia was 55.39% (95% CI: 48.52, 62.25). Preterm birth (odds ratio (OR): 3.49; 95% CI: 1.98-6.16), low birth weight (OR: 3.56; 95% CI: 2.36-5.39), no skin-to-skin contact (OR: 1.31; 95% CI: 0.55-3.13), lack of resuscitation (OR: 2.56; 95% CI: 1.75-3.76), delayed initiation of breast feeding (OR: 2.38; 95% CI: 1.57-3.61), admission during cold season (OR: 1.80; 95% CI: 1.33-2.44), home delivery (OR: 1.94; 95% CI: 1.51-2.50) and early bathing (OR: 3.03; 95% CI: 0.98-9.38) were the factors significantly associated with neonatal hypothermia. Conclusions: The observed high prevalence of hypothermia was associated with physiological, behavioral and environmental factors.

Soft smart surfaces, integrating flexible electronics and decorative materials, seamlessly combine sensors and light-emitting elements for user interaction. This allows minimalist designs for automotive interiors. To integrate uniform light-emitting elements into flexible materials, printed emissive layers like OLEDs or QLEDs can be used. These offer saturated colors but face challenges in cost, brightness, efficiency, and durability. Backlight-based technologies, such as edge-lit planar lightguides, provide a mature alternative. However, embedding such lightguides into thin, flexible stacks poses significant challenges, particularly in maintaining total internal reflection due to the need for air gaps. This work presents the design and fabrication of an edge-lit lightguide with a quantum dot (QD) color conversion layer, fully integrated into a soft, flexible polyurethane resin (PUR) layer laminated on a polyethylene terephthalate (PET) substrate containing electronic circuitry and blue LEDs. The spreading of the light within the lightguide, to obtain uniform light-emitting icons and symbols, is realized by employing diffuse reflective paint layers and optimizing the lightguide shape. Optical ray tracing simulations, based on accurately measured material properties, were used to determine the required QD loading in the 100 $\mu \mathrm{m}$ thick QD layer to achieve the targeted color, as well as analyze the performance of the configuration in detail. The final design was validated through light output measurements from a fabricated prototype.

Nowadays, with the aging population, the number of people in homes for the elderly is dramatically rising. Nearly, all of them suffer from a degree of incontinence and wear diapers on a daily basis, leading to a lot of superabsorbent polymer waste material. Smart diapers increase patient comfort owing to timely diaper changes. At the same time, the absorbent content of smart diapers can be reduced substantially, compared with regular diapers, as less margin for late changes is needed. From the medical perspective, smart diapers also reduce painful incontinence-associated dermatitis (IAD) caused by prolonged exposure to saturated diapers. This article proposes a novel contactless smart diaper system that allows caregivers to remotely read out information about diaper contents. The developed system is based on capacitive coupling to a printed structure in the diaper, including multiple detection zones distributed across its length. By printing the sensing pattern into the diaper in carbon ink, a low-cost, mass producible, and environmentally friendly sensor is obtained. A four-port differential transmission-measurement technique is employed, resulting in a higher system reliability than many existing smart diaper systems relying on impedance measurements only. This article includes both laboratory and in-field measurements to demonstrate the successful detection of moisture.

Electronic textiles (e-textiles) are a branch of wearable technology based on integrating smart systems into textile materials creating different possibilities, transforming industries, and improving individuals’ quality of life. E-textiles hold vast potential, particularly for use in personal protective equipment (PPE) by embedding sensors and smart technologies into garments, thus significantly enhancing safety and performance. Although this branch of research has been active for several decades now, only a few products have made it to the market. Achieving durability, reliability, user acceptance, sustainability, and integration into current manufacturing processes remains challenging. High levels of reliability and user acceptance are critical for technical textiles, such as those used in PPE. While studies address washing reliability and field tests, they often overlook end user preferences regarding smart textiles. This paper presents a narrow fabric-based e-textile system co-developed by engineers, garment and textiles’ manufacturers, and firefighters. It highlights material choices and integration methods, and evaluates the system’s reliability, sustainability, and user experience, providing comprehensive insights into developing and analyzing e-textile products, particularly in the PPE field.

Recent developments in flexible printed heaters (FPHs) for wearable thermal applications, driven by the advancement of printed electronics, show great promise in revolutionizing patient care through the development of wearable flexible heaters for medical applications. Wearable heaters with high thermal stability, heat uniformity, safety, flexibility, comfort, biocompatibility, biodegradability, recyclability, and power efficiency are desirable for standalone medical thermotherapy applications. This paper reviews recent advancements in the design of FPHs for wearable thermal applications. Materials used in the FPHs, fabrication methods, design considerations, temperature control mechanisms, medical applications, and performance analysis of specific FPHs are all thoroughly discussed. Materials used in FPHs, such as conductive and substrate materials, receive special attention along with the heater design parameters. Additionally, the paper addresses the challenges and future directions for the advancement of FPHs in wearable medical applications.

