like poly (3,4-ethylenedioxythiophene):poly( styrene sulfonate) (PEDOT:PSS), stand out for this application due to their enhanced charge storage and coupled transport properties. [2][3][4] These functional materials are commonly used for recording physiological signals, assessing biochemical information, and electrical stimulation/ modulation. Ionic-electronic conductive hydrogels are another important family of soft conductors that have been broadly explored in healthcare technologies due to their similarities to biological tissues and tunability in terms of electronic, mechanical, and chemical properties. [5] In particular, natural biopolymers-based hydrogels are attractive platforms for wearable devices as they combine inherent renewable, non-toxic features, biocompatibility, and biodegradability. [6,7] Several examples of natural biopolymers have been reported as promising building blocks in stretchable devices, including cellulose, [8][9][10] chitosan, [11][12][13] alginate, [14][15][16] silk fibroin, [17,18] and gelatin. [19][20][21] Unfortunately, these conductive hydrogels fail in long-lasting signals recording due to the continuous water evaporation in open-air sensors and bioelectrodes. At this point, ionic liquid 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 reversible low-temperature gel transition for 3D printing manufacturing is reporting. The eutectogels consist of choline chloride/glycerol deep eutectic solvent, poly(3,4-ethylenedioxythiophene): lignin sulfonate, and gelatin as the biocompatible polymer matrix. These soft materials are flexible and stretchable, show high ionic and electronic conductivities of 7.3 and 8.7 mS cm −1 , respectively, and have high adhesion energy. Due to this unique combination of properties, they could be applied as strain sensors to precisely detect physical movements. Furthermore, these soft mixed ionic electronic conductors possess excellent capacity as conformal electrodes to record epidermal physiological signals, such as electrocardiograms and electromyograms, over a long time.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admt.202101680.

Conducting polymers (CPs) have been attracting great attention in the development of (bio)electronic devices. Most of the current devices are rigid two-dimensional systems and possess uncontrollable geometries and architectures that lead to poor mechanical properties presenting ion/electronic diffusion limitations. The goal of the article is to provide an overview about the additive manufacturing (AM) of conducting polymers, which is of paramount importance for the design of future wearable three-dimensional (3D) (bio)electronic devices. Among different 3D printing AM techniques, inkjet, extrusion, electrohydrodynamic, and light-based printing have been mainly used. This review article collects examples of 3D printing of conducting polymers such as poly(3,4-ethylene-dioxythiophene), polypyrrole, and polyaniline. It also shows examples of AM of these polymers combined with other polymers and/or conducting fillers such as carbon nanotubes, graphene, and silver nanowires. Afterward, the foremost applications of CPs processed by 3D printing techniques in the biomedical and energy fields, that is, wearable electronics, sensors, soft robotics for human motion, or health monitoring devices, among others, will be discussed.

Supramolecular hydrogels formed through non-covalent interactions of low molecular weight hydrogelators (LMWH) show great potential applications in different fields, such as delivery of therapeutics, injectable biomaterials, catalysis or materials chemistry. Generally, the self-assembly of LMWH is triggered by a sol-gel process through an external stimulus able to switch their solubility, such as temperature, pH or solvent change and chemical or enzymatic reactions. In this work, we introduced a new strategy to trigger and control the self-assembly of Fmoc-FFpY peptides: by direct electrostatic interactions with a polycation without dephosphorylation of the peptides. The resulting hydrogels show enhanced mechanical properties in comparison to gels of Fmoc-FFpY induced by enzymatic dephosphorylation. Peptide self-assembly yields -sheets, revealed by circular dichroism and infrared spectroscopy. Characteristic distances predicted by geometry optimization in the gas phase are in agreement with X-ray scattering data and TEM observations. It is proposed that core-shell cylinders are formed in which polycation chains decorate the micellar structures of Fmoc-FFpY peptides through electrostatic interactions between the charged amine groups of the polycations and the phosphate groups of the peptides. Since the gels form quickly and have superior mechanical properties, applications as injectable biomaterials are foreseen. This work opens a route towards a new class of self-assembled hydrogels, where Fmoc tripeptides can be self-assembled with specific polycations to obtain, for example, antimicrobial hydrogels.