Specific External Stimuli Research Articles

A homogenization model for multiple buckling response of axially compressed cellular cylindrical shells

Pattern transformation in periodic cellular structures induces significant property changes under specific external stimuli, resulting in unusual mechanical behavior. This paper proposes an efficient homogenization method for predicting multiple buckling responses of cellular cylindrical shells composed of such pattern-transformation metamaterial. FEM simulations reveal four distinct buckling modes and three kinds of post-buckling processes, achieved through controlled adjustments in the ratio of cylindrical shell thickness to the radius and structural porosity. An efficient homogenization method with the local buckling in the cellular cylindrical shell modeled as an equivalent plasticity in the homogenized shell enables us to predict the critical buckling stress and the post-buckling morphology in good agreement with FEM simulations, analytical analysis, and experiments. The derived solution for the critical buckling load of the cellular cylindrical shells provides practical insights for designing and applying such cylindrical cellular structures.

Engineering Stimuli-Responsive Materials for Precision Medicine.

Over the past decade, precision medicine has garnered increasing attention, making significant strides in discovering new therapeutic drugs and mechanisms, resulting in notable achievements in symptom alleviation, pain reduction, and extended survival rates. However, the limited target specificity of primary drugs and inter-individual differences have often necessitated high-dosage strategies, leading to challenges such as restricted deep tissue penetration rates and systemic side effects. Material science advancements present a promising avenue for these issues. By leveraging the distinct internal features of diseased regions and the application of specific external stimuli, responsive materials can be tailored to achieve targeted delivery, controllable release, and specific biochemical reactions. This review aims to highlight the latest advancements in stimuli-responsive materials and their potential in precision medicine. Initially, we introduce disease-related internal stimuli and capable external stimuli, elucidating the reaction principles of responsive functional groups. Subsequently, we provide a detailed analysis of representative pre-clinical achievements of stimuli responsive materials across various clinical applications, including enhancements in the treatment of cancers, injury diseases, inflammatory diseases, infection diseases, and high-throughput microfluidic biosensors. Finally, we discuss some clinical challenges, such as off-target effects, long-term impacts of nano-materials, potential ethical concerns, and offer insights into future perspectives of stimuli-responsive materials.

Structural Rigidification Strategy Based on Self-Assembly Enabled Reversible Excited-State Conversion of Iridium(III) Complexes for Multiple-Stimulus-Responsive Data Encryption.

Stimulus-responsive chromic materials exhibit color-switching properties under specific external stimuli and have been widely used in various fields. Transition-metal complexes show great potential applications as promising candidates for stimulus-responsive chromic materials, as their excited states not only depend on the chemical composition but are also affected by the intermolecular stacking modes. Owing to the intrinsic difficulty in the ordered stacking of the octahedral configuration, changing the stacking modes of iridium(III) complexes for multiple-stimulus responsiveness remains a significant challenge. In this work, we propose a structural rigidification strategy based on self-assembly to reversibly regulate the excited states of iridium(III) complexes, therefore achieving color switch under different stimulus conditions. We prepare cationic iridium(III) complexes by using tetrakis(perfluorophenyl)-borate ([B(PhF5)4]-) as the counterion, whose matching tetrahedral configuration and electron-deficient aromaticity enables polar-π interaction with the octahedral iridium(III) cations, inducing self-assembly to form structural rigidification. The structural rigidity restricts the large conformational changes of the metal-to-ligand charge transfer (3MLCT) excited state, and facilitates the conversion from the 3MLCT to the ligand-center (3LC) excited state in aggregated states. The excited-state conversion results in a 54 nm blue shift (from yellow to sky blue) in the photoluminescence spectra. As a result, we report a series of cationic iridium(III) complexes with different responses to low temperature, vapor fuming, and mechanical force, therefore achieving multiple-stimulus-responsive data encryption. Our work provides a novel strategy to achieve ordered stacking of octahedral complexes, shows a deeper understanding of the photophysical processes of transition-metal complexes, and offers a new perspective to develop multiple-stimulus-responsive chromic materials.

Oligo-Adenine Derived Secondary Nucleic Acid Frameworks: From Structural Characteristics to Applications.

