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A) FTIR spectra of gelatin, ChCl/Gly DES, and eGel‐0 eutectogel. B) Degradation profile of the as‐prepared eutectogels. C) Images of the tensile test of eGel‐0 (i) and eGel‐90 (ii). D) Stress versus strain curves for the electroactive materials.
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Eutectogels are a new class of soft ion conductive materials that are attracting attention as an alternative to conventional hydrogels and costly ionic liquid gels to build wearable sensors and bioelectrodes. Herein, the first example of mixed ionic and electronic conductive eutectogels showing high adhesion, flexibility, nonvolatility, and reversi...
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Mobile sensing—that is, the ability to unobtrusively collect sensor data from built-in phone and attached wearable sensors—have proven to be a powerful approach to understanding the behavior, well-being, and health of people in their everyday life. Different platforms for mobile sensing have been presented and significant knowledge on how to facili...
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... This potential technology can create geometrically complex pieces quickly compared to traditional production techniques [1]. Due to its ease of use, rapid manufacturing capabilities, and accurate and controlled deposition of multifunctional elements into bespoke 3D printed structures, and fabrics, it is now extensively used for wearable sensors [2], smart bandages [3], and textiles [4]. On the other hand, sensor mechanisms have undergone a profound metamorphosis through the assimilation of state-ofthe-art technologies such as the Internet of Things (IoT), Machine Learning (ML), and biochips [5][6][7]. ...
Technology is constantly evolving, and chronic health issues are on the rise. It is essential to have affordable and easy access to remote biomedical measurements. This makes flexible sensors a more attractive choice owing to their high sensitivity and flexibility along with low cost and ease of use. As an additional advantage, 3D printing has become increasingly popular in areas such as biomedicine, environment, and industry. This study demonstrates 3D-printed flexible sensors for tactile sensing. A biocompatible silicone elastomer such as polydimethylsiloxane (PDMS) with low elastic modulus and high stretchability makes an excellent wearable sensor material. Incorporating CNTs at varying concentrations (0.5, 1, 2) wt.% enhances the sensor’s mechanical strength, conductivity, and responsiveness to mechanical strain. In addition to enhancing the thermal stability of the composite by 44%, multi-walled carbon nanotubes (MWCNTs) also enhanced the breaking strength by 57% with a 2 wt.% CNT loading. Moreover, the contact angle values improved by 15%, making it a biomedical-grade hydrophobic surface. The electrical characteristics of these sensors reveal excellent strain sensitivity, making them perfect for monitoring finger movements and biomedical measurements. Overall, 2 wt.% CNT-PDMS sensors exhibit optimal performance, paving the way for advanced tactile sensing in biomedical and industrial settings.
... ICPs also have other properties. For example, PEDOT and its derivatives, which have high transparency in the visible range, also expand potential applications of flexible transparent electrodes in wearable devices [62][63][64]. ...
In recent years, the proliferation of wearable healthcare devices has marked a revolutionary shift in the personal health monitoring and management paradigm. These devices, ranging from fitness trackers to advanced biosensors, have not only made healthcare more accessible, but have also transformed the way individuals engage with their health data. By continuously monitoring health signs, from physical-based to biochemical-based such as heart rate and blood glucose levels, wearable technology offers insights into human health, enabling a proactive rather than a reactive approach to healthcare. This shift towards personalized health monitoring empowers individuals with the knowledge and tools to make informed decisions about their lifestyle and medical care, potentially leading to the earlier detection of health issues and more tailored treatment plans. This review presents the fabrication methods of flexible wearable healthcare devices and their applications in medical care. The potential challenges and future prospectives are also discussed.
... 3D-printed PEDOT-based eutectogels, known for their flexibility, stretchability, strong adhesion, and excellent capacity as conformal electrodes, can continuously record epidermal physiological signals such as electrocardiograms and electromyograms over extended periods. 122 However, when prepared as concentric ring electrodes, silver electrodes provide a more stable response (fewer saturations and alterations) to intentionally induced subject movement, as compared with PEDOT:PSS concentric rings. 123 When PEDOT conductive polymer inks are added to thermoplastic styrene-ethylene-butylenestyrene elastomers for micro-extrusion 3D printing, the resulting PEDOT composites demonstrate conductivity and stretchability lower than those of silver micro-flakes and carbon black nanoparticles. ...
