The sustainable integration of human activities into the global ecosystem is discussed, pointing out fatal anthropogenic heat as a major ecological problem and proposing global technical and economical solutions.

For human sake, we must get out of the “thermal age” and implement the “electroprotonic era” as soon as possible. Contrary to thermal power, electroprotonic is sustainable and can be produced by photoenzymatic systems, a cheap way to produce hydrogen (H2) or ammonia (NH3). We can accelerate the advent of this new era if we re-integrate external costs generated by thermal energies into their final prices. The author is leading the H2GREEN project in Belgium as an entrepreneur for more than a decade, which develops the photoenzymatic production of dihydrogen from water. The aim of the H2GREEN project is to contribute to the launch of a low-cost, renewable Hydrogen-based local economy as an energy carrier. Among the difficulties of this launch, the most important is certainly the lack of competitiveness due to the unfair competition of carbon products that externalizes their costs (CO2, oil spills, lethal pollution, armed conflicts, political oppression, foreign dependence, etc.).

Biological entities are capable of amazing material feats, such as self-organization, self-repair, self-replication, and self-immolation. Indeed, the most intriguing feature of living biomaterials, whether they are tissues, cells, or intracellular structures, is their ability to autonomously sense, decide, and perform work without the need of a project manager. The effect is multiscale—from enzymes to full organisms, each level is capable of such autonomous activities. Further, each scale has similar energy-using units that work together to compose the larger-scale material. For instance, autonomous cells work together to create tissues. In this article, we will discuss some of the outstanding and desirable properties of active biological materials that we might consider mimicking in future materials. We will discuss how such active materials are powered and explore some fundamental lessons we can learn to direct future fundamental scientific inquiries to begin to understand and use these properties to make synthetic, autonomous materials of the future.

Defined chemical reactions in a physiological environment are a prerequisite for the in situ synthesis of implant materials potentially serving as matrix for drug delivery systems, tissue fillers or surgical glues. ‘Click’ reactions like thiol Michael-type reactions have been successfully employed as bioorthogonal reaction. However, due to the individual stereo-electronic and physical properties of specific substrates, an exact understanding their chemical reactivity is required if they are to be used for in-situ biomaterial synthesis. The chiral (S)-2-mercapto-carboxylic acid analogues of L-phenylalanine (SH-Phe) and L-leucine (SH-Leu) which are subunits of certain collagenase sensitive synthetic peptides, were explored for their potential for in-situ biomaterial formation via the thiol Michael-type reaction.

In model reactions were investigated the kinetics, the specificity and influence of stereochemistry of this reaction. We could show that only reactions involving SH-Leu yielded the expected thiol-Michael product. The inability of SH-Phe to react was attributed to the steric hindrance of the bulky phenyl group. In aqueous media, successful reaction using SH-Leu is thought to proceed via the sodium salt formed in-situ by the addition of NaOH solution, which was intented to aid the solubility of the mercapto-acid in water. Fast reaction rates and complete acrylate/maleimide conversion were only realized at pH 7.2 or higher suggesting the possible use of SH-Leu under physiological conditions for thiol Michael-type reactions. This method of in-situ formed alkali salts could be used as a fast approach to screen mercapto-acids for thio Michael-type reactions without the synthesis of their corresponding esters.

We have developed high affinity Molecularly Imprinted Polymers (MIPs) for neurotransmitters such as dopamine, noradrenaline and caffeine. These polymer particles are mixed within the bulk of screen-printed ink allowing masss-producible bulk modified MIP Screen-Printed Electrodes (MIP-SPEs) to be realised. We have explored different SPE supporting surfaces, such as polyester, tracing paper and household-printing paper. The performance of those MIP-SPEs is studied using the Heat-Transfer Method (HTM), a patented thermal method. With the combination of screen-printing techniques and thermal detection, it is possible to develop a portable sensor platform that is capable of low-cost and straightforward detection of biomolecules on-site. In the future, this unique sensor architecture holds great promise for the use in biomedical devices.

