Equibiaxial Strain Research Articles

Strain-induced enhancement of surface self-diffusion on strontium titanate (001) surfaces

We present a numerical investigation of self-diffusion on strontium titanate TiO2-terminated (001) surfaces via density functional theory. Our calculations first indicate that Ti has the highest diffusion barrier with approximately 2.20 eV, thus representing the rate-limiting step for surface self-diffusion. Furthermore, the higher energy barriers of O and Ti in comparison to O2 and TiO2 indicate electronic activity with the surface atoms. Under the consideration of equi-biaxial strain as it would be encountered in e.g. heteroepitaxial thin films, the diffusion barriers for surface self-diffusion decrease for both compressive and tensile strains between −6% and 2%. For larger strains, we observe plastic deformations. This possibility to lower the energy barrier paves the way for accelerated and possible new mechanisms of surface diffusion and reconstruction of strontium titanate structures in a wide range of applications.

New test rig for biaxial and plane strain states on uniaxial testing machines

The increasing interest in hydrogen technology and storage systems has also significant influence on material characterization. Storage solutions such as cryo-compressed hydrogen (CcH2) or compressed gaseous hydrogen (CGH2) use high pressure to improve the energy density. The pressurized hydrogen is stored in a pressure vessel. This leads to various strain states in the vessel, which are difficult to reproduce with standard testing equipment, such as a uniaxial testing machine. This contribution presents a new test rig for uniaxial testing machines that is able to generate a biaxial load on a cruciform specimen. A hinged structure converts the uniaxial load into a biaxial load. Different attachments allow both equi-biaxial and plane strain states. In addition, the test rig provides access to both sides of the specimen, extending the possibilities for testing under load, such as optical measurement, specimen cooling or permeability measurement. Finally, experiments show the functionality of the test rig and the desired strain states in the specimen.

Physiological stress improves stem cell modeling of dystrophic cardiomyopathy.

Heart failure contributes to Duchenne muscular dystrophy (DMD), which arises from mutations that ablate dystrophin, rendering the plasma membrane prone to disruption. Cardiomyocyte membrane breakdown in patients with DMD yields a serum injury profile similar to other types of myocardial injury with the release of creatine kinase and troponin isoforms. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are highly useful but can be improved. We generated hiPSC-CMs from a patient with DMD and subjected these cells to equibiaxial mechanical strain to mimic in vivo stress. Compared to healthy cells, DMD hiPSC-CMs demonstrated greater susceptibility to equibiaxial strain after 2 h at 10% strain. We generated an aptamer-based profile of proteins released from hiPSC-CMs both at rest and subjected to strain and identified a strong correlation in the mechanical stress-induced proteome from hiPSC-CMs and serum from patients with DMD. We exposed hiPSC-CMs to recombinant annexin A6, a protein resealing agent, and found reduced biomarker release in DMD and control hiPSC-CMs subjected to strain. Thus, the application of mechanical strain to hiPSC-CMs produces a model that reflects an in vivo injury profile, providing a platform to assess pharmacologic intervention.

First-principle study on the photoelectric properties of monolayer h-BN under different strain types.

Two-dimensional materials are a new and promising research field in materials science. This is mainly attributed to their unique photoelectric and chemical properties. In addition to possessing unique optoelectronic and chemical properties, two-dimensional materials also have important application prospects in the field of field-effect devices. Based on density functional theory, the effects of uniaxial strain and equibiaxial strain on the mechanical properties, electronic structure, and optical properties of monolayer h-BN were studied using first principles. The results indicate that compressive strain has a significant impact on the stability of monolayer h-BN. The band gap width of monolayer h-BN decreases with increasing strain, and the optical properties of monolayer h-BN exhibit a relative trend under tensile and compressive strains. The influence of biaxial strain on the mechanical properties, electronic structure, and optical properties of monolayer h-BN is greater than that of uniaxial strain. All the calculations were done by the VASP software based on density functional theory. The interaction between atomic nuclei and electrons is described by the projected added wave pseudopotential (PAW), using the generalized gradient approximation (GGA) to exchange the Perdew-Burke-Ernzerhof (PBE) of the functional. To avoid interlayer interactions, a 15-Å vacuum layer was set up. The Brillouin zone selects the Monkhorst-Pack method to generate 9 × 9 × 1 of k-point grid, the cut off energy is set to 500eV, the energy convergence standard of the system is 1 × 10-5eV, and the interaction force between atoms is 0.01eV/Å.

