Glycerol Water Research Articles

Optimization of Cultivation Conditions for the Lactobacillus reuteri LR1 Strain to Improve the Biosynthesis of Bacteriocin-Like Substances

The article presents the results of optimization of the culturing conditions to increase the production of bacteriocin-like compounds (presumably including reuterin) by the Lactobacillus reuteri strain LR1. The strain Escherichia coli ATCC 25922, an opportunistic microorganism, the content of which is standardized in foods by the Food Safety Legislation, was selected as an indicator strain of antimicrobial activity. The nutrient medium for L. reuteri LR1 cultivation was optimized to increase the production of bacteriocin-like compounds, and the parameters of two-stage growth of the producer were established: (1) cultivation on the initial medium for biomass accumulation and (2) growth on a water–glycerol medium to convert glycerol to antimicrobial compounds, presumably reuterin. The first stage was carried out as follows: the L. reuteri LR1 culture (5%) was inoculated into a medium with the following composition: hydrolyzed milk—250 mL/L; yeast extract—10 g/L; peptone—5 g/L; glucose—20 g/L; sodium acetate—5.0 g/L; monosubstituted potassium phosphate—2.0 g/L; magnesium sulfate—0.2 g/L, and manganese sulfate—0.5 g/L, pH 6.4–6.6. The cultivation was carried out for 18 h at (37 ± 1)°С. The second stage included the incubation of the obtained biomass in 200 mM of glycerol-containing aqueous solution, pH 6.6, for 2 h at 37°С. The zone of E. coli inhibition caused by the produced bacteriocin-like compounds was 25 mm.

Self-Assembly of Fluorescent Photonic Crystal Structures in Binary Water–Glycerol Solvent Droplets

The morphology of photonic-crystal structures formed by the self-assembly of fluorescent marker nanoparticles from evaporating droplets of a binary water–glycerol solvent, the components of which differ appreciably from each other in the viscosity and evaporation rate, being infinitely mutually soluble under normal conditions, was has been studied experimentally for the first time. It has been shown that the main self-assembly disordering factor is Marangoni vortex flows, and the change in the initial concentration ratio between binary mixture components enables the control over the degree of disordering in the solid phase, which is formed after the solvent is evaporated from a droplet and distributed over the substrate. A low initial concentration of any component corresponds to the most ordered distribution, whereas their medium concentrations correspond to the most disordered distribution. The characteristic values of Marangoni numbers in experiments have been calculated. It has been demonstrated that the average radius of the distribution of an ensemble of marker particles over a substrate may serve as a descriptor for the degree of ordering.

Assessing the effectiveness of colloidal microcrystalline cellulose as a suspending agent for black and white liquid dyes

SummaryThis study aimed to determine the effect of the concentration (1, 5, or 8 wt%) of colloidal microcrystalline cellulose (MCCS) as suspending agent on the long‐term stability and rheology of the vegetable carbon (C) and calcium carbonate (CC) suspended in water–glycerine mixture. These suspensions as ready‐to‐use black and white liquid dyes containing 10 wt% C or CC were assessed for particle size, Turbiscan stability index (TSI), steady shear, thixotropy and dynamic viscoelasticity. After 370 days, the black dyes showed excellent stability (TSI ≪ 0.5) at 4 °C and 25 °C already at 1 wt% MCCS, while the white dyes showed reasonable stability (TSI 1–3) only at 5 and 8 wt% MCCS. Dye formulations exhibited a relatively liquid‐like viscoelastic behaviour, while they showed extremely shear‐thinning behaviour with a network structure dependent on the concentration of the MCCS as exhibited by the increase in thixotropy and the existence of the measurable yield stress.

Short-term supplementation of diets rich in lipids or glycogen precursors can affect intra-follicular environment, oocyte mitochondrial gene expression, and embryo development following parthenogenesis in goat

