Material Architecture Research Articles

An innovative wide and low-frequency bandgap metastructure for vibration isolation

Engineering the architecture of materials is a new and very promising approach to obtain vibration isolation properties. The biggest challenge for lattice structures exhibiting vibration isolation properties is the trade-off between compactness and wide and low-frequency bandgaps, i.e., frequency ranges where the propagation of elastic or acoustic waves is prohibited. Here, we, both numerically and experimentally, propose and demonstrate a new design concept for compact metamaterials exhibiting extraordinary properties in terms of wide and low frequency bandgap and structural characteristics. With its 4 cm side length unit cell, its bandgap opening frequency of 1478 Hz, its band-stop filter behavior in the range 1.48–15.24 kHz, and its structural characteristics, the proposed 1×1×3 metastructure represents great progress in the field of vibration isolation and a very promising solution for hand-held vibration probes applications that were unattainable so far through conventional materials.

Multi‐Electrode Printed Bioelectronic Patches for Long‐Term Electrophysiological Monitoring

AbstractA novel architecture of materials and fabrication techniques is proposed that serves as a universal method for implementation of thin‐film biostickers for high resolution electrophysiological monitoring. Unlike the existing wearable patches, the presented solution can be worn for several days, and is not affected by daily routines such as physical exercise or taking bath. A printable biphasic liquid metal silver composite is used, both as the electrical interconnects and the electrodes. This allows combining advantages of dry electrodes, i.e., printability and non‐smearing behavior, with benefits of wet electrodes, i.e., high‐quality signal. A human subject study showed that these biphasic printed electrodes benefit from a lower electrode‐skin impedance compared to clinical grade Ag/AgCl electrodes. Digital printing enables autonomous fabrication of biostickers that are taylor‐made for each user and each application. A universal miniaturized electronic system for biopotential acquisition and wireless communication is develpoed, and demonstrated multiple biopotential acquisition cases, including electrocardiography, electroencephalography, electromyography, and electrooculography.

8. Controlling the rate of presentation of BMP-2 from a highly structured composite for interbody fusion

<h3>BACKGROUND CONTEXT</h3> Clinical outcomes for patients with intervertebral disc injury or disease could be enhanced by a new generation of regenerative matrices that create tissue environments to control angiogenesis, chondrogenesis and bone formation. Regenerative matrices are a new class of controlled release biomaterials that use surface chemistry, materials architecture, and drug delivery kinetics to create optimised conditions for cell interactions that result in high quality tissue formation. A novel biodegradable polymer matrix that releases bone morphogenetic protein 2 (BMP-2) over a period of one month with a low Cmax and sustained presentation of active protein is investigated in this study. <h3>PURPOSE</h3> BMP-2 release kinetics and protein activity from a new regenerative matrix was quantified to develop an implant with 1-month release of the drug within a macroporous matrix. A rabbit posterolateral (PLF) vertebral fusion model was performed to assess bone formation and fusion outcomes as a function of dose and source of BMP-2 (E coli and CHO cells). <h3>STUDY DESIGN/SETTING</h3> The study was designed to investigate the effect of various biomaterial design factors and manufacturing methods on the rate of release of BMP-2, the activity of BMP-2 and the extent of in vivo bone formation. <h3>PATIENT SAMPLE</h3> This study did not involve patients. <h3>OUTCOME MEASURES</h3> Outcome measures were the mechanical properties of the regenerative matrix, the architecture and porosity of the matrix, BMP-2 release kinetics, BMP-2 activity as a function of release time and bone formation. <h3>METHODS</h3> BMP-2 activity was tested using two in vitro cell-based assays. BMP-2 solutions and regenerative matrix extracts were tested for their ability to induce alkaline phosphatase (ALP) activity in W-20-17 stromal cells using a modified version of the ASTM standard protocol for in vitro biological activity of recombinant human BMP-2 (F2131-02). Cells were exposed to serial dilutions of BMP-2 for 24 h, assayed for ALP activity and EC50s calculated allowing the relative potency to NIBSC WHO BMP-2 standard to be calculated. BMP-2 release was assessed with an in vitro assay of ALP activity in the mouse muscle myoblast cell line C2C12. Formulations were suspended above a C2C12 monolayer in an insert with a porous (8 µm) PET membrane. Following 3-4 days of exposure, the inserts containing LDGraft were transferred to fresh cells for a further 3-4 days. Cells exposed to LDGraft in this manner were assayed for ALP activity (normalised to protein content) once the inserts had been transferred to fresh cells. Fusion rate and new bone formation were compared to INFUSE in a single-level lumbar (L4-L5) posterolateral (PLF) vertebral fusion model in the New Zealand White rabbit based on standard protocols (Boden et al, 1995, ASTM F3207). Pre-formed implants (3 cc) of INFUSE (rhBMP-2 and absorbable collagen sponge) were implanted on decorticated dorsal surfaces of the transverse processes of L4 and L5 adjacent to the laminae. Fusion was assessed by radiograph at 6 weeks and by manual palpation, radiography and microCT at 12 weeks. <h3>RESULTS</h3> BMP-2 activity was retained over one month of release with the addition of protectants in the formulation and precise control of manufacturing processes. The matrix had a porosity of >70% with a high proportion of macropores (>200 micron diameter). Low doses of E. coli-produced BMP-2 induced fusion in the PLF model. <h3>CONCLUSIONS</h3> A one-month releasing BMP-2 formulation is described. This new regenerative matrix had internal architecture designed to host angiogenesis. Manufacturing and design challenges can be overcome to retain high biologic activity throughout the release period. <h3>FDA DEVICE/DRUG STATUS</h3> BMP-2, not approved for this indication.

