# Mechanical properties of carboxymethyl cellulose aerogels and cryogels

Sujie Yu, Christophe Pradille, Tatiana Budtova

► To cite this version:

Sujie Yu, Christophe Pradille, Tatiana Budtova. Mechanical properties of carboxymethyl cellulose aerogels and cryogels. Cellulose, 2025, 32 (12), pp.7173-7186. 10.1007/s10570-025-06647-z. hal-05428050

HAL Id: hal-05428050

https://hal.science/hal-05428050v1

Submitted on 21 Dec 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Mechanical properties of carboxymethyl cellulose aerogels and cryogels

Sujie Yu · Christophe Pradille · Tatiana Budtova

Received: 15 February 2025 / Accepted: 13 June 2025 / Published online: 28 June 2025
© The Author(s) 2025

**Abstract** Lightweight and highly porous carboxymethyl cellulose (CMC) aerogels were prepared from CMC solutions *via* non-solvent induced phase separation, followed by supercritical CO₂ drying. Direct freeze-drying of CMC solutions was used to obtain “cryogels” for comparative analysis. The influence of CMC concentration and of drying method on the morphology, density, porosity and mechanical response of CMC aerogels and cryogels under uniaxial compression were evaluated. Two methods were used: direct data collection from the machine sensors and the digital image correlation (DIC) technique. It was demonstrated that DIC method is more precise; video-monitoring of the changes in sample shape and dimensions was also performed. Nominal stress–strain dependences were constructed, and compressive modulus, yield stress, absorbed energy and sample volume evolution under compression were analyzed as a function of density and material

morphology. The elastic recovery of cryogels is slightly higher than that of aerogels at the similar density. The “equivalent” Poisson’s ratio (at 50% strain) was nearly zero for cryogels, while for aerogels it was non-zero and decreased with increasing density. The difference in the mechanical response of aerogels vs cryogels was attributed to their different morphology.

**Keywords** CMC · Supercritical drying · Freez drying · Porosity · Uniaxial compression · Digital image correlation

## Introduction

Lightweight and porous cellulose-based materials have attracted significant attention due to polymer renewability, tuneable architecture, and broad spectrum of applications. These materials have been explored in diverse areas such as biomedical and pharmaceutical engineering (e.g., controlled release, scaffolds), environmental remediation (e.g., absorption and adsorption), optics, electrochemical devices, catalysis, thermal insulation, and more recently, thermoelectric energy conversion (Lavoine and Bergström 2017; Budtova 2019; Rahmanian et al. 2021; Alias et al. 2023; Liu et al. 2023, 2024; Ashori et al. 2024; Shi et al. 2025). In this work, we consider two types of porous materials: aerogels and so-called “cryogels”. Aerogels are open-pores low-density nanostructured materials with high specific surface

<footnote>**Supplementary Information** The online version contains supplementary material available at https://doi.org/10.1007/s10570-025-06647-z.</footnote>

<footnote>S. Yu · T. Budtova (✉)
Center for Materials Forming (CEMEF), Mines Paris, PSL University, UMR CNRS 7635, CS 10207, 06904 Sophia Antipolis, France
e-mail: tatiana.budtova@minesparis.psl.eu</footnote>

<footnote>C. Pradille
Mat Xper, 19 Traverse du Barri, 06560 Sophia Antipolis,
France</footnote>
area; aside some exceptions, they are usually obtained by evacuation of a liquid from gel pores' by drying in supercritical conditions; in certain cases, freeze-drying and even evaporative drying may also result in aerogel-like materials (Fumagalli et al. 2013; Druel and Budtova 2023). By “cryogels” we will name materials obtained by freeze-drying; they are usually highly macroporous with large pores being replicas of sublimated large ice crystals.

Cellulose porous materials can be fabricated either from various types of nanocellulose or *via* cellulose dissolution-coagulation-drying route (Lavoine and Bergström 2017; Budtova 2019). Nanocellulose-based materials will not be considered here as they fall beyond the scope of our work. The use of porous cellulose materials prepared *via* dissolution-coagulation-drying route in life science applications is limited due to the potential presence of residual solvents, most of which are considered unacceptable for biomedical use. As a result, cellulose is frequently chemically modified to enhance its water solubility and material biocompatibility, enabling its broader application in these fields.

Carboxymethyl cellulose (CMC), a widely used cellulose derivative, is valued for its excellent compatibility with skin and mucous membranes, enabling its broad application in the food, cosmetic, pharmaceutical and biomedical industries (He et al. 2021; Martins et al. 2021; Pourmadadi et al. 2023; Verger et al. 2024). The majority of literature reports CMC cryogels based on crosslinked CMC (Nayak and Kundu 2014; Lin et al. 2015; Diaz-Gomez et al. 2022). Compared to “wet” CMC porous materials like hydrogels, aerogels and cryogels exhibit several advantages: (1) high breathability and absorption capacity, (2) ease of storage and transportation due to low density, (3) no concerns related to bacterial growth. Very recently, the first CMC aerogels were reported; no additives or crosslinkers, which could compromise biocompatibility, were used (Yu and Budtova 2024; Yu et al. 2025). These aerogels were obtained by polymer dissolution, solvent exchange (leading to network formation due to non-solvent induced phase separation), and drying with supercritical CO₂. CMC cryogels, also prepared without any additives or crosslinkers, were made by freeze-drying CMC solutions (Yu and Budtova 2024).

In all practical applications, understanding and controlling the mechanical properties of materials is essential. For porous materials, a critical focus is

placed on the correlation between mechanical properties and the material's density and morphology. Extensive experimental work has been performed on silica aerogels to improve their mechanical properties and address their inherent brittleness caused by weak Si-O-Si necking connections (Karamikamkar et al. 2020). Four main strategies have been used: (1) increasing aging temperature (Reichenauer 2004; He et al. 2009), (2) crosslinking the silica backbone with polymers (Leventis 2007; Boday et al. 2009; Karamikamkar et al. 2020; Meti et al. 2022), (3) introducing a secondary phase before gelation (Yim et al. 2002; Maleki et al. 2014; Karamikamkar et al. 2020; Meti et al. 2022), and (4) incorporating flexible silica precursors (Boday et al. 2010; Maleki et al. 2014; Matias et al. 2016; Karamikamkar et al. 2020). Compared to silica aerogels, synthetic polymer-based aerogels (e.g., polyurea, resorcinol-formaldehyde) exhibit superior mechanical properties and are not brittle (Leventis et al. 2010; Shinko et al. 2015; Schwan et al. 2016). However, bio-aerogels' mechanical properties and their correlation with material morphology are far from being explored, most probably because they are rather “young” materials. Nothing is known on the mechanical properties of CMC aerogels, and no comparison between CMC aerogel and cryogel exists.