Within our internal FITEP technology platform (FITEP: Flexible Implantable Thin Electronic Package), a novel implantable packaging technology is under development in order to realize a very small, flexible, biomimetic package for electronic implants. This new platform enables a radical miniaturization of the final implanted device, which opens many new possibilities for the medical world, since it will be possible to insert electronic sensors in very small locations, such as arteries, nerves, glands,... The device encapsulation consists of a multilayer of biocompatible polymers and ultrathin ceramic diffusion barriers deposited using ALD techniques (ALD: atomic layer deposition) in order to fabricate a very thin and flexible but also highly hermetic device packaging. Concerning the selection of biocompatible polymers, polyimide can offer a profound mechanical support for the various device components, while Parylene with its excellent step coverage creates a highly conformal coating surrounding all components. Hermeticity can be realized by the use of ultrathin ceramic ALD layers such as Al2O3 and HfO2. An optimized ALD process will result in layers from very high quality with very good step coverage. As such, selected ALD layers of only a few tens of nm thick, can exhibit very low Water Vapor Transmission Rates (WVTR), making these ALD materials ideal as ultrathin diffusion barriers. The tested polyimide/ALD stack proved to be a very hermetic enclosure: copper patterns protected with the polyimide/ALD stack are still in perfect condition after more than 2 years of immersion in saline at 60 °C (test is still ongoing), while Cu patterns protected by the polyimide stack without ALD barriers showed first signs of damage already after 6 weeks exposure to saline. Platinum and gold are best suited for metallization of implanted electronics, but these noble metals do not adhere easily to polymers, hence dedicated measures to promote metal-polymer adhesion are essential. The FITEP platform is applied on a Si-probe for implantation in the peripheral nerves, consisting of a CMOS chip with recording and stimulation electrodes [Op de Beeck, M. 2017]. The chip is thinned down to 35um and packaged using polyimide and ALD multi-stacks, resulting in a 75um thin fully encapsulated chip, optimized to reduce the Foreign Body Reaction to obtain optimum electrode-nerve contact. Flexible interconnects are fabricated using gold and platinum sandwiched between polymers and ALD layers. For optimal charge injection, iridium oxide is used as electrode material. After this hermetic FITEP-based chip encapsulation, the CMOS chip is still fully functional, which was tested dry (in air) as well as during submersion in saline. First acute in vivo stimulation tests have shown good electrode stimulation capabilities. Mechanical bending tests on long 5um thick gold interconnects are performed, showing that even after up to 1.5 million bending cycles, no cracks occurred in the gold patterns (testing in air). Longer term immersion in saline and in-vivo testing showed some problems related to loss of adhesion and to galvanic effects of the metallization. These observations were leading to some improvements in the fabrication of the encapsulation. In a second packaging iteration of the CMOS chip, these improvements were realized and a new series of encapsulated devices is fabricated. First results are promising, showing improved metal adhesion. Longer term stability tests are on its way.

In this work, the development of an active high-density transverse intrafascicular micro-electrode (hd-TIME) probe to interface with the peripheral nervous system is presented. The TIME approach is combined with an active probe chip, resulting in improved selectivity and excellent signal-to-noise ratio. The integrated multiplexing capabilities reduce the number of external electrical connections and facilitate the positioning of the probe during implantation, as the most interesting electrodes of the electrode array can be selected after implantation. The probe chip is packaged using thin-film manufacturing techniques to allow for a minimally invasive electronic package. Special attention is paid to the miniaturization, the mechanical flexibility and the hermetic encapsulation of the device. A customized probe chip was designed and packaged using a flexible, implantable thin electronic package (FITEP) process platform. The platform is specifically developed for making slim, ultra-compliant, implantable complementary metal-oxide-semiconductor based electronic devices. Multilayer stacks of polyimide films and HfO2/Al2O3/HfO2 layers deposited via atomic layer deposition act as bidirectional diffusion barriers and are key to the hermetic encapsulation. Their efficacy was demonstrated both by water vapor transmission rate tests and accelerated immersion tests in phosphate buffered saline at 60 degrees C. Using the hd-TIME probe, an innovative implantation method is developed to prevent the fascicles from moving away when the epineurium is pierced. In addition, by transversally implanting the hd-TIME probe in the proximal sciatic nerve of a rat, selective activation within the nerve was demonstrated. The FITEP process platform can be applied to a broader range of integrated circuits and can be considered as an enabler for other biomedical applications.

