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Labs-on-chips are promising candidates for the realization of chemical information systems, where data are embodied in the form of chemical concentrations. In this paper we present the concept of microchemomechanical systems, a lab-on-a-chip technology based on intrinsically active components. The active components are chemical transistors fabricated from phase-changeable polymers that provide a direct feedback mechanism. Therefore this microfluidic platform facilitates the realization of logic operations, if-then structures and the sampling of chemical signals. In analogy with electronic von Neumann CPUs, control and execution unit are integrated on a single chip. Due to the intrinsic activity of the chemical transistors and their small size, microchemomechanical systems are highly suitable for large-scale integration.

The non-homogeneity and complexity of micro network distribution of hydrogel matrices prepared with two scleroglucan biopolymers obtained with different fermentation times were analyzed using environmental scanning electron microscopy (ESEM) and dynamic rheology.

ESEM images were processed with the tools of multifractal theory using the box-counting method in order to obtain the gels multifractal spectra. Dynamic rheological measurements indicate that both polymeric networks correspond to physical gels that exhibit a solid like behavior. These results suggest the existence of a relationship between the fermentation time used in the polymer production, the degree of self-similarity and the rigidity of the scleroglucan gel structure.

In classical surface plasmon-based optical biosensors, a surface plasmon mode is resonantly excited on the metallic sensor surface to probe any analyte-binding-induced refractive index changes. The field of the surface plasmon mode evanescently decays from the metal into an adjacent analyte solution with a typical penetration depth of 200 nm. In order to maximize the sensitivity of SPR biosensors, interfacial polymer architectures with binding site densities that considerably exceed planar arrangements through the use of three-dimensional microstructures were introduced. For biosensors based on surface plasmon fluorescence spectroscopy, this type of matrix offers the additional advantage of preventing fluorescence quenching, which is caused by the proximity of the chromophore label to the acceptor states of the noble metal. By means of probing the binding events with long range surface plasmon modes of which field extend much farther into the analyte solution (up to the micrometer range), substantially thicker sensor matrix layers can be used. Into such matrices larger amounts of ligands can be loaded, which enables one to increase the surface density of binding sites and thus to enhance the sensitivity of the biosensor. We present results which show that functionalized hydrogels are very well suited for meeting the demands of these novel biosensor platforms.

Singapore-Based AAMG To Lead Project Management to Establish Zhuhai-Singapore Life Science Park which will offer World-Class Health & Medical Services in Southern China

Boston Therapeutics’ Hong Kong Affiliate Advance Pharmaceutical’s BTI-320 Clinical Trial Reaches Mid-Point by Enrolling 30 Patients at the Chinese University of Hong Kong

China Green Agriculture’s Online Sales Platform Begins Operations

Mixed-species Flocks Important for Biodiversity Conservation in Tropics

LICP Designs Hydrogels with Extraordinary Mechanical Properties and Good Self-recovery

AstraZeneca and Ironwood Report Positive Top-Line Data from Phase III IBS-C Trial Designed to Support Linaclotide Approval in China

GE to Build Wind Education Centre in China

Chinese Scientists Edit Genes to Produce Artificial Sperm Capable of Creating “army of half-cloned mice”

Brain ‘switch’ can Turn off Drug Addiction, Say Shanghai Scientists

Mindray Medical Completes Acquisition of Wuhan Dragonbio

China Nepstar Chain Drugstore Ltd. Announces Formation of Special Committee to Consider “Going Private” Proposal

BioNano Genomics Announces Addition of Gene Company as China Mainland and HK/Macau Distributor

Novel Imaging Technology REFI takes Clinicians closer to detecting Stage 0 Tumour Lesions

ASIA-PACIFIC – Quick thinking? It’s all down to timing.

ASIA-PACIFIC – New study exposes need for better management of anaemia.

ASIA-PACIFIC – New technique shows promise for heart muscle regeneration.

ASIA-PACIFIC – Programming T cells to treat liver cancer.

ASIA-PACIFIC – Instilling new life into cells with hydrogels.

ASIA-PACIFIC – Marine sponge tests point to human microbiome answers.

REST OF THE WORLD – Wheat that fights celiac disease.

REST OF THE WORLD – Studies give new insights on immunotherapy in elderly patients with lung cancer.

