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Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications

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A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Applications".

Deadline for manuscript submissions: closed (28 February 2026) | Viewed by 19462

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Dr. Zhaohan Yu

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Guest Editor

Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824, USA
Interests: hydrogels; 3d printing; elastocaloric polymers; energy conversion
Special Issues, Collections and Topics in MDPI journals

Dr. Xiaolin Qiu

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Guest Editor

School of Mechanical Engineering, Jiangnan University, Wuxi 214122, China
Interests: smart hydrogels; functional packaging materials; active packaging system; thermal storage and heat transfer; energy-efficient equipment

Special Issue Information

Dear Colleagues,

The Special Issue, entitled “Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications” focuses on the development of functional gel materials with unique chemical or mechanical properties, offering significant potential for applications in tissue engineering, soft robots, drug delivery, energy-saving buildings, and so forth. The Special Issue aims to explore the latest advancements in the synthesis, characterization, mechanical performance, and innovative applications of functional gel materials for various applications. By emphasizing on molecular composition design, microstructural optimization, fabrication strategies, and functional customization, this Special Issue provides a comprehensive overview of how functional gels can revolutionize biomedical applications and sustainable construction. Contributions will explore the challenges, opportunities, and future possibilities for functional gel materials, highlighting their potential to make a real difference in a wide range of applications.

Overall, this Special Issue aims to provide an in-depth understanding of the recent advancements in and applications of gel materials. We hope that the research articles we publish contribute to the growing body of knowledge on gel materials and inspire further exploration and innovation in this exciting field.

Dr. Zhaohan Yu
Dr. Xiaolin Qiu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

functional gel materials
gel synthesis
tough hydrogel
biomedical
energy harvesting
elastocaloric polymer
self-healing
flexible electronics

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Related Special Issue

Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications (2nd Edition) in Gels

Published Papers (9 papers)

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Research

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24 pages, 8726 KB

Open AccessArticle

Study on a Thermally Crosslinking Clay-Free Weak Gel Water-Based Drilling Fluid

by Taifeng Zhang, Jinsheng Sun, Kaihe Lv, Jingping Liu, Lei Nie, Yufan Zheng, Yuanwei Sun, Ning Huang, Delin Hou, Han Yan and Yecheng Li

Gels 2026, 12(4), 280; https://doi.org/10.3390/gels12040280 - 27 Mar 2026

Viewed by 404

Abstract

In this study, a thermally crosslinking clay-free weak gel water-based drilling fluid based on salt-responsive polymers and crosslinking agents was investigated as a promising and feasible strategy. Firstly, a salt-tolerant polymer was synthesized using N,N-dimethylacrylamide (DMAA), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonopropyl)ammonium hydroxide (DMAPS), and acrylamide (AM). BPEI_10,000 was selected as the thermal crosslinking agent. The optimal crosslinking was achieved at 180 °C and 36% NaCl, with RMFL at 2.0% and BPEI_10,000 at 0.1%. Performance evaluation demonstrated that the crosslinking between RMFL and BPEI_10,000 could enhance the AV, PV, and YP of the RMFL(BPEI_10,000)/CF-WBDFs after aging at 180 °C for 16 h and reduce FL_API. The RMFL(BPEI_10,000)/CF-WBDFs exhibited appropriate shear-thinning behavior, viscoelasticity, thixotropy, and recoverable viscosity under high-temperature, high-salinity, and high-pressure conditions. Mechanism analysis revealed that RMFL and BPEI_10,000 could form a predominantly negatively charged, three-dimensional crosslinking weak gel at high temperatures. The crosslinking weak gel could form dense filter cakes, improving rheological properties and reducing filtration loss of CFWBDFs in high-temperature, high-salinity environments. This paper proposed a novel method to address the technical challenge of rheological performance failure of CFWBDFs, offering valuable insights for subsequent investigations. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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24 pages, 13944 KB

Open AccessArticle

Alkali-Activated Materials from Diverse Solid Precursors: Structural, Mechanical and Radiological Properties

by Nataša Mladenović Nikolić, Marija Ivanović, Snežana Nenadović, Jelena Potočnik, Sabina Dolenec, Dušan Bučevac, Aleksandar Kandić and Ljiljana Kljajević