The mechanical properties of bio-aerogels are analysed mainly using uniaxial compression tests because of practical reasons: making dumbbell-shape samples for tensile testing or thin rectangular samples for impact or flexural tests is challenging. The standard way to obtain stress-strain dependences is to use data recorded by equipment (we will name them “machine method”). However, it is known from the mechanics of polymers, that displacement data taken using the machine method include not only the compression of the sample within the gauge region, but also the displacement caused by the stiffness of the machine itself, which can lead to inaccurate assessments of the sample's mechanical properties (G'Sell et al. 1992; Chen et al. 2021). To address this problem, which is inherent for all types of equipment used for testing mechanical properties, non-contact displacement measurement methods were developed. The idea is to track the displacement of speckles, randomly applied on sample's and/or machine's surface, using digital image correlation (DIC) technique (Sutton et al. 2009; Candau et al. 2016; Chen et al. 2021). Only few publications use
this approach to analyze the mechanical properties of some classical aerogels such as resorcinol–formaldehyde aerogels (Schwan et al. 2015), carbon aerogels (Rege et al. 2020), ceramic-based aerogel (Sun et al. 2013) and silica-based aerogels (Haj-Ali et al. 2016; Ji et al. 2020). As far as bio-aerogels are concerned, their mechanical properties have been studied using a machine method applied on cellulose, pectin, chitosan and alginate aerogels (Sescousse et al. 2011; Rudaz et al. 2014; Martins et al. 2015; Ganesan et al. 2016; Buchtová et al. 2019; Tabernero et al. 2020; Guerrero-Alburquerque et al. 2020). Two articles report on using DIC method to analyse bio-aerogels’ mechanical properties: for silk fibroin aerogel (Viola et al. 2024) and for cellulose aerogel (Rege and Itskov 2018). Very few articles report on the mechanical properties of aerogels based on cellulose derivatives. One utilized mercury porosimetry, monitoring volumetric changes of cellulose acetate aerogels under applied pressure rather than directly measuring the stress-strain relationships (Fischer et al. 2006). Mechanical properties of methyl cellulose aerogels were analysed under compression using machine method (Iglesias-Mejuto et al. 2024). Finally, impact properties of cellulose acetate and cellulose acetate butyrate aerogels were reported (Tan et al. 2001).

The goal of this work was to analyse and compare the mechanical properties of two types of CMC porous materials, aerogels and cryogels, under uniaxial compression. CMC were of similar molecular weight but different degree of substitution (DS), and the initial solutions were of various polymer concentrations. CMC aerogels and cryogels were prepared following the protocol described in ref. (Yu and Budtova 2024; Yu et al. 2025). The prepared materials were first characterized in terms of density, porosity, specific surface area and morphology. Stress-strain dependences were analysed using machine and DIC approaches. Sample volume variation during compression, loading-unloading cycles at low strains and main characteristics, such as compressive modulus, yield stress and absorbed energy, were correlated with the properties of porous CMC.

# Materials and methods

## Materials

Two CMC samples were kindly supplied by IFF (Walsrode, Germany) with molecular weight of 16×10⁴ g mol⁻¹ and 17×10⁴ g mol⁻¹, and DS of 0.9 and 0.7, respectively (Yu and Budtova 2024). These CMC samples will be named M16D9 and M17D7, respectively. Absolute ethanol was obtained from Fisher Chemical. All solutions were prepared using distilled water.

## Preparation of CMC aerogels and cryogels

The preparation of CMC aerogels and cryogels has been detailed previously (Yu and Budtova 2024). In brief, dried CMC powder was dissolved in distilled water at concentrations ranging from 3 to 7 wt% at room temperature. The resulting solutions were then poured into cylindrical polypropylene vials serving as moulds. To obtain CMC cryogels, the solutions were frozen using liquid nitrogen (without applying any directional freezing techniques) and then immediately freeze-dried in a freeze-dryer (Cryotec Cosmos 80, cold trap temperature -80 °C, pressure 5×10⁻⁵ bar) for 48 h. To obtain aerogels, water should be replaced by a fluid miscible with CO₂ to further perform drying in supercritical conditions, ethanol was used for this purpose. It was poured on top of CMC solutions to form the CMC coagulated network via non-solvent induced phase separation. Several washing steps were applied to replace water with ethanol.

Drying with supercritical CO₂ was performed at the PERSEE center of Mines Paris-PSL, following established protocols (Groult et al. 2021a; Zou and Budtova 2021; Yu and Budtova 2024; Yu et al. 2025) with some minor modifications. First, the aerogel precursor was placed in an autoclave (1 L), and an excess of ethanol was added to cover the sample. The autoclave was sealed, and the CO₂ was introduced until the pressure reached that of the CO₂ bottle (approximately 50 bar). As the pressure increased, the excess ethanol was purged. Subsequently, the temperature was set at 37 °C, and the pressure was further raised to 80 bar, above the critical point of CO₂. The system was maintained at 80 bar and 37 °C for 3–4 h while dynamic washing was performed at a flow rate of 50 g CO₂/min. The system was then slowly depressurized.
overnight at a rate of 4 bar/h until ambient conditions were reached, after which the aerogels were collected. The aerogels and cryogels were stored in a desiccator to prevent moisture uptake from the air.

## Shrinkage, bulk density and porosity

The volume shrinkage during the preparation of aerogels was calculated using Eq. 1:

$$ \text{Volume shrinkage}(\%) = \frac{V_0 - V_i}{V_0} \times 100\% \quad (1) $$

where $V_0$ is the volume of the CMC solution before solvent exchange, and $V_i$ is the volume of the sample at the corresponding step, either after solvent exchange or after drying.

The bulk (or envelope) density $\rho_{\text{bulk}}$ was calculated from sample mass measured with high-precision balance and volume measured using a GeoPyc 1360 (Micromeritics) with a 19.1 mm diameter chamber. The applied force was 21 N, and each sample was measured five times. Standard deviations of density values were below 0.01 g/cm³.

The porosity and pore volume $V_p$ were calculated using the bulk density and skeletal density:

$$ \text{Porosity}(\%) = \left( 1 - \frac{\rho_{\text{bulk}}}{\rho_{\text{skeletal}}} \right) \times 100\% \quad (2) $$

$$ V_p(\text{cm}^3/\text{g}) = \frac{1}{\rho_{\text{bulk}}} - \frac{1}{\rho_{\text{skeletal}}} \quad (3) $$

where $\rho_{\text{skeletal}} = 1.5 \text{ g/cm}^3$.

## Specific surface area

The specific surface area was determined using nitrogen adsorption with the ASAP 2020 (Micromeritics) and the Brunauer–Emmett–Teller (BET) method. All samples were degassed under vacuum at 70 °C for 10 h before measurement.

