Deformable Polymer Research Articles

All‐In‐One Photonic Crystals With Multi‐Stimuli‐Chromic, Color‐Recordable, Self‐Healable, and Adhesive Functions

AbstractFabricating photonic crystals (PCs) with dynamic multi‐stimuli‐responsive structural colors, recordable colors, and self‐healable properties is significant for their emerging applications, yet remains a big challenge. Here, an all‐in‐one multifunctional PC (MFPC) film with outstanding mechanochromic, thermochromic, solvatochromic, color/shape‐recordable, self‐healable, and adhesive functions is designed and prepared by simply non‐close‐assembling silica particles into the unique 2‐[[(Butylamino)carbonyl]oxy]ethyl acrylate (BCOEA) followed by photopolymerization. The success is mainly due to the rational combination of non‐close‐packing structures and BCOEA's characteristics, including its urethane groups with numerous sacrificial hydrogen bonds, temperature‐dependent refractive index, swellable and deformable polymer network, as well as low glass‐transition temperature. The MFPC's hue and color saturation can be reversibly and dynamically modulated by strain/pressure/solvents and temperature, respectively, thereby realizing visually and spectrally sensing these stimuli. More interestingly, the color‐responsiveness combined with other functions endows MFPCs with fascinating emerging applications, including multilayer optical filters, inkless printing, reconfigurable multicolor patterns, stretching‐based anti‐counterfeiting, etc. This work offers a new perspective for designing next‐generation smart photonic materials and will facilitate their all‐round applications.

Seeded Growth of Plasmonic Nanostructures in Deformable Polymer Confinement.

Plasmonic nanostructures exhibit optical properties highly related to their morphologies, enabling diverse applications in various areas such as biosensing, bioimaging, chemical detection, cancer therapy, and solar energy conversion. The expansive uses of these nanostructures necessitate robust and versatile synthesis methods suitable for large-scale production. Here, we introduce our recent efforts in developing a new strategy for controlling the seeded growth of plasmonic metal nanostructures, employing deformable polymer capsules to regulate the growth kinetics and the resulting particle morphology. Employing sol-gel-derived resorcinol-formaldehyde (RF) resin as a typical capsule material, we highlight its advanced features, including mechanical deformability and molecular permeability, that can be manipulated by tuning the capsule thickness and cross-linking degree. These features enable highly controllable confined seeded growth of plasmonic nanostructures. We reveal the significant role of the Ostwald ripening process of the seeds and the capsule structures in determining the morphological evolution of the plasmonic nanostructures. Moreover, we highlight some distinctive plasmonic nanostructures resulting from this unique synthesis strategy and their intriguing functionalities in various potential applications. Our discussion concludes with potential research directions to advance the development of the deformable polymer-confined seeded growth strategy into a general and robust synthesis platform for creating cutting-edge functional plasmonic nanostructures.

The Investigation of Broad-Spectrum Sealing Drilling Fluid Based on Horsfield Close-Packing Theory

Summary In shale gas drilling operations, oil-based drilling fluids have proved to be effective in addressing the issue of shale reservoir hydration expansion, serving as the primary working fluid for complex subsurface shale formations. However, the presence of shale laminations and the development of microfractures with varying widths require drilling fluids with excellent sealing capabilities. In this study, a comprehensive investigation was conducted to develop a drilling fluid system with broad-spectrum high-sealing performance. The porosity of bridging particles was determined by using the Archimedean drainage method. The bridging particle size and quantity at each level were meticulously designed through leveraging the Horsfield close-packing theory. The incorporation of deformable nanoscale polymer sealing materials further enhanced the sealing performance of the drilling fluid system. Additionally, hydrophobic nanoscale silica particles were introduced as coemulsifier to prepare Pickering emulsions, thereby improving emulsion stability and enhancing particle-size distribution for improved sealing. Through formulation optimization, a drilling fluid system with broad-spectrum, high-sealing performance capabilities was developed. The study revealed a reduction in porosity of closely packed bridging particles from 35.36% to 11.38%. The drilling fluid system exhibited a remarkable sealing efficiency of 99.2% for microfractures in the 1–10 μm range and 95.8% for microfractures in the 30–50 μm range. Furthermore, it demonstrated excellent sedimentation stability, with a sedimentation factor of less than 0.52 after 48 hours of static sedimentation at 150°C. The drilling fluid system also exhibited favorable rheological, lubrication, and inhibition properties, thus meeting the demands of field applications.