Gels 2026, 12(3), 200; https://doi.org/10.3390/gels12030200 - 27 Feb 2026

Viewed by 705

Abstract

This study investigates the gel characteristics of alkali-activated materials (AAMs) synthesized using wood ash (WA), and metakaolin (MK) as solid precursors. The research explores the influence of precursor type and sodium hydroxide (NaOH) concentrations in the alkali activator solution on the resulting physicochemical, microstructural, mechanical, and radiological properties of gels. The alkaline activators were prepared by mixing sodium hydroxide solutions (6 M and 12 M) with a sodium silicate (water glass) solution at a volume ratio of 1.5. The physicochemical characteristics of raw materials and AAMs were thoroughly analyzed using X-ray fluorescence (XRF), Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) with EDS elemental mapping. FTIR analysis confirmed the formation of an amorphous gels geopolymer network. XRD revealed the presence of characteristic crystalline phases (quartz, calcite) within an amorphous matrix. Mechanical properties, such as compressive strength, depended on precursor type and alkali molarity: metakaolin (12 M) reached ~14 MPa, while wood ash showed ~4 MPa (6 M) and ~0.5 MPa (12 M) due to high CaO, low Si and Al, and unfavorable SiO₂/Al₂O₃ (5.71) and Na₂O/Al₂O₃ (3.19) ratios. Furthermore, this research estimates radiological doses by quantifying radionuclide content via gamma-spectrometry. Alkali activation significantly reduced radiological hazard parameters, with radium equivalent activity (Ra_eq) decreasing to 238.0 Bq/kg and the external hazard index (H_ex) to 0.643 for A₁₂MK, while the annual effective dose rate for A₁₂WA was only 0.265 nSv/y-all values remaining well below the recommended safety limit of 370 Bq/kg (≤1 mSv/y). The decrease in activity concentration index (I_γ), Ra_eq, and H_ex with increasing NaOH concentration indicates effective radionuclide immobilization within the geopolymer matrix, confirming the suitability of these alkali-activated materials for safe use in construction from a radiation protection perspective. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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27 pages, 16684 KB

Open AccessArticle

pH-Sensitive Dextrin-Based Nanosponges Crosslinked with Pyromellitic Dianhydride and Citric Acid: Swelling, Rheological Behavior, Mucoadhesion, and In Vitro Drug Release

by Gjylije Hoti, Sara Er-Rahmani, Alessia Gatti, Ibrahim Hussein, Monica Argenziano, Roberta Cavalli, Anastasia Anceschi, Adrián Matencio, Francesco Trotta and Fabrizio Caldera

Gels 2026, 12(1), 90; https://doi.org/10.3390/gels12010090 - 19 Jan 2026

Viewed by 843

Abstract

Dextrin-based nanosponges (D-NS) are promising candidates for oral drug delivery due to their biocompatibility, mucoadhesive properties, and tunable swelling behavior. In this study, pH-sensitive nanosponges were synthesized using β-cyclodextrin (β-CD), GluciDex^®2 (GLU2), and KLEPTOSE^® Linecaps (LC) as building blocks, crosslinked with pyromellitic dianhydride (PMDA) and citric acid (CA). The nanosponges were mechanically size-reduced via homogenization and ball milling, and characterized by FTIR, TGA, dynamic light scattering (DLS), and zeta potential measurements. Swelling kinetics, cross-linking density (determined using Flory–Rehner theory), rheological behavior, and mucoadhesion were evaluated under simulated gastric and intestinal conditions. The β-CD:PMDA 1:4 NS was selected for drug studies due to its optimal balance of structural stability, swelling capacity (~863% at pH 6.8), and highest apomorphine (APO) loading (8.23%) with 90.58% encapsulation efficiency. All nanosuspensions showed favorable polydispersity index values (0.11–0.30), homogeneous size distribution, and stable zeta potentials, confirming suspension stability. Storage at 4 °C for six months revealed no changes in physicochemical properties or apomorphine (APO) degradation, indicating protection by the nanosponge matrix. D-NS exhibited tunable swelling, pH-responsive behavior, and mucoadhesive properties, with nanoparticle–mucin interactions quantified by the rheological synergism parameter (∆G′ = 53.45, ∆G″ = −36.26 at pH 6.8). In vitro release studies demonstrated slow, sustained release of APO from D-NS in simulated intestinal fluid compared to free drug diffusion, highlighting the potential of D-NS as pH-responsive, mucoadhesive carriers with controlled drug release and defined nanoparticle–mucin interactions. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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27 pages, 4961 KB