## Scanning electron microscopy (SEM)

The morphology of the CMC aerogels and cryogels was analyzed using a SEM MAIA3 Triglav™ (Tescan) equipped with a secondary and backscattered electron detector. Samples were broken and internal

surfaces were sputtered with a 14 nm layer of platinum using a Q150T ES metallizer (Quorum) to prevent electrostatic charge build-up and image defaults. Observations were carried out under an accelerating voltage of 3 kV.

## Mechanical properties

The mechanical properties of aerogels and cryogels were evaluated under the uniaxial compression using an Instron 5967 testing machine equipped with a 30 kN load cell. The load sensor is calibrated in class 0.5 until 1/250 of the maximum load. Samples were polished with P240 sandpaper (grain size approximately 60 µm) to achieve parallel and planar surfaces. The diameter-to-height ratio was approximately 2.5–2.7. Compression tests were performed at room temperature and relative humidity around 60%, with a compression rate of 0.05 mm/min. A preload of 0.5 N to 1 N was applied to ensure the contact between the compression plates and the sample. To evaluate the elastic behavior of the material, three loading and unloading cycles were performed at strains of 5%, 10% and 15%. Compression was then increased to 80% strain, following previously reported protocol (Viola et al. 2024).

Two approaches were used to obtain stress–strain dependences. One was the force–displacement data collected directly from the Instron equipment (so-called “machine method”). The second was the DIC technique. To monitor the displacement of the sample, the surface of the compression plates of the machine was sprayed with black ink to create a random speckle pattern (Fig. 1). A dual-camera stereovision

<figure><img src="image_2.png" /><figcaption>Fig. 1 Experimental setup with the stereovision system and schematic presentation of a sample with speckles on machine plates</figcaption></figure>
system was used to monitor the local displacement of the compression plates, therefore providing the real displacement, and also recording all transformations sample underwent under compression (e.g. the evolution of diameter). DIC was then used to construct a displacement field. The 3D DIC system was calibrated until the error was minimized to 0.05 (Sutton et al. 2009).

The displacement was determined by tracking the position of speckle patterns on the machine surface during compression. The collection of pixel values is referred to as a subset (Chen et al. 2021). The displacement field was constructed from images captured by a pair of AVT Alvium 12Mpx cameras equipped with 2/3” CCD sensors and 75 mm Ricoh lenses. Images were captured every second and post-processed using VIC-3D software (VIC-3D 2009). The initial step of the analysis involved creating a regular mesh in the region of interest, which facilitated the tracking of the speckle pattern during the compression test. In this work, the subset was set to

53 pixels, with a step of 20 for the two plates. Subsequently, the DIC method was used as a video compression gauge.

## Results and discussion

Density, specific surface area and morphology of aerogels and cryogels

First, CMC aerogels and cryogels were characterised. Bulk density of M17D7 and M16D9 aerogels and cryogels is shown in Fig. 2a as a function of CMC concentration in the initial solution. For comparison, the theoretical density was also calculated for a hypothetical case of zero shrinkage. The higher the concentration, the higher the density, as expected and reported for other bio-aerogels (Innerlohinger et al. 2006; Takeshita et al. 2019; Buchtová et al. 2019; Zou and Budtova 2021; Zou et al. 2022). Bulk density of aerogels was between 0.1 and 0.55 g/cm³, the values

<figure><img src="image_3.png" /><figcaption>**Fig. 2** Characterisation of M17D7 (filled points) and M16D9 (open points) aerogels (in red) and cryogels (in black): a Bulk density as a function of CMC concentration with solid line representing the theoretical density in case of zero volume shrinkage; b specific surface area as a function of the density; inner</figcaption></figure>

morphology of CMC cryogels c and aerogels d made from 5% M17D7 solutions. If the error bars are not seen, they are smaller or equal to symbols. Dashed lines are given to guide the eye
similar to the bulk density of bio-aerogels reported in the literature for similar initial concentrations of a dissolved polysaccharide (Buchtová and Budtova 2016; Buchtová et al. 2019; Yu and Budtova 2024). The CMC DS had no significant influence on the bulk density within the studied range. The density of aerogels is higher than the theoretical one because of volume shrinkage occurring during solvent exchange and drying processes (see Eq. 1 and Fig. S1 in the Supporting Information demonstrating shrinkage associated with each processing step). Total volume shrinkage during the transition from CMC solution to the final aerogel is high, ranging from approximately 75 to 90 vol % (Fig. S1). Solvent exchange resulted in a shrinkage of 66 – 70 vol %, with higher shrinkage observed at lower polymer concentration in solution. The bulk density of cryogels is lower than that of aerogels, ranging between 0.04 and 0.08 g/cm³, and it is nearly equal to the theoretical density due to minimal volume shrinkage (around 10–20 vol %, see Fig. S1). Consequently, the porosity (Eq. 2) of cryogels is higher (95% – 97%) than that of aerogels (63% – 93%). The pore volume (Eq. 3) of cryogels, ranging from 12 to 24 cm³/g, is much higher than that of aerogels (1 – 8 cm³/g), as expected from density and reported for various bio-aerogels and cryogels (Korhonen and Budtova 2020; Chartier et al. 2022; Ciuffarin et al. 2023).

Specific surface area of aerogels and cryogels based on M17D7 and M16D9 is presented in Fig. 2b as a function of material density. As reported in previous studies, the specific surface area and inner morphology of porous materials are strongly influenced by the drying method (Buchtová and Budtova 2016; Zou and Budtova 2021; Groult et al. 2021b; Chartier et al. 2022; Zou et al. 2022). Aerogels demonstrated much higher specific surface area than cryogels, as expected, from 31 to 143 m²/g vs 4 – 10 m²/g, respectively (Fig. 2b). A similar trend has been reported in the literature for other bio-aerogels and cryogels (Buchtová et al. 2019; Zou and Budtova 2021; Groult et al. 2021b; Chartier et al. 2022; Yu and Budtova 2024). This difference is attributed to much larger pores (typically, around several microns) in cryogels (Fig. 2c), which are formed due to ice crystals’ growth during water freezing process. In contrast, although some shrinkage occurs during supercritical CO₂ drying (Fig. S1), likely due to the low affinity between CMC and CO₂, the latter being highly

non-polar while CMC is hydrophilic, the morphology of the coagulated CMC network (alcogel) is well preserved (Fig. 2d). As a result, a fine nanostructure fibrillated texture with pore sizes ranging from approximately 150 nm to 230 nm is retained, contributing to the significantly higher specific surface area of the aerogels. Such nanostructured fibrillated texture is typical for aerogels based on polysaccharides, including those made from pectin (Groult and Budtova 2018), starch (Zou and Budtova 2023) and alginate (Paraskevopoulou et al. 2021). The specific surface area slightly decreased as the CMC density (or polymer concentration in the solution) increased (Fig. 2b).