P(N-isopropylacrylamide) (PNIPAM) prepared by reversible addition fragmentation chain transfer (RAFT) polymerization exhibited gelation retardation. The intermediate before gelation was characterized and indicated the presence of branched or hyperbranched chains. The swelling behavior was investigated, and the gel by RAFT polymerization (RAFT gel) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional gels (CG). The study was extended to gels prepared by using 2-hydroxy-1-ethanethiol as chain transfer agent and by using low concentration solutions. The two systems also exhibited retardation effects and improved deswelling kinetics. The different swelling behaviors of these gels and CG could be attributed to the presence of dangling chains caused by gelation retardation.

Hydrogels and shape memory polymers (SMPs) possess excellent and interesting properties that may be harnessed for future applications. However, this is not achievable if their mechanical behaviors are not well understood. This paper aims to discuss recent advances of the constitutive models of hydrogels and SMPs, in particular the theories associated with their deformations. On the one hand, constitutive models of six main types of hydrogels are introduced, the categorization of which is defined by the type of stimulus. On the other hand, constitutive models of thermal-induced SMPs are discussed and classified into three main categories, namely, rheological models; phase transition models; and models combining viscoelasticity and phase transition, respectively. Another feature in this paper is a summary of the common hyperelastic models, which can be potentially developed into the constitutive models of hydrogels and SMPs. In addition, the main advantages and disadvantages of these constitutive modes are discussed. In order to provide a compass for researchers involved in the study of mechanics of soft materials, some research gaps and new research directions for hydrogels and SMPs constitutive modes are presented. We hope that this paper can serve as a reference for future hydrogel and SMP studies.

The coupled transient chemo-mechanical behavior as well as the large deformation behavior under various complex load conditions must be taken into account when designing a functional responsive polymer actuator or sensor. One sort of deformation that can be used to characterize the properties of materials with complicated behavior, like soft hydrogels, is coupled extension and torsion with internal pressure. It is important to thoroughly research the complex kinetics of pH-hydrogels with coupled diffusion and massive deformation behavior. The transient behavior of cylindrical hydrogels under coupled extension–torsion with internal pressure under indifferent conditions is proposed in this work using a reliable semi-analytical method. In this regard, an analytical solution is offered to inspect this problem, which is used as a common experimental methodology for the characterization and modeling of polymeric materials. The results show that the rate of deformation and the physical characteristics of the material have a substantial impact on the cylindrical hydrogel’s transient behavior under coupled extension–torsion and internal pressure. For the same problem, a 3D finite element study was done to assess the analytical solution. The accuracy of our method is supported by the results’ agreement in both the FE analysis and the proposed approach. However, offering such a solution for this complex problem is of tremendous relevance given the significantly cheaper computational cost of analytical methods when compared to FEM. Additionally, the calculations indicate a complex reaction force and moment because the hydrogel experiences nonlinear Poynting-type effects in this deformation domain. The suggested semi-analytical procedure’s resilience behavior is demonstrated by the visualization of the effects of various material properties. This method can be used to calibrate constitutive models and to develop and improve hydrogel structures.

Hydrogels are excellent soft materials that can absorb large amounts of water and have applications ranging from biocompatible sensors to soft robots. Experiments have demonstrated that the equilibrium swelling state of hydrogels strongly depends on their preparation and external conditions, such as the as-prepared water content, cross-linking density, and temperature. However, traditional theories based on Flory’s work have failed to capture these dependence effects. In particular, these theories ignore the existence of solvents in the as-prepared state of hydrogels, making them unable to characterize the sensitivity of the swelling and mechanical behaviors to the as-prepared water content. In this study, we propose a constitutive theory that considers the preparation conditions based on statistical thermodynamics. Our theory can precisely predict the swelling ability of hydrogels under diverse preparation conditions and capture the phase transitions of temperature-sensitive hydrogels. We further derived the governing equations for large deformations and solvent diffusion considering their strong coupling effects. Based on our theory, the inhomogeneous deformation-induced solvent migration and delayed fracture of hydrogels were investigated. From theoretical investigations, we revealed the underlying mechanism of these interesting hydrogel behaviors. The theoretical results were further used to guide the design of diverse intelligent structures that can be applied as soft actuators, flexible robots, and morphing the growth of plants.