Equibiaxial strain regulates the electronic structure and mechanical, piezoelectric, and thermal transport properties of the 2H-phase monolayers CrX2 (X = S, Se, Te).

A superior piezoelectric coefficient and diminutive lattice thermal conductivity are advantageous for the application of a two-dimensional semiconductor in piezoelectric and thermoelectric devices, whereas an imperfect piezoelectric coefficient and large lattice thermal conductivity limit the practical application of the material. In this study, we investigate how the equibiaxial strain regulates the electronic structure, and mechanical, piezoelectric, and thermal transport properties. Tensile strain can deduce the bandgap of the monolayer CrX2 (X = S, Se, Te), whereas compressive strain has an opposite effect. Additionally, the transition from a semiconductor to a metal state and the transition between direct and indirect band gaps will occur at appropriate strain values, so the electronic structure can be effectively regulated. The reason is the different sensitivities of the energy corresponding to K and Γ on the valence band to the strain due to the changes in different orbital overlaps. The tensile strain can effectively improve the flexibility of monolayers CrX2, which provides a possibility for the application of flexible electronic devices. Furthermore, the tensile strain can improve the piezoelectric strain coefficient of monolayers CrX2. Using Slacks formulation, we calculate the lattice thermal conductivity, and the tensile biaxial strain can reduce the lattice thermal conductivity. Our research provides a strategy to enhance the piezoelectric and flexible electronic applications and decrease the lattice thermal conductivity, which can benefit the thermoelectric applications.

Impact of endoplasmic reticulum stress on chondrocyte apoptosis in rat model of DDH.

Developmental dysplasia of the hip (DDH) is a developmental disorder characterized by acetabular dysplasia leading to early osteoarthritis. This study examines the role of endoplasmic reticulum stress (ERS) in chondrocyte apoptosis and cartilage degeneration within a DDH model. In the rat model of DDH, created using a swaddling technique, significant deformities in the femoral head and acetabulum were observed, alongside an upregulation of matrix metalloproteinase-13 in acetabular cartilage. We also noted increased levels of apoptosis and ERS-related factors in the acetabular cartilage of DDH models. Additionally, rat chondrocytes exposed to high-magnitude cyclic tensile strain (CTS, 1 Hz, 10% equibiaxial strain) in vitro exhibited elevated ERS and increased apoptosis. Importantly, treatment with the ERS inhibitor 4-phenylbutyric acid effectively suppressed apoptosis induced by CTS in chondrocytes. Our findings suggest that ERS contributes to the upregulation of apoptosis-related factors in chondrocytes within the DDH model, indicating the potential of ERS modulation as a therapeutic approach for DDH-related cartilage degeneration.

The cellular responses of corneal fibroblasts to cyclic stretching loads

Mechanical signaling plays a crucial role in maintaining extracellular matrix (ECM) homeostasis in various structures. In this study, we investigated the responses of corneal fibroblasts to cyclic stretching loads using an in vitro cell culture system. Bovine corneal fibroblasts were cultured and subjected to equibiaxial cyclic strain of 15% for 72 h at a frequency of 0.25 Hz, with bovine skin fibroblasts used as a comparison. We explored various cellular behaviors, including morphological changes, cell proliferation, and metabolism in response to mechanical stretching loads. The expression of genes, protein secretion, and enzymatic activity for several major metalloproteinases was also determined through Q-PCR, Western blot, and gel zymography. Additionally, we investigated the involvement of mitogen-activated protein kinases (MAPKs) signaling pathways in the corneal fibroblasts when subjected to mechanical stimuli. Our findings revealed that, compared to skin fibroblasts, corneal fibroblasts were reluctant to morphological changes in response to a prolonged (72 h) and high-amplitude (15% of strain) cyclic stretching load. However, cyclic stretching loads stimulated the upregulation of MMP-2 expression in corneal fibroblasts via the MAPK signaling pathways involving extracellular signal-regulated kinase and p38. Together with a lack of upregulation in type I collagen expression, our results indicate the induction of the ECM degradation process in corneal fibroblasts in response to cyclic stretching. These findings emphasize the mechanoresponsive nature of corneal fibroblasts and shed light on the potential impact of intense mechanical stress on the cornea in both normal and pathological conditions such as keratoconus, providing valuable insights for understanding corneal mechanobiology.