Oligo-adenine (polyA) is primarily known for its critical role in mRNA stability, translational status, and gene regulation. Beyond its biological functions, extensive research has unveiled the diverse applications of polyA. In response to environmental stimuli, single polyA strands undergo distinctive structural transitions into diverse secondary configurations, which are reversible upon the introduction of appropriate counter-triggers. In this review, we systematically summarize recent advances of noncanonical structures derived from polyA, including A-motif duplex, A-cyanuric acid triplex, A-coralyne-A duplex, and T ⋅ A-T triplex. The structural characteristics and mechanisms underlying these conformations under specific external stimuli are addressed, followed by examples of their applications in stimuli-responsive DNA hydrogels, supramolecular fibre assembly, molecular electronics and switches, biosensing and bioengineering, payloads encapsulation and release, and others. A detailed comparison of these polyA-derived noncanonical structures is provided, highlighting their distinctive features. Furthermore, by integrating their stimuli-responsiveness and conformational characteristics, advanced material development, such as pH-cascaded DNA hydrogels and supramolecular fibres exhibiting dynamic structural transitions adapting environmental cues, are introduced. An outlook for future developments is also discussed. These polyA derived, stimuli-responsive, noncanonical structures enrich the arsenal of DNA "toolbox", offering dynamic DNA frameworks for diverse future applications.

Influence of Infill Patterns on the Shape Memory Effect of Cold-Programmed Additively Manufactured PLA.

In four-dimensional additive manufacturing (4DAM), specific external stimuli are applied in conjunction with additive manufacturing technologies. This combination allows the development of tailored stimuli-responsive properties in various materials, structures, or components. For shape-changing functionalities, the programming step plays a crucial role in recovery after exposure to a stimulus. Furthermore, precise tuning of the 4DAM process parameters is essential to achieve shape-change specifications. Within this context, this study investigated how the structural arrangement of infill patterns (criss-cross and concentric) affects the shape memory effect (SME) of compression cold-programmed PLA under a thermal stimulus. The stress-strain curves reveal a higher yield stress for the criss-cross infill pattern. Interestingly, the shape recovery ratio shows a similar trend across both patterns at different displacements with shallower slopes compared to a higher shape fixity ratio. This suggests that the infill pattern primarily affects the mechanical strength (yield stress) and not the recovery. Finally, the recovery force increases proportionally with displacement. These findings suggest a consistent SME under the explored interval (15-45% compression) despite the infill pattern; however, the variations in the mechanical properties shown by the stress-strain curves appear more pronounced, particularly the yield stress.

Novel 4D-printing pellets with infrared-light responsive shape memory effect

Four-dimensional (4D)-printing technology is attractive to researchers since it combines 3D printing with smart materials to produce 3D structures with various shapes and change shapes under specific external stimuli. Herein, novel shape memory polymer (SMP) pellets with infrared-light responsive shape memory effect were developed for 4D printing applications. The structures, properties, and infrared-light responsive shape memory performances of the resulting (SMP) pellets were thoroughly investigated. The results showed PDA/SMP pellets prepared by direct loading of polydopamine (PDA) particles on SMP pellets displayed less influence on the basic properties of SMP while fluidity was enhanced. The obtained PDA/SMP pellets employed as feed materials for particle 3D printers revealed good thermal-induced shape memory performance and photo-responsive shape memory performance in printed 3D structures. Under infrared-light irradiation, the curled shape recovered to straight splines within 60 s due to the strong absorption and good photo-thermal conversion of the loaded PDA nanoparticles under infrared light. Overall, the as-prepared PDA/SMP pellets look promising for use in biomedical fields and smart devices, as well as remote control deformation with 4D printing technology.

Physico-chemical features and functional relevance of tomato rhomboid proteases

In plants, regulated intramembrane proteolysis (RIP) is crucial for proper growth, development, and stress management. Rhomboid proteases (RPs) residing in the membrane play a vital role in orchestrating RIP. Although RPs can be found in most sequenced genomes, tomato rhomboids (SlRPs) have not yet been studied. Using alternative and comprehensive strategies, we found ten SlRPs encoded in the tomato genome. These SlRPs possess signature motifs and transmembrane domains, showing structural similarity to other members of the RP family. Also, SlRPs are genetically related to other known RPs of the Solanaceae family. Seven of the SlRPs retain serine-histidine catalytic dyads, making them proteolytically active, while three iRhoms lack the dyad and other structural motifs. Although SlRPs could have functional redundancy, their distribution and expression pattern indicate tissue specificity and responsiveness to specific external stimuli. The presence of development and stress-response-related cis-elements in the promoters of SlRPs supports this view. Furthermore, our strategically designed substrate-reporter assay shows that SlRPs have proteolytic activity similar to that of known RPs. This study provides a detailed understanding of all SlRPs and their physico-chemical features, shedding light on their involvement in physiological processes.

