Circularity in Practice: Review of Main Current Approaches and Strategic Propositions for an Efficient Circular Economy of Materials

This paper aims to summarize, propose, and discuss existing or emerging strategies to shift towards a circular economy of materials. To clarify the landscape of existing circular practices, a new spectrum is proposed, from product-based strategies, where entire products go through several life cycles without being reprocessed, to material-based approaches, extracting, recycling, and reprocessing materials from the waste flow. As refillable packaging does not lose any functionality or value, when re-used through many life cycles, product-based strategies are globally extremely efficient and must be promoted. It appears however that their implementation is only possible at the scale of individual products such as packaging containers, relying on the cooperation of involved companies and consumers. It appears more and more urgent to focus as well on a more systematic and flexible material-oriented scheme. The example of circular glass recycling is a success in many countries, and technologies become nowadays available to extend such practices to many other materials, such as rigid plastics. An ideal would be to aim at an economy of materials that would imitate the continuous material cycle of the biosphere. Technological and business strategies are presented and discussed, aiming at a relevant impact on circularity.

Flexible Material Formulations for 3D Printing of Porous Beds with Applications in Bioprocess Engineering

Background: 3D printing is revolutionizing many industrial sectors and has the potential to enhance also the biotechnology and bioprocessing fields. Here, we propose a new flexible material formulation to 3D print support matrices with complex, perfectly ordered morphology and with tuneable properties to suit a range of applications in bioprocess engineering. Findings: Supports for packed-bed operations were fabricated using functional monomers as the key ingredients, enabling matrices with bespoke chemistry such as charged groups, chemical moieties for further functionalization, and hydrophobic/hydrophilic groups. Other ingredients, e.g. crosslinkers and porogens, provide the opportunity to further tune the mechanical properties of the supports and the morphology of their porous network. Through this approach, we fabricated and demonstrated the operation of Schoen gyroid columns with I) positive and negative charges for ion-exchange chromatography, II) enzyme bioreactors with immobilized trypsin to catalyse hydrolysis, and III) bacterial biofilms bioreactors for fuel desulfurization. Conclusions: This study demonstrates a simple, cost-effective and flexible fabrication of customized 3D printed supports for different biotechnology and bioengineering applications.

Generating Electricity from Water Evaporation Through Microbial Biofilms

Sustainable strategies for energy production are required to reduce reliance on fossil fuels and to power electronics without generating toxic waste.1-7 Generating electricity from water evaporation through engineered materials is a promising approach,8,9 but power outputs have been low and the materials employed were not sustainably produced. Microorganisms can be mass produced with renewable feedstocks. Here, we demonstrate that it is possible to engineer microbial biofilms as a cohesive, flexible material for long-term continuous electricity production from evaporating water. The biofilm sheets were the functional component in devices that continuously produced power densities (~1 μW/cm2) higher than that achieved with non-biological materials. Current production scaled directly with biofilm-sheet size and skin-patch devices harvested sufficient electricity from the moisture on skin to continuously power wearable devices. The results demonstrate that appropriately engineered biofilms can perform as robust functional materials without the need for further processing or maintaining cell viability. Biofilm-based hydroelectric current production was comparable to that achieved with similar sized biofilms catalyzing current production in microbial fuel cells,10,11 without the need for an organic feedstock or maintaining cell viability. The ubiquity of biofilms in nature suggests the possibility of additional sources of biomaterial for evaporation-based electricity generation and the possibility of harvesting electricity from diverse aqueous environments.

Research on High-Performance Antennas Based on Graphene Materials

With the rapid development of the Internet of Things and wearable electronic devices, China is about to enter the 5G era. The current materials have been difficult to meet the production needs of flexible antennas working in the 5G frequency band. Flexible antenna sensors have received widespread attention because they can detect signal changes caused by antenna deformation. In recent years, miniaturization and high sensitivity have been the development trend of flexible antennas. However, traditional metal materials have disadvantages such as high density, easy corrosion, and poor bending stability, Can no longer meet the further development of 5G frequency band flexible antennas. Therefore, it is necessary to find a light and flexible material to replace the traditional metal material. Graphene has excellent flexibility, conductivity, and stability, once discovered, it has aroused widespread concern among scientists. This article mainly conducts certain research on graphene material, hoping to contribute to the development of 5G in China.