Open AccessArticle

Highly Efficient Removal of PFAS from Water Using Surface-Modified Regenerable Quaternized Chitosan Hydrogels

by Mohammad Bagheri Kashani, Lingfei Fan, Weile Yan and Bridgette M. Budhlall

Gels 2026, 12(1), 14; https://doi.org/10.3390/gels12010014 - 24 Dec 2025

Cited by 4 | Viewed by 1913

Abstract

In this study, surface-modified bio-based hydrogels derived from crosslinked quaternized chitosan (MQCGs) were developed to treat PFAS-contaminated water. The novelty of this work lies in the surface modification and engineering of the hydrogels to enhance the surface area and positive charge of the hydrogels through sacrificial templating. By blending the chitosan solution with polyethylene glycol (PEG) and then removing PEG via sacrificial templating, microscale channels were created on the surface of the hydrogels. This increased the availability of the hydrogel’s positive charges for increased electrostatic interactions with PFAS, achieving >98% PFOS (a long-chain PFAS) adsorption in less than 30 min. Batch adsorption experiments demonstrated that surface-modified quaternized chitosan hydrogels (MQCGs) removed both long- and short-chain PFAS across a pH range of 3 to 12, maintaining their performance over 10 regeneration cycles. The adsorption behavior followed the Freundlich isotherm model and pseudo-second-order kinetics, indicating fast multilayer adsorption on heterogeneous active sites via the combined actions of electrostatic, hydrophobic, and physical interactions. Using PFOS and PFOA as model long-chain PFAS and PFBS and PFHxA as short-chain surrogates, respectively, MQCGs achieved a complete removal of PFOS and PFOA and over a 99.9% removal of PFBS and PFHxA, each at a low concentration of 500 µg/L in water. Moreover, MQCGs exhibited highly efficient removal of PFAS at environmentally relevant concentrations of 20 µg/L in tap water containing MgSO₄ and NaCl as competing electrolytes, demonstrating the potential of MQCGs as a new class of efficient, selective, and regenerable materials for PFAS sequestration. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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22 pages, 3800 KB

Open AccessArticle

Study on Carboxymethylation Modification of Konjac Gum and Its Effect in Drilling Fluid and Fracturing Fluid