The integration of conductive hydrogels and advanced three-dimensional (3D) printing is a trigger of the development of biomedical sensors for healthcare diagnostics and personalized treatment. Poly(3,4-ethylenedioxythiophene):poly(styr ene sulfonate) (PEDOT:PSS) is a versatile conductive hydrogel materials renowned for its exceptional conductivity and hydrophilicity, and 3D printing technology allows for precise and customized fabrication of electronic components and devices. In this review, we aim to explore the potential of 3D-printed PEDOT/PSS conductive hydrogel in the fabrication of biomedical sensors, with a focus on their distinct characteristics, application potential, and systematic classification. We also discuss the methods for fabricating PEDOT:PSS hydrogel electronic devices by employing 3D printing techniques, including extrusion-based 3D printing technology (fused deposition modeling, direct ink writing, and inkjet printing), powder-based 3D printing technology (selective laser sintering and selective laser melting), and photopolymerization-based 3D printing technology (stereolithography and digital light processing). The applications of 2D/3D-printed PEDOT:PSS hydrogels in biomedical sensors, such as strain sensors, pressure sensors, stretchable sensors, electrochemical sensors, temperature sensors, humidity sensors, and electrocardiogram sensor, are also summarized in this review. Finally, we provide insights into the development of 3D-printed PEDOT:PSS-based biomedical sensors and the innovative techniques for biomedical sensor integration.
... This glove could record the pressure existed in different parts of the hand, when holding or touching an object. Picchio et al. [127] investigated a composite material named Eutectogels with which flexible sensors could be made to monitor a person's health. This composite material consisted of choline chloride/glycerol eutectic solvent, lignin sulfonate and gelatin. ...
In recent years, the rapid advancement of technology has caused an increase in the development of wearable products. These are portable devices that can be worn by people. The main goal of these products is to improve the quality of life as they focus on the safety, assistance and entertainment of their users. The introduction of many new technologies has allowed these products to evolve into many different fields with multiple uses. The way in which the design of wearable products/devices is approached requires the study and recording of multiple factors so that the final device is functional and efficient for its user. The current research presents an in-depth overview of research studies dealing with the development, design and manufacturing of wearable products/devices and applications/systems in general. More specifically, in this review, a comprehensive classification of wearable products/devices in various sectors and applications was carried out, resulting in the creation of eight different categories. A total of 161 studies from the last 13 years were analyzed and commented on. The findings of this review show that the use of new technologies such as 3D scanning and 3D printing are essential tools for the development of wearable products. In addition, many studies observed the use of various sensors through which multiple signals and data could be recorded. Finally, through the eight categories that the research studies were divided into, two main conclusions emerged. The first conclusion is that 3D printing is a method that was used the most in research. The second conclusion is that most research directions concern the safety of users by using sensors and recording anthropometric dimensions.
... A supramolecular-polymer doublenetwork (DN) eutectogel was developed by the self-assembly of a DES and gelators, which integrated various properties, such as good stretchability, temperature tolerance, and self-healing ability [80][81][82]. Lignin-derived DN eutectogels with good adhesion and mechanical properties were synthesized by heating or cooling processing ( Figure 5A) [24,78,83]. A DES/lignin mixture after pretreatment was directly utilized to fabricate a lignin-based DN eutectogel by in situ polymerization ( Figure 5B) [23]. ...
... Ionic gel with the characteristics of high ionic conductivity, electrochemistry stability, exibility and mechanical toughness has been widely applied to fabricate the wearable sensor [6][7][8]. Importantly, the ionic gel could avoid the risk of sudden failure of the sensing functionality caused by the water evaporation or freezing that often occurs in the hydrogel-based wearable sensors, which allowed the ionic gel to long-time stable work in dry/cold environments [9,10]. ...
Ionic gel-based wearable electronic devices with robust sensing performance have gained extensive attention. However, the development of mechanical robust, multifunctional, and water resistance ionic gel-based wearable sensors still is a challenge because of their intrinsic structure weakness such as swelling-induced function degradation in a water environment. Herein, we first report the preparation of 3D printed cellulose derived ionic conductive elastomers (ICEs) with high mechanical toughness, multifunctional, and water/organic solvent resistance through one-step photo-polymerization of polymerizable deep eutectic solvents. The well-defined structural design combining multiple hydrogen bonds with strong coordination bonds allows the ICE to be stabilized in aquatic environments. The introduction of polyaniline modified carboxylate cellulose nanocrystals (C-CNC@PANI) not only yields a high conductivity (58.7 mS/m) but also contributes to constructing dense networks to achieve extremely high mechanical strength (4.4 MPa), toughness (13.33 MJ*m ⁻³ ), elasticity and improved anti-swelling performance. Given these features, the ICE-based multifunctional sensor is used for real-time detecting human motions, respiration, and body temperature. More importantly, the ICE-based sensor shows reliable underwater mechanosensing applications for accurately monitoring human movements in aqueous environments. This work provides a promising strategy for designing the new generation of strong, tough, multifunctional, and water-resistant wearable electronic devices that required multi-scene applications.
