Magnetically responsive soft materials are soft composites where magnetic fillers are embedded into soft polymeric matrices. These active materials have attracted extensive research and industrial interest due to their ability to realize fast and programmable shape changes through remote and untethered control under the application of magnetic fields. They would have many high-impact potential applications in soft robotics/devices, metamaterials, and biomedical devices. With a broad range of functional magnetic fillers, polymeric matrices, and advanced fabrication techniques, the material properties can be programmed for integrated functions, including programmable shape morphing, dynamic shape deformation-based locomotion, object manipulation and assembly, remote heat generation, as well as reconfigurable electronics. In this review, an overview of state-of-the-art developments and future perspectives in the multifunctional magnetically responsive soft materials is presented.

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ISSN: 2399-7532
Multifunctional Materials is a new multidisciplinary journal devoted to publishing original research of the highest quality and impact covering all aspects of multifunctional materials, including fundamental concepts to integrate multiple functions, characterisation of functions, novel applications and manufacturing techniques.
Multifunctional Materials to cease publication at the end of 2022
IOP Publishing has been working closely with the multifunctional materials community since 2018 in order to set up and establish the journal, Multifunctional Materials (MFM). Despite the publication of some high quality content the journal has unfortunately not been able to establish a large enough body of content in all targeted thematic areas to ensure longer term sustainability as a publishing option for the community. After full consideration we have therefore taken the decision to discontinue publication of MFM at the end of 2022, and the journal will be closing for new submissions on 29 July 2022.
We remain committed to serving the field of multifunctional materials and its research community through other journals in the IOP Publishing portfolio, especially the Journal of Physics: Materials as a fully open access journal that will consider multifunctional materials content. IOP Publishing will also continue to work with the community on new initiatives to highlight and make their research in the field available into the future.
The decision to close a journal is not an easy one to take however we feel confident that doing so positions IOP Publishing to more effectively serve the multifunctional materials community through its fully open access journals with broader scope.
We would like to take this opportunity to thank our founding Editors-in-Chief, Andreas Lendlein and Richard S. Trask, our editorial board, our authors, reviewers and guest editors for their committed support for MFM over the last five years.
All previously published content in MFM will be made freely available for perpetuity through https://iopscience.iop.org/journal/2399-7532 from the beginning of 2023. All articles have also been preserved with CLOCKSS and Portico, both widely used, trusted third-party resources that help protect the integrity of the scientific record.
Any questions about the journal and this decision should be sent to customerservices@ioppublishing.org.
Shuai Wu et al 2020 Multifunct. Mater. 3 042003
Barbara Mazzolai et al 2022 Multifunct. Mater. 5 032001
Soft robotics aims at creating systems with improved performance of movement and adaptability in unknown, challenging, environments and with higher level of safety during interactions with humans. This Roadmap on Soft Robotics covers selected aspects for the design of soft robots significantly linked to the area of multifunctional materials, as these are considered a fundamental component in the design of soft robots for an improvement of their peculiar abilities, such as morphing, adaptivity and growth. The roadmap includes different approaches for components and systems design, bioinspired materials, methodologies for building soft robots, strategies for the implementation and control of their functionalities and behavior, and examples of soft-bodied systems showing abilities across different environments. For each covered topic, the author(s) describe the current status and research directions, current and future challenges, and perspective advances in science and technology to meet the challenges.
Wilhelm Johannisson et al 2019 Multifunct. Mater. 2 035002
Structural batteries are materials that can carry mechanical load while storing electrical energy. This is achieved by combining the properties of carbon fiber composites and lithium ion batteries. There are many design parameters for a structural battery and in order to understand their impact and importance, this paper presents a model for multifunctional performance. The mechanical behavior and electrical energy storage of the structural battery are matched to the mechanical behavior of a conventional carbon fiber composite, and the electrical energy storage of a standard lithium ion battery. The latter are both monofunctional and have known performance and mass. In order to calculate the benefit of using structural batteries, the mass of the structural battery is compared to that of the two monofunctional systems. There is often an inverse relationship between the mechanical and electrochemical properties of multifunctional materials, in order to understand these relationships a sensitivity analysis is performed on variables for the structural battery. This gives new insight into the complex multifunctional design of structural batteries. The results show that it is possible to save mass compared to monofunctional systems but that it depends strongly on the structure it is compared with. With improvements to the design of the structural battery it would be possible to achieve mass saving compared to state-of-the-art composite laminates and lithium ion batteries.
