Fully carbon-backbone polymers, including polyethylene, polypropylene, polystyrene, polyacrylate, etc. are the most widely used commodity plastics, accounting for over 70% of the global plastics market. Their simple chemical structure, C–C single bonds, provides exceptional resistance to chemical reactions and degradation. While this stability is advantageous for durability, it also contributes significantly to persistent plastic pollution. A promising strategy to introduce degradability into these polymers is incorporating labile groups into the backbone. However, this approach often compromises material properties and reduces the polymer's lifespan, as the labile groups may activate prematurely.
Here, we present a novel cyclobutene-based monomer that can be copolymerized with many conventional monomers to impart mechanically triggered, on-demand degradability to polymers. The cyclobutene residues in the polymer backbone act as mechanophores, undergoing mechanical ring-opening upon activation. This transformation induces a structural rearrangement rendering the polymer susceptible to degradation under mild conditions. The resulting copolymers retain thermal and mechanical properties comparable to their conventional homopolymers, while enabling high-molecular-weight materials to degrade into low-molecular-weight fragments on-demand. These fragments can then be repolymerized into new polymers, establishing a sustainable cycle of material use. This approach offers a scalable and practical pathway for addressing polymer persistence while maintaining its desirable material properties.

The bioelectronics of tomorrow envisions ambitious challenges, including tissue-integrated biohybrid implants, long-term stable brain-machine interfaces, skin-integrated electronics, and neuromorphic organic circuits designed for ultra-low power consumption. Currently, Poly 3,4-(ethylene dioxythiophene) (PEDOT) doped with polystyrene sulfonate (PSS) is considered the gold standard material in bioelectronics when interfacing with the tissue, mainly due to its mix in-electronic conduction, volumetric capacitance, 2D solution-processability and commercial availability. However, some fundamental properties remain, particularly with respect to material characteristics such as tridimensionality, bio-functionality, swelling control, charge transport, and long-term stability under electrochemical conditions.

The development of new materials to create the next generation of electroceuticals, implantable or wearable electronics requires the introduction of novel features and innovative processes, such as 3D printing, controlled biological properties (e.g., more biologically compatible dopants), and rationally designed materials with mixed conduction mechanisms.

This presentation outlines our strategy for developing bioelectronic devices, highlighting the transformative impact of material synthesis and design, manufacturing, and innovations in final integration to shape the future of bioelectronics.

References
[1] A. Dominguez-Alfaro, George G. Malliaras et al. Light-Based 3D Multi-Material Printing of Micro-Structured Bio-Shaped, Conducting and Dry Adhesive Electrodes for Bioelectronics. Adv. Sci. 2024, 11, 2306424.
[2] A. Dominguez-Alfaro, Aitziber L. Cortajarena et al., Engineering Proteins for PEDOT Dispersions: A New Horizon for Highly Mixed Ionic-Electronic Biocompatible Conducting Materials. Small 2024, 20, 2307536.
[3] A. Dominguez-Alfaro, David Mecerreyes et al. Direct ink writing of PEDOT eutectogels as substrate-free dry electrodes for electromyography. Mater. Horiz., 2023,10, 2516-2524

Reactive oxygen species (ROS) have emerged as biologically relevant oxidants for redox medicine. The controlled production of ROS through exogenous stimuli such as light is expected to provide lower invasiveness, relying on wireless stimulation, reversibility, and high spatial selectivity. Semiconducting polymers are attracting increasing attention as phototriggers of ROS due to their biocompatibility, intrinsic conductivity and optical properties.
Here, poly(3-hexylthiophene) semiconducting polymer nanoparticles (P3HT SPNs) are used with a dual role to fabricate light-responsive hydrogels. First, P3HT SPNs act as visible-light photoinitiators to induce the photopolymerization of acrylic polymers such as poly(ethylene glycol) diacrylate (PEGDA) leading to the formation of hydrogels loaded with P3HT SPNs. Furthermore, P3HT SPNs are also successfully used as photoinitiators for digital light processing (DLP) 3D printing of shape-defined intelligent hydrogels. Interestingly, P3HT SPNs retain their photoelectrochemical properties when embedded within the polymer hydrogels, showing tunable photocurrent densities (0.2 - 1.1 µA/cm²) depending on the intensity of the visible light-lamp (λ = 467 nm). Second, they are used as photosensitizers (PS) to generate reactive oxygen species (ROS), 12 – 15 µM H₂O₂, on demand. The hydrogels do not exhibit cytotoxic effects under normal physiological conditions in the darkness against mouse glioma 261 (GL261) cells and S. aureus bacteria. However, they induce a ~ 50% reduction GL261 cancer cell viability and a ~ 99% S. aureus cell death in contact with them upon illumination (λ = 467 nm) due to the localized overproduction of ROS, which makes them attractive candidates for photodynamic therapies (PDT).

Plastics play an important role in our daily lives, sustaining current living standards and making a significant contribution to the Sustainable Development Goals. Nonetheless, there is still an urgent need to develop plastics that better align with the circular economy to avoid waste accumulation and negative environmental impacts. Sustainable end-of-life could consist of chemical and mechanical recyclability under mild conditions with retained properties to keep the materials in the cycle.1,2 Here we present, the synthesis and characterisation of circular biobased polyimine-amide networks. These materials were obtained from lignin-derivable monomers and different diamines and triamines to yield corresponding linear and cross-linked polyimine-amide networks. All the monomers and polymers were in detail characterized for their chemical structure and thermal properties. In addition, stress-relaxation, shape memory, self-healing, mechanical reprocessability and chemical recyclability of the polyamide-imines was demonstrated revealing a fascinating set of properties. Finally, the adhesive properties of the polyimine-amide networks were tested.3