Lithium-Rich Layered Oxide with a Porous Prism Architecture for High-Performance Cathode Materials of Lithium-Ion Batteries

Lithium-rich layered oxides are among the most promising cathode materials for high-energy-density lithium-ion batteries (LIBs). Besides the composition and structure, the morphology of Li-rich layered materials also has significant effects on their electrochemical performance. In this work, a porous prism architecture of Li1.2Mn0.54Ni0.13Co0.13O2 materials is constructed via a coprecipitation solvothermal method and subsequent heat treatment. Appropriate concentrations of transition metal ions and oxalic acid as the precipitant used in synthesis govern the growth of the porous prism structure. When employed as a cathode material for LIBs, the optimized material achieves a high initial discharge capacity of 295.3 mAh g–1 at 0.1C and excellent rate capability of 150.6 mAh g–1 even at 5.0C. These outstanding performances can be attributed to the synergistic effect of the porous morphology and one-dimensional prism architecture. In particular, the porous morphology promotes the intercalation and extraction of Li+ while the prism architecture is associated with the observed superior structural stability. This architecture opens a promising avenue for the development of high-performance cathode materials in LIBs.

Community-Driven Methods for Open and Reproducible Software Tools for Analyzing Datasets from Atom Probe Microscopy.

Atom probe tomography, and related methods, probe the composition and the three-dimensional architecture of materials. The software tools which microscopists use, and how these tools are connected into workflows, make a substantial contribution to the accuracy and precision of such material characterization experiments. Typically, we adapt methods from other communities like mathematics, data science, computational geometry, artificial intelligence, or scientific computing. We also realize that improving on research data management is a challenge when it comes to align with the FAIR data stewardship principles. Faced with this global challenge, we are convinced it is useful to join forces. Here, we report the results and challenges with an inter-laboratory call for developing test cases for several types of atom probe microscopy software tools. The results support why defining detailed recipes of software workflows and sharing these recipes is necessary and rewarding: Open source tools and (meta)data exchange can help to make our day-to-day data processing tasks become more efficient, the training of new users and knowledge transfer become easier, and assist us with automated quantification of uncertainties to gain access to substantiated results.