A B M Tahidul Haque et al 2020 Multifunct. Mater. 3 044001
Wearable electronics, conformable sensors, and soft/micro-robotics require conductive yet stretchable thin films. However, traditional free standing metallic thin films are often brittle, inextensible, and must be processed in strict environments. This limits implementation into soft technologies where high electrical conductivity must be achieved while maintaining high compliance and conformability. Here we show a liquid metal elastomeric thin film (LET) composite with elastomer-like compliance (modulus < 500 kPa) and stretchability (>700%) with metallic conductivity (sheet resistance < 0.1 Ω/□). These 30–70 µm thin films are highly conformable, free standing, and display a unique Janus microstructure, where a fully conductive activated side is accompanied with an opposite insulated face. LETs display exceptional electro-mechanical characteristics, with a highly linear strain-resistance relationship beyond 700% deformation while maintaining a low resistance. We demonstrate the multifunctionality of LETs for soft technologies by leveraging the unique combination of high compliance and electrical conductivity with transfer capabilities for strain sensing on soft materials, as compliant electrodes in a dielectric elastomeric actuator, and as resistive heaters for a liquid crystal elastomer.
Reece L Lincoln et al 2019 Multifunct. Mater. 2 043001
Multifunctional composites offer the ability to increase the efficiency, autonomy and lifespan of a structure by performing functions that would have been considered by designers as mutually exclusive. In the present perspective paper, a subclass of multifunctional composites is considered: metamaterials. In this perspective, a multifunctional composite is defined as ‘made of two or more materials that perform two or more functions in a manner that is constructive to the overall purpose of the structure’ where there is no differentiation between structural or non-structural functions. Equally, we define metamaterials are a class of man-made structures that display properties that are opposite to those typically found in nature. These ‘engineered’ architected materials continue to revisit and extend the boundaries of traditional materials science, opening up a wealth of new opportunities impacting on all aspects of human life. In our work, multifunctional metamaterials are delineated: electrodynamic, acoustic and mechanical. We review the current progress in these types of multifunctional metamaterials in terms of their bandwidth, fabrication techniques and applicability; noting that lattice structures offer considerable potential across all three functionalities. It culminates in the discussion of three key challenges which are seen by the authors as critical in the development of the next generation of lattice-type multifunctional metamaterials; namely, bandwidth, fabrication technique and proof of applicability. Success by the scientific community in these areas will lead to 3D multi-scale and multimedia lattice frameworks capable of influencing all three types of waves instantly; such a system would be a major technological breakthrough and will redefine our concept and understanding of multifunctional metamaterials in the next 10–20 years.
Marko Mihajlovic et al 2021 Multifunct. Mater. 4 032001
Soft materials, such as hydrogels, are used as scaffolds in tissue engineering and regenerative medicine to help tissues regenerate and heal. Recently, supramolecular hydrogels, based on non-covalent interactions, have grown in popularity, especially in the development of materials for biomedical use. Their potential lies in the dynamic, reversible and temporary nature of their crosslinks, which can make them responsive to stimuli, injectable and suitable for 3D printing. Such versatility and processability is important when developing new biomaterials for drug delivery or as implantable scaffolds. The behavior and properties of such hydrogels are different compared to those of chemically crosslinked hydrogels. In this review, we give an overview on supramolecular hydrogels which contain hyaluronic acid (HA) as one of the building blocks. HA is particularly interesting, due to its hydrophilicity, biofunctionality and ease of chemical modification. Specifically, we focus on HA-based hydrogels that make use of hydrogen bonding, hydrophobic interactions, electrostatic interactions, metal–ion coordination and guest–host interactions, and are intended for applications in the biomedical field, with potential for clinical translation.