by Yongfei Li, Pengli Guo, Kun Qu, Weichao Du, Yanling Wang and Gang Chen

Gels 2025, 11(10), 792; https://doi.org/10.3390/gels11100792 - 2 Oct 2025

Cited by 1 | Viewed by 1041

Abstract

With the continuous progress and innovation of petroleum engineering technology, the development of new oilfield additives with superior environmental benefits has attracted widespread attention. Konjac glucomannan (KGM) is a natural resource characterized by abundant availability, low cost, biodegradability, and environmental compatibility. Konjac gum easily forms a weak gel network in water, but its water solubility and thermal stability are poor, and it is easily degraded at high temperatures. Therefore, its application in drilling fluid and fracturing fluid is limited. In this paper, a method of carboxymethyl modification of KGM was developed, and a carboxymethyl group was introduced to adjust KGM’s hydrogel forming ability and stability. Carboxymethylated Konjac glucomannan (CMKG) is a water-soluble anionic polysaccharide derived from natural Konjac glucomannan. By introducing carboxymethyl groups, CMKG overcomes the limitations of the native polymer, such as poor solubility and instability, while retaining its safe and biocompatible nature, making it an effective natural polymer additive for oilfield applications. The results show that when used as a drilling fluid additive, CMKG can form a stable three-dimensional gel network through molecular chain cross-linking, significantly improving the rheological properties of the mud. Its unique gel structure can enhance the encapsulation of clay particles and inhibit clay hydration expansion. When used as a fracturing fluid thickener, the viscosity of the gel system formed by CMKG at 0.6% (w/v) is superior to that of the weak gel system of KGM. The heat resistance/shear resistance tests confirm that the gel structure remains intact under high-temperature and high-shear conditions, meeting the sand-carrying capacity requirements for fracturing operations. The gel-breaking experiment shows that the system can achieve controlled degradation within 300 min, in line with on-site gel-breaking specifications. This modification process not only improves the rheological properties and water solubility of the CMKG gel but also optimizes the gel stability and controlled degradation through molecular structure adjustment. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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12 pages, 2943 KB

Open AccessArticle

Effect of Potassium-Ion-Triggered Double Helix Aggregation on Shakedown Behavior of κ-Carrageenan/Polyacrylamide Hydrogel

by Xueqi Zhao, Yudong Pan, Zhanrong Zhou, Yang Gao, Aijun Li, Binkai Shi, Jian Hu and Liuying Wang

Gels 2025, 11(6), 412; https://doi.org/10.3390/gels11060412 - 30 May 2025

Cited by 5 | Viewed by 1391

Abstract

This study investigates the effect of potassium ion (K⁺) concentration on double helix aggregation in κ-carrageenan-based hydrogels, which significantly influences their shakedown behavior. The shakedown behavior of κ-carrageenan/polyacrylamide (PAAm) hydrogels was characterized by the evolution of maximum stress and energy dissipation during cyclic load. The experimental results indicate that higher K⁺ concentrations significantly improve the maximum stress in the steady state, but barely influence the energy dissipation in the steady state. The improved maximum stress can be explained by the higher density of double helix aggregation. The steady energy dissipation elucidates that the K⁺ concentration does not affect the breaking–recovering balance of the sacrificial network in cyclic loading. These results provide mechanistic insights into how ion-triggered double helix aggregation influences the shakedown behavior of κ-carrageenan-based hydrogels. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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15 pages, 5319 KB

Open AccessArticle

Synthesis and Application of SAPO-11 Molecular Sieves Prepared from Reaction Gels with Various Templates in the Hydroisomerization of Hexadecane

by Dmitry V. Serebrennikov, Arthur R. Zabirov, Alexey N. Saliev, Roman E. Yakovenko, Tatyana R. Prosochkina, Zulfiya R. Fayzullina, Vladimir Yu. Guskov, Boris I. Kutepov and Marat R. Agliullin

Gels 2024, 10(12), 792; https://doi.org/10.3390/gels10120792 - 4 Dec 2024

Cited by 6 | Viewed by 2741

Abstract

Among the most selective catalytic systems for the hydroisomerization of C₁₆₊ n-paraffins, catalytic systems based on SAPO-11 are quite promising. In order to increase the activity and selectivity of these bifunctional catalysts, it is necessary to reduce the diffusion restrictions for the reacting molecules and their products in the microporous structure of SAPO-11 by reducing the crystal size. To solve this problem, we have studied the influence of different templates (diethylamine, dipropylamine, diisopropylamine, and dibutylamine) on the physicochemical properties of reaction gels and SAPO-11 silicoaluminophosphates during their crystallization. Using XRD, SEM, and NMR techniques, we found that regardless of the template used, the reaction gel after the aging process at 90 °C is an AlPO₄·2H₂O hydroaluminophosphate. At the same time, the nature of the template affects the morphology and crystal sizes of the intermediate alumophosphate, AlPO₄·2H₂O, and the molecular sieves, SAPO-11. The acidic properties and the porous structure characteristics of SAPO-11 are also affected by the template. A template was proposed to enable the synthesis of nanoscale SAPO-11 crystals. The influence of the morphology and crystal size of SAPO-11 on the catalytic properties of a bifunctional catalyst based on SAPO-11 in the hydroisomerization of hexadecane was investigated. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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13 pages, 2636 KB