Abstract This study aimed to verify the effects of short-term supplementation of diets rich in lipids or glycogen precursors on the follicular environment, oocyte mitochondrial gene expression, and in vitro embryo development. Thirty adult Anglo-Nubian multiparous crossbred goats were fed for 28 days with a total mixed ration (TMR) to satisfy the requirements of breeding for adult non-dairy goats. Seven days prior to the end of the feeding period, either ground flaxseed on a 10.5 % DM basis (Flaxseed Group - FG, n = 10), or a 200-mL/goat/day solution of crude glycerin in water at a 9:1 ratio (80 % Glycerin Group - GG, n = 10) were added to the TMR diet. The Control Group (CG) was maintained at the TMR diet (n = 10). Ovaries were collected upon slaughter for collection of follicular contents. Glucose, cholesterol and triglyceride concentrations and the glutathione peroxidase activity were determined in the follicular fluid, and the expression of Cox-1, NRF-1, PPARGC1-A and GDF-9 genes performed in granulosa cells and in oocytes by qPCR. Viable COCs were in vitro-matured for 24 h, to be parthenogenetically activated and in vitro-cultured for seven days up to the blastocyst stage. Intra-follicular glucose concentration was higher in the Glycerin (20.2 ± 2.5 mgdL GG vs. 5.6 ± 1.7 mgdL FG vs. 14.2 ± 3.5 mgdL CG; P

Moisturizing mechanism of glycerol and diglycerol on human stratum corneum studied by synchrotron X-ray diffraction.

Polyols are moisturizers used in cosmetics. Using X-ray diffraction, we studied the moisturizingmechanism of polyol solutions in the stratum corneum (SC). We examined whether glycerol disrupts the ordered hydrocarbon chain packing structure in isolated SC, as previously proposed in an SC lipid model. The SC samples were prepared by treatment with water and aqueous solutions of glycerol, diglycerol and glycerol/diglycerol. To examine the differences in the water-retention efficiency of polyols, using a solution cell, we performed dynamic X-ray diffraction to analyse the structural changes that occurred during water removal from the hydrated samples by a stream of dry nitrogen gas. We focused on two structures, the orthorhombic hydrocarbon chain packing structure in the intercellular lipids and the soft keratin in the corneocytes where most of the water is stored. The spacing formed by the soft keratin in the corneocytes immersed in a solution of water and diglycerol solution decreased rapidly by water removal. In contrast, it decreased gradually in the corneocytes immersed in a solution of glycerol and glycerol/diglycerol, indicating that the glycerol-containing solutions maintained the hydrated state of the corneocytes for longer. Furthermore, the characteristic change of the spacing in the orthorhombic hydrocarbon chain packing structure over time was observed during the drying process. The hydrated state was maintained longer, in water, followed by glycerol, diglycerol and glycerol/diglycerol, in increasing order. This is the first study to report such characteristic properties that could be indicators of the capacity of the SC to regulate water. The dynamic X-ray diffraction experiment on the structure of the soft keratin and the orthorhombic hydrocarbon chain packing structure during the drying of the hydrated SC provides an insight into the moisturizing mechanism of the polyol solutions in the SC. The results show that the glycerol/diglycerol solution functions as an effective SC moisturizer at the molecular level. Further, it was confirmed that the behaviour of glycerol in the isolated SC varies from that proposed in the SC lipid model, wherein glycerol was proposed to prevent the formation of a regular hydrocarbon chain packing structure.

Experimental study of miscible viscous fingering with different effective interfacial tension

Viscous fingering (VF) occurs when a more viscous fluid is displaced by a less viscous one in porous media or in Hele-Shaw cells. Generally, VF can be divided into two types: immiscible VF and miscible VF. The typical immiscible finger is wider than the equivalent miscible finger because of interfacial tension. Recently, it has been pointed out that an effective interfacial tension (EIT) is present even in miscible systems when there is a steep concentration gradient of chemical species at the interface. The effects of EIT on miscible VF have so far mainly been studied numerically showing that the fingers become wider owing to EIT. Here, we perform an experimental investigation of the effects of EIT on miscible VF by establishing two solution systems that have different concentration differences but the same viscosity contrast. One is a glycerol solution with a concentration of 99 wt. % and water and has a higher water concentration difference of ∆Cw = 99 wt. %. The other is a polymer solution with a concentration of 8.5 wt. % and water and has a lower water concentration difference of ∆Cw = 8.5 wt. %. We show by direct measurement with a spinning drop tensiometer that the glycerol–water system exhibits greater EIT, and we demonstrate experimentally that typical fingers with high EIT become wider than those with low EIT. We suggest that under the experimental condition employed, the VF in the glycerol–water system with high EIT exhibits a characteristic property of immiscible VF, although it has generally been regarded as a typical representative of classical miscible VF.

Assessing Changes in Dielectric Properties Due to Nanomaterials Using a Two-Port Microwave System.