Vibration-induced assembly of topologically interlocked materials

Dense architectured, granular, and other material systems based on the assembly of discrete building blocks provide mechanical responses not ordinarily achieved in monolithic materials. The performances of these material systems can be tuned and expanded by simply changing the building block geometry, their packing arrangement, and/or their jamming states. Applications for these material systems have however remained limited, in part because of fabrication challenges and scalability. We explored the vibration-driven assembly method to form periodic arrangements of convex polyhedral building blocks into large-piece free-standing topologically interlocked panels. We used a combination of experiments and discrete elements modeling (DEM) to explore how vibration can be manipulated to steer polyhedral building blocks into one of three possible states: static, assembly, and fluttering and study the governing physics and mechanics underlying these states. The results specified the role of the normalized relative acceleration of mechanical agitation, bouncing, and rotation mechanisms on both phase transitions and crystallization and/or interlocking. The geometry-dependency, re-fragmentation, re-crystallization, and re-configurability of athermal out-of-equilibrium material systems can be understood and optimized based on our findings and provided guidelines in this study.

A Process-Based Pore Network Model Construction for Granular Packings Under Large Plastic Deformations

We propose a process-based method for constructing a pore network model of granular packings under large deformations. The method uses the radical Voronoi tessellation and constructive solid geometry operations on meshes of deformed particles, to construct a three-dimensional solid of the pore network and estimate its geometric characteristics, CTS-model parameters and flow transport properties, and it uses the particle mechanics approach to model consolidation of powders under large deformations. This process-based method thus explicitly simulates not only a packing of grains but also its corresponding consolidation process, which in this work is restricted to powder die compaction up to a relative density close to one (i.e., to die filling, compaction to low porosity, unloading and ejection). The efficacy of the proposed method is borne out by studying granular packings with the same composition, namely a 50–50 binary mixture of two monodisperse systems comprised by elasto-plastic spheres with bonding strength, but with microstructures which are topologically different, namely a random packing, a bilayer and core-shell structures. These simulations reveal that topological differences affect the formation and evolution of the pore space statistical signature during consolidation and, therefore, showcase that process-based approaches for constructing PNM are of paramount relevance to understanding architectured granular material systems.

A hackable, multi-functional, and modular extrusion 3D printer for soft materials

Three-dimensional (3D) printing has emerged as a powerful tool for material, food, and life science research and development, where the technology’s democratization necessitates the advancement of open-source platforms. Herein, we developed a hackable, multi-functional, and modular extrusion 3D printer for soft materials, nicknamed Printer.HM. Multi-printhead modules are established based on a robotic arm for heterogeneous construct creation, where ink printability can be tuned by accessories such as heating and UV modules. Software associated with Printer.HM were designed to accept geometry inputs including computer-aided design models, coordinates, equations, and pictures, to create prints of distinct characteristics. Printer.HM could further perform versatile operations, such as liquid dispensing, non-planar printing, and pick-and-place of meso-objects. By ‘mix-and-match’ software and hardware settings, Printer.HM demonstrated printing of pH-responsive soft actuators, plant-based functional hydrogels, and organ macro-anatomical models. Integrating affordability and open design, Printer.HM is envisaged to democratize 3D printing for soft, biological, and sustainable material architectures.

On the role of the microstructure in the deformation of porous solids

This study explores the role that the microstructure plays in determining the macroscopic static response of porous elastic continua and exposes the occurrence of position-dependent nonlocal effects that are strictly correlated to the configuration of the microstructure. Then, a nonlocal continuum theory based on variable-order fractional calculus is developed in order to accurately capture the complex spatially distributed nonlocal response. The remarkable potential of the fractional approach is illustrated by simulating the nonlinear thermoelastic response of porous beams. The performance, evaluated both in terms of accuracy and computational efficiency, is directly contrasted with high-fidelity finite element models that fully resolve the pores’ geometry. Results indicate that the reduced-order representation of the porous microstructure, captured by the synthetic variable-order parameter, offers a robust and accurate representation of the multiscale material architecture that largely outperforms classical approaches based on the concept of average porosity.