Biomimetic Method has been widely used to prepare calcium phosphate coatings on Ti and its alloys. This modification is based on a Synthetic/simulated Body Fluid (BSF) which facilitates the mimicking of the biological process in order to provide hard tissue repairs. The formation of HA and other calcium phosphates under biological medium and SBF occurs in the presence of Ca2+ and PO43- ions, as well as essential ions such as: Mg2+, HCO3-, K+ and Na+. Ti-15Mo alloy samples were irradiated by pulsed Yb: YAG pulsed laser beam under air and atmospheric pressure. Sequentially, calcium phosphate coatings were deposited on the irradiated surfaces by the biomimetic method. The biomimetic calcium phosphates-based surfaces were submitted to heat treatment conditions at 350°C and 600°C. The present study correlates two conditions of fluency (1,91 and 5,54 J.cm-2) as established have a sufficient energy to promote ablation on the laser beam irradiated surfaces. Likewise, it has been demonstrated the processes of fusion and fast solidification from the laser beam irradiation, under ambient atmosphere, inducing the formation of stoichiometric TiO2 and non-stoichiometric titanium oxides, including Ti3O5, TiO, Ti3O and Ti6O with different oxide percentages depending on the fluency applied. Besides that, laser modification has allowed a clean and reproducible process, providing no traces of contamination, an important feature for clinical applications. The physico-chemical and morphological analysis indicated the formation of a multiphase coatings depending on the heat treatment temperature performed to 350 °C (ACP1 and 2, HAD, HA phases) and 600 °C (HAD, HA and β-TCP phases). It is worth noting that multiphasic bioceramic systems has been gaining attention for biomedical applications. Thus, the laser beam irradiation associated to bioactive coatings of calcium phosphates of biological interest have shown to be promising and economically feasible for use in dental and orthopedic implants.

The use of natural materials in paper and textiles, and in support of tunable and mechanically robust systems for sensing toxic gases, removing pollutants from water, and constructing functional biodegradable scaffolds, is a topic of great scientific and practical importance. The social, environmental, and economic impact of using natural materials to functionalize integrated systems for new designs is imperative, as the need to reuse and recycle natural resources has increased in current manufacturing. The inclusion of sustainability in the design of new materials and processes is almost a common practice; concurrently, the usage of “being more sustainable” is becoming a more conjointly used term in urban conversations. That said, systems integration and natural materials are intrinsically related to produce novel materials that can function as sensors, switches, platforms, and building blocks in a sustainable fashion. The contributions in this issue of MRS Bulletin highlight the importance and benefits to society that systems integration of functional materials can provide.

Future electronics will be conformal, bendable, and wearable. Taking inspiration from the characteristics of human skin, we are developing a new generation of electronic materials to enable devices that are flexible, stretchable, biodegradable, and self-healable. We have developed various sensors and circuits, all of which are based on organic materials, polymers, and carbon nanomaterials. These materials will provide us with a long-term path toward adding various skin-inspired functions.

We have recently reported the repair of carious enamel using a full-length amelogenin–chitosan hydrogel through guided stabilization and growth of mineral clusters. The objective of this study was to further evaluate the enamel repair potential of smaller amelogenin peptides like LRAP (leucine-rich amelogenin peptide) and compare their efficiency with their full-length counterpart. The demineralized tooth slices treated with a single application of LRAP–chitosan hydrogel for 3 days showed a dense mineralized layer consisting of highly organized enamel-like apatite crystals. Focus-ion beam technique showed a seamless growth at the interface between the repaired layer and native enamel. There was a marked improvement in the surface hardness after treatment of the demineralized sample with almost 87% recovery of the hardness value to that of sound enamel sections. This current approach can inspire the design of smaller peptide analogues based on naturally occurring amelogenin as a competent, low-cost, and safe strategy for enamel biomimetics to curb the high prevalence of incipient dental caries.