The synergistic regulation effect on the structure and electronic properties of graphene by methane plasma, Stone-Wales defect and equibiaxial strain

The synergistic regulation effects on the structure and electronic properties of graphene by methane plasma, Stone-Wales defect and equibiaxial strain has been investigated. It is found that the graphene containing Stone-Wales defect (SWG77) has metallicity, when surface adsorbing a CH3+ion, CH3+@SWG77 is a semiconductor with 0.339 eV indirect band gap. The stress-strain curve results indicate that adsorbing different plasma fragments in methane may influence to varying degrees on the ultimate strain of the SWG77 system. The hole mobility has an enhanced tendency as the tensile strain increases for the CH3+@SWG77 system. In addition, the hole mobilities seem to reach saturation when applied equibiaxial strain increase to 2 % or larger. Applying equibiaxial strain on the system substrate, the band gaps of CH3+@ SWG77 and 2CH3+@ SWG77 systems are almost unaffected. In addition, the concentration of CH3+ ion has a certain effect on the light absorption coefficient, reflectivity, and energy loss of the SWG77 system in the visible light region (1.62 eV–3.11 eV) and ultraviolet regions (3.11 eV–5.50 eV). Therefore, defect graphene with appropriate carrier mobility and band gap may be designed by adjusting the equiaxial strain and methyl concentration, which provides useful theoretical support for the development of optical electrical multifunctional electronic devices based on graphene, and is conducive to promoting the application of graphene materials in the field of band gap engineering.

Tensile strain as an efficient way to tune transport properties of Graphdiyne/Borophene hetero-bilayers; a first principle investigation

Thermoelectric materials have attracted much attention due to their crucial role in heat conversion and cooling applications. Transport properties effectively conduct thermoelectricity efficiency, and therefore, many studies have particularly focused on enhancing these features. In the present study, through periodic density functional theory combined with semi-classical transport formulations, the influence of strain on thermoelectric characteristics of Graphdiyne/Borophene hetero-bilayers has been investigated. Based on mechanical properties data, we have shown that bilayer construction causes an increase in the ultimate stress of constituent monolayers. The maximum strain that each hetero-bilayer can withstand is determined by using stress-strain behavior. Among the studied hetero-bilayers, GBS0 has the most value of Young’s modulus [1,2] under equibiaxial strain. Temperature-dependent transport properties of strained hetero-bilayers suggest strain as an efficient way to tune the thermoelectric behavior of hetero-bilayers. The introduction of uni- and biaxial strains affects the electrical and thermal conductivity of GBS0 and GBS1. Furthermore, the power factor and figure of merit, as the key elements of thermoelectric devices, can be significantly engineered under external tensions. The impact of tensile strain on the Seebeck effect is disclosed. Surprisingly, the studied hetero-bilayers can possess either positive or negative Seebeck coefficients under different modes of external strains. The present research extends the strain field, particularly in the rational design of thermoelectric devices.

High Energy Harvesting Performances Silicone Elastomer via Filling Soft Dielectric with Stretching Deformability.

Dielectric elastomer generators (DEGs) with high generated energy density and high conversion efficiency are of great interest. Among several dielectric elastomers (DEs), silicone elastomer filled with ceramic fillers have been extensively studied for their high elasticity, insulation and permittivity. However, the stretched breakdown strength (Ebs ) of such composites decreases significantly under large strain, thus sharply reduces its energy harvesting performances. In this study, a polar rubber-based dielectric (GNBR) is synthetized and creatively used as "soft filler" for silicone elastomer. Benefiting from the deformability under stretching and its inherent strong interface bonding with silicone elastomer, this soft filler effectively avoids the formation of weak interface under large strain and reduces the local field strength of interface area. As expected, the composite filled with soft filler (GNBR/PMVS) shows enhanced Ebs of 2.8 times that of composite with traditional hard filler (TiO2 /PMVS) under equibiaxial strain of 200%. As a result, GNBR/PMVS composite exhibits maximum energy density of 130.5 mJ/g with up-to-date highest power conversion efficiency of reported DEG (44.5%). The findings will provide new insights in the rational design of DE composites characterized by high stretched breakdown strength for advanced energy harvesting system. This article is protected by copyright. All rights reserved.

Bandgap Change in Short‐Period InN/AlN Superlattices Induced by Lattice Strain

III–V GaN‐based nitride semiconductors have attracted interest because their bandgaps can be tuned by constructing alloys and superlattices, and by applying lattice strain. Herein, the influence of uniaxial and equibiaxial strains on the bandgaps of short‐period InN/AlN superlattices is examined using first‐principles calculations. For the uniaxial strain, the bandgaps change in the same manner when the superlattices are strained in the a‐ and m‐axis directions; however, the bandgaps change in a different manner when the superlattices are strained in the c‐axis direction. Even when equibiaxial strain is applied, the change in bandgap depends on the direction in which the strain is applied.