Analysing the shape memory behaviour of MWCNT-enhanced nanocomposites: a comparative study between experimental and finite element analysis

Shape memory polymers (SMPs) are known for their unique ability to withstand large deformations and revert to their original shape under specific external stimuli. However, their broader application in biomedical and structural applications is restricted by limited mechanical and thermal properties. Introducing multi-walled carbon nanotubes (MWCNTs) into SMPs has proven to significantly enhance these characteristics without affecting their inherent shape memory features. This study investigates shape memory nanocomposites (SMNCs) through dynamic and thermogravimetric analyses, along with tensile, flexural, and shape memory testing, and explores fracture interfaces using scanning electron microscopy. Findings indicate optimal shape memory, thermal, and mechanical properties with 0.6 wt% MWCNT content, showcasing a shape recovery ratio of 93.11%, storage modulus of 4127.63 MPa, tensile strength of 55 MPa, and flexural strength of 107.94 MPa. Moreover, incorporating MWCNTs into epoxy demonstrated a reduction in recovery times by up to 50% at 0.6 wt% concentration. Despite a slight decrease in shape fixity ratio from 98.77% to 92.11%, shape recoverability remained nearly consistent across all samples. The study also introduces a novel finite element (FE) method in ABAQUS for modeling the thermomechanical behavior of SMNCs, incorporating viscoelasticity, validated by matching experimental results with FE simulations, highlighting its accuracy and practical applicability in engineering.

Exploring GPCR conformational dynamics using single-molecule fluorescence

G protein-coupled receptors (GPCRs) are membrane proteins that transmit specific external stimuli into cells by changing their conformation. This conformational change allows them to couple and activate G-proteins to initiate signal transduction. A critical challenge in studying and inferring these structural dynamics arises from the complexity of the cellular environment, including the presence of various endogenous factors. Due to the recent advances in cell-expression systems, membrane-protein purification techniques, and labeling approaches, it is now possible to study the structural dynamics of GPCRs at a single-molecule level both in vitro and in live cells. In this review, we discuss state-of-the-art techniques and strategies for expressing, purifying, and labeling GPCRs in the context of single-molecule research. We also highlight four recent studies that demonstrate the applications of single-molecule microscopy in revealing the dynamics of GPCRs. These techniques are also useful as complementary methods to verify the results obtained from other structural biology tools like cryo-electron microscopy and x-ray crystallography.

Investigating the effect of pH on the swelling process, mechanical and thermal attributes of polyacrylamide hydrogel structure: A molecular dynamics study

Stimuli-responsive hydrogels are a class of hydrogels that undergo reversible changes in their physical or chemical properties in response to specific external stimuli. The pH is a critical environmental stimulus for stimuli-responsive hydrogels. When the pH of the surrounding environment changes, it can lead to significant alterations in the properties of the hydrogel, such as swelling behavior, mechanical strength, etc. So, understanding how pH affects the swelling behavior and mechanical properties of these hydrogels is crucial to optimize their performance in biomedical applications. Therefore, in the present study, the effect of pH on the swelling process, mechanical and thermal attributes of polyacrylamide hydrogel structure were studied using molecular dynamics simulation and LAMMPS software. The results reveal that as the pH increased from 2 to 11, the structural volume increased from 342,583 to Å3. The increase in the volume of the structure was in terms of the increase in atomic fluctuations by increasing the pH, and consequently, it led to more swelling. The mechanical properties show that the ultimate strength and Young’s modulus of the sample increase from 0.0298 to 0.0007 to 0.0359 and 0.0012 MPa, respectively. The reason for the increase in these parameters was that by increasing the pH, the attraction force among different components of the PAM hydrogel structure increased. This issue led to an increase in the stability of the nanostructure. Finally, the thermal properties showed that thermal conductivity increased from 0.51 to 0.62 W/m K by increasing pH to 11. The findings may lead to the development of pH-responsive hydrogels with enhanced properties, offering more effective and tailored solutions for biomedical applications.

Magnetic-assisted sequential templated self-assembly of hybrid colloid nanoparticle systems.

