Rigid Gel Research Articles

APPLICATION OF VISCOUS GEL SOLUTIONS AND WATER SHUTOFF TECHNIQUES FOR LAYERS DURING WELL CONSTRUCTION

Most of the oil fields are at the decline stage of development. This stage of development is characterized by a decrease in the oil production level, an increase in the water cut of the extracted fluids (up to 90%). Reducing the water cut of the produced products is facilitated by water shutoff measures. Based on the analysis of the causes of growth of water cut in wells, the most common causes of high water cut in production wells include water filtration through fractured systems and highly permeable reservoir intervals, behind-the-casing crossflows and the formation of a water cut cone. Rational control over the water cut in the produced products increases the economic efficiency of the field development and reduces the costs of treatment and utilization of extracted water. There are different approaches for solving the problem of water shutoff: creating screens and barriers using various chemical compositions, using technical means and technological methods. These technologies are classified according to the nature of the impact of the injected water-insulating mass on the permeability of the oil-saturated part of the reservoir, opened by perforation. Taking this into account, water shutoff technologies are divided into selective and non-selective ones. The use of rigid gels is one of the methods of water shutoff in the near-well area. Gels can be injected selectively into the formation using coiled tubing (CT) and a packer. In case of absence of interlayer crossflows, an injection of a rigid gel into a watered-out formation can prevent unwanted water from penetration into the well.

Exploring the Role of Fibrin Gels in Enhancing Cell Migration for Vasculature Formation.

A hallmark of angiogenesis is the sprouting of endothelial cells. To replicate this event in vitro, biomaterial approaches can play an essential role in promoting cell migration. To study the capacity of a scaffold of fibrin (fibrinogen:thrombin mix) to support the movement of the endothelial cells, the migration area of spheroids formed with the HULEC cell line was measured. The cells were first allowed to form a spheroid using the hanging drop technique before being encapsulated in the fibrin gel. The cells' migration area was then measured after two days of embedding in the fibrin gel. Various conditions affecting fibrin gel polymerization, such as different concentrations of fibrinogen and thrombin, were evaluated alongside rheology, porosity, and fiber thickness analysis to understand how these factors influenced cell behavior within the composite biomaterial. Data point toward thrombin's role in governing fibrin gel polymerization; higher concentrations result in less rigid gels (loss tangent between 0.07 and 0.034) and increased cell migration (maximum concentration tested: 5 U/mL). The herein presented method allows for a more precise determination of the crosslinking conditions of fibrin gel that can be used to stimulate angiogenic sprouting.

Encapsulation of Bovine Primordial Follicles in Rigid Alginate Does Not Affect Growth Dynamics.

The only fertility preservation and subsequent restoration option for many patients facing gonadotoxic treatments is ovarian tissue cryopreservation and transplantation. While this process is successful for some, there is significant room for improvement to extend the life of the transplant and to make it safe for patients that may have metastatic disease within their ovarian tissue. We need a deeper understanding of how the physical properties of the ovarian microenvironment may affect folliculogenesis to engineer an environment that supports isolated follicles and maintains primordial follicle quiescence. Bovine ovaries were used here as a monovulatory model of folliculogenesis to examine the effects of primordial follicle activation and growth under different physical conditions. We found that there were no differences in activation, growth or survival when primordial follicles were cultured in isolation or in situ (remaining in the tissue) under two significantly differently rigid alginate gels. To determine if the extra rigid environment did not affect activation in isolated follicles due to an immediate activation event, we used 5-ethynyl-2'-deoxyuridine (EdU) to track follicle activation during the isolation process. We identified EdU incorporation in granulosa cells after primordial follicles were isolated from the surrounding extracellular matrix (ECM). These findings support that isolation of primordial follicles from the ECM is an activating event and that the differentially rigid environments assessed here had no effect on follicle growth. Further work is needed to suppress activation in primordial follicles to maintain the ovarian reserve and extend the life of an ovarian tissue transplant.