Vinh Tu et al 2020 Multifunct. Mater. 3 025001
Structural power composites are multifunctional materials with simultaneous load bearing and energy storing functionality. This is made possible due to carbon fibers’ ability to act not only as structural reinforcement materials, but also as electrode components. A crucial component of structural power composites is the structural electrolyte that is required to have both high stiffness and high ionic conductivity. To explore microstructure properties that bear optimal bifunctional performance a procedure is presented to generate various classes of synthetic microstructures with a wide span of properties for computer simulation. The effective properties of the generated artificial structural electrolytes are obtained via virtual material testing and compared with experimentally obtained data. Ultimately, a microstructure class with very good bifunctional properties is identified.
Teresa A Kent et al 2020 Multifunct. Mater. 3 025003
We present a soft actuator composed of fluidic channels of liquid metal alloy embedded in a liquid crystal elastomer (LCE). The LM channels function as stretchable Joule heating elements that deliver heat to the LCE to induce a shape memory phase transition. Because the heater is fluidic, it can deform with the surrounding LCE as the actuator extends and contracts during actuation. In addition to contractile actuation, the LCE can be programmed to perform in-plane or out-of-plane flexural actuation, which exhibit deformations predictable using a simple finite element analysis model. By combining a liquid metal heater with a shape memory polymer, we achieve a soft actuator that does not require an external heat source and can instead be directly activated with electrical current. Finally, we show that the liquid metal channels can also function as a sensor during the actuation cycle, allowing for closed-loop control of the soft actuator.
Islam Zmerli et al 2021 Multifunct. Mater. 4 022001
Polydopamine (PDA) is a mussel-inspired and a melanin-mimicking material that has attracted considerable attention during the recent years. This ‘polymer’ displays diverse promising properties, like its simple preparation procedures, easy functionalization, free radicals scavenging activity, outstanding photothermal and photoacoustic performance, and its great biocompatibility and biodegradability. A remarkable feature of PDA is its ability to form colloidal nanosized particles or nanoscaled coatings, allowing the preparation of various nanoparticulate structures. The first studies into PDA mainly explored the polymerization mechanisms of this material and the development of controlled preparation protocols. Later works focused on the investigation of these nanomaterials for the design and development of multifunctional platforms and their implementation in multiple biomedical fields, particularly in cancer treatment and bio-imaging. The purpose of this review is to (a) give a detailed overview about the synthesis methods of PDA and the formation mechanisms proposed so far in the literature, (b) outline the remarkable physico-chemical and functional properties of PDA nanomaterials, and (c) summarize the application of PDA-derived nanosystems in cancer theranostics and particularly in drug delivery and light-mediated cancer therapy with a special emphasis on the different strategies that can be used for the design of smart nanosystems with bimodal photothermal/photodynamic properties. Finally, a comparison of physicochemical properties and biomedical applications between PDA and other catecholamine derivatives is made.
Giulia Fredi et al 2018 Multifunct. Mater. 1 015003
Carbon fibres (CFs), originally made for use in structural composites, have also been demonstrated as high capacity Li-ion battery negative electrodes. Consequently, CFs can be used as structural electrodes; simultaneously carrying mechanical load and storing electrical energy in multifunctional structural batteries. To date, all CF microstructural designs have been generated to realise a targeted mechanical property, e.g. high strength or stiffness, based on a profound understanding of the relationship between the graphitic microstructure and the mechanical performance. Here we further advance this understanding by linking CF microstructure to the lithium insertion mechanism and the resulting electrochemical capacity. Different PAN-based CFs ranging from intermediate- to high-modulus types with distinct differences in microstructure are characterised in detail by SEM and HR-TEM and electrochemical methods. Furthermore, the mechanism of Li-ion intercalation during charge/discharge is studied by in situ confocal Raman spectroscopy on individual CFs. Raman G band analysis reveals a Li-ion intercalation mechanism in the high-modulus fibre reminiscent of that in crystalline graphite. Also, the combination of a relatively low capacity of the high-modulus CFs (ca. 150 mAh g−1) is shown to be due to that the formation of a staged structure is frustrated by an obstructive turbostratic disorder. In contrast, intermediate-modulus CFs, which have significantly higher capacities (ca. 300 mAh g−1), have Raman spectra indicating a Li-ion insertion mechanism closer to that of partly disordered carbons. Based on these findings, CFs with improved multifunctional performance can be realised by tailoring the graphitic order and crystallite sizes.