Stress–strain dependences and elastic recovery of aerogels and cryogels

The nominal stress-nominal strain dependences obtained from the uniaxial unconfined compression of CMC aerogels and cryogels are shown in Fig. 3a and 3b, respectively. The samples are not brittle, and no dust release during compression was observed. These figures compare stress–strain curves obtained via the DIC method with those obtained directly from machine sensors. For aerogels, for the same nominal stress, the nominal strain measured by machine sensors was higher than that obtained via the DIC method due to the input of machine stiffness. Similar results were obtained for all-cellulose composites (Chen et al. 2021) and for polypropylene composites (Jerabek et al. 2010). No significant differences were observed between the results obtained using DIC method and the machine method for cryogels (Fig. 3b). We assume that the reason is very low stresses exhibited by very low-density cryogels; the “input” of the machine is thus very low. Considering the systematic errors caused by machine stiffness recorded for aerogels, we used the data obtained via the DIC method for all subsequent analyses.

As previously reported for various bio-aerogels and cryogels (Sescousse et al. 2011; Luo et al. 2019; Guerrero-Alburquerque et al. 2020; Xiao et al. 2021; Joshi et al. 2023) and well known for porous materials (Gibson and Ashby 1997), the stress–strain curves of CMC aerogels and cryogels exhibit three zones. At low strains, a linear elastic region is recorded, allowing for the determination of the compressive modulus. With strain increase, the material undergoes a plastic
<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /><figcaption>**Fig. 3** Stress–strain curves for **a** CMC aerogels, **b** cryogels, and **c** M17D7 aerogel and cryogel of similar density. Solid lines represent data from DIC analysis and dashed lines represent data directly from machine sensors. “Den” indicates material density</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>**Fig. 4** Examples of stress–strain curves for loading–unloading cycles at low strains for M17D7 aerogel and cryogel. “Den” represents the density of samples</figcaption></figure>

deformation due to the buckling and breaking of pore walls, enabling the absorption of large amounts of energy. The latter is usually calculated as the area under the stress–strain curve up to 40% strain. Finally, at high strains, the material undergoes densification, as evidenced by an abrupt increase in stress. After the completion of the compression experiment, CMC aerogels and cryogels do not recover their shape, resulting in more than double increase of density. Consequently, they behave as elasto-plastic foams. The same trends were observed for cellulose-based aerogels and cryogels (Sescousse et al. 2011; Buchtová et al. 2019).

Aerogels and cryogels of similar densities, as shown in Fig. 3c, exhibit distinct mechanical behavior in the low-strain range. Cryogels demonstrate significantly higher stress at low strains compared to aerogels, and larger elastic region. The reason is very different morphology of cryogels and aerogels (Fig. 2c and 2d, respectively): CMC aerogels possess a fine nanostructured fibrillated texture with very thin pore walls of approximately 10–30 nm (as estimated from SEM images), whereas CMC cryogels have sheet-like pore walls of thickness ten times higher than that of aerogels, around 0.3 to 0.8 µm (Fig. 2c).

The elastic properties of aerogels and cryogels were evaluated by applying loading–unloading compression cycles (see example in Fig. 4 and more results in Fig. S2 of the Supporting Information). The elastic recovery was evaluated as the difference
between the maximum and minimum strain values in the first loading-unloading cycle (see a similar approach for silk fibroin aerogels (Viola et al. 2024). Aerogels exhibit slightly lower elastic recovery compared to cryogels (1–3% vs. 2–3%, respectively), this difference falling almost within the experimental error. Nevertheless, M17D7 cryogel (density: 0.08 g/cm³) demonstrated higher elastic recovery, about 2.5% compared to 1.3% for the M17D7 aerogel (density: 0.11 g/cm³), Fig. S2. As the loading/unloading curves do not overlap, the viscous component of the viscoelastic solid dominates the elastic component in all CMC aerogels and cryogels (Fig. S2).

Poisson’s ratio is an important parameter used to characterize porous material mechanical properties. However, limited analysis has been performed of the Poisson’s ratio of bio-aerogels which is usually considered to be zero (Sescousse et al. 2011; Rudaz et al. 2014; Rege et al. 2016; Schestakow et al. 2016), and only few reports have focused on the Poisson’s ratio of cellulose II aerogels (Ganesan et al. 2016; Buchtová et al. 2019). The Poisson’s ratio should be calculated in the elastic region. However, as the latter is very small for CMC aerogels and cryogels, an “equivalent” Poisson ratio was calculated using the following equation:

$$ \text{Poisson's ratio}_{50} = - \frac{\epsilon_{\text{lateral}}_{50}}{\epsilon_{\text{longitudinal}}_{50}} \qquad (4) $$

where $\epsilon_{\text{lateral}}_{50}$ and $\epsilon_{\text{longitudinal}}_{50}$ represent strains in lateral (here, relative diameter $\frac{D_{50}-D_0}{D_0}$) and longitudinal (here, relative height $\frac{L_{50}-L_0}{L_0}$) directions at 50% deformation, with $D_0$ and $L_0$ being sample initial diameter and height.

The evolution of samples’ diameter and height during compression was recorded with stereovision system (see Methods) and the equivalent Poisson’s ratio is plotted in Fig. 5a for all studied samples. A slight decrease in the diameter of the cryogels (Fig. 5b) was observed resulting in negative- to close-to-zero Poisson’s ratio (Fig. 5a). Equivalent Poisson ratio equal to zero was reported for cellulose II cryogels (Buchtová et al. 2019). A slightly negative Poisson ratio may be attributed to large macropores of CMC cryogels (Fig. 2c) with pore walls bending inward the pore upon compression. However, this effect is small.

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /><figcaption>Fig. 5 a Poisson’s ratio and b relative diameter, both at 50% deformation, as a function of density for M17D7 (open points) and M16D9 (filled points) aerogels and cryogels</figcaption></figure>

The diameter of aerogels expanded under compression (Fig. 5b), and the equivalent Poisson’s ratio slightly decreases from 0.36 to 0.28 with density increase (Fig. 5a). Similar, but a more pronounced trend was reported for cellulose II aerogels (Buchtová et al. 2019). No influence of CMC DS was obtained for the samples studied. For classical silica and silica-based aerogels, the Poisson’s ratio ranges from 0.13 to 0.22 (Gross et al. 1988; Nadargi et al. 2009; Woignier et al. 2020). For graphene aerogels, the Poisson’s ratio varies significantly, spanning from positive values (0 to 0.4) to negative values (0 to -0.3) (Xu et al. 2016).

When an object is deformed, it may change its volume or not. We estimated the volume change of our aerogels and cryogels as $(V_0 - V_{50})/V_0$, where $V_0$ is the sample initial volume and $V_{50}$ is the sample volume at 50% deformation. In all cases studied,
sample volume decreased, as expected, due to high
deformation and not very large increase in diameter
of aerogels and practically no change in diameter for
cryogels. For aerogels, volume decrease was within
30–45%, and for cryogels, it was higher and close to
the theoretical value of 50%, within 50–53%.

