3D Cues Research Articles

Detection of unusual shadows is faster in scenes with weaker 3D cues

Detection of unusual shadows is faster in scenes with weaker 3D cues

Robust real-time tracking combining 3D shape, color, and motion

Real-time tracking algorithms often suffer from low accuracy and poor robustness when confronted with difficult, real-world data. We present a tracker that combines 3D shape, color (when available), and motion cues to accurately track moving objects in real-time. Our tracker allocates computational effort based on the shape of the posterior distribution. Starting with a coarse approximation to the posterior, the tracker successively refines this distribution, increasing in tracking accuracy over time. The tracker can thus be run for any amount of time, after which the current approximation to the posterior is returned. Even at a minimum runtime of 0.37 ms per object, our method outperforms all of the baseline methods of similar speed by at least 25% in root-mean-square (RMS) tracking error. If our tracker is allowed to run for longer, the accuracy continues to improve, and it continues to outperform all baseline methods. Our tracker is thus anytime, allowing the speed or accuracy to be optimized based on the needs of the application. By combining 3D shape, color (when available), and motion cues in a probabilistic framework, our tracker is able to robustly handle changes in viewpoint, occlusions, and lighting variations for moving objects of a variety of shapes, sizes, and distances.

Controlled surface topography regulates collective 3D migration by epithelial–mesenchymal composite embryonic tissues

Cells in tissues encounter a range of physical cues as they migrate. Probing single cell and collective migratory responses to physically defined three-dimensional (3D) microenvironments and the factors that modulate those responses are critical to understanding how tissue migration is regulated during development, regeneration, and cancer. One key physical factor that regulates cell migration is topography. Most studies on surface topography and cell mechanics have been carried out with single migratory cells, yet little is known about the spreading and motility response of 3D complex multi-cellular tissues to topographical cues. Here, we examine the response to complex topographical cues of microsurgically isolated tissue explants composed of epithelial and mesenchymal cell layers from naturally 3D organized embryos of the aquatic frog Xenopus laevis. We control topography using fabricated micropost arrays (MPAs) and investigate the collective 3D migration of these multi-cellular systems in these MPAs. We find that the topography regulates both collective and individual cell migration and that dense MPAs reduce but do not eliminate tissue spreading. By modulating cell size through the cell cycle inhibitor Mitomycin C or the spacing of the MPAs we uncover how 3D topographical cues disrupt collective cell migration. We find surface topography can direct both single cell motility and tissue spreading, altering tissue-scale processes that enable efficient conversion of single cell motility into collective movement.

Collective 3D Migration of Embryonic Epithelial Mesenchymal Composite Tissues are Regulated by Surface Topology

Cells in tissues encounter a range of physical cues as they migrate. Probing single cell and collective migratory responses to physically defined three-dimensional (3D) microenvironments and the factors that modulate those responses are critical to understanding how tissue migration is regulated during development, regeneration, and cancer. One key physical factor that regulates cell migration is topology. Most studies on surface topology and cell mechanics have been carried out with single migratory cells, yet little is known about the spreading and motility response of 3D complex multicellular tissues to topological cues. Here, we examine the behaviors of microsurgically isolated tissue explants composed of epithelial and mesenchymal cell layers from naturally 3D organized embryos of the aquatic frog Xenopus laevis to complex topological cues. We control topology using fabricated micropost arrays (MPAs) with different diameters (e.g., different spacing gaps) and investigate the collective 3D migration of these multicellular systems in these MPAs. Our topographical controlled approach for cellular application enables us to achieve a high degree of control over micropost positioning and geometry via simple, accurate, and repeatable microfabrication processes. We find that the topology regulates both collective and individual cell migration and that dense MPAs reduce but do not eliminate tissue spreading. By modulating cell size through the cell cycle inhibitor Mitomycin C or the spacing within MPAs we discover a role for topology in disrupting collective enhancement of cell migration. We find 3D topological cues can direct both single cell motility and tissue spreading, altering tissue-scale processes that enable efficient conversion of single cell motility into collective movement.

Do you hear where I hear?: isolating the individualized sound localization cues.