Development of modular wrist, hand and finger orthesis by additive manufacturing

Additive Manufacturing (AM) has been considered an innovative technology for the development of orthoses. Even so, the use of AM, utilizing low cost rigid and flexible material which can be used in different ways by the same user, to produce a modular orthosis has yet to be explored. Purpose: Develop a modular wrist, hand and finger orthosis that can be utilized as a functional or static orthosis, depending on the therapeutic objective. This being produced by low cost Additive Manufacturing, through a single anatomy acquisition process. Approach: Firstly, requirements for modularization and development were defined in a team with occupational therapists and mechanical engineers, After indirect anatomy acquisition of a volunteer, without disabilities, two parts of the same orthosis were modeled, one flexible (functional) and the other rigid (static). These were printed on PLA (rigid part) and flexible TPU (functional part) with an Open Source printer. In addition, fastening strips were also made in flexible TPU. Findings: Three parts of which make up the modular orthosis were produced. This can be used in two different ways; one being to maintain the static posture of the wrist, hand and fingers and the other to provide functionality of the hands, but with the correct positioning of the wrist and thumb. Originality: Even with low-cost material and an open source machine, it was possible to generate an innovative proposal with the use of AM as the orthosis manufacturing process.

An Artificial Magnetic Conductor-Backed Compact Wearable Antenna for Smart Watch IoT Applications

Smart watch antenna design is challenging due to the limited available area and the contact with the human body. The strap of smart watch can be utilized effectively for integration of the antenna. In this study, an antenna integrated on a smart watch strap model using computer simulation technology (CST) was designed. The antenna was designed for industrial, scientific, and medical (ISM) frequency bands at 2.45 and 5.8 GHz. Roger 3003C was used as substrate due to its semi-flexible nature. The antenna size is 28.81 × 19.22 × 1.58 mm3 and it has a gain of 1.03 and 5.97 dB, and efficiency of 80% and 95%, at 2.45 and 5.8 GHz, on the smart watch strap, respectively. A unit cell was designed having a dimension of 19.19 × 19.19 × 1.58 mm3 to mitigate the effect of back radiation and to enhance the gain. The antenna backed by the unit cell exhibited a gain of 2.44 and 6.17 dB with efficiency of 50% and 72% at 2.45 and 5.8 GHz, respectively. The AMC-backed antenna was integrated into a smart watch strap and placed on a human tissue model to study its human proximity effects. The specific absorption rate (SAR) values were calculated to be 0.19 and 1.18 W/kg at the designed ISM frequencies, and are well below the permissible limit set by the FCC and ICINPR. Because the antenna uses flexible material for wearable applications, bending analysis was also undertaken. The indicated results prove that bending along the x- and y-axes has a negligible effect on the antenna’s performance and the antenna showed excellent performance in the human proximity test. The measured results of the fabricated antenna were comparable with the simulated results. Thus, the designed antenna is compact, has high gain, and can be used effectively for wireless IoT applications.

Design and Research of Bearing Reliability Test Bed Based on Multi-Dimensional Vibration Loading

Rolling bearings are widely used in aviation, aerospace and other important fields, and their reliability is greatly affected by external vibration excitation during service. Due to the large volume and high cost of the combined structure of shaking table and test chamber, this paper designed a dynamic reliability test bed specially for rolling bearings to study the influence of external vibration excitation with different directions, frequencies and amplitudes on vibration signals and service life of rolling bearings. The test bed is loaded with external excitation by means of electromagnetic shakers in two directions, and the flexible material is used to realize the displacement of the test chamber under two external excitation directions at the same time. The bearing vibration loading life test carried out by this test bed has important guiding significance for the design of rolling bearing. The experimental results show that the test bed can apply axial and radial vibration loads of 1-800Hz sinusoidal waveform, and the vibration acceleration can reach 1g, which can simulate the effect of actual working conditions.

Synthesis and Characterization of the Chitosan Silver Nanoparticle-Reinforced Borassus flabellifer Trichome- and Prosopis juliflora Wood-Based Nanocomposite for Environmental Application

Wood is a wide flexible material appreciated extremely for its cost-effectiveness, great quantity, and biocompatibility. In addition, naturally existing materials possess prominent biomedical applications, and they can withstand efficiently when compared to other materials like glass, steel, and plastics. The present study revealed the prepared chitosan, silver nanoparticles incorporated with Borassus flabellifer trichome, and fabrication of Prosopis juliflora wood-based biomaterial. A characterization study was done by UV-visible spectroscopic analysis, FTIR analysis, and SEM analysis expressing and confirming a significant characteristic and morphological property of the prepared biomaterial.