Effects of strain and Al doping on monolayer h-BN: First-principles calculations

In this paper, the effects of Al doping and equibiaxial strain on monolayer h-BN were investigated by first-principles calculations. The results show that with tensile strain applied, the structure of the material is more stable, while the structural stability of the material decreases when compressive strain is applied. When the monolayer h-BN is doped with Al, the band gap decreases, and the higher the doped Al concentration, the lower the band gap. Equibiaxial strain is very effective for band gap tuning of monolayer h-BN. The optical calculation results show that the peaks of dielectric function and optical constant of the material decrease after Al doping, and the peaks decrease with the increase of Al concentration. When the strain is tensile, the optical properties of the material will be red-shifted as a whole, and the optical properties of the material will be blue-shifted when compressive strain is applied. After the monolayer h-BN was doped with two Al atoms and a strain of −9% was applied, the optical properties of the material were significantly affected. Our study provides some theoretical implications for the application of monolayer h-BN in the field of spintronic devices and optoelectronic devices. • The effect of equbiaxial strain and Al doping on monolayer h-BN were investigated. • Using first principles based on density functional theory. • When tensile strain is applied, the structure of the material is more stable, while when compressive strain is applied, the structural stability of the material decreases. • Band gap decreases with increasing Al doping concentration. • Optical properties of the material are red-shifted with tensile strain and blue-shifted with compressive strain.

Strain effect on the defect formation and diffusion in Ti2AlC and Ti3AlC2: A first-principles study

Mn+1AXn phases have the prospect of being the candidate materials as coating and fuel cladding in advanced nuclear systems. It is well known that nuclear materials are subjected to harsh environments such as high temperature, high pressure, and neutron radiation et al. during their application. Consequently, defects and strains inevitably arise in Mn+1AXn phases used as nuclear materials. In this work, by using a first-principles method, the strain effects on the defect formation and diffusion in Ti2AlC and Ti3AlC2 were studied by imposing an equibiaxial in-plane strain along the a and b (denoted as ab) axes. The formation energies of Ti vacancies are substantially larger than those of Al and C vacancies. As the imposed equibiaxial strain goes from compressive to tensile state with strain ranges from −4% to 4%, the formation energies of Ti and C vacancies increase, while the formation energy of Al vacancy decreases. The formation energies of the antisite defect TiAl-AlTi, the substitutional defect AlTi, and the substitutional defect TiAl all increase with the applied biaxial strain. In both Ti2AlC and Ti3AlC2, the process of Al atom diffusing to the Ti vacancy is energetically favorable, conversely, the process of Ti atom diffusing to the Al vacancy is energetically unfavorable. Therefore, the diffusion of Al atom is expected to play an important role in the microstructural evolution under irradiation environments. According to our research about the atomic diffusions at different strains, atomic diffusion across the atomic layer can be slowed down under the compressive strain along the ab axes. As a consequence, the MAX materials show better microstructural stability and improved radiation resistance. That is, the irradiation resistance of the MAX materials can be improved when they are applied under a certain compressive strain in nuclear systems.

Numerical simulation of sheet metal forming of an Al-Mg alloy incorporating plane strain properties in the yield criterion

In this work, numerical simulation of AA5083-O aluminum alloy sheets is carried out using Yld2000-2d yield criterion to predict thinning and variation of load with displacement in sheet metal forming. It has been found that the accuracy of predictions in numerical simulation depends on the coefficients and the stress exponent used in the yield criterion. Hydraulic bulge tests with circular and elliptical die cavities are performed to characterize the material in equi-biaxial and plane strain conditions. An improved stress exponent is determined by incorporating the material properties obtained in plane strain in the existing criterion. The improved stress exponent is validated by using it in the numerical simulations of cylindrical cup deep drawing and stretch forming at room temperature. The same exponent is also used in the numerical simulations carried out for the case of experiments conducted at 250°C. The predicted thinning and load-displacement variations from the numerical simulations are validated with the experimental measurements. A considerable improvement in the results predicted using the improved stress exponent is observed at both the temperatures.