Modeling, design and tailoring of a tough, strong and stiff multilayered bone graft material

Damage tolerance, stiffness, and strength are critical mechanical properties that are difficult to achieve concurrently in synthetic monolithic materials. This limits the range of certain applications, including in bone graft materials where bone-like mechanical reliance is desired. For example, calcium sulfate (CS) is a biologically compatible ceramic that possesses several properties of an ideal bone graft material, but its applications in medicine is limited by its brittleness. Brittleness may be alleviated by the addition of stronger and more ductile reinforcements, with the best mechanical improvements obtained when the layered architecture and the interfaces for these reinforcements are tailored. Here we propose a systematic modeling and design approach to tailor the architecture and properties of a multilayered bone graft material composed of a brittle ceramic and a more ductile material such as metals. More specifically, the volume fraction, moduli, number of layers, and the toughness of the interfaces between the different phases are tailored to maximize overall stiffness, strength, and energy absorption capacity. Our model predicts that when the stiffness of the reinforcement is higher (lower) than the ceramic, the beams with lower (higher) number of layers and higher (lower) volume fraction of metal are stronger. However, while the higher number of layers is always desired in terms of energy dissipation, the effects of other variables is more complex to understand and should thus be studied in conjunction with each other.

A multi-objective optimization design of industrial robot arms

This paper introduces a multi-objective design mechanism to minimize both the initial and running costs of industrial robot arms. The goal of the design problem is to decide the type of material and physical dimensions of the robot arm to withstand high loads at vulnerable locations using stress analysis. Additionally, it selects the material architecture for the robot links based on a vibration analysis to avoid robot failure at or close to the resonance frequency. Hence, a set of design equations based on stress analysis are developed using analytical approaches while the findings are supported by finite element simulations in ANSYS. These decide the type of material, cross-section area, factor of safety (FoS), and maximum deflection of the robot links in terms of the mass-loads. Moreover, the vibration analysis is conducted to enhance the dynamic characteristics of the robot arm. Therefore, the excitation frequency is modified by changing the mass and the robot segment-material to evade working at the natural frequency. Modal analysis is conducted using ANSYS to identify the fundamental frequencies and their modal shapes. Then, a material selection mechanism based on finite element analysis is considered to allow a safe frequency operation range for the robot arm. A customized robot arm structure that combines Magnesium and Aluminum alloy with highly improved FoS and minimizes the initial and operating costs is proposed. In addition to the body structure of the robot arm, the influence of the reducers and motors on the stiffness and vibration of the robot arm is presented. Finally, the motion of the robot arm is optimized using a Genetic Algorithm subject to a set of boundary conditions imposed by the desired mission. The effect of rotation angle value in the power consumption is presented. The coefficients of a developed angular displacement function are optimized to ensure minimum power consumption during the robot missions.

(Invited) Development of New Strategies for Bringing Photoelectrochemical Biosensing to the Point-of-Need

Photoelectrochemistry combines light excitation with electrochemical readout for lowering the bias voltage needed for performing electrochemical reactions. As a result, when used in biosensing, photoelectrochemical signal readout reduces the background signals, lowering the limit-of-detection of such biosensors. To enable photoelectrochemical (PEC) signal readout to be applied to point-of-need biosensing, we have taken a three tiered approach focused on improving the understanding of signal transduction in PEC Biosensing, developing label-free assays, and creating handheld readout platforms.In this work, we developed a system using DNA as a nano-ruler to control the distance between plasmonic nanoparticles and PEC electrodes. This system was used to rationally-design PEC material systems for signal-on biosensing. Using this materials architecture, we developed a signal-on biosensor without target labeling for detecting DNA hybridization. This assay uses sequential DNA hybridization to generate a PEC signal. First, the DNA target is captured on probe-modified photoelectrodes. This is followed by hybridization of the unbound probes with DNA strands modified with plasmonic labels. The plasmonic label modulates the PEC signal, increasing the measured PEC current at low target concentrations. To enable biosensing at the point-of-need, we also developed a handheld PEC reader. The integration of plasmonic nanoparticles with PEC electrodes, label-free DNA assays, and handheld PEC readout paves the way toward bringing point-of-need PEC Biosensing.

3R Electronics: Scalable Fabrication of Resilient, Repairable, and Recyclable Soft-Matter Electronics.