Photoinduced deformation behavior of poly(aryl ether)s with different azobenzene groups in the side chain.

Azobenzene-containing poly(aryl ether)s are a potential type of photoinduced deformable high-performance polymer. However, research on photoinduced deformation of azobenzene-containing poly(aryl ether)s focuses mainly on poly(aryl ether)s containing azobenzene groups in the main chain. In this paper, the photoinduced deformation of poly(aryl ether)s containing azobenzene groups in the side chain was studied for the first time. Two novel poly(aryl ether)s containing azobenzene groups in the side chain were synthesized, and their photoinduced isomerization behavior and photoinduced deformation behavior were studied. It could be seen that the match of the excitation luminescence to the maximum absorption peak of the azobenzene groups was more compatible, and the photoinduced motion of the polymers was faster. In addition, poly(aryl ether)s containing azobenzene groups in the side chain showed highly stable photoinduced deformation. The results of this work will be helpful for designing polymers which could be controlled by lasers of different wavelengths.

Selective near-infrared laser programming for shape-memory polymer–carbon nanotube composite material 4D printing

Abstract Light stimulation can realise the remote control of the deformation of the specific position of 4D printing structure. Shape-memory polymer–carbon nanotube (CNT) composite materials, with outstanding near-infrared photothermal conversion rate and shape-memory ability, is one type of the most popular light responsive smart materials. However, current studies focused on the photothermal effect and shape-memory applications of light-responsive shape-memory polymer composite (SMPC) sheet structures, and there is no research on the photothermal effect in the depth direction of light-responsive SMPC three-dimensional structures. Here, we prepared a UV curable, mechanically robust, and highly deformable shape-memory polymer (IBBA) as the matrix of light responsive SMPC. CNTs were added as photothermal conversion materials. We explore the photothermal effect of near-infrared laser on the surface and depth of IBBA–CNT composites cube. Shape-memory experiments show that different folded shapes can be obtained by selective near-infrared laser programming. Selective near-infrared laser programming three-dimensional movable type plate shows a programming application in depth direction of three-dimensional light-responsive intelligent structure. This research extends the application of near-infrared laser in 4D printing to the depth direction of intelligent structures, which will bring more complex and interesting 4D printing structures in the future.

Correlating structural changes in thermoresponsive hydrogels to the optical response of embedded plasmonic nanoparticles.

Stimuli-responsive microgels, composed of small beads with soft, deformable polymer networks swollen through a combination of synthetic control over the polymer and its interaction with water, form a versatile platform for development of multifunctional and biocompatible sensors. The interfacial structural variation of such materials at a nanometer length scale is essential to their function, but not yet fully comprehended. Here, we take advantage of the plasmonic response of a gold nanorod embedded in a thermoresponsive microgel (AuNR@PNIPMAm) to monitor structural changes in the hydrogel directly near the nanorod surface. By direct comparison of the plasmon response against measurements of the hydrogel structure from dynamic light scattering and nuclear magnetic resonance, we find that the microgel shell of batch-polymerized AuNR@PNIPMAm exhibits a heterogeneous volume phase transition reflected by different onset temperatures for changes in the hydrodyanmic radius (RH) and plasmon resonance, respectively. The new approach of contrasting plasmonic response (a measure of local surface hydrogel structure) with RH and relaxation times paves a new path to gain valuable insight for the design of plasmonic sensors based on stimuli-responsive hydrogels.