The compressive modulus (E) was calculated from
nominal stress–strain curves derived from the DIC
approach as a function of bulk density, for both aero-
gels and cryogels (Fig. 6a). Unsurprisingly, the higher
the density, the higher the compressive modulus. This
dependence can be approximated by a power law
$E \sim \rho^n$, as predicted for foams (Gibson 1981; Gibson

<figure><img src="image_10.png" /><figcaption>**Fig. 6** a Compressive modulus as a function of density for aerogels (red) and cryogels (black) of M17D7 (filled points) and M16D9 (open points), respectively. The dashed lines represent the power law trends. b Summary of compressive modulus vs. bulk density of polysaccharide-based aerogels: results from the literature (Zhao et al. 2018) and from the current work (indicated by star symbols). Figure adapted with permission from the publisher (Zhao et al. 2018)</figcaption></figure>

and Ashby 1982, 1997) and observed for both bio-
based and non-bio-based aerogels (Gross et al. 1988;
Sescousse et al. 2011; Buchtová et al. 2019; Zou et al.
2022). The scaling exponent *n* is approximately 2.3
for CMC aerogels (Fig. 6a), falling in the range of
*n* of organic and inorganic aerogels (Woignier et al.
1989; Scherer et al. 1995; Sescousse et al. 2011;
Wong et al. 2014; Diascorn et al. 2015; Zhao et al.
2018). For cryogels *n* is around 4, however, this value
should be taken with care as density interval is too
small to deduce reliable trends.

At a similar density, the compressive modulus of
cryogel is higher than that of aerogel (Fig. 6a). A
similar result was obtained for cellulose II aerogels
and cryogels (Buchtová et al. 2019). As already men-
tioned above, the reason lies in the significantly dif-
ferent morphology of CMC aerogels and cryogels,
with more than tenfold difference in the thickness of
their pore walls (Fig. 2c and Fig. 2d). A comparison
of the compressive modulus vs. bulk density with
polysaccharide-based aerogels, reported in the litera-
ture and obtained in this work, is provided in Fig. 6b.
The results obtained for CMC aerogels and cryogels
fall within the trend shown for cellulose aerogels and
foams (blue line).

The compressive yield stress (σ), taken at the end
of the elastic regime, and absorption energy (W),
calculated at 40% strain, are plotted as a function of
density for CMC aerogels and cryogels in Fig. 7a
and Fig. 7b, respectively. Each is approximated as
power-law function of density. The exponent for the
yield stress of aerogels is lower than that reported for
cellulose II aerogels (Sescousse et al. 2011; Gane-
san et al. 2016). As shown in Fig. 7b, CMC aerogels
and cryogels effectively absorb energy under com-
pression with values similar to those of cellulose II
aerogels (Sescousse et al. 2011). The influence of DS
on the mechanical properties of CMC aerogels and
cryogels appears to be negligible, within the studied
range, compared to the influence of their density and
morphology.

Overall, the high porosity CMC aerogels prepared
in this work exhibit promising mechanical proper-
ties, with compressive modulus ranging from few to
160 MPa, compressive strength up to around 45 MPa,
yield stress between 420 and 3000 kPa, and absorp-
tion energy values between 200 and 5170 kJ/m³. The
cryogels made from the same solutions, but possess-
ing lower density, show compressive modulus from
<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /><figcaption>**Fig. 7** a Yield stress and b absorption energy as a function of density for aerogels (red) and cryogels (black) of M17D7 (filled points) and M16D9 (open points), respectively. The dashed lines represent the power law trends</figcaption></figure>

1 to 14 MPa, compressive strength up to around 4 MPa, yield stress of 30–370 kPa and energy absorption ranging from 20 to 220 kJ/m³. These properties fall within the ranges required for various biomedical applications. For example, human trabecular bone tissue exhibits porosity between 40 and 95% (Morgan et al. 2018), compressive modulus from 1 to 5000 MPa, and compressive strength ranging from 0.1 to 30 MPa (Eshraghi and Das 2010). Taken together, the mechanical properties of our CMC aerogels and cryogels suggest that they have potential in biomedical applications.

## Conclusions

The mechanical properties of CMC aerogels and cryogels under uniaxial compression were investigated. Two approaches were used to plot stress–strain

dependences: data directly collected from Instron machine and using DIC technique. While results obtained with machine and DIC method coincide for ultra-lightweight cryogels, a difference was recorded for the data collected for aerogels due to the stiffness induced by the machine. DIC method was thus selected as being more precise, video-monitoring was used to monitor the changes in sample shape and dimensions.

Under compression, CMC aerogels and cryogels do not break and do not release dust, similar to other bio-aerogels. The stress–strain dependences consist of three regions typical for aerogels and foams: linear (or elastic), plastic (deformation due to pore walls buckling and breaking), and strong stress increase due to material densification. The elastic recovery of aerogels and cryogels is low, within few percent, and it is slightly higher for cryogels compared to aerogels. The “equivalent” Poisson’s ratio was calculated for materials at 50% deformation: for cryogels it is close to zero and for aerogels around 0.3, slightly decreasing with material density. The reason is that under compression, cryogel diameter is practically unchanged, while aerogel diameter slightly extended; as a consequence, aerogel volume decreases less compared to cryogel.

Compressive modulus, yield stress and absorption energy were calculated and analysed as a function of density. The compressive modulus of cryogels is higher than that of aerogels of the same density due to much thicker pore walls of the former. The exponent correlating compressive modulus and density of CMC aerogels falls within the trends known for cellulose aerogels and foams. The mechanical properties of these porous materials suggest their suitability for life science applications requiring structural integrity and resilience.

**Acknowledgements** We are grateful to IFF for providing CMC samples, to J. Jaxel (PERSEE, Mines Paris) for supercritical drying, to I. Lahouij and F. Georgi (CEMEF, Mines Paris) for guiding in SEM analysis and to PACA region, France, for SEM MAIA3 funding.

**Author contributions** Tatiana Budtova: conceptualisation, formal analysis, investigation, methodology, project administration, resources, supervision, validation, writing – review & editing. Christophe Pradille: formal analysis, investigation, methodology, supervision, review & editing. Sujie Yu: data curation, formal analysis, investigation, methodology, writing – original draft, writing – review & editing.
**Funding** Open access funding provided by Mines Paris - PSL. This work was supported by China Scholarship Council.