E-waste is rapidly turning into another man-made disaster. It is proposed that a paradigm shift toward a more sustainable future can be made through soft-matter electronics that are resilient, repairable if damaged, and recyclable (3R), provided that they achieve the same level of maturity as industrial electronics. This includes high-resolution patterning, multilayer implementation, microchip integration, and automated fabrication. Herein, a novel architecture of materials and methods for microchip-integrated condensed soft-matter 3R electronics is demonstrated. The 3R function is enabled by a biphasic liquid metal-based composite, a block copolymer with nonpermanent physical crosslinks, and an electrochemical technique for material recycling. In addition, an autonomous laser-patterning method for scalable circuit patterning with an exceptional resolution of <30µm in seconds is developed. The phase-shifting property of the BCPs is utilized for vapor-assisted "soldering" circuit repairing and recycling. The process is performed entirely at room temperature, thereby opening the door for a wide range of heat-sensitive and biodegradable polymers for the next generation of green electronics. The implementation and recycling of sophisticated skin-mounted patches with embedded sensors, electrodes, antennas, and microchips that build a digital fingerprint of the human electrophysiological signals is demonstrated by collecting mechanical, electrical, optical, and thermal data from the epidermis.

Untethered small-scale magnetic soft robot with programmable magnetization and integrated multifunctional modules.

Intelligent magnetic soft robots capable of programmable structural changes and multifunctionality modalities depend on material architectures and methods for controlling magnetization profiles. While some efforts have been made, there are still key challenges in achieving programmable magnetization profile and creating heterogeneous architectures. Here, we directly embed programmed magnetization patterns (magnetization modules) into the adhesive sticker layers to construct soft robots with programmable magnetization profiles and geometries and then integrate spatially distributed functional modules. Functional modules including temperature and ultraviolet light sensing particles, pH sensing sheets, oil sensing foams, positioning electronic component, circuit foils, and therapy patch films are integrated into soft robots. These test beds are used to explore multimodal robot locomotion and various applications related to environmental sensing and detection, circuit repairing, and gastric ulcer coating, respectively. This proposed approach to engineering modular soft material systems has the potential to expand the functionality, versatility, and adaptability of soft robots.

Self-supported nickel iron selenide@nickel cobalt boride core-shell nanosheets electrode for asymmetric supercapacitors

Optimizing the electrode structure and interface is a promising approach to achieve high energy density asymmetric supercapacitors. In this study, a core–shell heterostructure based on crystalline nickel iron selenide (NiSe2-Fe3Se4) and amorphous nickel cobalt boride (NiCoB) is for the first time in-situ fabricated on carbon cloth substrate though a hydrothermal approach, a selenization process, followed by a chemical precipitation method. In this well-defined hybrid material (denoted as NiSe2-Fe3Se4@NiCoB), the close combination of NiSe2-Fe3Se4 nanosheets core and NiCoB nanosheets shell results in a large specific surface area with rich open channels, and numerous crystalline/amorphous interfaces with regulated electronic structure. Owing to its unique hierarchical pore architecture and synergistic effect of dual battery-type materials, the resultant NiSe2-Fe3Se4@NiCoB electrode displays a specific capacity of 887.0C g−1 at 1 A g−1, wonderful rate retention (71.3% at 20 A g−1), and good cycling stability (86.4% after 5000cycles). Additionally, the assembled NiSe2-Fe3Se4@NiCoB//porous carbon asymmetric supercapacitor illustrates a remarkable energy density of 72.7 Wh kg−1 at 710.7 W kg−1, and exceptional cycling life with capacity retention of 91.1% over 20,000cycles.

Continuous ice-templating of macro-porous materials with uniformly ordered architecture

Ice-templating technique offers a viable means for constructing ordered macro-porous architectures in materials; nevertheless, it is generally limited by a low efficiency for fabrication, large difficulty for manipulation, along with the small dimension, and poor structural uniformity of ice-templated materials. Here, a new approach was exploited for continuous ice-templating of uniformly ordered macro-porous materials based on the establishment of a large, stable temperature gradient with specific bi-directional designs at the freezing front by descending the front toward the cooling medium to accommodate its upward growth. The freezing rate was markedly increased with the dimension of frozen body notably enlarged as compared with the case for conventional static ice-templating technique. The macro-porous architecture of materials, taking zirconia ceramics as an example, was made much finer and more uniform over the entire sample, and exhibited better ordering of alignment and enhanced inter-connectivity between lamellae. This led to an improvement in the compressive strength and its stability along the height direction for ice-templated materials than those made by the static ice-templating technique at a similar porosity. This study may facilitate the scale up of ice-templating techniques and promote the exploitation and application of new high-performance materials.