Preparation of Nanocellulose Whisker/Polyacrylamide/Xanthan Gum Double Network Conductive Hydrogels

Hydrogels’ poor mechanical and recovery characteristics inhibited their application as a plastic deformable three-dimensional cross-linked network polymer with electrical properties for intelligent sensing and human motion detection. Cellulose has also been added to the hydrogel to enhance its mechanical properties. The hydrogel has been enhanced this way, and the double-network hydrogel has superior recovery and mechanical capabilities. This study used the traditional free radical polymerization method to prepare double-mesh hydrogels, with polyacrylamide as the backbone network, xanthan gum double-helix structure, and Al3+ complex structure as the second cross-linked network, and endowing the hydrogels with good mechanical recovery and mechanical properties. Adding cellulose nanowafers (CNWs) improved the mechanical properties of the hydrogels. The hydrogel could detect body movements and various postures in the same environment. Moreover, the hydrogel has excellent recovery, mechanical properties, and tensile strain; the maximum fracture stress is 0.14 MPa, and the maximum strain is 707.1%. In addition, Fourier infrared spectroscopy (FTIR) of xanthan gum and Xanthan gum—Al3+ were analyzed, and thermogravimetric analysis (TGA) and LCR bridge were used to analyze the properties of hydrogels. Notably, hydrogel-based wearable sensors have been successfully constructed to detect human movement. Its mechanical properties, sensitivity, and wide range of properties make hydrogel a great potential for various applications in wearable sensors.

Improving nanoparticle superlattice stability with deformable polymer gels.

The self-assembly of colloidal nanoparticles into ordered superlattices typically uses dynamic interactions to govern particle crystallization, as these non-permanent bonds prevent the formation of kinetically trapped, disordered aggregates. However, while the use of reversible bonding is critical in the formation of highly ordered particle arrangements, dynamic interactions also inherently make the structures more prone to disassembly or disruption when subjected to different environmental stimuli. Thus, there is typically a trade-off between the ability to initially form an ordered colloidal material and the ability of that material to retain its order under different conditions. Here, we present a method for embedding colloidal nanoparticle superlattices into a polymer gel matrix. This encapsulation strategy physically prevents the nanoparticles from dissociating upon heating, drying, or the introduction of chemicals that would normally disrupt the lattice. However, the use of a gel as the embedding medium still permits further modification of the colloidal nanoparticle lattice by introducing stimuli that deform the gel network (as this deformation in turn alters the nanoparticle lattice structure in a predictable manner). Moreover, encapsulation of the lattice within a gel permits further stabilization into fully solid materials by removing the solvent from the gel or by replacing the solvent with a liquid monomer that can be photopolymerized. This embedding method therefore makes it possible to incorporate ordered colloidal arrays into a polymer matrix as either dynamic or static structures, expanding their potential for use in responsive materials.

Damage onset analysis of optimized shape memory polymer composites during programming into curved shapes

The unique shape memorizing ability of shape memory polymers (SMPs) and their fibre reinforced composites have offered the prospect of remedying challenging, unsolved engineering applications. Interestingly, research integrating deformable shape memory polymer composites (SMPCs) in prefabricated modular constructions, deployable outer space structures and other compactable structural components have emerged in the recent past. To ensure effective use in strength demanding applications, SMPC components must possess better mechanical properties. Increased fibre content in SMPCs will improve mechanical properties but can adversely affect the shape memory effect (SME), increasing the possibility of material damage when programming into curved shapes and bends. This will degrade the strength capacity of SMPCs in their applications. This paper details a complete study performed on this critical effect optimizing SMPC properties by means of a 3×3 Taguchi array. The study also provides an experimental framework demonstrating how these undesirable effects can be mitigated coupled with an ABAQUS finite element analysis (FEA) damage prediction strategy. Interestingly, the compression side of the specimen was found to be the most critical location prone to programming damage. In addition, a compressive stress level of 70 MPa was found to be the damage onset stress (σo) point for programming using FEA, and correlated with experimental results. The proposed experimental and FEA framework will enhance future SMPC component design, allowing researchers to predict the possibility of programming damage numerically, saving time and cost. We believe that these findings will aid researchers seeking to develop strong and efficient functional SMPCs for future engineering applications.