**Data Availability** No datasets were generated or analysed during the current study.

**Declarations**

**Competing interest** The authors declare no competing interests.

**Ethics and Consent to Participate declarations** Not applicable.

**Consent to Publish declaration** Not applicable.

**Open Access** This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

**References**

Alias BK, Peter S, Lyczko N et al (2023) Cellulose nanofiber aerogel as a potential receiver layer for solar application: a review. Mater Today Sustain 24:100510. https://doi.org/10.1016/j.mtsust.2023.100510

Ashori A, Chiani E, Shokrollahzadeh S et al (2024) Cellulose-based aerogels for sustainable dye removal: advances and prospects. J Polym Environ 32:6149–6181. https://doi.org/10.1007/s10924-024-03394-3

Boday DJ, Keng PY, Muriithi B et al (2010) Mechanically reinforced silica aerogel nanocomposites via surface initiated atom transfer radical polymerizations. J Mater Chem 20:6863. https://doi.org/10.1039/c0jm01448f

Boday DJ, Stover RJ, Muriithi B et al (2009) Strong, low-density nanocomposites by chemical vapor deposition and polymerization of cyanoacrylates on aminated silica aerogels. ACS Appl Mater Interfaces 1:1364–1369. https://doi.org/10.1021/am900240h

Buchtová N, Budtova T (2016) Cellulose aero-, cryo- and xerogels: towards understanding of morphology control. Cellulose 23:2585–2595. https://doi.org/10.1007/s10570-016-0960-8

Buchtová N, Pradille C, Bouvard J-L, Budtova T (2019) Mechanical properties of cellulose aerogels and cryogels.

Soft Matter 15:7901–7908. https://doi.org/10.1039/c9sm01028a

Budtova T (2019) Cellulose II aerogels: a review. Cellulose 26:81–121. https://doi.org/10.1007/s10570-018-2189-1

Candau N, Pradille C, Bouvard J-L, Billon N (2016) On the use of a four-cameras stereovision system to characterize large 3D deformation in elastomers. Polym Test 56:314–320. https://doi.org/10.1016/j.polymtesting.2016.10.017

Chartier C, Buwalda S, Van Den Berghe H et al (2022) Tuning the properties of porous chitosan: aerogels and cryogels. Int J Biol Macromol 202:215–223. https://doi.org/10.1016/j.ijbiomac.2022.01.042

Chen F, Bouvard J-L, Sawada D et al (2021) Exploring digital image correlation technique for the analysis of the tensile properties of all-cellulose composites. Cellulose 28:4165–4178. https://doi.org/10.1007/s10570-021-03807-9

Ciuffarin F, Négrier M, Plazzotta S et al (2023) Interactions of cellulose cryogels and aerogels with water and oil: structure-function relationships. Food Hydrocolloids 140:108631. https://doi.org/10.1016/j.foodhyd.2023.108631

Diascorn N, Calas S, Sallée H et al (2015) Polyurethane aerogels synthesis for thermal insulation–textural, thermal and mechanical properties. J Supercrit Fluids 106:76–84. https://doi.org/10.1016/j.supflu.2015.05.012

Diaz-Gomez L, Gonzalez-Prada I, Millan R et al (2022) 3D printed carboxymethyl cellulose scaffolds for autologous growth factors delivery in wound healing. Carbohydr Polym 278:118924. https://doi.org/10.1016/j.carbpol.2021.118924

Druel L, Budtova T (2023) Aerogel-like (low density and high surface area) cellulose monoliths and beads obtained without supercritical- or freeze-drying. Cellulose 30:8339–8353. https://doi.org/10.1007/s10570-023-05349-8

Eshraghi S, Das S (2010) Mechanical and microstructural properties of polycaprolactone scaffolds with one-dimensional, two-dimensional, and three-dimensional orthogonally oriented porous architectures produced by selective laser sintering. Acta Biomater 6:2467–2476. https://doi.org/10.1016/j.actbio.2010.02.002

Fischer F, Rigacci A, Pirard R et al (2006) Cellulose-based aerogels. Polymer 47:7636–7645. https://doi.org/10.1016/j.polymer.2006.09.004

Fumagalli M, Ouhab D, Boisseau SM, Heux L (2013) Versatile gas-phase reactions for surface to bulk esterification of cellulose microfibrils aerogels. Biomacromol 14:3246–3255. https://doi.org/10.1021/bm400864z

Ganesan K, Dennstedt A, Barowski A, Ratke L (2016) Design of aerogels, cryogels and xerogels of cellulose with hierarchical porous structures. Mater des 92:345–355. https://doi.org/10.1016/j.matdes.2015.12.041

Gibson LJ (1981) The elastic and plastic behaviour of cellular materials. University of Cambridge, Cambridge

Gibson LJ, Ashby MF (1997) Cellular solids: structure and properties, 2nd edn. Cambridge University Press

Gibson LJ, Ashby MF (1982) The mechanics of three-dimensional cellular materials. Proc R Soc Lond A 382:43–59. https://doi.org/10.1098/rspa.1982.0088
Gross J, Reichenauer G, Fricke J (1988) Mechanical properties of SiO2 aerogels. J Phys Appl Phys 21(9):1447–1451.
https://doi.org/10.1088/0022-3727/21/9/020

Groult S, Budtova T (2018) Tuning structure and properties of pectin aerogels. Eur Polym J 108:250–261. https://doi.org/10.1016/j.eurpolymj.2018.08.048

Groult S, Buwalda S, Budtova T (2021a) Tuning bio-aerogel properties for controlling theophylline delivery. Part 1: Pectin aerogels. Mater Sci Eng C Mater Biol Appl 126:112148. https://doi.org/10.1016/j.msec.2021.112148

Groult S, Buwalda S, Budtova T (2021b) Pectin hydrogels, aerogels, cryogels and xerogels: influence of drying on structural and release properties. Eur Polym J 149:110386. https://doi.org/10.1016/j.eurpolymj.2021.110386

G'Sell C, Hiver JM, Dahoun A, Souahi A (1992) Video-controlled tensile testing of polymers and metals beyond the necking point. J Mater Sci 27:5031–5039. https://doi.org/10.1007/BF01105270

Guerrero-Alburquerque N, Zhao S, Adilien N et al (2020) Strong, machinable, and insulating chitosan-urea aerogels: toward ambient pressure drying of biopolymer aerogel monoliths. ACS Appl Mater Interfaces 12:22037–22049.
https://doi.org/10.1021/acsami.0c03047

Gupta P, Singh B, Agrawal AK, Maji PK (2018) Low density and high strength nanofibrillated cellulose aerogel for thermal insulation application. Mater des 158:224–236.
https://doi.org/10.1016/j.matdes.2018.08.031

Haj-Ali R, Elias R, Fourman V et al (2016) Mechanical characterization of aerogel materials with digital image correlation. Microporous Mesoporous Mater 226:44–52.
https://doi.org/10.1016/j.micromeso.2015.12.035

He F, Zhao H, Qu X et al (2009) Modified aging process for silica aerogel. J Mater Process Technol 209:1621–1626.
https://doi.org/10.1016/j.jmatprotec.2008.04.009