The assembly of hybrid nanoparticles is a pioneering route for developing nanoscale functional devices, enabling breakthroughs in various fields, including electronics, photonics, energy, sensing, and biomedical applications. Here, we focus on the templated assembly of nano-sized colloidal systems using a combination of silica-coated superparamagnetic beads (MBs) and polymer-coated gold nanoparticles (AuNPs) or silver nanoparticles (AgNPs). These hybrid nanoparticles introduce new functionalities that allow them to be used as nanomachines with numerous possible applications. Using sequential capillarity-assisted particle assembly (sCAPA), we deposit MBs with activating nano-transducers made of PNIPAm@AuNPs, which respond to specific external stimuli such as temperature variations. We deposit MBs with surface-enhanced Raman scattering (SERS) AgNPs, which have the ability to detect molecules at low concentrations. A key achievement of our study is demonstrating the successful CAPA assembly of nanoparticles with ingenious surface chemistry and retrieving these assembled structures from nanotraps in a liquid medium. This ability highlights the potential of hybrid colloids in precisely targeted drug delivery systems and highly effective mobile sensors. It represents a significant leap forward in using nanotechnology to create more complex and responsive nanoscale assemblies.

Self-Defensive Antimicrobial Shape Memory Polyurethanes with Honey-Based Compounds.

Infection treatment plays a crucial role in aiding the body in wound healing. To that end, we developed a library of antimicrobial polymers based on segmented shape memory polyurethanes with nondrug-based antimicrobials (i.e., honey-based phenolic acids (PAs)) using both chemical and physical incorporation approaches. The antimicrobial shape memory polymers (SMPs) have high transition temperatures (>55 °C) to enable maintenance of temporary, programmed shapes in physiological conditions unless a specific external stimulus is present. Polymers showed tunable mechanical and shape memory properties by changing the ratio, chemistry, and incorporation method of PAs. Cytocompatible (∼100% cell viability) synthesized polymers inhibited growth rates of Staphylococcus aureus (∼100% with physically incorporated PAs and >80% with chemically incorporated PAs) and Escherichia coli (∼100% for samples with cinnamic acid (physical and chemical)). Crystal violet assays showed that all formulations inhibit biofilm formation in surrounding solutions, and chemically incorporated samples showed surface antibiofilm properties with S. aureus. Molecular dynamics simulations confirm that PAs have higher levels of interactions with S. aureus cell membranes than E. coli. Long-term antimicrobial properties were measured after storage of the sample in aqueous conditions; the polymers retained their antimicrobial properties against E. coli after up to 20 days. As a proof of concept, magnetic particles were incorporated into the polymer to trigger user-defined shape recovery by applying an external magnetic field. Shape recovery disrupted preformed S. aureus biofilms on polymer surfaces. This antimicrobial biomaterial platform could enable user- or environmentally controlled shape change and/or antimicrobial release to enhance infection treatment efforts.

From touch to tingles: Assessing ASMR triggers and their consistency over time with the ASMR Trigger Checklist (ATC)

Autonomous Sensory Meridian Response (ASMR) is a term describing a complex sensory-perceptual phenomena characterised by relaxing and pleasurable scalp tingling sensations. A central defining feature of ASMR is that the sensation is elicited by a core set of stimuli or so-called “triggers”. The idea that ASMR is triggered by specific external stimuli is frequently invoked in conceptual definitions of ASMR and implicit in its operationalisation as a trait and state; however, it is rarely explicitly measured. In this paper, we present the 37-item ASMR Trigger Checklist (ATC), a new tool to assist researchers in ASMR-responder identification and to capture individual differences in the number and intensity of ASMR triggers across auditory (vocal, non-vocal), visual, and tactile/interpersonal stimulus domains. The ATC is related to existing measures of trait-ASMR that tap into the sensations and phenomenological aspects of the experience (ASMR-15 and AEQ) and provides a complementary assessment for researchers interested in common ASMR elicitors. Importantly, the ATC addresses concerns regarding the over-reliance of audio-visual ASMR stimuli in existing measures and conceptualisations of ASMR by emphasising tactile and interpersonal stimuli. Physical touch to the body was both the most endorsed (98%) and intense (average 5/6) ASMR trigger. 24 of the 37 ATC items were endorsed by 75% of the sample and might therefore be considered prototypical ASMR triggers. The ATC has appropriate convergent validity through its association with other individual differences known to be related to ASMR (e.g., absorption, openness to experience, aesthetic experiences). Re-administration of the ATC after 5 months showed high consistency in reports of ASMR triggers with 84% of endorsements remaining the same over time. We hope that the ATC will prove a useful tool for researchers in participant selection and recruitment as well as for measuring individual differences within the ASMR population.