It is widely acknowledged that individualized head-related transfer function (HRTF) measurements are needed to adequately capture all of the 3D spatial hearing cues. However, many perceptual studies have shown that localization accuracy in the lateral dimension is only minimally decreased by the use of non-individualized head-related transfer functions. This evidence supports the idea that the individualized components of an HRTF could be isolated from those that are more general in nature. In the present study we decomposed the HRTF at each location into average, lateral and intraconic spectral components, along with an ITD in an effort to isolate the sound localization cues that are responsible for the inter-individual differences in localization performance. HRTFs for a given listener were then reconstructed systematically with components that were both individualized and non-individualized in nature, and the effect of each modification was analyzed via a virtual localization test where brief 250 ms noise bursts were rendered with the modified HRTFs. Results indicate that the cues important for individualization of HRTFs are contained almost exclusively in the intraconic portion of the HRTF spectra and localization is only minimally affected by introducing non-individualized cues into the other HRTF components. These results provide new insights into what specific inter-individual differences in head-related acoustical features are most relevant to sound localization, and provide a framework for how future human-machine interfaces might be more effectively generalized and/or individualized.

2D‐D Lifting for Shape Reconstruction

AbstractWe present an algorithm for shape reconstruction from incomplete 3D scans by fusing together two acquisition modes: 2D photographs and 3D scans. The two modes exhibit complementary characteristics: scans have depth information, but are often sparse and incomplete; photographs, on the other hand, are dense and have high resolution, but lack important depth information. In this work we fuse the two modes, taking advantage of their complementary information, to enhance 3D shape reconstruction from an incomplete scan with a 2D photograph. We compute geometrical and topological shape properties in 2D photographs and use them to reconstruct a shape from an incomplete 3D scan in a principled manner. Our key observation is that shape properties such as boundaries, smooth patches and local connectivity, can be inferred with high confidence from 2D photographs. Thus, we register the 3D scan with the 2D photograph and use scanned points as 3D depth cues for lifting 2D shape structures into 3D. Our contribution is an algorithm which significantly regularizes and enhances the problem of 3D reconstruction from partial scans by lifting 2D shape structures into 3D. We evaluate our algorithm on various shapes which are loosely scanned and photographed from different views, and compare them with state‐of‐the‐art reconstruction methods.

Abstract 2344: 3D extracellular stiffness cues drive localized changes in gene expression

Abstract The stiffness of the extracellular matrix (ECM) stimulates mechanotransduction pathways that regulate tissue development and tumor progression. We previously showed that a stiff ECM potentiates cell growth and survival, enhances cell migration to drive tumor cell invasion, and drives malignant progression of the mammary gland in culture and in vivo, but the specific transcriptional and molecular events that occur as cells acquire these phenotypic changes are not well understood. To clarify this process, we used expression microarrays, tandem mass spectrometry, and RNA sequencing to identify changes in gene expression levels, isoform usage, and protein abundance that occur as intact ascini respond to distinct stiffness environments. We found that in stiffer ECM conditions ascini acquire consistent changes in gene expression related to cell adhesion and mRNA splicing, and specifically induce the expression of a set of genes involved in epithelial cell differentiation that includes multiple SPRR and S100 proteins. Remarkably, these genes map to an apparent stiffness-mediated transcriptional hotspot on chromosome 1q21, a region containing elevated transcription in many cancers but whose activity has not been related to mechanotransduction. We then used a heuristic approach to identify additional candidate force-mediated transcriptional hotspots throughout the genome that contain multiple genes that are coordinately activated or silenced in response to elevated ECM stiffness. Provocatively, we find that genes whose expression levels are responsive to ECM stiffness cues are disproportionately located within chromosomal regions that associate with the nuclear lamina, suggesting that these transcriptional changes may be due in part to force-dependent alteration of genomic contacts with the nuclear envelope. These studies provide biological insight into the divergent cellular responses to distinct stiffness environments and suggest that genome regulatory responses to the force environment may specifically target distinct chromosomal regions via a mechanism that remains to be elucidated. Citation Format: Russell Bainer, Yoshihiro Yui, Shannon Mumenthaler, Parag Mallick, Ondrej Podlaha, Franziska Michor, Jan Liphardt, Jonathan Licht, Valerie Weaver. 3D extracellular stiffness cues drive localized changes in gene expression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2344. doi:10.1158/1538-7445.AM2014-2344

A novel technique for the production of electrospun scaffolds with tailored three-dimensional micro-patterns employing additive manufacturing