Hydrogels can change their size upon swelling. The swelling ratio is the same for all directions in the stress-free state. Dielectric elastomers can reduce their thickness and expand the area upon an electric field. Similarly, the expansion ratio in the plane is also the same for different directions. This isotropic shape change effect limits the function of these soft materials in certain circumstances. To address this issue, recent works have shown that the incorporation of fibers into the polymer matrix can induce an anisotropic response upon external stimulus. In this work, we develop multi-field coupling models for both fiber-reinforced hydrogels and dielectric elastomers. For the former, the change in free energy is caused by the stretching of polymer chains and fibers and the mixing of solvents and polymer networks. The Fickian-type law is adopted for the solvent diffusion. The free energy density for the latter consists of a mechanical part, considering the deformation of both polymer matrix and fibers, and an electric polarization component. Gauss’s law is adopted to obtain the distribution of the electric field. The multi-field models are then implemented for finite element analysis. We consider the stimulus-responsiveness of bilayer strips with an active layer and a passive layer. Without fibers, the strips bend upon the external stimulus. In contrast, the shape changes to helix shapes, which can be further tuned by changing the distribution of fibers. The work provides an efficient design tool for self-folding structures based on stimulus-responsive polymers.

Cellulose nanofibers, detached from natural plants, are very promising for applications in the energy storage devices. The swelling of cellulose nanofibers provides abundant paths in the hybrid hydrogels for ion diffusion towards the active material. There is an optimal composition of 50wt.% for cellulose nanofibers in the hybrid hydrogels due to the balance between ion diffusion and electron transport, that is, facilitated by conductive graphite nanoplatelets. The aqueous Zn-ion batteries, assembled from the optimized hybrid hydrogels, have a high-specific capacity of 149.4mAh/g and energy density of 113.2mWh/g, respectively. Moreover, high flexibility of the aqueous Zn-ion batteries is guaranteed by the hybrid hydrogels. There is only a little decay in the electrochemical performance under mechanical bending.

Tissue engineering strategies for regenerating damaged cartilage using hydrogels have garnered significant attention due to the limited self-healing capacity of damaged cartilage tissue and the restrictions of current medical treatment methods. In particular, using human mesenchymal stem cells (hMSCs) as the cell source has shown the potential to differentiate along a chondrogenic lineage. Hydrogels, whether made of synthetic polymers, natural polymers, or combinations, are widely explored as scaffolding materials mimicking the natural cartilage environment. Based on the understanding of the importance of surface nanotopographies and mechanical stiffness, hydrogels have been presented in various forms and tested for the differentiation of hMSCs. The primary focus of this review is to provide a summary of recent advances in physically and chemically modified hydrogels promoting the chondrogenesis of hMSCs. Advances in micromachining have helped in forming surfaces with the required roughness or an array of micropillars of defined architecture. Hydrogels have been combined with various stimulants such as small peptides, growth factors, and many modified matrix elements. Creating anisotropic hydrogels mimicking the extracellular matrix of cartilage has also been reported. These studies show promising results and identify a niche for in-vitro differentiation of chondrocytes from hMSCs.

Four-dimensional (4D) printing is an up-and-coming technology for the creation of dynamic devices which have shape changing capabilities or on-demand capabilities over time. Through the printing of adaptive 3D structures, the concept of 4D printing can be realized. Modern manufacturing primarily utilizes direct assembly techniques, limiting the possibility of error correction or instant modification of a structure. Self-building, programmable physical materials are interesting for the automatic and remote construction of structures. Adaptive materials are programmable physical or biological materials which possess shape changing properties or can be made to have simple logic responses. There is immense potential in having disorganized fragments form an ordered construct through physical interactions. However, these are currently limited to only self-assembly at the smallest scale, typically at the nanoscale. The answer to customizable macro-structures is in additive manufacturing, or 3D printing. 3D printing is a 30 years old technology which is beginning to be widely used by consumers. However, the main gripes about this technology are that it is too inefficient, inaccessible, and slow. Cost is also a significant factor in the adoption of this technology. 3D printing has the potential to transform and disrupt the manufacturing landscape as well as our lives. 4D printing seeks to use multi-functional materials in 3D printing so that the printed structure has multiple response capabilities and able to self-assemble on the macroscale. In this paper, we will analyze the early promise of this technology as well as to highlight potential challenges that adopters could face. The primary focus will be to have a look at the application of materials to 3D printing and to show how these materials can be tailored to create responsive customized 4D structures.