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.

Combining stretchable circuits and thermoforming technology, a method to produce 3D multifunctional polymer composites is described by Yang Yang, Jan Vanfleteren, and co-workers in article number 1800071. A demonstrator consisting of a seven-segment display with integrated LEDs and capacitive touch sensors is fabricated using the proposed method. The cover image was designed and illustrated by Xiao-Meng Wu and Dong Tao.

Compact and highly-integrated wearable medical devices can improve patient comfort and device performance. Many barriers exist to achieving this, one of them being the current standard electronic manufacturing practices; this especially applies to circuit board technology. In this paper, we demonstrate a technique to integrate the circuit board within a 3D thermoplastic device shell, allowing the creation of light-weight ergonomic devices with improved functionality. At the same time the device is completely encapsulated; greatly enhancing user-safety and resistance to environmental factors. Possible applications range from wearable health monitoring systems, to improved medical imaging hardware (e.g. surface coils for magnetic resonance imaging), and intuitive user-interfaces.

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.

To realize optimal recording and stimulation of peripheral nerve cells, a CMOS chip is made with a multitude of electrodes which can be individually addressed in order to select after implantation the 16 best positioned electrodes. Since the Foreign Body Reaction should be minimal for optimum electrode-nerve contact, the CMOS chip is thinned down to 35um and fully packaged resulting in a 75um thin encapsulated chip. The chip is embedded in a biocompatible stack consisting of polymers and inorganic diffusion barriers deposited using atomic layer deposition (ALD). A biocompatible metallization is realized using gold and platinum sandwiched between polymers and ALD layers for flexible interconnects, and iridium oxide (IrOx) is selected as electrode material for optimal charge injection during stimulation. After this dedicated packaging based on the FITEP technology platform (Flexible Implantable Thin Electronic Package), the CMOS chip is still fully functional, which was tested dry (in air) as well as during submersion in saline. The form factor of the packaged chip is optimized for intra-fascicular implantation with minimum tissue damage. First acute in vivo stimulation tests proved that the stimulation capabilities of the IrOx electrodes are very good.

This contribution describes the technology used to produce thermoplastically deformable electronics, based on flexible circuit board technology, to achieve low-cost 2.5D free-form rigid smart objects. These one-time deformable circuits employ a modified version of the previously developed meander-based “polymer-last” technology for dynamically stretchable elastic circuits. This is readily achieved by substituting the dynamically stretchable elastomeric materials (e.g. silicone) with thermoplastic polymers (e.g. polycarbonate). Afterwards the circuit is given its final form using widely available thermoforming techniques, such as vacuum forming, where the material is heated above its glass transition temperature and drawn against a forming tool by a strong vacuum. After cooling down the thermoplastic retains its shape without inducing large internal stresses. The presented method allows for the production of these circuits on a flat substrate, using standard printed circuit board production equipment, with deformation only taking place afterwards; eliminating the need for large investments and reducing the cost of fabrication. Potential advantages over competitive methods are reductions in weight and material usage, decrease of mechanical complexity; lower tooling cost, increased resilience, and a higher degree of manufacturer independence due to adhering to standard industrial practices. This is realized by starting production from a flexible circuit board, manufactured by an industrial supplier using polyimide flexible copper clad laminate, which is attached to a temporary reusable carrier board through means of a silicone based high-temperature pressure sensitive adhesive. Through selective laser structuring the meander and island outlines of the flexible circuit are defined, without causing damage to the carrier board or pressure sensitive adhesive. After removing the residual material the circuit is assembled using high-temperature lead-free solder, made possible by the temporary carrier keeping the circuit in place at these elevated temperatures. The circuit is then transferred into a thermoplastic laminate, which is deformed into its final shape. After demonstrating the need for stretchable electronics for this application, this contribution describes the method used to design, fabricate, and test the first one-time deformable circuits manufactured using the presented technology. Using the initial set of observations a series of preliminary design rules is established, both for the circuit and choice of materials. The feasibility of this manufacturing method was then demonstrated through a small scale production run using lab scale equipment, where a large quantity of high power LEDs was integrated into a one-time deformable device made out of polystyrene and thermoplastic polyurethane. These devices were then tested by exposing them to real world conditions for several days.

A power amplifier (PA) with a saturated output power of 24.1 dBm at 32 GHz, fabricated in a 250 nm SiGe BiCMOS technology, is presented. This PA operates in Class AB and achieves a power-added efficiency (PAE) of 7.2% with a gain of approximately 25 dB and a die area of 1.70 mm(2). A differential cascode output stage with a self-shielded balun is used, allowing to maximize the output voltage swing. The driver stage consists of translinear loops to bias and linearize the output stage while a transformer-type power combiner is implemented to achieve broadband on-chip power combination. (C) 2015 Wiley Periodicals, Inc.