Electrospinning is a common technique used to fabricate fibrous scaffolds for tissue engineering applications. There is now growing interest in assessing the ability of collector plate design to influence the patterning of the fibres during the electrospinning process. In this study, we investigate a novel method to generate hybrid electrospun scaffolds consisting of both random fibres and a defined three-dimensional (3D) micro-topography at the surface, using patterned resin formers produced by rapid prototyping (RP). Poly(D,L-lactide-co-glycolide) was electrospun onto the engineered RP surfaces and the ability of these formers to influence microfibre patterning in the resulting scaffolds visualized by scanning electron microscopy. Electrospun scaffolds with patterns mirroring the microstructures of the formers were successfully fabricated. The effect of the resulting fibre patterns and 3D geometries on mammalian cell adhesion and proliferation was investigated by seeding enhanced green fluorescent protein labelled 3T3 fibroblasts onto the scaffolds. Following 24 h and four days of culture, the seeded scaffolds were visually assessed by confocal macro- and microscopy. The patterning of the fibres guided initial cell adhesion to the scaffold with subsequent proliferation over the geometry resulting in the cells being held in a 3D micro-topography. Such patterning could be designed to replicate a specific in vivo structure; we use the dermal papillae as an exemplar here. In conclusion, a novel, versatile and scalable method to produce hybrid electrospun scaffolds has been developed. The 3D directional cues of the patterned fibres have been shown to influence cell behaviour and could be used to culture cells within a similar 3D micro-topography as experienced in vivo.

Improving awareness for 3D virtual collaboration by embedding the features of users’ physical environments and by augmenting interaction tools with cognitive feedback cues

The feeling of presence is essential for efficient interaction within Virtual Environments (VEs). When a user is fully immersed within a VE through a large immersive display system, his/her feeling of presence can be altered because of disturbing interactions with his/her physical environment, such as collision with hardware parts of the system or loss of tracking. This alteration can be avoided by taking into account the physical features of the user as well as those of the system hardware and embedding them in the VE. Moreover, the 3D abstract representation of these physical features can also be useful for collaboration between distant users because they can make a user aware of the physical limitations of the others he/she is collaborating with. In this paper we present how we use the Immersive Interactive Virtual Cabin (IIVC) model to obtain this virtual representation of the user’s physical environment and we illustrate how this representation can be used in a collaborative navigation task in a VE. We also present how we can add 3D representations of 2D interaction tools in order to cope with asymmetrical collaborative configurations, providing 3D cues for a user to understand the actions of the others even if he/she is not fully immersed in the shared VE. Last, we briefly explain how we plan to enhance 3D interaction and collaboration by embedding a symbolic 3D user representation that will give 3D information about his/her posture.

Application of stereoscopic visualization on surgical skill acquisition in novices

This study examines the influence of monoscopic vs. stereoscopic visualization in novice trainees performing the MISTELS, a validated laparoscopic skill evaluation system consisting of 5 distinct tasks. We hypothesize a difference in performance based on visualization modality. First and second year medical students (n=31) performed the MISTELS battery of tasks using either monoscopic or stereoscopic visualization displays. Regression analysis indicates performance was not correlated to participant manual dexterity or visual spatial ability (p>;0.05). Monoscopic visualization was shown to produce significantly better performance in the peg transfer task alone (p=0.001), with visualization modality producing no significant difference in performance of the remaining tasks (p>;0.05). Qualitatively, 57.1% of participants believed their performance was aided by stereoscopic visualization. Most participants rated the peg transfer task the least difficult task (60%), and the intracorporeal knot‐tying task the most difficult (65.9%). These results suggest the intrinsic difficulty of the MISTELS tasks may exceed a novice user's skill, rendering no benefit with additional 3D cues in naïve surgical trainees, and may serve to increase cognitive load, potentially decrease skill acquisition and learning.Grant Funding Source: Summer Research Training Program, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Canada

Symmetry facilitates shape constancy for smoothly curved 3d objects.