Self-healing, elastic and deformable novel composite phase change polymer based on thermoplastic elastomer SEBS for wearable devices

Self-healing, elastic and deformable novel composite phase change polymer based on thermoplastic elastomer SEBS for wearable devices

SEBS-Polymer-Modified Slag–Cement–Bentonite for Resilient Slurry Walls

In spite of the well-established design and construction approaches of slag–cement–bentonite slurry walls, the materials deteriorate inevitably in contaminated land. The development of effective materials which are sustainable, resilient and self-healing over the lifetime of slurry walls becomes essential. This study, for the first time, adopts a styrene–ethylene/butylene–styrene (SEBS) polymer to modify slag–cement–bentonite materials to enhance mechanical and self-healing performance. The results show that the increase in SEBS dosage results in significantly increased strain at failure, indicating the enhanced ductility thanks to the modification by the deformable polymer. The increased ductility is beneficial as the slurry wall could deform to a greater extent without cracks. After the permeation of liquid paraffin, the SEBS exposed on the crack surface swells and seals the crack, with the post-healing permeability only slightly higher than the undamaged values, which exhibits good self-healing performance. Scanning electron microscopy and micro-computed tomography analyses innovatively reveal the good bonding and homogeneous distribution of SEBS in slag–cement–bentonite. SEBS acts as a binder to protect the slag–cement–bentonite sample from disintegration, and the swollen SEBS particles effectively seal and heal the cracks. These results demonstrate that the SEBS-modified slag–cement–bentonite could provide slurry walls with resilient mechanical properties and enhanced self-healing performance.

DNA based microparticle tension sensors for measuring cell mechanics in non-planar geometries and for high throughput quantification

Mechanotransduction, the interplay between physical and chemical signaling, plays vital roles in many biological processes ranging from cell differentiation to metastasis. The state-of-the-art techniques to quantify cell forces employ deformable polymer films or molecular probes tethered to glass substrates. These types of flat substrates limit applications in investigating mechanotransduction on non-planar geometries where physiological activities such as phagocytosis and immunological synapse formation mostly occur.

Sliding Mechanism for Release of Superlight Objects from Micropatterned Adhesives

AbstractRobotic handling and transfer printing of micrometer‐sized superlight objects is a crucial technology in industrial fabrication. In contrast to the precise gripping with micropatterned adhesives, the reliable release of superlight objects with negligible weight is a great challenge. Slanted deformable polymer microstructures, with typical pillar cross‐section 150 µm × 50 µm, are introduced with various tilt angles that enable a reduction of adhesion by a switching ratio of up to 500. The experiments demonstrate that the release from a smooth surface involves sliding of the contact during compression and subsequent peeling of the object during retraction. The handling of a 0.5 mg perfluorinated polymer micro‐object with high accuracy in repeated pick‐and‐place cycles is demonstrated. Based on beam theory, the forces and moments acting at the tip of the microstructure are analyzed. As a result, an expression for the pull‐off force is proposed as a function of the sliding distance and a guide to an optimized design for these release structures is provided.

Design of an Affordable, Modular Implant Device for Soft Tissue Tension Assessment and Range of Motion Tracking During Total Hip Arthroplasty.

Background: In hip arthroplasties, surgeons rely on their experience to assess the stability and balance of hip tissues when fitting the implant to their patients. During the operation, surgeons use a modular, temporary set of implants to feel the tension in the surrounding soft tissues and adjust the implant configuration. This process is naturally subjective and therefore depends on the operator. Inexperienced surgeons undertaking hip arthroplasties are twice as likely to experience errors than their experienced colleagues, leading to dislocations, pain and discomfort for the patients. Methods: To address this issue, a new, 3DOF force measurement system was developed and integrated into the modular, trial implants that can quantify forces and movements intraoperatively in 3D. The prototypes were evaluated in three post-mortem human specimens (PMHSs), to provide surgeons with objective data to help determine the optimal implant fit and configuration. The devices comprise a deformable polymer material providing strain-based displacements measured with electromagnetic-based sensors and an inertial measurement unit (IMU) for motion data. Results: Device results show a relative accuracy of approx. 2% and a sensitivity of approx. 1%. PMHS results indicated that soft tissue forces on the hip joint peak in the order of ~100 N and trend with positions of the leg during range of motion (ROM) tests, although force patterns differ between each PMHS. Conclusion: By monitoring forces and force patterns of hip soft tissues, in combination with standardised ROM tests, the force patterns could shed a light on potential anomalies that can be addressed during surgery. Clinical and Translational Impact Statement: The development of an instrumented hip implant device for use during surgery knowledge will eventually allow us to develop a predictive model for soft tissue balancing, that can be used for pre- and intra-operative planning for each patient on a tailored and personalised basis. Ultimately, we hope that with this device, patients will benefit from a faster recovery, from a more-precisely fitted hip, and an improved quality of life.