Nacre (mother of pearl) is an attractive model for the development of newmaterials. Its sheet structure of alternating layers of calcium carbonate and anorganic matrix confers it highly desirable properties such as high toughness andstrength. In this study, we produce a nacre-inspired composite material usingonly bacterially-produced components. Calcium carbonate is crystallized via theaction of ureolytic bacteria. After each crystallization event, we applybacterially produced γ-polyglutamate (PGA) to the sample, whichpromotes layering compared to the PGA-free control. We show that the combinationof these two compounds yields a layered material reminiscent of nacre, showing away towards the biotechnological production of new, nacre-inspiredmaterials.

In Japan, scallop shells are considered to be industrial waste. Thus far, attempts for reusing these shells have been mainly limited to the commercial production of CaCO3. Nevertheless, there are no clear economic benefits associated with the use of scallop shells as a source of CaCO3. Hence, we are attempting to investigate a new value-added use for scallop shells as an advanced functional material. In this regard, we focused our attention on nuclear wastewater, which contains radioactive Sr and Cs. Sr, which tends to accumulate in bones, is believed to cause bone cancer. Hence, it is highly desirable to develop a method for removing Sr from contaminated water. In this study, we investigate whether scallop shells demonstrate the ability to remove Sr from a solution. From the results obtained, scallop shells can remove Sr solutes from a solution; furthermore, as compared to CaCO3, they demonstrate superior ability for removing Sr.

The photosynthetic reaction center (RC) from the purple Rhodobacter (R.)sphaeroides bacterium is a protein with unique photoconversioncapability that can be exploited in hybrid systems for energy conversion. Wehave developed a tailored aryleneethynylene organic fluorophore (AE750) actingas efficient light harvesting antenna and successfully bioconjugated it to thephotosynthetic RC. We have also demonstrated that, under suitable conditions,the biohybrid AE750-RC system can outperform the energy photoconversion abilityof the native protein.

Covalent functionalisation of collagen has been shown to be a promising strategyto adjust the mechanical properties of highly swollen collagen hydrogels. At thesame time, secondary interactions between for example, amino acidic terminationsor introduced functional groups also play an important role and are oftenchallenging to predict and control. To explore this challenge, 4-vinylbenzylchloride (4VBC) and methacrylic anhydride (MA) were reacted with type Icollagen, and the swelling and rheological properties of resultingphoto-activated hydrogel systems investigated. 4VBC-based hydrogels showedsignificantly increased swelling ratio, in light of the lower degree of collagenfunctionalisation, with respect to methacrylated collagen networks, whilstrheological storage moduli were found to be comparable between the two systems.To explore the role of benzyl groups in the mechanical properties of the4VBC-based collagen system, model chemical force microscopy (CFM) was carriedout in aqueous environment with an aromatised probe against an aromatisedgold-coated glass slide. A marked increase in adhesion force(F: 0.11±0.01 nN) was measured between aromatisedsamples, compared to the adhesion force observed between the non-modified probeand a glass substrate (F: 2.64±1.82 nN). These resultssuggest the formation of additional and reversible π-πstacking interactions in aromatic 4VBC-based networks and explain the remarkablerheological properties of this system in comparison to MA-based hydrogels.

Modern materials design is largely based on composite structures aimed at a synergistic integration of multiple components with a diverse range of properties. Biologically grown minerals provide an intriguing example of sophisticated organic–inorganic nanocomposite structures resulting in excellent mechanical characteristics. Among the mineral phases utilized by living organisms to generate hard tissues, calcium carbonate—especially the calcite polymorph—is ubiquitous and has been studied intensively. Biogenic calcite crystals often show hierarchical organization spanning multiple length scales, and the occluded organic phases are now known to be intimately associated with the mineral host. Here, we discuss the internal micro- and nanostructure of two selected types of calcite biominerals—the sea urchin spine and prismatic single crystals extracted from mollusk shells. This article highlights recent advances in translating the key principles of biological mineralization into design strategies for synthetic materials and presents analogies between biogenic and synthetic calcite single crystals.