KAJIAN ADSORPSI LOGAM CU DENGAN ADSORBEN SILIKA GEL

Adsorption is a separation process on a particular substance based on the affinity of a compound to a solid. The adsorption process requires an adsorbent as an absorbent material and an adsorbate as an absorbed component. The adsorbent that is often used to absorb Cu2+ ions is silica gel. Silica gel is a rigid gel that is amorphous. In silica gel there are two main bonding groups, namely siloxane and silanol groups which cause silica gel to easily absorb polar molecules, especially water. The purpose of this research is to get the best mass of silica and the effect of the initial concentration of Cu ions on the final concentration of Cu metal. In this study, two operating conditions were varied, namely the mass of silica gel adsorbent 0.4 grams; 0.6 grams; 0.8 grams; 1 gram; 1.2 grams and the initial concentration of Cu metal 3 ppm; 4 ppm; 5 ppm; 6 ppm; 7 ppm. The results of this study showed that the silica content of bagasse ash was 70.97% with a surface area of 283.802 m2/g. The best result of this study reduced the content of copper metal (Cu) by 88% in the condition of silica gel mass of 1.2 grams. The adsorption isotherm shows that the data is more in line with the Freundlich equation. The resulting equation is y = 0.4268x + 0.4969 with an R2 value of 0.9837.

Methacrylic acid grafted inulin and carboxymethyl cellulose as additives in the development of pH sensitive hydrogel matrix for colon targeting

AbstractCompression‐coated matrix tablets were developed to target budesonide (BUD) in the colonic region using methacrylic acid (MAA) grafted inulin (INU) and carboxymethyl cellulose (CMC). INU was grafted with MAA to impart anionic characteristics to the gum, making it feasible to form a hydrogel by cross‐linking with calcium gluconate (CG). The core matrix made up of MAA‐g‐INU alone disintegrated within 30 min and the core matrix made up of CMC alone completely released BUD within 6 h. The combination of MAA‐g‐INU and CMC produced a rigid matrix, which was able to completely release BUD after 7 h. Compression coating of the core tablets with MAA‐g‐INU and CMC did not release BUD in the first 4 h, and complete BUD release took place in the next 4 h. Compression coating led to the formation of a rigid and viscous gel layer outside the core matrices, which hindered BUD release. We conclude that compression coating with CG cross‐linked CMC and MAA‐g‐INU could be used as a matrix for colonic delivery of drugs.Highlights Compression coated matrices were developed for colonic delivery of BUD. The matrix retained drug release up to 4 h in upper gastrointestinal tract (GIT). The matrix exhibited complete drug release in the next 4 h in the colon.

Impact of Deformability and Rigidity of Starch Granules on Linear and Non-Linear Rheological Behavior of Waxy Rice Starch Gels and Applicability for Food End Uses.

The objective of this study was to investigate granule size and distribution and deformability of granules and their effect on the rheological properties of waxy starch gels. Native (granular) waxy rice gels (10%) were prepared, and their response in oscillatory shear was investigated in the linear and non-linear viscoelastic regime. The results show the gels were mainly composed of aggregated and deformed swollen granules. Significance of granule size and its distribution, deformability of granules, and the molecular characteristics of amylopectin (AP) on storage modulus of those gels was demonstrated. A low degree of deformability of granules, typical for small granules with a broad size distribution and small molecular size of AP with short external chains, resulted in rigid and brittle gels. Highly deformed granules and high AP leachates, however, yielded soft gels. It was found that the transition of elastic to plastic behavior in the non-linear regime (LAOS) was gradual when AP had long external chains, but an abrupt transition was observed with the gel with short exterior chains of AP. Differences in rheological properties of cohesive waxy starch gels appear to be mainly impacted by the varying degrees of granule deformability and rigidity, which is further attributed to a combination of factors, including granule size, particle size distribution, molecular size, the external chain length of amylopectin (AP), and lipid content. The significance of this study is that it will assist the food industry in selecting suitable waxy rice starches to gain desired textural properties of end products.

Retentive bio-based chemical gel for removing glues from water-sensitive wooden artworks

Aged animal glues degrade and weaken over time, resulting in flakes and cracks on the material employed by wooden manufacturers and luthiers. Because of this deterioration, conservators and restorers remove aged water-soluble glues with a water swab, smoothing enough to clean them mechanically and putting on new reversible glues. However, it raises the question of whether a water swab can control moisture delivery while removing glue from wood, a hygroscopic and water-sensitive material.This study formulated a chemically crosslinked film-forming hydrogel based on sodium alginate (SA) with (3-Glycidoxypropyl)trimethoxysilane (GPTMS) and calcium chloride, named as CA-GPTMS to construct a retentive gel. Synthesized gel materials were characterized using several methods: liquid state NMR, FTIR-ATR, and SEM-EDS analyses were involved in examining the cross-linking process, while moisture and mechanical properties were examined to understand its suitability for the cleaning application process. The strategies for applying the CA-GPTMS gel on wood surface were to selectively soften the glue and to remove it as well as leave no residues on the wood surface. The cleaning process was investigated by using different techniques, i.e., stereomicroscopy, reflection-FTIR, and SEM-EDS. Compared to traditional rigid Agar gel, the CA-GPTMS gel appeared successfully resistant to destruction and was suitable for application on highly water-sensitive surfaces.