He Y, Li H, Fei X, Peng L (2021) Carboxymethyl cellulose/ cellulose nanocrystals immobilized silver nanoparticles as an effective coating to improve barrier and antibacterial properties of paper for food packaging applications. Carbohydr Polym 252:117156. https://doi.org/10.1016/j.carbpol.2020.117156

Iglesias-Mejuto A, Magariños B, Ferreira-Gonçalves T et al (2024) Vancomycin-loaded methylcellulose aerogel scaffolds for advanced bone tissue engineering. Carbohydr Polym 324:121536. https://doi.org/10.1016/j.carbpol.2023.121536

Innerlohinger J, Weber HK, Kraft G (2006) Aerocellulose: aerogels and aerogel-like materials made from cellulose. Macromol Symp 244:126–135. https://doi.org/10.1002/masy.200651212

Jerabek M, Major Z, Lang RW (2010) Strain determination of polymeric materials using digital image correlation. Polym Test 29:407–416. https://doi.org/10.1016/j.polymertesting.2010.01.005

Ji X, Hao Z, Su L et al (2020) Characterizing the constitutive response of plain-woven fibre reinforced aerogel matrix composites using digital image correlation. Compos Struct 234:111652. https://doi.org/10.1016/j.compstruct.2019.111652

Joshi P, Gupta K, Uniyal P et al (2023) Cassava starch-derived aerogels as biodegradable packaging materials. Mater

Chem Phys 296:127282. https://doi.org/10.1016/j.matchemphys.2022.127282

Karamikamkar S, Naguib HE, Park CB (2020) Advances in precursor system for silica-based aerogel production toward improved mechanical properties, customized morphology, and multifunctionality: a review. Adv Colloid Interface Sci 276:102101. https://doi.org/10.1016/j.cis.2020.102101

Korhonen O, Budtova T (2020) All-cellulose composite aerogels and cryogels. Compos Part A Appl Sci Manuf 137:106027. https://doi.org/10.1016/j.compositesa.2020.106027

Lavoine N, Bergström L (2017) Nanocellulose-based foams and aerogels: processing, properties, and applications. J Mater Chem A 5:16105–16117. https://doi.org/10.1039/C7TA02807E

Leventis N (2007) Three-dimensional core-shell superstructures: mechanically strong aerogels. Acc Chem Res 40:874–884. https://doi.org/10.1021/ar600033s

Leventis N, Sotiriou-Leventis C, Chandrasekaran N et al (2010) Multifunctional polyurea aerogels from isocyanates and water. A structure–property case study. Chem Mater 22:6692–6710. https://doi.org/10.1021/cm102891d

Lin R, Li A, Lu L, Cao Y (2015) Preparation of bulk sodium carboxymethyl cellulose aerogels with tunable morphology. Carbohydr Polym 118:126–132. https://doi.org/10.1016/j.carbpol.2014.10.075

Liu C, Li M-C, Liu X et al (2023) 3D printing of customized lignocellulose nanofibril aerogels for efficient thermal insulation. Addit Manuf 78:103841. https://doi.org/10.1016/j.addma.2023.103841

Liu C, Liu X, Shi X et al (2024) 3D printing of phase change material-based Pickering emulsion gel for solar-thermal-electric conversion. Chem Eng J 499:155940. https://doi.org/10.1016/j.cej.2024.155940

Luo Q, Huang X, Gao F et al (2019) Preparation and characterization of high amylose corn starch-microcrystalline cellulose aerogel with high absorption. Materials 12:1420. https://doi.org/10.3390/ma12091420

Maleki H, Durães L, Portugal A (2014) An overview on silica aerogels synthesis and different mechanical reinforcing strategies. J Non-Cryst Solids 385:55–74. https://doi.org/10.1016/j.jnoncrysol.2013.10.017

Martins D, Rocha C, Dourado F, Gama M (2021) Bacterial cellulose-carboxymethyl cellulose (BC:CMC) dry formulation as stabilizer and texturizing agent for surfactant-free cosmetic formulations. Colloids Surf A Physicochem Eng Asp 617:126380. https://doi.org/10.1016/j.col surfa.2021.126380

Martins M, Barros AA, Quraishi S et al (2015) Preparation of macroporous alginate-based aerogels for biomedical applications. J Supercrit Fluids 106:152–159. https://doi.org/10.1016/j.supflu.2015.05.010

Matias T, Varino C, De Sousa HC et al (2016) Novel flexible, hybrid aerogels with vinyl- and methyltrimethoxysilane in the underlying silica structure. J Mater Sci 51:6781–6792. https://doi.org/10.1007/s10853-016-9965-9

Meti P, Mahadik DB, Lee K-Y et al (2022) Overview of organic–inorganic hybrid silica aerogels: progress and perspectives. Mater des 222:111091. https://doi.org/10.1016/j.matdes.2022.111091

<figure><img src="image_13.png" /></figure>
Morgan EF, Unnikrisnan GU, Hussein AI (2018) Bone mechanical properties in healthy and diseased states. Annu Rev Biomed Eng 20:119–143. https://doi.org/10.1146/annurev-bioeng-062117-121139

Nadargi DY, Latthe SS, Hirashima H, Rao AV (2009) Studies on rheological properties of methyltriethoxysilane (MTES) based flexible superhydrophobic silica aerogels. Microporous Mesoporous Mater 117:617–626. https://doi.org/10.1016/j.micromeso.2008.08.025

Nayak S, Kundu SC (2014) Sericin-carboxymethyl cellulose porous matrices as cellular wound dressing material: Sericin-carboxymethyl cellulose porous matrices. J Biomed Mater Res A 102:1928–1940. https://doi.org/10.1002/jbm.a.34865

Paraskevopoulou P, Raptopoulos G, Len A et al (2021) Fundamental skeletal nanostructure of nanoporous polymer-cross-linked alginate aerogels and its relevance to environmental remediation. ACS Appl Nano Mater 4:10575–10583. https://doi.org/10.1021/acsnan.1c02072

Pourmadadi M, Rahmani E, Shamsabadipour A et al (2023) Novel carboxymethyl cellulose based nanocomposite: a promising biomaterial for biomedical applications. Process Biochem 130:211–226. https://doi.org/10.1016/j.procbio.2023.03.033

Rahmanian V, Pirzada T, Wang S, Khan SA (2021) Cellulose-based hybrid aerogels: strategies toward design and functionality. Adv Mater 33:2102892. https://doi.org/10.1002/adma.202102892

Rege A, Schestakow M, Karadagli I et al (2016) Micro-mechanical modelling of cellulose aerogels from molten salt hydrates. Soft Matter 12:7079–7088. https://doi.org/10.1039/C6SM01460G

Rege A, Itskov M (2018) A microcell-based constitutive modeling of cellulose aerogels under tension. Acta Mech 229:585–593. https://doi.org/10.1007/s00707-017-1987-0