Barbara Mazzolai et al 2022 Multifunct. Mater. 5 032001
Soft robotics aims at creating systems with improved performance of movement and adaptability in unknown, challenging, environments and with higher level of safety during interactions with humans. This Roadmap on Soft Robotics covers selected aspects for the design of soft robots significantly linked to the area of multifunctional materials, as these are considered a fundamental component in the design of soft robots for an improvement of their peculiar abilities, such as morphing, adaptivity and growth. The roadmap includes different approaches for components and systems design, bioinspired materials, methodologies for building soft robots, strategies for the implementation and control of their functionalities and behavior, and examples of soft-bodied systems showing abilities across different environments. For each covered topic, the author(s) describe the current status and research directions, current and future challenges, and perspective advances in science and technology to meet the challenges.
Nuttanit Pramounmat et al 2022 Multifunct. Mater. 5 012002
Platinum-binding (Pt-binding) peptides have been used for fabrication of complex platinum nanomaterials such as catalysts, metallopharmaceuticals, and electrodes. In this review, we present an understanding of the mechanisms behind Pt-binding peptides and their applications as multifunctional biomaterials. We discuss how the surface recognition, roles of individual amino acids, and arrangement of amino acid sequences interplay. Our summary on the current state of understanding of Pt-binding peptides highlights opportunities for interdisciplinary research which will expand the applicability of these multifunctional peptides.
Neng Xia et al 2022 Multifunct. Mater. 5 012001
Miniature robots and actuators with micrometer or millimeter scale size can be driven by diverse power sources, e.g. chemical fuels, light, magnetic, and acoustic fields. These machines have the potential to access complex narrow spaces, execute medical tasks, perform environmental monitoring, and manipulate micro-objects. Recent advancements in 3D printing techniques have demonstrated great benefits in manufacturing small-scale structures such as customized design with programmable physical properties. Combining 3D printing methods, functional polymers, and active control strategies enables these miniature machines with diverse functionalities to broaden their potentials in medical applications. Herein, this review provides an overview of 3D printing techniques applicable for the fabrication of small-scale machines and printable functional materials, including shape-morphing materials, biomaterials, composite polymers, and self-healing polymers. Functions and applications of tiny robots and actuators fabricated by 3D printing and future perspectives toward small-scale intelligent machines are discussed.
Hafeesudeen Sahabudeen et al 2021 Multifunct. Mater. 4 042001
From synthesis through storage to disposal, contact lenses (CLs) interact with different system environments throughout their functional life cycle. To fulfill their therapeutic purpose, they need to exhibit a distinct behavior in each of them, which is achieved through a combination of different material functions. As such, CL materials are a showcase of highly advanced and mass-produced multifunctional biomaterials. Their great relevance and long history mean that a vast amount of work has gone into the implementation of ever more advanced functions. From understanding the approaches used to achieve multifunctionality in CLs, a lot of inspiration for the design of other multifunctional medical devices can be drawn. Therefore, here, we provide a systematic overview of the different functions that are combined in today’s CL materials, together with their quantification methods, chemical design principles and fabrication techniques. We further provide an outlook on the functions that are currently under investigation for the next generation of commercial CLs.
Nirav Joshi et al 2021 Multifunct. Mater. 4 032002
Highly sensitive and selective gas sensors with low energy consumption and amenable to miniaturization are required for real-time gas monitoring applications. The challenge is to produce sensing units at a sufficiently low cost to allow for broad deployment, which can only be reached with efficient materials and fabrication procedures. In this context, metal oxides are promising for next-generation gas sensors due to their high surface-area-to-volume ratio, efficient electron transfer, enhanced and tunable surface reactivity, fast response, and short recovery time. However, sensors from metal oxides are normally not sufficiently selective and have to be operated at high temperatures. These limitations have been overcome with strategies such as doping with other oxides, UV-illumination, and noble metal decoration. This review concentrates on the design and mechanisms of heterostructures for gas sensors, which are obtained with metal oxides in conjunction with other materials (e.g. other metal oxides and 2D materials). The key topics discussed include: (a) synthesis of metal oxide heterostructures (MOHs); (b) semiconducting heterostructures comprising n–n, n–p, and p–p heterojunctions, with emphasis on their sensing mechanisms; (c) sensors produced with heterostructures involving 2D materials. The challenges and prospects for gas sensors based on MOHs are also discussed.