Detecting changes in the dielectric properties of tissues at microwave frequencies can offer simple and cost effective tools for cancer detection. These changes can be enhanced by the use of nanoparticles (NPs) that are characterised by both increased tumour uptake and high dielectric constant. This paper presents a two-port experimental setup to assess the impact of contrast enhancement on microwave signals. The study focuses on carbon nanotubes, as they have been previously shown to induce high microwave dielectric contrast. We investigate multiwall carbon nanotubes (MWNT) and their -OH functionalised version (MWNT-OH) dispersed in tissue phantoms as contrast enhancing NPs, as well as salt (NaCl) solutions as reference mixtures which can be easily dissolved inside water mixtures and thus induce dielectric contrast changes reliably. MWNT and MWNT-OH are characterised by atomic force microscopy, and their dielectric properties are measured when dispersed in 60% glycerol–water mixtures. Salt concentrations between 10 and 50 mg/mL in 60% glycerol mixtures are also studied as homogeneous samples known to affect the dielectric constant. Contrast enhancement is then evaluated using a simplified two-port microwave system to identify the impact on microwave signals with respect to dielectric contrast. Numerical simulations are also conducted to compare results with the experimental findings. Our results suggest that this approach can be used as a reliable method to screen and assess contrast enhancing materials with regards to a microwave system’s ability to detect their impact on a target.

Self-Pillared MFI-Type Zeolite Nanosheets as Selective Catalysts for Glycerol Dehydration to Acrolein

The surplus production of glycerol as a by-product of biodiesel has become a serious problem for the sustainability of the biodiesel industry. Glycerol dehydration over MFI zeolites offers a green route to acrolein production. However, conventional MFI zeolites suffer diffusion limitation, which inhibits accessibility to active sites and causes quick deactivation of catalysts because of severe coke deposition. In this study, self-pillared MFI nanosheet catalysts were prepared with different Si/Al ratios to catalyze glycerol dehydration. The nanosheets with interlayered meso-space possessing wide a,c-planes of ∼2 nm thickness in the b-axis provide a shortened diffusion pathway to easily access the active acid sites. In contrast to conventional MFI zeolites, the nanosheet morphology significantly enhanced the catalyst selectivity, activity, and stability; gave a high acrolein selectivity (92%) at a higher WHSV of 4 h–1; and remained stable after up to 100 h of the reaction of 5% glycerol in water.

Inclusion of low cost activated carbon for improving hydrogen production performance of TiO2 nanoparticles under natural solar light irradiation

Photocatalytic studies are primarily focused on the low cost and sustainable materials with suitable bandgap and high surface area. The ultra-fast electron-hole pair recombination and limited light absorptions affect the efficiency of photocatalyst in an adverse manner, which can be unravelled by choosing an efficient combination of photocatalysts and suitable co-catalyst/support materials. The present work explores the combination of low-cost and high potential activated carbon and TiO2 as a nanocomposite, prepared through a one-pot hydrothermal process for hydrogen production under natural solar light irradiation. Among the synthesized photocatalysts, the one calcined at 400 °C for 2 h was found to be the best catalyst, which exhibited 3.5 times higher hydrogen production rate than the pristine TiO2 while tested with water containing 5 vol.% glycerol. Importantly, the optimized nanocomposite was also tested for hydrogen production from simulated seawater under same conditions and it showed a hydrogen production rate of 20,383 μmol g−1 h−1, which is 2.4 times higher than the glycerol water solution. The enhanced hydrogen production rate is due to the reduced bandgap of AC-TiO2 nanocomposite which offered more light absorption in the visible region compared to the pristine TiO2. The XRD, Raman spectroscopy, TEM, and PL analysis were also examined to investigate the crystallinity, purity, morphology, and charge carrier recombination life time of the synthesized catalysts.