Molecular design on dual stimuli-responsive azobenzene-containing ionic complexes toward self-healing materials under photoirradiation or humid condition at room temperature

Self-healing materials working at room temperature are attractive in the field of materials chemistry. Compared to those requiring one specific external stimulus, one smart material that can launch the self-healing process under multiple stimuli would accommodate more various working conditions. In this work, a double-chain azobenzene-containing surfactant AZO with good molecular flexibility and hydrophilicity is designed for developing self-healing materials with dual responses to light and humidity. By mixing AZO and surfactants containing linear aliphatic chains, the resulted composites gain crystal-to-isotropic liquid phase change ability under the trigger of either light or humidity, thanks to the formation of sufficient free volume for AZO molecules. This leads to the light-/humidity-induced self-healing materials at room temperature. Meanwhile, the composite of AZO and double-chain surfactant has been proved with better responsive sensitivity to light and humidity by forming a homogeneous molecular distribution. This study provides a new designing strategy for gaining dual self-healing materials working via an athermal way, promoting the development of smart materials with multiple stimuli-responsive property.

Stimuli‐responsive photonic actuators for integrated biomimetic and intelligent systems

AbstractPhotonic actuators, serving as an emerging kind of intelligent stimuli‐responsive material, can exhibit the abilities to change their structural colors/fluorescence and shapes under specific external stimuli, which have demonstrated essential applications in the fields of intelligent soft robotics, sensors, bionics, information storage, anti‐counterfeiting, and energy harvesting. In this review, we reported the state‐of‐the‐art research progress of stimuli‐responsive photonic actuators classified on the basis of the material type and focusing on the actuation mechanisms, design principles, and processing techniques. We also broadly summarized the relative applications of photonic actuators in bionics, intelligent robots, sensors, and so on. Finally, a vision for the challenges in the area and future promising directions of stimuli‐responsive photonic actuators is presented.

Micronutrients and Plant Food Bioactive Compounds Against Obesity Related Diseases.

The adipose tissue influences by an extensive crosstalk at the local and systemic level the energy balance, including storage, mobilization, and utilization at both central and peripheral sites in response to specific external stimuli or metabolic changes. The balance between energy intake and expenditure is a delicate equilibrium among multifactorial aspects ranging from genetic to environmental influences. The evidence from several recently published papers dealing with the topic of the beneficial health effects of micronutrient and plant bioactive compounds on obesity and/or comorbidities has been reported in this paper. MEDLINE database (PubMed database; National Library of Medicine, Bethesda, MD and Google Scholar) was searched by combining the terms of specific micronutrients and/or plant bioactive compounds associated with obesity and related comorbidities. All English language manuscripts published between 2005 and 2021 in the MEDLINE database were searched, selected, and reviewed here. People do not consume single food or ingredients but global composite diets; thus, the evaluation of mechanisms of action, efficacy and safety of vitamins and mineral and natural bioactive compounds is still a challenge in research on nutrition and food supplements.

Conceptual Analysis on Severe Plastic Deformation Processes of Shape Memory Alloys: Mechanical Properties and Microstructure Characterization

Shape memory alloys (SMAs) are types of materials that can restore their original shape upon severe or quasi-plastic deformation, being exposed to specific external stimuli, including heating, electric current, magnetic field, etc. They are a category of functional materials that provides superelasticity as a significant material property. The roots of this unintentional discovery were in the 20th century, and later it attracted the attention of various industries, including aerospace, medical, mechanical, manufacturing industries, etc. Later developments mainly focused on improving the properties of these materials. One of the ways in which this is achieved is the application of intensive plastic strains on SMAs through severe plastic deformation (SPD) methods, leading to extreme grain refinement. Superelasticity is a key characteristic of SMAs and is known as the capacity of a polycrystalline material to display extremely high elongations before failure, in a typically isotropic way, with an approximate strain rate of 0.5. Utilization of SPD techniques can also affect and lead to superior superelasticity responses in SMAs. Several SPD methodologies have been introduced over the decades, to produce ultrafine-grained and even nanostructured materials, including constrained groove pressing, equal-channel angular pressing, high-speed high-pressure torsion, accumulative roll bonding, etc. This paper aims to present a clear view of the mechanical properties and microstructure evolution of shape memory alloys after processing by some SPD methods, and to show that SPD methods can be a great option for developing SMAs and expanding their industrial and technological applications.