Barbara Mazzolai et al 2022 Multifunct. Mater. 5 032001
Soft robotics aims at creating systems with improved performance of movement and adaptability in unknown, challenging, environments and with higher level of safety during interactions with humans. This Roadmap on Soft Robotics covers selected aspects for the design of soft robots significantly linked to the area of multifunctional materials, as these are considered a fundamental component in the design of soft robots for an improvement of their peculiar abilities, such as morphing, adaptivity and growth. The roadmap includes different approaches for components and systems design, bioinspired materials, methodologies for building soft robots, strategies for the implementation and control of their functionalities and behavior, and examples of soft-bodied systems showing abilities across different environments. For each covered topic, the author(s) describe the current status and research directions, current and future challenges, and perspective advances in science and technology to meet the challenges.
Maria Francesca Pernice et al 2022 Multifunct. Mater. 5 025002
This work investigated and developed a protocol for establishing the multifunctional performance of a structural supercapacitor: a composite which can simultaneously carry mechanical load whilst storing electrical energy. The Structural Supercapacitor consisted of carbon aerogel (CAG) reinforced carbon fibre electrodes which sandwiched a woven glass fibre lamina and was infused with a structural electrolyte (SE). This was compared to two monofunctional devices: a Monofunctional Supercapacitor and a Monofunctional Laminate in which the SE had been replaced by ionic liquid and a structural epoxy, respectively. In the Monofunctional Supercapacitor, the considerable surface area of the CAG and ionic capacity of the liquid electrolyte resulted in a high device normalised capacitance (1731 mF g−1). However, in the Structural Supercapacitor the SE presented meso-scale heterogeneity, obstructing the CAG pores with thin films of epoxy. This resulted in a considerable reduction in electrochemical performance, with a drop in the device normalised capacitance to 212 mF g−1. Regarding mechanical performance, it was shown that the CAG had promoted brittle fracture, leading to a severe depression in the tensile and in-plane shear strengths. The Structural Supercapacitor presented a tensile modulus and strength of 33 GPa and 110 MPa, respectively: a 15% and 11% drop in tensile modulus and strength, respectively, compared to that of the Monofunctional Laminate. However, under in-plane shear the soft SE dominated, leading to about a 44% drop in shear modulus (1.7 GPa) and strength (13.7 MPa at 1% shear strain). This work has provided an insight into the hurdles associated with demonstrating multifunctionality, including the scaling challenges for electrochemical and mechanical characterisation and the need to report both active material and device normalised data. The emergence and development of such structural power composites could address the issue of parasitic battery mass in transportation, and hence realise full electrification of aircraft and cars.
Hongshuang Guo et al 2022 Multifunct. Mater. 5 024001
Stimuli-responsive polymers provide unmatched opportunities for remotely controlled soft robots navigating in complex environments. Many of the responsive-material-based soft robots can walk on open surfaces, with movement directionality dictated by the friction anisotropy at the robot-substrate interface. Translocation in one-dimensional space such as on a tubular surface is much more challenging due to the lack of efficient friction control strategies. Such strategies could in long term provide novel application prospects in, e.g. overhaul at high altitudes and robotic operation within confined environments. In this work, we realize a liquid-crystal-elastomer-based soft robot that can move on a tubular surface through optical control over the grasping force exerted on the surface. Photoactuation allows for remotely switched gripping and friction control which, together with cyclic body deformation, enables light-fueled climbing on tubular surfaces of glass, wood, metal, and plastic with various cross-sections. We demonstrate vertical climbing, moving obstacles along the path, and load-carrying ability (at least 3 × body weight). We believe our design offer new prospects for wirelessly driven soft micro-robotics in confined spacing.