Synthesis of Ni- and N-Doped Titania Nanotube Arrays for Photocatalytic Hydrogen Production from Glycerol–Water Solutions

Synthesis of Ni- and N-doped Titania Nanotube Arrays (Ni-N-TiNTAs) was conducted to produce photocatalysts for hydrogen production from a glycerol–water mixture. Ni-N-TiNTAs were synthesized in two steps, namely anodization and chemical reduction. Ti foil was anodized at 50 V for two h in an electrolyte solution containing 0.2% urea as a source of N atoms. Ni doping (at various content of 5%, 10%, 15%, and 20% wt) was performed by one-hour chemical reduction with sodium borohydride as a reducing agent. The photocatalyst was annealed at different temperatures, i.e., 500 °C, 550 °C, and 600 °C under 60 mL/min N2 gas for two h. On the basis of X-ray Diffraction (XRD) patterns, Ni-N-TiNTAs are mostly of anatase crystallite phase when annealed at 500 °C and 550 °C, while that of rutile was observable when calcination was done at 600 °C. The morphology of the photocatalysts was scrutinized by means of Field Emission Scanning Electron Microscopy (FESEM) imaging, which reveals nanotubular structures, with elemental composition measured by Energy Dispersive X-ray (EDX). The bandgap of the photocatalysts was analyzed using Ultraviolet Diffuse Reflectance Spectroscopy (UV DRS), which showed a lower value for the case of Ni-N-TiNTAs as compared to those of TiNTAs and N-TiNTAs. Photocatalytic tests showed that the highest amount of hydrogen produced (ca. 30973 μmol/m2) was obtained in the case of Ni-N-TiNTAs with a Ni content of 10wt%.

A human milk-mimicking fluid for PIV experiments

It is essential to formulate a refractive index (RI)-matched fluid to use in silicone phantom models for particle image velocimetry (PIV) experiments. In this work, an extensive effort to develop a non-Newtonian human milk-mimicking fluid (HMMF) with different concentrations of sodium iodide (NaI), glycerol (Gly), xanthan gum (XG), and distilled water (DW) is conducted. Measurements of RI and density are fitted onto a linear empirical expression relating to the NaI and Gly concentration. The Cross model was utilized to find the nonlinear viscosity model of raw human milk. HMMF solution is generated from a multi-constrained optimization. The matched HMMF, suitable for use in the lactating human breast phantom with bifurcated ductal structures, is achieved with composition of 15.69% NaI, 30.27% Gly, 54.02% water and 0.02% XG by weight percentage resulting in a non-Newtonian viscosity matched with that of human milk.

Toward Smart Selective Sensors Exploiting a Novel Approach to Connect Optical Fiber Biosensors in Internet

The selective detection of pollutants in water in a laboratory scenario has been presented by authors exploiting low-cost optical biosensors based on plastic optical fibers (POFs) and biological or biomimetic receptors. So, for instance, the detection in water of naphthalene, perfluoroalkyl substances (PFAs) and polyfluoroalkyl substances have been investigated with interesting detection limits when compared to those obtained by using different expensive traditional approaches (e.g., liquid chromatography-mass spectrometry with high performances). In this article, we have developed and tested a novel approach used in a smart measuring system to use POF sensors in situ for the remote measures of pollutants in water for smart cities applications. More specifically, we have used different water–glycerin solutions to test the novel sensor system based on a Raspberry Pi connected to the Internet and to a spectrometer, a light source, a POF sensor, and two computers connected to Internet used as client and server.

Direct measurement of small spherical particle rotation driven by the acoustic viscous torque

We report a new method for measuring fast rotations up to 13500 rpm of micrometer sized spherical particles utilizing an optical trap [A. Lamprecht et al., Lab Chip 16, 2682–2693 (2016)]. In an acoustofluidic flow cell, a single spherical particle rotates due to the acoustic viscous torque produced by two phase-shifted orthogonal standing waves. The Lorentzian power spectrum of the trapped and rotating particle has additional peaks at frequencies that correlate with its rotational speed. In one of our experiments the thickness of the viscous boundary layer δ around the particle is roughly as large as the particle radius R itself. We use a water glycerol mixture with a dynamic viscosity of μ_ff = 0.06 Pa s to increase δ. Our experiment validates recent numerical research that predicts power rotational speeds for the case δ ≈ R compared to the simplified theoretical formula valid for δ ≪ R [Lee and Wang, J. Acoust. Soc. Am. 85, 1081–1088 (1989)].

Variations in Constitutive Properties of the Fluid Elicit Divergent Vibrational and Pressure Response Under Shock Wave Loading.