Rege A, Schwan M, Chernova L et al (2020) Microstructural and mechanical characterization of carbon aerogels: an in-situ and digital image correlation-based study. J Non-Cryst Solids 529:119568. https://doi.org/10.1016/j.jnoncrystol.2019.119568

Reichenauer G (2004) Thermal aging of silica gels in water. J Non-Cryst Solids 350:189–195. https://doi.org/10.1016/j.jnoncrysol.2004.07.073

Rudaz C, Courson R, Bonnet L et al (2014) Aeropectin: fully biomass-based mechanically strong and thermal superinsulating aerogel. Biomacromol 15:2188–2195. https://doi.org/10.1021/bm500345u

Scherer GW, Smith DM, Qiu X, Anderson JM (1995) Compression of aerogels. J Non-Cryst Solids 186:316–320. https://doi.org/10.1016/0022-3093(95)00074-7

Schestakow M, Karadagli I, Ratke L (2016) Cellulose aerogels prepared from an aqueous zinc chloride salt hydrate melt. Carbohydr Polym 137:642–649. https://doi.org/10.1016/j.carbpol.2015.10.097

Schwan M, Naikade M, Raabe D, Ratke L (2015) From hard to rubber-like: mechanical properties of resorcinol-formaldehyde aerogels. J Mater Sci 50:5482–5493. https://doi.org/10.1007/s10853-015-9094-x

Schwan M, Tannert R, Ratke L (2016) New soft and spongy resorcinol-formaldehyde aerogels. J Supercrit Fluids 107:201–208. https://doi.org/10.1016/j.supflu.2015.09.010

Sescousse R, Gavillon R, Budtova T (2011) Aerocellulose from cellulose–ionic liquid solutions: preparation, properties and comparison with cellulose–NaOH and cellulose–NMMO routes. Carbohydr Polym 83:1766–1774. https://doi.org/10.1016/j.carbpol.2010.10.043

Shinko A, Jana SC, Meador MA (2015) Crosslinked polyurea aerogels with controlled porosity. RSC Adv 5:105329–105338. https://doi.org/10.1039/C5RA20788F

Shi X, Liu C, Luo Y et al (2025) Tree transpiration-inspired 3D-printed wastewater processors with hybrid nanocellulose for a broad range of oil-based effluents. Carbohydr Polym 357:123426. https://doi.org/10.1016/j.carbpol.2025.123426

Sun YT, Shi DQ, Yang XG et al (2013) Stress state analysis of losipescu shear specimens for aerogel composite with different properties in tension and compression. Procedia Eng 67:517–524. https://doi.org/10.1016/j.proeng.2013.12.052

Sutton MA, Orteu J-J, Schreier H (2009) Image correlation for shape, motion and deformation measurements: basic concepts, theory and applications. Springer, Boston

Tabernero A, Baldino L, Misol A et al (2020) Role of rheological properties on physical chitosan aerogels obtained by supercritical drying. Carbohydr Polym 233:115850. https://doi.org/10.1016/j.carbpol.2020.115850

Takeshita S, Akasaka S, Yoda S (2019) Structural and acoustic properties of transparent chitosan aerogel. Mater Lett 254:258–261. https://doi.org/10.1016/j.matlet.2019.07.064

Tan C, Fung BM, Newman JK, Vu C (2001) Organic aerogels with very high impact strength. Adv Mater 13:644–646

Verger A, Kichou H, Huang N et al (2024) Effects of hydrophilic natural deep eutectic solvents on the rheological, textural, and sensory properties of carboxymethylcellulose-based cosmetic hydrogels. ACS Sustain Chem Eng 12:7187–7199. https://doi.org/10.1021/acssuschemeng.4c01866

Viola M, Chartier C, Mihajlovic M et al (2024) Exploring silk fibroin aerogels via different coagulation approaches. Eur Polym J 205:112722. https://doi.org/10.1016/j.eurpolymj.2023.112722

Woignier T, Phalippou J, Vacher R (1989) Parameters affecting elastic properties of silica aerogels. J Mater Res 4:688–692. https://doi.org/10.1557/JMR.1989.0688

Woignier T, Primera J, Alaoui A et al (2020) Techniques for characterizing the mechanical properties of aerogels. J Sol-Gel Sci Technol 93:6–27. https://doi.org/10.1007/s10971-019-05173-2

Wong JCH, Kaymak H, Brunner S, Koebel MM (2014) Mechanical properties of monolithic silica aerogels made from polyethoxydisiloxanes. Microporous Mesoporous Mater 183:23–29. https://doi.org/10.1016/j.micromeso.2013.08.029

Xiao W, Wang P, Song X et al (2021) Facile fabrication of anisotropic chitosan aerogel with hydrophobicity and thermal superinsulation for advanced thermal management. ACS Sustain Chem Eng 9:9348–9357. https://doi.org/10.1021/acssuschemeng.1c02217
Xu X, Zhang Q, Yu Y et al (2016) Naturally dried graphene aerogels with superelasticity and tunable Poisson’s ratio. *Adv Mater* 28:9223–9230. https://doi.org/10.1002/adma.201603079

Yim TJ, Kim SY, Yoo KP (2002) Fabrication and thermophysical characterization of nano-porous silica-polyurethane hybrid aerogel by sol-gel processing and supercritical solvent drying technique. *Korean J Chem Eng* 19:159–166. https://doi.org/10.1007/BF02706890

Yu S, Budtova T (2024) Creating and exploring carboxymethyl cellulose aerogels as drug delivery devices. *Carbohydr Polym* 332:121925. https://doi.org/10.1016/j.carbpol.2024.121925

Yu S, Castellani R, Pereira A et al (2025) Additive-free 3D-printed nanostructured carboxymethyl cellulose aerogels. *Int J Biol Macromol* 300:140277. https://doi.org/10.1016/j.ijbiomac.2025.140277

Zhao S, Malfait WJ, Guerrero-Alburquerque N et al (2018) Biopolymer aerogels and foams: chemistry, properties, and applications. *Angew Chem Int Ed* 57:7580–7608. https://doi.org/10.1002/anie.201709014

Zou F, Bouvard J-L, Pradille C, Budtova T (2022) Ice-tem-
plated additive-free porous starches with tuned morphol-
ogy and properties. Eur Polym J 176:111403. https://doi.
org/10.1016/j.eurpolymj.2022.111403

Zou F, Budtova T (2021) Tailoring the morphology and prop-
erties of starch aerogels and cryogels via starch source and
process parameter. *Carbohydr Polym* 255:117344. https://
doi.org/10.1016/j.carbpol.2020.117344

Zou F, Budtova T (2023) Starch alcogels, aerogels, and aero-
gel-like xerogels: adsorption and release of theophylline.
ACS Sustain Chem Eng 11:5617–5625. https://doi.org/10.
1021/acssuschemeng.2c07762

**Publisher’s Note** Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

<figure><img src="image_14.png" /></figure>