Emerging Polymer Materials in Trackable Endovascular Embolization and Cell Delivery: From Hype to Hope.

Minimally invasive endovascular embolization is a widely used clinical technique used for the occlusion of blood vessels to treat various diseases. Different occlusive agents ranging from gelatin foam to synthetic polymers such as poly(vinyl alcohol) (PVA) have been commercially used for embolization. However, these agents have some drawbacks, such as undesired toxicity and unintended and uncontrolled occlusion. To overcome these issues, several polymer-based embolic systems are under investigation including biocompatible and biodegradable microspheres, gelling liquid embolic with controlled occlusive features, and trackable microspheres with enhanced safety profiles. This review aims to summarize recent advances in current and emerging polymeric materials as embolization agents with varying material architectures. Furthermore, this review also explores the potential of combining injectable embolic agents and cell therapy to achieve more effective embolization with the promise of outstanding results in treating various devastating diseases. Finally, limitations and challenges in developing next-generation multifunctional embolic agents are discussed to promote advancement in this emerging field.

Biomaterial–Related Cell Microenvironment in Tissue Engineering and Regenerative Medicine

An appropriate cell microenvironment is key to tissue engineering and regenerative medicine. Revealing the factors that influence the cell microenvironment is a fundamental research topic in the fields of cell biology, biomaterials, tissue engineering, and regenerative medicine. The cell microenvironment consists of not only its surrounding cells and soluble factors, but also its extracellular matrix (ECM) or nearby external biomaterials in tissue engineering and regeneration. This review focuses on six aspects of biomaterial–related cell microenvironments: ① chemical composition of materials, ② material dimensions and architecture, ③ material–controlled cell geometry, ④ effects of material charges on cells, ⑤ matrix stiffness and biomechanical microenvironment, and ⑥ surface modification of materials. The present challenges in tissue engineering are also mentioned, and eight perspectives are predicted.

Nanoparticles constructed mesoporous coral-like Mn2O3 as high performance anode for lithium-ion batteries

As well established, the morphology and architecture of electrode materials greatly contribute to the electrochemical properties. Herein, a novel structure of mesoporous coral-like manganese (III) oxide (Mn2O3) is synthesized via a facile solvothermal method coupled with the carbonization under air. When fabricated as anode electrode for lithium-ion batteries (LIBs), the as-prepared Mn2O3 exhibits good electrochemical properties, showing a high discharge capacity of 1090.4 mAh g−1 at 0.1 A g−1, and excellent rate performance of 410.4 mAh g−1 at 2 A g−1. Furthermore, it maintains the reversible discharge capacity of 1045 mAh g−1 at 0.1 A g−1 after 380 cycles, and 755 mAh g−1 at 1 A g−1 after 450 cycles. The durable cycling stability and outstanding rate performance can be attributed to its unique 3D mesoporous structure, which is favorable for increasing active area and shortening Li+ diffusion distance.

Architecture effects for mode I trans-laminar fracture in over-height compact tension tests: Damage propagation and fracture response

An experimental study was carried out to investigate the effect of material architecture on the damage evolution in carbon/epoxy composites through Overheight Compact Tension (OCT) tests. Four representative lay-ups were designed for both the unidirectional (UD) and woven-based laminates. Interrupted tests were carried out to characterise specimen damage using X-Ray Micro-Computed Tomography. Digital Image Correlation and Acoustic Emission were used to support measurements. Damage analysis was carried out for each architecture to determine the sequence of damage mechanisms occurring and to assess the development of the Damage Zone (DZ). It was found that in woven architectures, damage is more localized to a narrow band around the artificial crack tip and tends to propagate in a more sudden manner. In UD laminates, extensive subcritical damage occurs prior to fibre fracture, a more prolonged load bearing capability was exhibited, and the developing DZ did not reach a plateau during loading.