We performed a characterization of the shock wave loading on the response of the specimen representing a simplified head model. A polycarbonate cylinder (2-in. outer diameter, wall thickness: 0.06 or 0.12 in.) was filled with two fluids: pure de-ionized water and 40% glycerol in water, which differ only slightly in their constitutive material properties. These two fluids were selected to represent the cerebrospinal fluid and cerebral blood, using their high strain rate viscosity as a primary selection criterion. The model specimen was exposed to a single shock wave with two nominal intensities: 70 and 130 kPa overpressure. The response of the model was measured using three strain gauges and three pressure sensors, one mounted on the front face of the cylinder and two embedded in the cylinder to measure the pressure inside of the fluid. We noted several discriminant characteristics in the collected data, which indicate that the type of fluid is strongly influencing the response. The vibrations of the cylinder walls are strongly correlated with the fluid kind. The similarity analysis via the Pearson coefficient indicated that the pressure waveforms in the fluid are only moderately correlated, and these results were further corroborated by Euclidean distance analysis. Continuous wavelet transform of pressure waveforms revealed that the frequency response is strongly correlated with the properties of the fluid. The observed differences in strain and pressure modalities stem from relatively small differences in the properties of the fluids used in this study.

Development of a deep learning-based image processing technique for bubble pattern recognition and shape reconstruction in dense bubbly flows

This work presents a Convolutional Neural Network (CNN) based method for the shape reconstruction of bubbles in bubbly flows using high-speed camera images. The bubble identification and shape reconstruction adopted a methodology based on a set of anchor points and boxes, where a single anchor point is used for different anchor boxes with various sizes. These anchor points are determined, based on the internal features of the bubble images, which are more easily identifiable, in particular, in regions of the images with high bubble overlapping. This makes possible the application of the procedure to high void fraction bubbly flows. For a given anchor point, different ellipsoidal shapes are suggested as bubble shape candidates and are then correctly chosen by a trained CNN. The CNN training used labeled images from air–water system data set and a hyper-parameter analysis was performed to find the best configuration of the CNN architecture. From this optimal CNN architecture, different high-speed camera acquisitions of bubbly flows were analyzed by the CNN-based bubble shape reconstruction method. In order to gain a better comprehension of the method, experiments were conducted in two gas–liquid systems, air–water and air-aqueous glycerol solution, which resulted in different image parameters, such as brightness, contrast and edge definition. The CNN method trained only with air–water data, showed excellent performance in the cases with air-aqueous glycerol, demonstrating its generalization capability. In addition, the results showed that the deep learning method used in this work is able to detect most of the bubbles present in the high-speed camera images, even in dense bubbly flow configurations. The method developed in this work can be used to further analyze bubbly flows and generate experimental data for the implementation and validation of CFD models.

Applying visualization techniques to study the fluid flow pattern and the particle distribution in the casting of metal matrix composites

Abstract For a past few decades, metal matrix composite has a significant role in the various industrial and automobile applications. Production of metal matrix composite using stir casting technique is one of the most effective and economical technique. Achieving the uniform distribution of the reinforced particles was the major problem facing during the production of particle reinforced metal matrix composites and also achieving the effective fluid flow pattern was the greatest challenge to the research community. In this research, some of the major stir casting process parameters such as blade geometry, stirring speed and impeller position were optimized based on the vortex height of the fluid and settling time of the reinforced particles using visualization experiments and Grey relation analysis. Flow pattern of the fluid and the trace of the particles was analysed using a new technique called streak photography. Streak photography was one of the visualization experiments using glycerol water based model. Al8011/SiC metal matrix composites were manufactured based on the optimized stir casting process parameters. Finally, the fabricated composites were carried out for OM, SEM analysis and Brinell hardness testing for confirming the uniform distribution of the reinforced particles. Based on the confirmation results, 45ᴼ stirrer blade angle, impeller position 40 % from the base and 250 rpm stirring help to produce uniform distribution of the particles.

Transcatheter mitral valve repair devices - in vitro studies on the influence of device-width on mitral regurgitation