We tested whether the presence of symmetry improves shape discrimination across changes in viewpoint and lighting for smoothly curved 3D objects. We constructed symmetric and asymmetric versions of random 3D shapes by manipulating their spherical harmonic representations. Matched objects had the same power spectra and appear highly similar except for the presence of symmetry. Observers discriminated sequentially presented pairs of either symmetric or asymmetric objects. Objects were presented in conditions that provided different 3D cues: shading only, stereo only, and combined shading and stereo. To control for 2D cues, standard and test objects had matched boundary contours and were rendered with different light sources. Test objects were also rotated in depth by variable amounts (0° to 60°). Across all viewpoint and 3D cue conditions, we found that shape discrimination for symmetric objects was better than for asymmetric objects. The symmetry benefit was not limited to monocular viewing or to conditions with large rotations in depth. In a second experiment, we blocked trials by viewpoint rotation to eliminate uncertainty in object orientation. This improved performance for asymmetric objects relative to symmetric objects, suggesting that symmetry contributes by providing a cue to object orientation. However, a symmetry advantage was still observed in all shape cue conditions, so this was not the sole source of benefit. Our results demonstrate that symmetry improves shape constancy for smooth 3D objects and suggest that one role of symmetry is to provide a reference orientation for an object.

Mesenchymal stem cell response to TGF-β1 in both 2D and 3D environments.

Smooth muscle cells (SMC) are critical in stabilizing developing vascular networks, and transforming growth factor β1 (TGF-β1) has been shown to promote SMC differentiation from stem cells. Previously, our lab has developed a chemically modified fibrin-based hydrogel that induces endothelial cell (EC) phenotype and network formation from human mesenchymal stem cells (hMSCs) without exogenous cytokines. Additionally, we have shown that this hydrogel system is capable of releasing growth factors in a controlled manner. In the present work, the effects of TGF-β1 on hMSCs in both monolayer and fibrin-based gel culture systems were demonstrated. The objective was to enhance SMC properties through TGF-β1 signaling for vessel stability while maintaining EC gene expression and morphology. Proliferation was decreased with higher TGF-β1 concentration in both monolayer and 3D gel cultures. EC genes were predominantly downregulated in the presence of TGF-β1 in monolayer cultures, while SMC genes were generally upregulated. In fibrin-based gels, several SMC genes were significantly upregulated at high concentrations of TGF-β1. Even at elevated TGF-β1 concentrations, no significant differences were seen in EC genes for hMSCs in gels compared to controls. Network formation and growth occurred in PEGylated fibrin gels loaded with TGF-β1 and were not significantly different from gels without loaded growth factor. Additionally, production of smooth muscle α-actin (SMA) was significantly increased in gels loaded with TGF-β1. These results demonstrate a simultaneous response of hMSCs to both the 3D biomatrix and cytokine signaling cues.

Deploying a modeling framework for reusable robot behavior to enable informed strategies for domestic service robots

For the development of multi-purpose robots that can operate in a wide range of different situations we will need sophisticated behavioral building blocks to compose the desired performances. In this paper we argue for a behavior modeling framework which provides specific behavior interfaces for implementing robot skills that stay close to evaluation cycles and to rich fused sensory data. This way we ensure reusability and facilitate what we call Informed Strategies. As a specific application we deploy the framework to an object search task for a domestic service robot. The presented behavior involves an attention mapping mechanism based on 2D and 3D visual cues. We show the advantages of the proposed approach by conducting an evaluation in a real-world apartment scenario as well as by successfully taking part in the RoboCup@HOME competition.

Stereoscopic Depth Cues Outperform Monocular Ones on Autostereoscopic Display

The aim of this study is two-fold; first, to compare how certain visual aids contribute in depth estimation tasks on a portable autostereoscopic display; and second, how these depth cues impact on perceived quality. These were studied on a quantitative subjective study using a portable autostereoscopic display in controlled laboratory environment. Test participants evaluated object depths on three-dimensional images, where either 2D cues, 3D cues, or their combinations were provided. The study was conducted using three different compression levels in order to study how image quality affects the perception of depth. The results indicate that the depth estimation task is faster conducted when the participants relied on stereoscopic depth cues compared to situations where only monocular cues were present. Also, depth estimation task is faster conducted with higher quality images. Depth estimation accuracy was also higher with stereoscopic depth cues than with monocular ones. These results suggest that the human visual system can make more reliable depth estimates on portable autostereoscopic displays when stereoscopic cues are present. However, the results of the quality evaluations indicate that, as stated also on previous studies, the added stereoscopic depth does not seem to increase the subjective image quality.