Advanced Composite Retrofit of RC Columns and Frames with Prior Damages—Pseudodynamic Finite Element Analyses and Design Approaches

This study develops three-dimensional (3D) finite element (FE) models of composite retrofits in deficient reinforced concrete (RC) columns and frames. The aim is to investigate critical cases of RC columns with inadequate lap splices of bars or corroded steel reinforcements and the beneficial effects of external FRP jacketing to avoid their premature failure and structural collapse. Similarly, the RC-frame FE models explore the effects of an innovative intervention that includes an orthoblock brick infill wall and an advanced seismic joint made of highly deformable polymer at the boundary interface with the RC frame. The experimental validation of the technique in RC frames is presented in earlier published papers by the authors (as well as for a four-column structure), revealing the potential to extend the contribution of the infills at high displacement ductility levels of the frames, while exhibiting limited infill damages. The analytical results of the advanced FE models of RC columns and frames compare well with the available experimental results. Therefore, this study’s research extends to critical cases of FE models of RC frames with inadequate lap splices or corroded steel reinforcements, without or with brick wall infills with seismic joints. The advanced pseudodynamic analyses reveal that for different reinforcement detailing of RC columns, the effects of inadequate lap-spliced bars may be more detrimental in isolated RC columns than in RC frames. It seems that in RC frames, additional critical regions without lap splices are engaged and redistribution of damage is observed. The detrimental effects of corroded steel bars are somewhat greater in bare RC frames than in isolated RC columns, as all reinforcements in the frame are considered corroded. Further, all critical cases of RC frames with prior damages at risk of collapse may receive the innovative composite retrofit and achieve higher base shear load than the original RC frame without corroded or lap-spliced bars, at comparable top displacement ductility. Finally, the FE analyses are utilized to propose modified design equations for the shear strength and chord rotation in cases of failure of columns with deficiencies or prior damages in RC structures.

Electrical characterization of flexible hafnium oxide capacitors on deformable softening polymer substrate

In this work, we investigate the electrical performance and compatibility of low-temperature hafnium oxide (HfO2) thin-film capacitors on a novel softening polymer substrate. Metal-insulator-metal HfO2 capacitors were fabricated using HfO2 as the dielectric material, deposited at 100 °C by atomic layer deposition (ALD), and gold as the top and bottom contacts. The HfO2 capacitors were fabricated on silicon and on softening polymer substrates with a dielectric thickness of 50, 40, 30, and 20 nm. The electrical performance of the MIM capacitors was measured and compared to determine the quality and compatibility of the low-temperature HfO2 deposition with the silicon and polymer substrate. The dielectric constant varied from 12 to 17 as the HfO2 thickness increased from 20 to 50 nm. Moreover, the capacitance density and dielectric constant of the capacitors on the polymer substrate differed by 3.9% ± 2% and 3.4% ± 2% with respect to the silicon substrate. The polymer substrate devices also have a higher leakage current, which suggests a higher number of defects in the dielectric film relative to Si substrates. Finally, the devices on the polymer substrate were subjected to bending cycles (up to 105 cycles) with a 5 mm bending radius to evaluate the resilience of the HfO2 capacitors against mechanical stress. The results show that the fabrication of the HfO2 thin-film capacitors on the softening polymer substrate is achievable with high stability and mechanical resilience. Overall, this research could assist the production of flexible biomedical devices on softening polymer substrates.

DNA‐Based Microparticle Tension Sensors (μTS) for Measuring Cell Mechanics in Non‐planar Geometries and for High‐Throughput Quantification

AbstractMechanotransduction, the interplay between physical and chemical signaling, plays vital roles in many biological processes. The state‐of‐the‐art techniques to quantify cell forces employ deformable polymer films or molecular probes tethered to glass substrates. However, the applications of these assays in fundamental and clinical research are restricted by the planar geometry and low throughput of microscopy readout. Herein, we develop a DNA‐based microparticle tension sensor, which features a spherical surface and thus allows for investigation of mechanotransduction at curved interfaces. The micron‐scale of μTS enables flow cytometry readout, which is rapid and high throughput. We applied the method to map and measure T‐cell receptor forces and platelet integrin forces at 12 and 56 pN thresholds. Furthermore, we quantified the inhibition efficiency of two anti‐platelet drugs providing a proof‐of‐concept demonstration of μTS to screen drugs that modulate cellular mechanics.