Designers and engineers have been dreaming for decades with motors sensing, by themselves, working and surrounding conditions, as biological muscles do originating proprioception. The evolution of the working potential, or that of the consumed electrical energy, of electrochemical artificial muscles based on electroactive materials (intrinsically conducting polymers, redox polymers, carbon nanotubes, fullerene derivatives, grapheme derivatives, porphyrines, phtalocyanines, among others) and driven by constant currents senses, while working, any variation of the mechanical (trailed mass, obstacles, pressure, strain or stress) thermal or chemical conditions. They are linear faradaic polymeric motors: applied currents control movement rates and applied charges control displacements. One physically uniform artificial muscle includes one motor and several sensors working simultaneously under the same driving chemical reaction. Actuating (current and charge) and sensing (potential and energy) magnitudes are present, simultaneously, in the only two connecting wires and can be read by the computer at any time. From basic polymeric, mechanical and electrochemical principles a basic equation is attained for the muscle working potential evolution. It includes and describes, simultaneously, the polymeric motor characteristics (rate of the muscle movement and muscle position) and the working variables (temperature, electrolyte concentration and mechanical conditions). By changing working conditions experimental results overlap theoretical predictions. The ensemble computer-generator-muscle-theoretical equation constitutes and describes artificial mechanical, thermal and chemical proprioception of the system. Proprioceptive tools, zoomorphic or anthropomorphic soft robots can be envisaged.

So far we ignore how brain stores memory. Neurons communicate by pulses where the charges are carried between them by ions flowing through channels. Those pulses present a characteristic maximum related to the conformational movements of the channel protein opening and closing. Electrochemical responses from dense gel electrodes of conducting polymers mimic those pulses. Here we proved that the biomimetic pulse includes simultaneously electrical, chemical and conformational information related to the energy stored by the initial conformational packed state of the polymer. This energetic memory increases linearly with the potential used to reduce and pack (write) the initial state: hundreds of different values can be written (stored) in a full reproducible way (multivalent memory). Every state constitutes a chemo-ionic-conformational (CHEMICONF) memory. Each multivalent memory is read and erased by the reverse electrochemical reaction. Crosslinking states produce permanent memories not erased while reading. Developing CHEMICONF memories can provide new hypothesis to reveal brain memory mechanisms.

Photo-actuating structures inspired by the chemical sensing and signal transmission observed in sun-tracking leaves have recently been proposed by Dicker et al. The proposed light tracking structures are complex, multicomponent material systems, principally composed of a reversible photoacid or base, combined with a pH responsive hydrogel actuator. New modelling and characterization approaches for pH responsive hydrogels are presented in order to facilitate the development of the proposed structures. The model employs Donnan equilibrium for the prediction of hydrogel swelling in systems where the pH change is a variable resulting from the equilibrium interaction of all free and fixed (hydrogel) species. The model allows for the fast analysis of a variety of combinations of material parameters, allowing for the design space for the proposed photo-actuating structures to be quickly established. In addition, experimental examination of the swelling of a polyether-based polyurethane and poly(acrylic acid) interpenetrating network hydrogel is presented. The experiment involves simultaneously performing a titration of the hydrogel, and undertaking digital image correlation (DIC) to determine the hydrogel’s state of swelling. DIC allows for the recording of the hydrogel’s state of swelling with previously unattained levels of resolution. Experimental results provide both model material properties, and a means for model validation.

Advanced biomaterials that mimic the structure and function of native tissues and permit stem cells to adhere and differentiate is of paramount importance in the development of stem cell therapies for bone defects. Successful bone repair approaches may include an osteoconductive scaffold that permits excellent cell adhesion and proliferation, and cells with an osteogenic potential. The objective of this study was to evaluate the cell proliferation, viability and osteocyte differentiation of equine-derived bone marrow mesenchymal stem cells (EqMSCs) when seeded onto biocompatible and biodegradable calcium-deficient hydroxyapatite (CdHA) tubular-shaped bacterial cellulose scaffolds (BC-TS) of various sizes. The biocompatible gel-like BC-TS was synthesized using the bacterium Gluconacetobacter sucrofermentans under static culture in oxygen-permeable silicone tubes. The BC-TS scaffolds were modified using a periodate oxidation to yield biodegradable scaffolds. Additionally, CdHA was deposited in the scaffolds to mimic native bone tissues. The morphological properties of the resulting BC-TS and its composites were characterized using scanning electron microscopy. The ability of the BC-TS and its composites to support and maintain EqMSCs growth, proliferation and osteogenic differentiation in vitro was also assessed. BC-TS and its composites exhibited aligned nanofibril structures. MTS assay demonstrated increasing proliferation and viability with time (days 1, 2 and 3). Cell-scaffold constructs were cultured for 8 days under osteogenic conditions and the resulting osteocytes were positive for alizarin red. In summary, biocompatible and biodegradable CdHA BC-TS composites support the proliferation, viability and osteogenic differentiation of EqMSCs cultured onto its surface in vitro, allowing for future potential use for tissue engineering therapies.