Abstract Mitral regurgitation (MR) is the most prevalent valvulopathy in the USA and the second most prevalent valvulopathy in Europe. Despite excellent clinical results of surgical mitral valve repair (SMVR), transcatheter-based mitral valve repair (MVR) procedures emerged as a feasible treatment option for surgically inoperable or high-risk patients suffering from clinically relevant MR. The current study investigates the impact of device-induced coaptationwidth on the hydrodynamic performance of insufficient mitral valves (MV) during left ventricular (LV) systole. A non-calcified, pathological MV model (MVM) featuring a D-shaped MV annulus with an area of 7.6 cm2 and a flail gap in the A2-P2 region was employed in an experimental setup. Pressure gradient-volumetric flow rate (Δp-Q) relations were investigated for steady-state backward flow with transvalvular pressure gradients ranging from (0.75 ≤ Δp ≤ 177.36) mmHg. Glycerol-water mixture (36 % (v/v) glycerol in water) at 37 °C with a density of (1 098.2 ± 1.3) kg·m-3 and a dynamic viscosity of 3.5 mPa∙s was used as circulatory fluid. In order to determine the impact of the width of transcatheter MVR devices during LV-systole Δp-Q relations were investigated for three MVM-configurations: (i) MVM without MVR device, (ii) MVM with one MVR device and (iii) MVM with two MVR devices implanted in the A2-P2 region. The MVR devices were manufactured from steel sheets with a thickness of 0.2 mm and feature arm lengths of 9.0 mm and a width of 5.0 mm. The conducted investigations show that the implantation of MVR devices in the A2-P2 region prevents the manifestation of an A2-P2 flail gap and thereby effectively reduces the retrograde blood flow during the LV-systole by 13 % with one MVR device and 27 % with two MVR devices implanted. Thus, the application of two MVR devices with a combined device-induced width of 10 mm results in a better MR reduction than the implantation of one MVR device with a device-induced width of 5 mm.

Actuation of a magnetically coated swimmer in viscous media with a magnetic particle imaging scanner

Abstract Magnetic actuation of medical devices is of great interest in improving minimally invasive surgery and enabling targeted drug delivery. With untethered, magnetically coated swimmers it is aimed at reaching regions of the body difficult to access with catheters. Such a swimmer was previously presented, which is suitable for the navigation by the magnetic fields of a magnetic particle imaging (MPI) scanner. The swimmer could be imaged with MPI as well, enabling the tomographic real-time tracking of the actuation process. In this work the steerability of the swimmer is further investigated in media of varying viscosities. For this, glycerol-water-mixtures of different mixing ratios were used. The velocities of the swimmer were measured for viscosities between those of pure glycerol and pure water. The experiments were performed with an MPI scanner at maximal magnetic field strength of the actuating fields. A viscosity range was found in which the swimmer is steerable by the fields of an MPI scanner, which leads to a prediction of the applicability of the swimmer in different body fluids.

Maternal physical activity significantly alters the placental transcriptome

IntroductionMaternal lifestyle, in particular physical activity (PA), influences many of the physiological adaptations during pregnancy associated with feto-placental development and growth. There is limited to no information on the link between PA during pregnancy and the molecular mechanisms governing placental function. The aim of this study was to investigate the molecular mechanisms through which maternal PA may influence placental function. MethodsThe level of PA was measured by accelerometry and gene expression was measured in term placenta with custom polymerase chain reaction (PCR) arrays and microarray analysis followed by a pathway analyses on significantly differentially expressed genes (DEGs). ResultsMicroarray analysis showed 43 significantly DEGs between active and non-active participants. RT-qPCR validation of a sub-sample of DEGs revealed significant changes in the level of expression between active and non-active moms (student's t-test, p < 0.05, n = 11). Genes involved in transport of water (p = 0.00236) and uptake of glycerol (p = 0.00219) were enriched in active moms. PA was also associated with the alteration of alternative splicing patters. The most consistent splicing changes were observed for AQP9 where active moms lacked exon 2. DiscussionVariations in maternal PA influences placental gene. We show significant expression changes of genes that are involved in transport and localization between active and non-active women. Most notably, the expression of the aquaporin family of genes (e.g. AQP1 and AQP9) were found to be significantly higher in the placentas of active women suggesting an adaptive response for the transport of water and glycerol in this population.

Tuning the hygro-mechanical response of paper-based systems using glycerol

In recent years, the need for portable, low-cost, and eco-friendly devices for testing and monitoring has arisen. Paper-based devices have emerged as a response to these needs due to the properties induced by capillarity, flexibility, disposability, and biodegradability. In this work, the authors explored the possibility of tuning the hygro-mechanical response of paper-based cantilever beams using glycerol. A lumped-parameter model with non-linear stiffness is used to describe the dynamic response of the beams using three parameters. An experimental method based on resonance frequency tests is used to study the influence of glycerol on the dynamic response of four different beam configurations. The obtained results demonstrate that the resonance frequency of paper-based mechanical systems can be easily tuned by the imbibition of a glycerol–water solution. This study could lead to the development of tunable paper-based mechanical systems for specific applications such as energy harvesters and hygro-mechanical-based sensors.