Instrumented indentation for determining stress and strain levels of pre-strained DC01 sheets

In classical mechanical testing, determining the stress and strain states of complex shape specimens turns out to be very challenging, especially in the most deformed regions. In the latter case, when not enough material is present, non-destructive testing is needed for determining the corresponding mechanical state. In this study, a novel approach, based on the local quasi-non-destructive instrumented indentation technique (IIT) coupled with the inverse analysis technique (IAT), is used to determine the stress and strain levels of pre-strained DC01 specimens using monotonic and non-monotonic loading paths. Monotonic and cyclic shear tests as well as Marciniak tests, in both plane and equi-biaxial strain states, are used to apply different pre-strain levels. For monotonic loading paths, i.e. monotonic shearing and Marcianiak tests, the applied methodology showed very satisfying results in determining the stress and strain states of the pre-strained specimens, especially for pre-strain values close to the representative indentation strain values. A maximum stress error of less than 15% was obtained in the case of the highest applied pre-strain value (29.04%). The purely isotropic Voce hardening law was adopted for determining the hardening behavior of the studied specimens in both cases: as-received and pre-strained. In the case of cyclic shear, a mixed isotropic-kinematic hardening law is to be used to determine the stress and strain states of the pre-strained specimens. Adopting a mixed isotropic-kinematic Chaboche hardening law led to satisfying results where the estimation errors of the applied pre-strain value and corresponding yield stress didn't exceed 6% and 1.3%, respectively. The obtained results show that the proposed indentation-based method can be very useful in estimating the work-hardening level and corresponding plastic deformation of pre-strained parts under various loading paths

Abstract P2107: Improving Stem Cell Models Of Duchenne Muscular Dystrophy-related Cardiomyopathy By Incorporation Of Physiologic Mechanical Stress

Background: Cardiomyopathy in Duchenne muscular dystrophy (DMD) is a significant driver of disease morbidity and mortality. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) offer the opportunity to study patient-specific mutations in the dish, however they generally suffer from immaturity. DMD is caused by mutations in the gene DMD , which codes for the protein dystrophin. Dystrophin localizes to the sarcolemma, forming part of a critical transmembrane mechanical and signaling complex that bridges the sarcomere to the extracellular matrix. Disruption of this axis leads to membrane fragility and mechanical stress is a main driver of DMD pathology. New therapies for DMD are in clinical development, including exon skipping, micro-dystrophin gene therapy, CRISPR-based gene editing, and membrane resealants, with some exon skipping strategies receiving FDA approval. The main outcomes of these therapies have been tied to improvement in skeletal muscle function with cardiac efficacy remaining understudied, despite its clear importance for patient outcomes. Results: Equibiaxial strain was employed as a physiologic mechanical stressor to simulate the in vivo mechanism of myocyte injury in an in vitro format using patient-derived DMD iPSC-CMs. By titrating strain, we determined that application of 10% strain for 2 hours robustly differentiates DMD and control iPSC-CMs using the clinically relevant biomarker LDH release as a proxy for membrane damage (control LDH release fold change: no significant change; DMD LDH release fold change: 2.51, p<0.0001). We evaluated DMD biomarkers released into the media using aptamer-based proteomics profiling and identified a striking strong correlation with serum biomarkers from DMD patients. Longer duration strain (24 hours) led to cell injury in both control and DMD iPSC-CMs. A membrane resealant was evaluated in this platform, which demonstrated enhanced recovery following treatment for both DMD and control iPSC-CMs with concomitant reduction in biomarker release. Conclusions: iPSC-CM models can be improved by incorporating physiologic mechanical stress, which is a main driver pathology. This platform is especially useful for evaluating dystrophic cardiomyopathy therapeutics.

Influence of the Anisotropic Behavior on Equibiaxial Paths

Marciniak and Nakajima tests are commonly used in building FLD's, since they allow covering all regions from uniaxial to almost equibiaxial strain paths. In this work, the deviation from equibiaxial strain paths is analyzed as function of the material anisotropic behavior. The numerical results show that material with present equibiaxial stress and strain paths, while for the ones with the paths are neither equibiaxial in stress nor strain. Moreover, it is shown that despite the similarities between the two tests, they present different sensitivity to the control of the blank holder force and to the friction coefficient. Namely, the stress and strain paths in the Marciniak specimen center are more sensitive to the control of the blank holder force. On the other hand, the stress and strain paths in the Nakajima specimen center are more sensitive to the friction coefficient. The deviation from the equibiaxial strain path indicates that the stress ratio is also not necessarily 1.0, meaning that the stress triaxiality and the Lode parameter also present some deviation from the reference values for an equibiaxial stress state. This should be taken into account when analyzing forming limit results.