Molecular modulation spectroscopy: Individual molecular spectra accurately deconvoluted from interfering systems via orthogonal reactions

To accurately analyze strongly interfering species in a system, current analytical methodologies separate and purify each chemical species before individual characterization. Herein, we introduce a new concept to analyze individual molecules in interfering systems, provided the target molecules offer orthogonal modulation by external stimuli. Using optical and thermal modulation simultaneously, we demonstrated that two interfering molecules, one photoswitching while the other thermal switching, could be accurately identified in a mixture because they underwent orthogonal chemical reactions when stimulated by both light and heat. The broad impact of the newly developed molecular modulation spectroscopy (MMS) is significant because molecular species in interfering systems can be analyzed directly in situ and in detail without time-consuming chemical separation and purification. Conversely, such stimuli-induced switching molecules can function as molecular sensors, gauging the presence and magnitude of that specific external stimulus.

Nanotechnology Transition Roadmap toward Multifunctional Stimuli-Responsive Face Masks.

In recent times, the use of personal protective equipment, such as face masks or respirators, is becoming more and more critically important because of common pollution; furthermore, face masks have become a necessary element in the global fight against the COVID-19 pandemic. For this reason, the main mission of scientists has become the development of face masks with exceptional properties that will enhance their performance. The versatility of electrospun polymer nanofibers has determined their suitability as a material for constructing "smart" filter media. This paper provides an overview of the research carried out on nanofibrous filters obtained by electrospinning. The progressive development of the next generation of face masks whose unique properties can be activated in response to a specific external stimulus is highlighted. Thanks to additional components incorporated into the fiber structure, filters can, for example, acquire antibacterial or antiviral properties, self-sterilize the structure, and store the energy generated by users. Despite the discovery of several fascinating possibilities, some of them remain unexplored. Stimuli-responsive filters have the potential to become products of large-scale availability and great importance to society as a whole.

(Digital Presentation) 4D Printing of Inter-Crosslinking Network Structure Gel with Hinge Structure

4D printing [1] is a new interdisciplinary research area made possible by the merger of scientific developments in additive manufacturing and smart materials [2]. It is a technology that allows 3D printed objects to be deformed over time by applying specific external stimuli [3] and is currently attracting attention as a technology to program biological-like movements into the internal structure of 3D printed objects. In previous research, the movement and deformation of the model has been controlled by devising the shape of the structure, such as a bilayer structure consisting of two materials with different physical properties [4]. However, it is difficult to realize the deformation in different directions simultaneously. The purpose of this research is to develop a 4D printing technology that can simultaneously deform each part of the same object in any direction.To develop a 4D printing technology that can simultaneously deform each part of the same object in any direction, we analyzed the principle of 4D printing by swelling. We measured the swelling rate, swelling speed, compression test, and deformation amount in order to investigate the effects of material and laser irradiation frequency. As a result, it was confirmed that the swelling rate and swelling velocity increased when the amount of the initiator, TPO, was increased from a specific laser irradiation frequency. It was also confirmed that the Young's modulus increased with the increase in the number of laser irradiation. Finally, based on these results, the deformation was measured by varying the amount of initiator and the number of laser irradiations, and it was confirmed that the deformation increased with increasing the amount of initiator and the specific number of irradiations.References Skylar Tibbits, " 4D printing: multi-material shape change", Archit. Des. 84, 116–121 (2014). https://doi.org/10.1002/ad.1710MD Nahin Islam Shiblee, Kumkum Ahmed, Ajit Khosla, Masaru Kawakami, Hidemitsu Furukawa, "3D printing of shape memory hydrogels with tunable mechanical properties." Soft Matter 2018, 14, 7809. https://doi.org/10.1039/C8SM01156GKumkum Ahmed, MD Nahin Islam Shiblee, Ajit Khosla, Larry Nagahara, Thomas Thundat, and Hidemitsu Furukawa. "Recent progresses in 4D printing of gel materials." Journal of The Electrochemical Society 167, no. 3 (2020): 037563. https://doi.org/10.1149/1945-7111/ab6e60MD Nahin Islam Shiblee, Kumkum Ahmed, Masaru Kawakami, Hidemitsu Furukawa, "4D Printing of Shape-Memory Hydrogels for Soft-Robotic Functions." Adv. Mater. Technol. 2019, 4, 1900071. https://doi.org/10.1002/admt.201900071