Utilizing Synchrotron-Based X-ray Micro-Computed Tomography to Visualize the Microscopic Structure of Starch Hydrogels In Situ.

This study aimed to visualize the microstructures of starch hydrogels using synchrotron-based X-ray micro-computed tomography (μCT). Waxy maize starch (WMS, 3.3% amylose, db), pea starch (PS, 40.3% amylose), and high-amylose maize starch (HMS, 63.6% amylose) were cooked at 95 and 140 °C to prepare starch hydrogels. WMS and HMS failed to form a gel after 95 °C cooking and storage, while PS developed a firm gel. At 140 °C cooking, HMS of a high amylose nature was fully gelatinized and generated a rigid gel with the highest strength. Both scanning electron microscopy (SEM) and μCT revealed the unique structural features of various starch hydrogels/pastes prepared at different temperatures, which were greatly affected by the degree of swelling and dispersity of the starches. As a nondestructive method, μCT showed certain advantages over SEM, including minimal shrinkage of the hydrogels, relatively simple sample preparation, and allowing for three-dimensional reconstruction of the hydrogel microstructure. This study indicated that synchrotron-based μCT could be a useful technique in visualizing biopolymer-based hydrogels.

Brown rice protein–dietary fibre conjugate improves bioaccessibility of minerals via modifying gelling structure of yoghurt

SummaryThe present study aims to provide an overview of the impact of brown rice protein (BRP) conjugated with microcrystalline cellulose via the Maillard reaction on characteristic features of yoghurt and the bioaccessibility of essential minerals in this dairy product. The confirmation of conjugation was conducted using FTIR spectroscopy. Adding BRP or Maillard conjugate (MC) proved beneficial in enhancing the water‐holding capacity and decreasing the syneresis of samples. Additionally, yoghurt (MCY) containing the Maillard conjugate demonstrated superior performance in these properties. A lower number of pores and a stronger gel network (structural integrity) were identified in MCY compared to the other samples (BRPY: yoghurt containing BRP and PY: plain yoghurt). On the other hand, in general, supplementation of BRP and MC led to slight alteration in the concentration of aroma compounds. Similarly, the impact of BRP and MC on changes in the molecular weight distribution of proteins during in vitro gastrointestinal digestion was negligible. Bioaccessibility values of Ca and Mg in PY were 53.72% and 10.72%, respectively. The improvement in these values was observed in BRPY (Ca: 57.33% and Mg: 15.60%). Moreover, adding MC to yoghurt led to a tighter interface structure (indicating rigid gel), which allowed more minerals to bind, increasing mineral bioaccessibility (Ca: 64.40% and Mg: 31.14%). A higher general acceptability in sensory evaluation was scored for PY followed by MCY and BRPY. Ultimately, the positive effect of ingredients (especially MC) on yoghurt quality was obvious.

Optimization of alginate extraction conditions from the brown seaweed Dictyota mertensii using a central composite design

This work extracts alginate from Dictyota mertensii, a brown macroalga found on the north coast of northeastern Brazil. A Central Composite Design (CCD) using Response Surface Methodology (RSM) was used to optimize the process of extracting the alginate present in the brown alga Dictyota mertensii, considering the factors of time, temperature, and concentration Na2CO3. Extraction yield (η), sulfate content, intrinsic viscosity ([η]), viscosimetric molar mass (Mv), color parameters (a*, b* e L*), M/G ratio and inhibitory concentration IC50 are model response variables. The Dictyota mertensii algae has its chemical composition expressed. Response surfaces are plotted from the variables studied, a quadratic model was predicted, the influence of factors is analyzed, and response variables are subjected to analysis of variance (ANOVA) and F-test at 95 % confidence. The predicted conditions are experimentally validated. The antioxidant potential was evaluated at seven concentrations (0.2–5.0 mg/mL) based on the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging. The maximum extraction yield was 29.28±0.02 %, and sulfate content ranged from 3.50±0,00 % to 12.33±0.29 %. The maximum values of [η] and Mv were 5.84±0.06 dL/g and 278.00±2.66 kDa, respectively. The alginate showed a dark brown color and M/G ratio < 1, indicating that the extracted alginate provides rigid and compact gels, which allows its application in films, encapsulations, and protecting probiotics. The maximum antioxidant capacity and the IC50 were 54.93±0.27 % and 0.51±0.07 mg/mL, respectively, indicating the material obtained as a moderate natural antioxidant.