Effect of Tensile Frequency on the Osteogenic Differentiation of Periodontal Ligament Stem Cells.

PurposeThe role of periodontal ligament stem cells (PDLSCs) in mediating osteogenesis involved in orthodontic tooth movement (OTM) is well established. However, various relevant in vitro studies vary in the frequency of tension. The effect of tensile frequency on the mechanotransduction of PDLSCs is not clear. The current study aimed to determine the effect of different tensile frequencies on the osteogenic differentiation of PDLSCs and to identify important mechano-sensitivity genes.MethodsHuman PDLSCs were isolated, identified, and subjected to cyclic equibiaxial tensile strain of 12% at different frequencies of 0.1 Hz, 0.5 Hz, 0.7 Hz, or static cultures. Osteogenic differentiation of PDLSCs was assessed by using Western blotting. High-throughput sequencing was used to identify differential mRNA expression. Short time-series expression miner (STEM) was utilized to describe the frequency patterns of the mRNAs. The functions and enriched pathways were identified, and the hub genes were identified and validated.ResultsWe found that the osteoblastic differentiation capacity of PDLSCs increased with tensile frequency in the range of 0.1–0.7 Hz. Eight frequency-tendency gene expression profiles were identified to be statistically significant. Tensile frequency-specific expressed genes, such as SALL1 and EYA1, which decreased with the increase in tensile frequency, were found.ConclusionThe osteoblastic differentiation of PDLSCs under mechanical tensile force is frequency dependent. EYA1 and SALL1 were identified as potential important tensile frequency-sensitive genes, which may contribute to the cyclic tension-induced osteogenic differentiation of PDLSCs in a frequency-dependent manner.

First-principles study of optical properties of monolayer h-BN and its defect structures under equibiaxial strain

First-principles study of optical properties of monolayer h-BN and its defect structures under equibiaxial strain

Active force generation contributes to the complexity of spontaneous activity and to the response to stretch of murine cardiomyocyte cultures.

Cardiomyocyte cultures exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. In such preparations, beat rate variability exhibits features similar to those of heart rate variability in vivo. Mechanical deformations and forces feed back on the electrical properties of cardiomyocytes, but it is not fully elucidated how this mechano‐electrical interplay affects beating variability in such preparations. Using stretchable microelectrode arrays, we assessed the effects of the myosin inhibitor blebbistatin and the non‐selective stretch‐activated channel blocker streptomycin on beating variability and on the response of neonatal or fetal murine ventricular cell cultures against deformation. Spontaneous electrical activity was recorded without stretch and upon predefined deformation protocols (5% uniaxial and 2% equibiaxial strain, applied repeatedly for 1 min every 3 min). Without stretch, spontaneous activity originated from the edge of the preparations, and its site of origin switched frequently in a complex manner across the cultures. Blebbistatin did not change mean beat rate, but it decreased the spatial complexity of spontaneous activity. In contrast, streptomycin did not exert any manifest effects. During the deformation protocols, beat rate increased transiently upon stretch but, paradoxically, also upon release. Blebbistatin attenuated the response to stretch, whereas this response was not affected by streptomycin. Therefore, our data support the notion that in a spontaneously firing network of cardiomyocytes, active force generation, rather than stretch‐activated channels, is involved mechanistically in the complexity of the spatiotemporal patterns of spontaneous activity and in the stretch‐induced acceleration of beating. Key points Monolayer cultures of cardiac cells exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. Beating variability in these preparations recapitulates the power‐law behaviour of heart rate variability in vivo. However, the effects of mechano‐electrical feedback on beating variability are not yet fully understood.Using stretchable microelectrode arrays, we examined the effects of the contraction uncoupler blebbistatin and the non‐specific stretch‐activated channel blocker streptomycin on beating variability and on stretch‐induced changes of beat rate.Without stretch, blebbistatin decreased the spatial complexity of beating variability, whereas streptomycin had no effects.Both stretch and release increased beat rate transiently; blebbistatin attenuated the increase of beat rate upon stretch, whereas streptomycin had no effects.Active force generation contributes to the complexity of spatiotemporal patterns of beating variability and to the increase of beat rate upon mechanical deformation. Our study contributes to the understanding of how mechano‐electrical feedback influences heart rate variability.