Hafeesudeen Sahabudeen et al 2021 Multifunct. Mater. 4 042001
From synthesis through storage to disposal, contact lenses (CLs) interact with different system environments throughout their functional life cycle. To fulfill their therapeutic purpose, they need to exhibit a distinct behavior in each of them, which is achieved through a combination of different material functions. As such, CL materials are a showcase of highly advanced and mass-produced multifunctional biomaterials. Their great relevance and long history mean that a vast amount of work has gone into the implementation of ever more advanced functions. From understanding the approaches used to achieve multifunctionality in CLs, a lot of inspiration for the design of other multifunctional medical devices can be drawn. Therefore, here, we provide a systematic overview of the different functions that are combined in today’s CL materials, together with their quantification methods, chemical design principles and fabrication techniques. We further provide an outlook on the functions that are currently under investigation for the next generation of commercial CLs.
Quan Wendong et al 2021 Multifunct. Mater. 4 035003
Structural electrolytes provide mechanical properties approaching structural resin combined with a high degree of ionic conductivity. Here, structural electrolytes based on bisphenol A diglycidyl ether and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIM-TFSI) were synthesised through reaction induced phase separation (RIPS) using isophorone diamine (iPDA) as a curing agent. The microstructure and properties of the resulting materials were controlled through both the initial formulations and the curing temperature. Curing at room temperature generated a bi-continuous structure and improved both mechanical performance and ionic conductivity of the resulting structural electrolytes. The balance between properties can be systematically adjusted; for example, a promising Young’s modulus of 800 MPa was obtained simultaneously with an ionic conductivity of 0.28 mS cm−1, for a formulation containing 35 vol% EMIM-TFSI. The lengthscale of the structural features was reduced by an order of magnitude by introducing multifunctional block-copolymers (MF-bcP) based on glycidyl methacrylate (GMA) and quaternised (2-dimethylamino)ethyl methacrylate (DMAEMA). Small angle neutron scattering (SANS), obtained during curing, identified at least two structural phases of different length scale, for the formulations containing MF-bcP, in agreement with microstructures observed using scanning electron microscopy. Such structural electrolytes may be required when using structural electrodes that also have finer characteristic lengthscales. The addition of the MF-bcP to formulations containing 35 vol% EMIM-TFSI produced structural electrolytes with a Young’s modulus of 530 MPa and an ionic conductivity of 0.64 mS cm−1.
Wilhelm Johannisson et al 2021 Multifunct. Mater. 4 035002
Structural carbon fibre composite batteries are a type of multifunctional batteries that combine the energy storage capability of a battery with the load-carrying ability of a structural material. To extract the current from the structural battery cell, current collectors are needed. However, current collectors are expensive, hard to connect to the electrode material and add mass to the system. Further, attaching the current collector to the carbon fibre electrode must not affect the electrochemical properties negatively or requires time-consuming, manual steps. This paper presents a proof-of-concept method for screen-printing of current collectors for structural carbon fibre composite batteries using silver conductive paste. Current collectors are screen-printed directly on spread carbon fibre tows and a polycarbonate carrier film. Experimental results show that the electrochemical performance of carbon fibre vs lithium metal half-cells with the screen-printed collectors is similar to reference half-cells using metal foil and silver adhered metal-foil collectors. The screen-printed current collectors fulfil the requirements for electrical conductivity, adhesion to the fibres and flexible handling of the fibre electrode. The screen-printing process is highly automatable and allows for cost-efficient upscaling to large scale manufacturing of arbitrary and complex current collector shapes. Hence, the screen-printing process shows a promising route to realization of high performing current collectors in structural batteries and potentially in other types of energy storage solutions.
Marko Mihajlovic et al 2021 Multifunct. Mater. 4 032001
Soft materials, such as hydrogels, are used as scaffolds in tissue engineering and regenerative medicine to help tissues regenerate and heal. Recently, supramolecular hydrogels, based on non-covalent interactions, have grown in popularity, especially in the development of materials for biomedical use. Their potential lies in the dynamic, reversible and temporary nature of their crosslinks, which can make them responsive to stimuli, injectable and suitable for 3D printing. Such versatility and processability is important when developing new biomaterials for drug delivery or as implantable scaffolds. The behavior and properties of such hydrogels are different compared to those of chemically crosslinked hydrogels. In this review, we give an overview on supramolecular hydrogels which contain hyaluronic acid (HA) as one of the building blocks. HA is particularly interesting, due to its hydrophilicity, biofunctionality and ease of chemical modification. Specifically, we focus on HA-based hydrogels that make use of hydrogen bonding, hydrophobic interactions, electrostatic interactions, metal–ion coordination and guest–host interactions, and are intended for applications in the biomedical field, with potential for clinical translation.