Hydrogel actuators were prepared by combining ionoprinting technique with reversible metal ion coordination chemistry found in mussel adhesive proteins. Hydrogels were formulated with biomimetic dopamine moiety, which contains a catechol side chain that is capable of forming mono-, bis-, and tris-complexes with ferric (Fe3+) ions with increasing pH. Catechol-Fe3+ complexation increased local crosslinking density, which induced hydrogel bending at the site of Fe3+ ionoprinting. The effect of pH on the dynamic response of hydrogel actuation was tracked by following the radius of curvature at the ionoprinting site. Both the rate of change and the maximum radius of curvature increased when the pH with increasing pH (2.5-9.5), indicating that pH can be used to modulate hydrogel actuation. Additionally, hydrogels containing Fe3+ demonstrated higher extent of deswelling when equilibrated at a basic pH. Similarly, dynamic mechanical analysis in the compression mode revealed that both the storage and loss modulus values for Fe3+-containing hydrogels increased with increasing pH. These results indicated that bis- and tris-complexes formed at an elevated pH level contributed to a faster rate of actuation and a more condensed network architecture. Hydrogel actuation and deswelling were also observed at pH of 3.5 although to a lesser degree, potentially due to a stronger affinity between network-bound catechol and Fe3+ ions as compared to complexes formed in a dilute solution.

Neuromodulation devices such as deep brain stimulators (DBS), spinal cord stimulators (SCS) and cochlear implants (CIs) use electrodes in contact with tissue to deliver electrical pulses to targeted cells. In general, the neuromodulation industry has been evolving towards smaller, less invasive devices. Improving power efficiency of these devices can reduce battery storage requirements. Neuromodulation devices can realize significant power savings if the impedance to charge transfer at the electrode-tissue interface can be reduced. High electrochemical impedance at the surface of stimulation microelectrodes results in larger polarization voltages. Decreasing this polarization voltage response can reduce power required to deliver the current pulse. One approach to doing this is to reduce the electrochemical impedance at the electrode surface. Previously we have reported on a novel electrochemically deposited 60:40% platinum-iridium (Pt-Ir) electrode material that lowered the electrode impedance by two orders of magnitude or more.

This study compares power consumption of an electrochemically deposited Pt-Ir stimulating microelectrode to that of standard Pt-Ir probe microelectrode produced using conventional techniques. Both electrodes were tested using in-vitro in phosphate buffered saline (PBS) solution and in-vivo (live rat) models.

Watson and Crick’s discovery of the structure of DNA in 1953 and the near-simultaneous advent of the first silicon transistor in 1954 spurred parallel historic advances over the following decades in molecular biology and materials technology. As these two expansive fields of research have progressed, important areas of overlap have included the extensive use of materials innovations in biological research, such as in microscopy and measurement systems, while materials research has benefited from efforts to mimic design principles utilized in nature. Until relatively recently, however, the molecular mechanisms that underpin nature’s biological orchestra have remained largely outside the purview of materials research. Now, with new abilities to harness and modify biomolecular and cellular systems, evidence is mounting that biology can be fruitfully utilized to directly engineer technological materials. This article aims to highlight the importance of DNA-driven routes to new materials while providing a brief overview of the genetic engineering platforms that make these routes possible. Emphasis is placed on the fact that it is now possible to genetically evolve materials technologies in a manner that mimics the genetic evolution of biominerals in nature.