Open AccessEditor’s ChoiceArticle

Leveraging Deep Learning and Generative AI for Predicting Rheological Properties and Material Compositions of 3D Printed Polyacrylamide Hydrogels

by Sakib Mohammad, Rafee Akand, Kaden M. Cook, Sabrina Nilufar and Farhan Chowdhury

Gels 2024, 10(10), 660; https://doi.org/10.3390/gels10100660 - 15 Oct 2024

Cited by 18 | Viewed by 3982

Abstract

Artificial intelligence (AI) has the ability to predict rheological properties and constituent composition of 3D-printed materials with appropriately trained models. However, these models are not currently available for use. In this work, we trained deep learning (DL) models to (1) predict the rheological properties, such as the storage (G’) and loss (G”) moduli, of 3D-printed polyacrylamide (PAA) substrates, and (2) predict the composition of materials and associated 3D printing parameters for a desired pair of G’ and G”. We employed a multilayer perceptron (MLP) and successfully predicted G’ and G” from seven gel constituent parameters in a multivariate regression process. We used a grid-search algorithm along with 10-fold cross validation to tune the hyperparameters of the MLP, and found the R² value to be 0.89. Next, we adopted two generative DL models named variational autoencoder (VAE) and conditional variational autoencoder (CVAE) to learn data patterns and generate constituent compositions. With these generative models, we produced synthetic data with the same statistical distribution as the real data of actual hydrogel fabrication, which was then validated using Student’s t-test and an autoencoder (AE) anomaly detector. We found that none of the seven generated gel constituents were significantly different from the real data. Our trained DL models were successful in mapping the input–output relationship for the 3D-printed hydrogel substrates, which can predict multiple variables from a handful of input variables and vice versa. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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Review

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24 pages, 1538 KB

Open AccessReview

Multifunctional Hydrogels for Advanced Cancer Treatment: Diagnostic Imaging and Therapeutic Modalities

by Kyung Kwan Lee, Kwangmo Go, Eonjin Lee, Hongki Kim, Seonwook Kim, Ji-Hyun Kim, Min Suk Chae and Jin-Oh Jeong

Gels 2025, 11(6), 426; https://doi.org/10.3390/gels11060426 - 1 Jun 2025

Cited by 14 | Viewed by 5607

Abstract

Multifunctional hydrogels represent an emerging technological advancement in cancer therapeutics, integrating diagnostic imaging capabilities with therapeutic modalities into comprehensive, multifunctional systems. These hydrogels exhibit exceptional biocompatibility, biodegradability, high water retention capacity, and tunable mechanical properties, enabling precise drug delivery while minimizing systemic side effects. Recent innovations in stimuli-responsive components facilitate intelligent, controlled drug release mechanisms triggered by various stimuli, including changes in pH, temperature, magnetic fields, and near-infrared irradiation. Incorporating diagnostic imaging agents, such as magnetic nanoparticles, fluorescent dyes, and radiolabeled isotopes, substantially improves tumor visualization and real-time therapeutic monitoring. Multifunctional hydrogels effectively integrate chemotherapy, photothermal therapy, photodynamic therapy, immunotherapy, and their synergistic combinations, demonstrating superior therapeutic outcomes compared to conventional methods. Particularly, injectable and in situ-forming hydrogels provide sustained local drug delivery postoperatively, effectively reducing tumor recurrence. However, challenges persist, including initial burst release, mechanical instability, regulatory barriers, and scalability concerns. Current research emphasizes advanced nanocomposite formulations, biofunctionalization strategies, and innovative manufacturing technologies like 3D bioprinting to facilitate clinical translation. This review comprehensively summarizes recent advancements, clinical applications, and future perspectives of multifunctional hydrogel systems for enhanced cancer treatment, underscoring their potential to revolutionize personalized oncology. Full article

(This article belongs to the Special Issue Functional Gel Materials: Chemistry, Processing, Mechanical Performance, and Applications)

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