Mathew Schwartz et al 2021 Multifunct. Mater. 4 022002
The ability to label and track physical objects that are assets in digital representations of the world is foundational to many complex systems. Simple, yet powerful methods such as bar- and QR-codes have been highly successful, e.g. in the retail space, but the lack of security, limited information content and impossibility of seamless integration with the environment have prevented a large-scale linking of physical objects to their digital twins. This paper proposes to link digital assets created through building information modeling (BIM) with their physical counterparts using fiducial markers with patterns defined by cholesteric spherical reflectors (CSRs), selective retroreflectors produced using liquid crystal self-assembly. The markers leverage the ability of CSRs to encode information that is easily detected and read with computer vision while remaining practically invisible to the human eye. We analyze the potential of a CSR-based infrastructure from the perspective of BIM, critically reviewing the outstanding challenges in applying this new class of functional materials, and we discuss extended opportunities arising in assisting autonomous mobile robots to reliably navigate human-populated environments, as well as in augmented reality.
Sébastien Rochat et al 2021 Multifunct. Mater. 4 025002
Owing to their large surface area and good solvent processability, polymers of intrinsic microporosity (PIMs) have been widely investigated for gas storage and separation processes. In this article, we show how chemically modifying the polymers can fine-tune their properties for specific, targeted applications. We find that converting the archetypal microporous polymer PIM-1 into a polycarboxylate salt enhances its separation capabilities for H2/CO2 mixtures (relevant to hydrogen production), whereas appending multiple amine groups significantly improves gas separation properties for N2/CO2 mixtures (relevant to flue gas treatment). Adsorption-based separation processes have received less attention than size-sieving processes in porous polymeric materials, however they could provide a suitable alternative technology to energy-intensive separation processes such as cryogenic distillation. We also report the hydrogen storage properties of the modified polymers, which we find to depend on the chemical modification carried out. By coupling the simplicity of the proposed chemical modifications with the scalability and porous properties of PIMs, we provide a blueprint to create new multifunctional materials with adapted properties for targeted applications.
Vanessa J Neubauer et al 2021 Multifunct. Mater. 4 014002
Mineral deposition in biological systems is often templated by organic matrices including proteins directing the nucleation and growth of bioceramics by interacting with early stage species of the mineralization process or coordinating specific facets of the forming crystal. Structurally, charged surface patches are a characteristic motif of biomineralization-associated proteins, which are able to accumulate and bind ions from the surrounding media and, therefore, initiate, promote or inhibit mineralization. Controlled protein engineering enables the manipulation and control of bioinspired in vitro precipitation systems, and thus not only opens prospects for the design of environmentally benign synthetic strategies towards hierarchically structured functional materials, but also enhances the understanding of fundamental interaction mechanisms in biomineralization processes. Here, two recombinant variants of the spider silk protein ADF4 were engineered with oppositely charged peptide tags. Both were processed into micrometer-sized particles and investigated for their influence on manganese carbonate mineralization. Micro- and nano-structured manganese carbonate represents an attractive material for diverse applications including catalysis and wastewater treatment. While both types of spider silk particles were incorporated into the mineral structure, the positively tagged proteins appeared to interact more strongly with the formed manganese carbonate crystals than their negatively charged counterparts. Combination of the spider silk particles and poly(acrylic acid) (PAA), a water-soluble structure-directing agent associated with the stabilization of amorphous precursor phases in carbonates, resulted in the formation of film-like non-equilibrium structures of MnCO3 entrapping the spider silk particles. With the aim to gain mechanistic insights and to elucidate the interaction between the different components involved in the mineralization process, we studied the interplay between PAA, positively or negatively tagged spider silk particles, and Mn(II) ions by time-resolved dynamic light scattering. The here used set-up affords the possibility to identify control strategies for the template-mediated mineralization of manganese carbonate.