DNA‐Based Microparticle Tension Sensors (μTS) for Measuring Cell Mechanics in Non‐planar Geometries and for High‐Throughput Quantification

AbstractMechanotransduction, the interplay between physical and chemical signaling, plays vital roles in many biological processes. The state‐of‐the‐art techniques to quantify cell forces employ deformable polymer films or molecular probes tethered to glass substrates. However, the applications of these assays in fundamental and clinical research are restricted by the planar geometry and low throughput of microscopy readout. Herein, we develop a DNA‐based microparticle tension sensor, which features a spherical surface and thus allows for investigation of mechanotransduction at curved interfaces. The micron‐scale of μTS enables flow cytometry readout, which is rapid and high throughput. We applied the method to map and measure T‐cell receptor forces and platelet integrin forces at 12 and 56 pN thresholds. Furthermore, we quantified the inhibition efficiency of two anti‐platelet drugs providing a proof‐of‐concept demonstration of μTS to screen drugs that modulate cellular mechanics.

Hybrid magnetic elastomers prepared on the basis of a SIEL-grade resin and their magnetic and rheological properties

Abstract Hybrid magnetic elastomers (HMEs) belong to a novel type of magnetocontrollable elastic materials capable of demonstrating extensive variations of their parameters under the influence of magnetic fields. Like all cognate materials, HMEs are based on deformable polymer filled with a mixed or modified powder. The complex of properties possessed by the composite is a reflection of interactions occurring between the polymer matrix and the particles also participating in interactions among themselves. For example, introduction of magnetically hard components into the formula results in the origination of a number of significantly different behavioral features entirely unknown to magnetorheological composites of the classic type. Optical observation of samples based on magnetically hard filler gave the opportunity to establish that initial magnetization imparts magnetic moments to initially unmagnetized grains, as a result of which chain-like structures continue to be a feature of the material even after external field removal. In addition, applying a reverse field causes them to turn into the polymer as they rearrange into new ring-like structures. Exploration of the relationship between the rheological properties and magnetic field conducted on a rheometer using vibrational mechanical analysis showed an increase of the relative elastic modulus by more than two orders of magnitude or by 3.8 MPa, whereas the loss factor exhibited steady growth with the field up to a value of 0.7 being significantly higher than that demonstrated by elastomers with no magnetically hard particles. At the same time, measuring the electroconductivity of elastomers filled with a nickel-electroplated carbonyl iron powder made it possible to observe that such composites demonstrated an increase of variation of the resistivity of the composite influenced by magnetic field in comparison to elastomers containing untreated iron particles. The studies conducted indicate that this material exhibits both magnetorheological and magnetoresistive effect and does indeed have the potential for use in various types of devices.

Design and implementation of dual pressure variation chambers for bone conduction microphone

This study presents a bone conduction microphone (BCM) to detect the variation of air pressure resulted from the skull vibration. The presented BCM consists of a commercial MEMS microphone, the sensing circuits, the bulk metal, the deformable polymer diaphragm, and two printed circuit board (PCB) covers. In this design, two chambers and a vibrating spring-mass structure are hermetic sealed by two PCB covers. As the spring-mass structure vibrates, the pressure of one chamber will increase and that of another will decrease. Thus, the vibration could introduce a higher pressure load as well as a larger sensing signal for the BCM. In application, the device with the dimensions of 3.5 × 2.65 × 1.48 mm3 is implemented. Measurements show the device has a sensitivity of −38.8 dBV, THD < 0.48% at 1 kHz with 1 g excitation, and ±5 dB bandwidth for 100 Hz∼6.7 kHz. Frequency responses of different samples show good repeatability. Furthermore, air leakage effect and crosstalk of the skull vibration sensing module have also been investigated in this paper. The results demonstrate the feasibility of the presented BCM.