Characterization of leukemic cell behaviors in a soft marrow mimetic alginate hydrogel

Alginate hydrogels possess tunable mechanical properties that can mimic soft marrow tissue and present three-dimensional (3D) cues. This study evaluates its utility for supporting leukemic cell growth in vitro and its impact on cell survival, growth, and differentiation. Our results showed that the standard viscosity alginates had compromised leukemia cell viability but lower viscosity alginates recovered cell viability and improved 3D cell proliferation (27 fold) compared to 2D cultures (18 fold). Conjugation with RGD peptides promoted further cell growth (43 folds). In general, 3D hydrogels supported high-density cultures better than 2D cultures. Leukemic cells formed densely packed cell clusters in alginate hydrogels and spontaneously differentiated into a more diverse myeloid population. The cell cycle data suggested that more cells go into active cycling with a G2/M arrest in alginate hydrogels and the presence of multiploidy confirmed maturation toward megakaryocytes. In summary, superior culture of leukemia cells in 3D hydrogels is demonstrated in this study accompanied by a potential role of physical cues influencing cell fate decision. Manipulation of biophysical and biochemical properties of alginate hydrogels permits the study of specific interactions and serves to provide a robust 3D platform for studying extrinsic contributions inside the bone marrow.

Malleability in the development of spatial reorientation

After becoming disoriented, organisms must re-establish their position in space. The core knowledge position argues that reorientation relies only on extended 3D surfaces, and that this sensitivity operates automatically and is innately present. In contrast, the adaptive combination perspective argues that reorientation is experience-expectant and malleable, and depends on both extended 3D surfaces and 2D feature cues. We test these divergent views by comparing young (Experiment 1) and mature (Experiment 2) C57BL/6 mice (Mus musculus) that have been housed in circular or rectangular environments. Malleability of feature cues was found for young mice. Malleability of incidental geometry coding was found for both age groups. The relative dependence on geometric and feature cues changed with age. Young mice weighted the feature cue more heavily than adult mice. In summary, as predicted by the adaptive combination approach, rearing environments influenced the relative use of feature and geometric cues in a reorientation task.

The neural basis of impossible figures: Evidence from an fMRI study of the two-pronged trident

In the present study, we used the two-pronged trident task to investigate the neural basis of impossible figures processing by using event-related functional magnetic resonance imaging (fMRI). Our fMRI results showed that there were no brain regions with significantly stronger responses to possible condition than to impossible condition. However, impossible condition showed significantly more activation in the right inferior temporal gyrus (ITG), the fusiform gyrus (FG) and the right superior parietal gyrus (SPG). The right SPG in the dorsal visual pathway might be related to spatial information processing and the right lateral occipital complex (LOC) (FG and ITG) in the ventral visual pathway (the object-selective regions) might be related to the representation of the impossible 3D structure. Therefore, our results indicated that the impossible 3D structure might be difficult to be represented by human visual system, and the impossible perception might be derived from the detecting and resolving the contradiction in the subjects’ interpretations according to different perceptions triggered by 3D cues.

Stereo improves 3D shape discrimination even when rich monocular shape cues are available

Stereo is a powerful 3D cue, but there is mixed evidence about whether stereo contributes to recognizing objects across changes in viewpoint. Some previous studies have demonstrated a stereo advantage for recognition of unfamiliar objects across viewpoints. However, in these studies, 3D structure was not well-specified by monocular information (e.g, bent paperclips). When rich monocular cues to 3D shape are available, does stereo still provide a benefit? We tested shape discrimination for smoothly-curved, solid random shapes in three viewing conditions: shading-only, stereo-only, and combined shading and stereo. Objects were simulated to have a fine homogeneous surface texture, and illumination was either ambient (stereo-only) or a diffused point light source (shading-only and combined conditions). A mirror haploscope was used to present binocular images. Observers performed same-different shape discrimination judgments for sequentially presented images. Standard and test objects were either the same orientation or differed by a rotation in depth of ±15°, ±30°, or ±60° around the vertical axis. To discourage a 2D strategy, pairs of comparison shapes were constructed to have the same occlusion contour when viewed from the base orientation, and light source direction was varied between standard and test objects. We found that rotation in depth markedly impaired discrimination performance in all viewing conditions, as evidenced by reduced sensitivity (d′) and increased bias toward judging same shapes as different. We also observed a consistent benefit from stereo for all viewpoint conditions. Although the shading-only images produce a strong subjective percept of 3D shape, observers were not able to reliably discriminate shapes across changes in viewpoint (30°: d′ = .86, 60°: d′ = .46). Discrimination was significantly better with binocular viewing (30°: d′ = 1.34, 60°: d′ = .78). Our results demonstrate that shape perception for random 3D objects is highly viewpoint-dependent, and that stereo information can reduce viewpoint costs.