Mechanically and Thermally Robust Gel Electrolytes Built from A Charged Double Helical Polymer.

Polymer electrolytes have received tremendous interest in the development of solid-state batteries, but often fall short in one or more key properties required for practical applications. Herein, a rigid gel polymer electrolyte prepared by immobilizing a liquid mixture of a lithium salt and poly(ethylene glycol) dimethyl ether with only 8 wt% poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT) is reported. The high charge density and rigid double helical structure of PBDT lead to formation of a nanofibrillar structure that endows this electrolyte with stronger mechanical properties, wider temperature window, and higher battery rate capability compared to all other poly(ethylene oxide) (PEO)-based electrolytes. The ion transport mechanism in this rigid polymer electrolyte is systematically studied using multiple complementary techniques. Li/LiFePO4 cells show excellent capacity retention over long-term cycling, with thermal cycling reversibility between ambient temperature and elevated temperatures, demonstrating compelling potential for solid-state batteries targeting fast charging at high temperatures and slower discharging at ambient temperature.

Low solid content mouldable chitin physical hydrogel prepared by atypical rupture-free swelling.

In this study, the atypical swelling gelation of chitin physical hydrogels was investigated. Just by tuning the amount of the N-acetylation reagent, the degree of acetylation varied and mouldable chitin hydrogels with a wide variety of gel concentrations (0.2-6.4 wt%) were obtained. In response to the gel concentration, the mechanical properties ranged from swollen soft gels to shrunken rigid gels (compressive moduli of 4-310 kPa). The thus-prepared chitin hydrogels, which were composed of only chitin and water, exhibited high transparency and integrity. The swelling gelation of chitin physical hydrogels was achieved owing to both the positive charges of the amino groups inducing the osmotic pressure and the toughness of the crystalline nanofibrous network structure of the chitin hydrogels that endured the large volume change. These previously unnoticed advantageous aspects of chitin have pioneered a novel area of swellable physical gels that has been exclusive to chemical gels so far.

Rheological and textural properties of sohphlang (Flemingia vestita) starch gels as affected by heat moisture treatment and annealing

Sohphlang being a tuberous crop exhibits rheological properties, which are expected to change with treatment. The main aim was to study the influence of heat-moisture treatment (HMT) and annealing (ANN) on rheological properties of sohphlang starch. HMT was done for 16 h using 20 %, 25 % and 30 % moisture levels, while ANN was performed at 70 %, 75 % and 80 % moisture levels for 24 h at 50 °C. Both HMT and ANN enhanced gel formation capacity and firmness. Starch gels presented a reduced apparent viscosity with an increase in shear rate, exhibiting shear thinning behavior. Frequency tests were well described by Power law and both HMT and ANN increased the structural gel strength. Starch gels containing 10 % of HMT-30 starch exhibited an improved elastic behavior (4289.79 Pa). Irrespective of starch concentration and for all samples, G′ > G″ was observed on heating beyond Tgel and during cooling, indicating the formation of rigid gel network. Gels prepared from 15 % of HMT-30 starch showed the highest resistance to temperature than other gels. HMT-30 showed more pronounced and significant changes in properties than ANN-80. The thermal stability of sohphlang starch gels may extend its application in foods requiring severe processing conditions such as pasteurized foods.