... As shown in Figure S21, the tensile properties, self-healing properties, and highest GF of this eutectogel are superior to those of the reported studies. 27,28,32,33,41,43,54 Meanwhile, many properties of the obtained zwitterionic eutectogel and the published zwitterionic hydrogels are compared in Table S7. The zwitterionic eutectogel is superior to those of the reported zwitterionic hydrogels. ...
Ionic conductive eutectogels have great application prospects in wearable strain sensors owing to their temperature tolerance, simplicity, and low cost. Eutectogels prepared by cross-linking polymers have good tensile properties, strong self-healing capacities, and excellent surface-adaptive adhesion. Herein, we emphasize for the first time the potential of zwitterionic deep eutectic solvents (DESs), in which betaine is a hydrogen bond acceptor. Polymeric zwitterionic eutectogels were prepared by directly polymerizing acrylamide in zwitterionic DESs. The obtained eutectogels owned excellent ionic conductivity (0.23 mS cm-1), superior stretchability (approximately 1400% elongation), self-healing (82.01%), self-adhesion, and wide temperature tolerance. Accordingly, the zwitterionic eutectogel was successfully applied in wearable self-adhesive strain sensors, which can adhere to skins and monitor body motions with high sensitivity and excellent cyclic stability over a wide temperature range (-80 to 80 °C). Moreover, this strain sensor owned an appealing sensing function on bidirectional monitoring. The findings in this work can pave the way for the design of soft materials with versatility and environmental adaptation.
... Alternatively, natural polymers with intrinsic biocompatibility and biodegradability are more appealing for constructing functional eutectogels in applications requiring skin con-tact 17,18 and degradable electronic devices. 19,20 Unluckily, biopolymer eutectogels commonly suffer from poor mechanical properties that have hampered the growth of the biodegradable electronics realm, finding only a few examples of these materials in the literature. ...
... The immobilization of these intriguing mixtures in polymer matrixes offers new opportunities for generating functional gel materials with promising applications in healthcare [3,4]. Due to the unique ionic conductivity of the DES component, recent studies have mainly focused on exploring eutectogels as wearable sensors or bioelectrodes, aiming to replace expensive and non-biocompatible ionic liquid gels [5][6][7]. However, eutectogels also benefit from several features that can be exploited in controlled drug delivery systems, such as good biocompatibility, adhesiveness, stiffness matching biological tissues, and non-volatile nature [8]. ...
... Thus, we selected the eutectic mixture glycerine, ChCl: Gly (1:3), to drive the protein gelation. Gelatin and Gly have shown excellent compatibility, mainly promoted by polar interactions between -NH 2 and -COOH groups from the protein and -OH groups from the polyol [5]. Indeed, FTIR analysis of Fig. 2A revealed a significant blue shift in the C--O stretching (from 1631 to 1650 cm À1 ) and N-H bending from 1525 to 1550 cm À1 ) bands of gelatin after eutectogel formation. ...
... Crucially, the thickness of both materials allowed the addition of a second layer on top of a first printed layer, highlighting the potential for constructing three-dimensional objects based on eutectogels. This result agrees with a recent report, where a semiconducting eutectogel was 3D printed as a wearable sensor [5]. ...
Eutectogels (Egels) are an emerging class of soft ionic materials outperforming traditional temperature-intolerant hydrogels and costly ionogels. Due to their excellent elasticity, non-volatile nature, and adhesion properties, Egels are attracting a great deal of interest in the biomedical space. Herein, we report the first example of adhesive Egels loading drug nanocrystals (Egel-NCs) for controlled delivery to mucosal tissues. These soft materials were prepared using gelatin, glycerine, a deep eutectic solvent (DES) based on choline hydrochloride and glycerol, and nanocrystallised curcumin, a model drug with potent antimicrobial and anti-inflammatory activities. We first explored the impact of the biopolymer concentration on the viscoelastic and mechanical properties of the networks. Thanks to the dynamic interactions between gelatin and the DES, the Egel showed excellent stretchability and elasticity (up to ≈160%), reversible gel-sol phase transition at mild temperature (≈50 °C), 3D-printing ability, and good adhesion to mucin protein (stickiness ≈40 kPa). In vitro release profiles demonstrated the ability of the NCs-based Egel to deliver curcumin for up to four weeks and deposit significantly higher drug amounts in excised porcine mucosa compared to the control cohort. All in all, this study opens new prospects in designing soft adhesive materials for long-acting drug delivery and paves the way to explore novel eutectic systems with multiple therapeutic applications.