Cobalt exhibits good wetting by lead-free solders (Humpston, 2010) [1], generates Sn-rich intermetallic compounds (IMC's) and has lower dissolution in solders than Cu and Ni, thus potentially being a more effective solder diffusion barrier with improved electro- and thermo-migration resistance in interconnect applications (Ishida et al., 1991; Okamoto etal., 2006; Wang et al., 2013; Kanatzidis et al., 2005; Liu et al., 2004; Labie, 2007) [5-7]. In this work, we extend prior data (Vakanas et al., 2013; M.O. et al., 2012; Vakanas etal., 2014) on formation, processing, characterization and quantification of Co-Sn IMC phases generated upon deposition, reflow and aging of electroplated and solder paste screen printed samples. Cobalt oxides growth (vs. Cu) was characterized by X-ray Photoelectron Spectroscopy (XPS) as a function of multiple reflows. Cobalt oxides cleaning by microwave Ar/H-2 plasma was also demonstrated. Co-Sn IMC growth rate (vs. Cu-Sn and Ni-Sn) was quantified after one reflow cycle and aging in solid-state temperature range of 180-220 degrees C. Relevant kinetic parameters were calculated assuming a diffusion-driven, parabolic growth model. IMC phases were identified by Energy-Dispersive X-ray Spectroscopy (EDS) verifying Sn-rich Co IMC's. Young's modulus (E) and hardness (H) were measured by nanoindentation indicating that Co-Sn IMC's are more compliant and softer than Cu-Sn IMC's. Implications of the findings for material selection in 3D micro-bumping and stacking integration are discussed with a future outlook and recommendations to improve interconnect reliability. (C) 2015 Elsevier B.V. All rights reserved.

Sn whiskering remains a reliability concern in electronic applications. Despite extensive research on growth rates and mitigation strategies, no predictive theory is in place. Literature data are available for Cu/Sn-based films and coatings as well as for board-level and flip-chip solder bumps but data are scarce for scaled-down solder volumes and for higher intermetallic-to-solder ratios. The current work investigates whiskers in “isolated geometries” for 3D solder-capped Cu microbumps with >2 orders of magnitude smaller solder volumes compared to state-of-the-art. To the best of the authors’ knowledge, this is the first time Sn whisker growth is reported in isolated solder volumes (e.g. <8 μm-side cube). Whiskers propensity was evaluated using JEDEC industrial specifications. The tested structures were: 5/3.5 μm-thick Cu/Sn films and 15 μm-diameter electroplated solder capping (Sn, SnAg, SnCu) on Cu microbumps (as-plated vs. reflowed). Selected Sn whiskers and “whisker-like” features were analysed and identified experimentally with SEM, EDX and FIB. In the absence of a predictive model, first-order and “what if” calculations based on IMC molar volume and oxide cracking hypotheses were carried out. This approach quantifies “figures of merit” for Sn whisker propensity with (1) different bump-limiting metallization (BLM) cases e.g. Cu, Ni, Co and (2) further microbump scaling. Future research recommendations are outlined to mitigate manufacturing risks by controlling “sit time” between bumping and stacking.

This contribution describes considerations and very preliminary results in the technology development of thermoplastically deformable electronics and sensor circuits, with the intention to eventually achieve the low-cost fabrication of 2.5D free-form rigid smart objects. The technology is based on the one for elastic circuits, developed and characterized before, which is using soft elastic polymers as materials for the circuit carrier. For 1-time deformable circuits the elastic carrier needs to be substituted by a thermoplastic material. An additional step of thermoforming is necessary after the entire circuit is fabricated on a flat surface, which is the normal industrial practice for circuit fabrication and which thus is also pursued here. First tests have been executed and simple circuits fabricated, using meandered Cu tracks as 1-time stretchable interconnects, PET-G as the thermoplastic carrier and SMD LEDs and zero-ohm resistors as circuit components.

We developed a new type of conductive polymer (CP) actuator, specifically designed for miniaturized pumps and valves for lab-on-a-chip (LoC) applications. CP films soaked in an electrolyte solution reversibly change their thickness upon bias application. A large stroke actuator was fabricated by stacking several CP layers, bonded together by means of epoxy dots. The CP deposition process was optimized for obtaining the low surface roughness required for stacking. The maximum strain of stacked actuators and of individual layers was identical (13%), indicating that the dot gluing process eliminates strain losses previously observed in multi-layers actuators. Pumps and valves were fabricated and mounted on a microfluidic chip.