Experimental study on the development mode and evolution mechanism of sodium silicate solidified sand under different temperatures and curing paths

Water glass, which can be cured by rapid dehydration, is an ideal environmentally friendly material for engineering grouting solidification and ecological environment restoration. The curing efficiency of water glass at room temperature was low, the curing mechanism and strength characteristics at high temperature were not clear, and the engineering applicability and optimal curing methods were to be explored. In this paper, 10 curing paths were designed within 100 °C. The mechanical and acoustic characteristics of water glass-cured sandy soils were tested by uniaxial compressive tests and acoustic emission (AE). The relationship between strength, wave velocity and curing age was established based on the “logistics” model. The characteristic parameter “Q” value was proposed based on the AE characteristic value. Combined with the results of scanning electron microscopy (SEM), the solidification evolution process was revealed in terms of gel structure, crystal morphology and pore space. The process of water glass curing sandy soil was divided into a “strength rising period” and a “strength deterioration period”. The enhancement and weakening effects of high temperature on the gel layer were stronger than those at room temperature. The longer the room temperature curing time is, the weaker the effect of high temperature on the specimen. After high-temperature curing, the maximum strength of the specimens increased by 107.85 %, and the strength growth rate and strength deterioration rate increased by 586.34 % and 3738.79 %, respectively. The conversion rate of the gel under high temperature conditions determined the strength of the specimen. The rate of strength deterioration of the specimen was determined by the hardening effect of the undehydrated gel and the excessive dehydration effect of the rigid gel.

Heat-induced gelation of SAM myofibrillar proteins as affected by ionic strength, heating time and temperature: With emphasis on protein denaturation and conformational changes

There is a growing consumption of scallop adductor muscle (SAM) based food due to its great nutritional value and high digestibility. SAM gelation has a key effect on final products, however, the gelling properties of SAM, particularly the denaturation and conformational changes of proteins, are far less known. Thus, the present study aimed to improve our understanding on the gelation of SAM as affected by different heating temperatures, time, and ionic strength at low salt concentration ranges. Protein denaturation is the primary reason for the physicochemical changes of minced SAM during thermal gelling. Both gel strength and storage modulus showed positive correlations with heating temperature and time. However, the water holding capacity decreased gradually from 60 to 90 °C due to the shrinkage of myofibril proteins induced by protein denaturation, resulting in the transformation of immobilized water into free water, as proved by LF-NMR results. DSC and FTIR results indicated that heating at 90 °C led to complete degeneration of myosin and actin, and partial conversion of α-helices to β-sheets and random coil, resulting in a more rigid gel. It was further discovered that rapid heating (90 °C-10min) of low salt SAM at 1.5% NaCl concentration during gelation contributed to a superior gel strength and the reinforcement of fine-stranded three-dimension gel matrix as revealed by SEM. The investigation of heat-induced SAM provides a practical value for the processing of low-salt minced SAM products for the food industry.

Experiment and Improvement Mechanism Analysis on the Mechanical Properties of Improved Chlorine Saline Soil

Chlorine saline soil has adverse engineering geology such as dissolution, collapse, and pulping, the recycling of saline soil in subgrade treatment is of great research significance. First, the unconfined compressive strength (UCS) test was conducted using an orthogonal test design, and the optimal ratios of salt content, cement content, lime content, fiber content, and fiber length were determined. Second, the cyclic loading (CL) test was conducted using an orthogonal test design, and the influence of five factors, including freeze–thaw (FT) times, CL times, stress level (SL), amplitude, and frequency, on peak intensity, peak strain, and cumulative strain under FT cycles and natural air-drying (A-D) conditions were determined. Finally, the improvement mechanism of the above inorganic materials was microscopically analyzed by scanning electron microscope-energy dispersive spectrometer and X-ray diffraction tests. The UCS test results show that the improving effect of the optimal ratio for chlorine saline soil was best when the optimal ratio values were 3% (salt content), 8% (cement content), 12% (lime content), 0.2% (fiber content), and 18 mm (fiber length). CL test results show that with the increase in natural A-D time, it was found that the FT number and SL have significant effects on the strength, the number of FT times and cycle times have significant effects on the deformation, and the frequency and cycle times have significant effects on the cumulative deformation. From the microstructure analysis, the improvement mechanism is mainly the filling of pores and linking particles by water-hard gels and gas rigid gels to make the microstructure dense, effectively reduce pores, and effectively improve the engineering characteristics of chlorine saline soil. The results of this study provide a scientific basis for the engineering design of subgrade in arid areas and the in situ recycling of saline soil.

Electrostatic hindrance to diffusion in flexible crosslinked gels: A coarse-grained simulation study.