Conductive hydrogels are emerging as an advanced electronic platform for wearable sensors by synergizing the advantageous features of conductivity and flexibility. Especially conductive polymer hydrogels have widespread applications in the fields of catalysis, biomedicine, monitoring, and wearable electronic skin owing to the outstanding strain sensitivity and resilience thereof. Nevertheless, how to maintain the conductivity of hydrogels and electronic skins under strain or deformation remains a significant challenge. To tackle the said bottleneck, a multiple H-bonding MXene-based conductive hydrogel was established in the present study. With the participation of MXene and Fe${}^{2+}$ ions, the hydrogel network was strengthened, which might be attributed to the H-bonding among the polymer chain, MXene, and Fe${}^{2+}$ ions. Meanwhile, the elongation at break and compression modulus of Poly(vinyl alcohol) (PVA)- M3F hydrogels increased to 513% and 85.6kPa compared with the initial PVA hydrogel, respectively. After incorporating Fe${}^{2+}$ ions, the PVA-M3F hydrogels exhibited greater conductivity, which was $7.9\times 10^{-4}$S/cm. Notably, the PVA-M3F hydrogels displayed good resilience, leading to stable conductivity and strain sensitivity. Subsequently, a finger joint was designed to verify the maintenance of conductivity and monitoring behaviors. PVA-M3F conductive hydrogel was found to possess an outstanding capability for electrical signals feedback and was expected to be applied to electronic sensors or monitors. In summary, the introduction of MXene and Fe${}^{2+}$ ions into PVA hydrogels can not only tune the conductivity but also have promising prospects as a countermeasure for wearable electronics.

Current clinical practice in ocular disease treatment dosage forms primarily relies on eye drops or eye ointments, which face significant challenges in terms of low bioavailability profiles, rapid removal from the administration site, and thus ineffective therapeutic efficiency. Hydrogel has several distinct properties in semi-solid thermodynamics and viscoelasticity, as well as diverse functions and performance in biocompatibility and degradation, making it extremely promising for overcoming the challenges in current ocular treatment. In this review, the most recent developments in the use of hydrogel biomaterials in ocular therapy are presented. These sophisticated hydrogel biomaterials with diverse functions, aimed at therapeutic administration for ocular treatment, are further classified into several active domains, including drug delivery system, surface repair patch, tissue-engineered cornea, intraocular lens, and vitreous substitute. Finally, the possible strategies for future design of multifunctional hydrogels by combining materials science with biological interface are proposed.

The cellulose-based hydrogels have received immense interest for various biomedical applications owing to their unique structural, physico-chemical, mechanical, and biological properties. This chapter provides an overview of different cellulose-dissolving systems, cellulose derivatives, cellulose nanostructures, and cellulose-producing microorganisms, with emphasis on the fabrication, properties, and biomedical applications of cellulose-based hydrogels. Further, it highlights the current developments of the latest synthesis methods and technologies, such as 3D and 4D printing, inspired from the naturally occurring biomaterials or soft/hard tissues with numerous excellent properties, to fabricate cellulose-based hydrogels with a highly ordered microstructure, to further improve their properties and applications.

Natural methacrylate polysaccharides and proteins represent a versatile group of modified macromolecules. The methacrylic group is capable of undergoing a gelling process through a photo-crosslinking polymerization into the macromolecule backbone. This chapter presents an overview of the methacrylation reaction of biopolymers, such as chitosan, laminarin, hyaluronic acid, dextran, gellan gum, gelatin and platelet lysates, developed by our research group. The biomedical applications, such as tissue engineering, therapeutic delivery and stem cells modulation, are highlighted.

Current clinical practice in ocular disease treatment dosage forms primarily relies on eye drops or eye ointments, which face significant challenges in terms of low bioavailability profiles, rapid removal from the administration site, and thus ineffective therapeutic efficiency. Hydrogel has several distinct properties in semi-solid thermodynamics and viscoelasticity, as well as diverse functions and performance in biocompatibility and degradation, making it extremely promising for overcoming the challenges in current ocular treatment. In this review, the most recent developments in the use of hydrogel biomaterials in ocular therapy are presented. These sophisticated hydrogel biomaterials with diverse functions, aimed at therapeutic administration for ocular treatment, are further classified into several active domains, including drug delivery system, surface repair patch, tissue-engineered cornea, intraocular lens, and vitreous substitute. Finally, the possible strategies for future design of multifunctional hydrogels by combining materials science with biological interface are proposed.