Substrate Three-Dimensionality Induces Elemental Morphological Transformation of Sensory Neurons on a Physiologic Timescale

The natural environment of a neuron is the three-dimensional (3D) tissue. In vivo, embryonic sensory neurons transiently express a bipolar morphology with two opposing neurites before undergoing cytoplasmic and cytoskeletal rearrangement to a more mature pseudo-unipolar axonal arbor before birth. The unipolar morphology is crucial in the adult for correct information transmission from the periphery to the central nervous system. On two-dimensional (2D) substrates this transformation is delayed significantly or absent. We report that a 3D culture platform can invoke the characteristic transformation to the unipolar axonal arbor within a time frame similar to in vivo, overcoming the loss of this essential milestone in 2D substrates. Additionally, 3D substrates alone provided an environment that promoted axonal branching features that reflect morphological patterns observed in vivo. We have also analyzed the involvement of soluble cues in these morphogenic processes by culturing the neurons in the presence and absence of nerve growth factor (NGF), a molecule that plays distinct roles in the development of the peripheral and central nervous systems. Without NGF, both 2D and 3D cultures had significant decreases in the relative population of unipolar neurons as well as shorter neurite lengths and fewer branch points compared to cultures with NGF. Interestingly, branching features of neurons cultured in 3D without NGF resemble those of neurons cultured in 2D with NGF. Therefore, neurons cultured in 3D without NGF lost the ability to differentiate into unipolar neurons, suggesting that this morphological hallmark requires not only presentation of soluble cues like NGF, but also the surrounding 3D presentation of adhesive ligands to allow for realization of the innate morphogenic program. We propose that in a 3D environment, various matrix and soluble cues are presented toward all surfaces of the cell; this optimized milieu allows neurons to elaborate their genuine phenotype and follow programmed instructions that are intrinsic to the neuron, but disrupted when cells were dissected from the embryo. Thus, this study presents quantitative data supporting that 3D substrates are critical for sustaining the in vivo ontogeny of neurons and deciphering signaling mechanisms necessary for designing biomaterial scaffolds for nerve generation and repair.

Pluripotent stem cell-derived cardiac tissue patch with advanced structure and function

Recent advances in pluripotent stem cell research have provided investigators with potent sources of cardiogenic cells. However, tissue engineering methodologies to assemble cardiac progenitors into aligned, 3-dimensional (3D) myocardial tissues capable of physiologically relevant electrical conduction and force generation are lacking. In this study, we introduced 3D cell alignment cues in a fibrin-based hydrogel matrix to engineer highly functional cardiac tissues from genetically purified mouse embryonic stem cell-derived cardiomyocytes (CMs) and cardiovascular progenitors (CVPs). Procedures for CM and CVP derivation, purification, and functional differentiation in monolayer cultures were first optimized to yield robust intercellular coupling and maximize velocity of action potential propagation. A versatile soft-lithography technique was then applied to reproducibly fabricate engineered cardiac tissues with controllable size and 3D architecture. While purified CMs assembled into a functional 3D syncytium only when supplemented with supporting non-myocytes, purified CVPs differentiated into cardiomyocytes, smooth muscle, and endothelial cells, and autonomously supported the formation of functional cardiac tissues. After a total culture time similar to period of mouse embryonic development (21 days), the engineered cardiac tissues exhibited unprecedented levels of 3D organization and functional differentiation characteristic of native neonatal myocardium, including: 1) dense, uniformly aligned, highly differentiated and electromechanically coupled cardiomyocytes, 2) rapid action potential conduction with velocities between 22 and 25 cm/s, and 3) significant contractile forces of up to 2 mN. These results represent an important advancement in stem cell-based cardiac tissue engineering and provide the foundation for exploiting the exciting progress in pluripotent stem cell research in the future tissue engineering therapies for heart disease.