In this work, we study how electrostatic forces slow down the diffusion of solute in flexible gels through coarse-grained simulations. The model used explicitly considers the movement of solute particles and polyelectrolyte chains. These movements are performed by following a Brownian dynamics algorithm. The effect of three electrostatic parameters characterizing the system (solute charge, polyelectrolyte chain charge, and ionic strength) is analyzed. Our results show that the behavior of both the diffusion coefficient and the anomalous diffusion exponent changes upon the reversal of the electric charge of one of the species. In addition, the diffusion coefficient in flexible gels differs significantly from that in rigid gels if the ionic strength is low enough. However, the effect of chain flexibility on the exponent of anomalous diffusion is significant even at high ionic strength (100 mM). Our simulations also prove that varying the polyelectrolyte chain charge does not have exactly the same effect as varying the solute particle charge.

Fabrication of a double-network high internal phase emulsion gel stabilized by bacterial cellulose nanofibrils: Enhancement of heat stability and 3D printing

The semi-fluid properties required for 3D printing of high internal phase emulsion (HIPE) gels are incompatible with high mechanical strength, thereby limiting the application of HIPE gels in simulated meat products. In this study, pea protein (PeaP)-stabilized HIPEs reinforced with bacterial cellulose nanofibrils (BCNFs) were constructed and deformed into PeaP/sodium alginate (SA) double-network HIPE gels by further cross-linking of transglutaminase (TGase) and Ca2+. Increasing the BCNF concentration decreased the interfacial tension of water-in-oil HIPE emulsions from 11.91 mN/m to 9.49 mN/m, and reduced the average diameter of the droplets from 27 ± 3.1 μm to 11.3 ± 0.6 μm. The HIPEs also showed a thicker interfacial layer and improved viscoelastic properties at higher BCNF concentrations. The HIPEs were transformed from a semi-solid material to a rigid solid HIPE gel after the formation of a double-network structure. The fracture stress of the double-network HIPE gel containing 0.16% BCNFs was 0.015 MPa, which was greater than that of 0.001 MP and 0.007 MPa for the single-network SA and PeaP HIPE gels. The double-network HPIE gels fabricated with 0.08%–0.16% BCNF concentrations had high-temperature stability. The synergistic effect of the PeaP covalent network and the SA-Ca2+ ionic network produced a HIPE gel with good extrusion printability and strong self-supporting properties. This work could provide new insights into the design of high-strength HIPE gels with 3D printability that will facilitate the use of emulsion gels in plant-based meat products.

Properties of whey protein isolation/konjac glucomannan composite gels: Effects of deacetylation degrees

The effects of konjac glucomannan (KGM) with different deacetylation degrees (DDs) on the gel properties of whey protein isolate (WPI) were investigated. The appropriately deacetylated KGM (DDs in the range of 0–53.85 %) incorporated within WPI and formed relatively uniform compound gels, while excessive deacetylated KGM (DDs = 63.46 or 71.63 %) caused macroscopic precipitation and aggregation in WPI-KGM system. The water holding capacity of WPI-KGM gels decreased with the gradual increase of DDs, and the removal of acetyl groups reduced the whiteness of the composite gels. The hardness and chewiness of the composite gel tended to increase and subsequently decrease with the enhancement of DDs, and reached the maximum (244.15 and 148.88 g, respectively) at the DDs of 53.85 %. The rheological analysis indicated that rigid structured WPI-KGM gels could be formed when incorporated with moderately deacetylated KGM. The deacetylated KGM (DDs = 53.85 %) enhanced the hydrogen bond and disulfide bond within the mixed system, resulting in a more compact network structure of the composite gels. Moreover, deacetylated KGM particles might also reinforce the gel strength by the “filling effects”. Overall, the gelation characteristics of the WPI-KGM system can be regulated by controlling the DDs of KGM.

Stress-stress correlations reveal force chains in gels.

We investigate the spatial correlations of microscopic stresses in soft particulate gels using 2D and 3D numerical simulations. We use a recently developed theoretical framework predicting the analytical form of stress-stress correlations in amorphous assemblies of athermal grains that acquire rigidity under an external load. These correlations exhibit a pinch-point singularity in Fourier space. This leads to long-range correlations and strong anisotropy in real space, which are at the origin of force-chains in granular solids. Our analysis of the model particulate gels at low particle volume fractions demonstrates that stress-stress correlations in these soft materials have characteristics very similar to those in granular solids and can be used to identify force chains. We show that the stress-stress correlations can distinguish floppy from rigid gel networks and that the intensity patterns reflect changes in shear moduli and network topology, due to the emergence of rigid structures during solidification.