Traditional methods to achieve stretchability in electronics often turn to ancient Japanese arts—origami and kirigami. Origami, the art of folding paper, uses carefully engineered hinge patterns to create foldable yet structurally stable configurations. Kirigami, which incorporates strategic cuts along with folds, allows materials to deform more dramatically, enabling extensive stretching and bending. While origami lends itself to the incorporation of rigid, mountable panels, it lacks the range of deformability offered by kirigami. Conversely, kirigami’s expansive slits provide large-area stretchability but impose limitations on mounting rigid electronic components securely. This dichotomy represents a significant engineering bottleneck in stretchable device fabrication.

Addressing this, Professor Eiji Iwase and his collaborator Nagi Nakamura from Waseda University’s Department of Applied Mechanics and Aerospace Engineering have devised an innovative hybrid structure, coined “kiri-origami.” This approach harmoniously blends the folding mechanisms of origami with the cutting strategies of kirigami to craft structures that optimize stretchability without sacrificing the mechanical benefits of rigid components. Their pioneering work was published in the prestigious journal npj Flexible Electronics in June 2025 and stands to set new milestones in stretchable electronics design.

The ingenious kiri-origami framework features a mutually orthogonal cutting line pattern, strategically arranged to synergize deformation with mechanical support. Triangular joint panels, connected by two folding lines acting as hinges, reconcile two adjoining square panels formed by the cuts. Upon stretching from a flat baseline, these square panels elevate and rotate, enabling the formation of slits and culminating in a distinctive Z-shaped configuration around the hinges. This morphing not only facilitates a remarkable degree of stretch but also permits the simultaneous mounting and movement of rigid electronic components—previously a significant limitation in kirigami designs.

Idealized kiri-origami structures, characterized as rigid-origami, assume perfectly rigid panels with frictionless hinge rotation. However, real-world applications encounter panel deformation and the influence of elastic repulsive forces within flexible electronic substrates. To realistically capture these phenomena, the research team developed what they term an “elastic origami model.” Through experimental uniaxial stretching tests on rectangular models of this elastic origami, the researchers observed deviations from the rigid model predictions. Specifically, the fixed clamping edges and non-uniform tension distributions led to distortions, highlighting important mechanical factors that must be addressed for practical device deployment.

To counteract the detrimental effects of fixed edges and inconsistent tension, the researchers introduced a novel buffer structure design. These buffer components are trapezoidal extensions strategically connected to the edges of the kiri-origami structure and its clamps. The smaller edges of these buffers match the original width of the kiri-origami, while their larger edges are tailored to the target stretched configuration. Under tensile load, these buffers elongate akin to mechanical springs, distributing tension uniformly and enabling the entire structure to deform in a controlled, two-dimensional manner. This advancement enhances the fidelity of mechanical response, aligning experimental outcomes with rigid-model predictions and ensuring device reliability.

Demonstrating the practical viability of their approach, the team engineered a stretchable display integrating over 500 hinges and embedding 145 light-emitting diodes (LEDs). Remarkably, every hinge folded simultaneously without compromising the device’s function, underscoring the method’s potential for scalable, complex electronics. This feat not only showcases the robustness of the kiri-origami design but also highlights its promise for future applications extending beyond conventional flexible electronics.

Professor Iwase underscored the wide-reaching implications of this technology, emphasizing that it paves the path for next-generation wearable sensors, curved displays, and dynamic actuators in robotics and human-assistive technologies. The kiri-origami structure negates the historical compromise between flexibility and electronic performance, enabling the integration of traditional high-performance materials into highly deformable frameworks. This could drastically expand the landscape of wearable and implantable devices, enhancing user comfort, device durability, and overall functionality.

One of the standout technical triumphs of this study is the ability of the kiri-origami design to maintain uniform tension during stretching, vital for electronic stability and longevity. Previous methods struggled with uneven strain distributions leading to material fatigue or electrical failure. The buffer structure, by functioning as an adaptive spring, mitigates these issues and embodies an elegant solution fusing structural mechanics with electronic engineering.

By integrating rudimentary mechanical principles from age-old Japanese arts into cutting-edge materials science, this approach redefines the future of electronic device fabrication. It resonates particularly well in the context of expanding fields such as soft robotics and biomedical instrumentation, where devices must conform reliably to complex, dynamic bodily shapes while maintaining sophisticated functionality.

Furthermore, the scalability of the kiri-origami technique marks a crucial advance. The capacity to fabricate devices with large numbers of repeating units suits mass production and broad deployment. This opens avenues for customizable stretchable electronics tailored to user-specific geometries, from flexible displays that seamlessly curve around wrists and fingers to sensors that adapt to unpredictable human body movements.

The breakthrough reported by Iwase and Nakamura offers a compelling paradigm shift, demonstrating that the limitations of material properties can be surmounted through innovative structural engineering. Their contribution stands as a testament to interdisciplinary synergy, where mechanical design principles align with materials science to unlock new technological horizons.

Looking ahead, this innovation holds the promise of transforming not just consumer electronics but also healthcare diagnostics and robotic assistance systems. Stretchable, high-performance electronic platforms energized by kiri-origami structures will likely become foundational enablers of futuristic applications, catalyzing advances in personalized medicine and bio-integrated robotics.

As this research gains traction, it may inspire further explorations into hybrid fold-and-cut geometries, adaptive mechanics, and integrated system design, inspiring a fresh wave of innovations that blend historical artistry with modern scientific tenacity.

Subject of Research: Not applicable

Article Title: Stretch-based kirigami structure with folding lines for stretchable electronics

News Publication Date: 5-Jun-2025

Web References: https://doi.org/10.1038/s41528-025-00409-4

References: Nakamura N, Iwase E. Stretch-based kirigami structure with folding lines for stretchable electronics. npj Flexible Electronics. 2025;9:Article 4. https://doi.org/10.1038/s41528-025-00409-4

Image Credits: Professor Eiji Iwase, Waseda University

Keywords

Electronics; Wearable devices; Applied physics; Applied sciences and engineering; Sensors; Robotics; Mechanical engineering; Materials science

Thermoelectric devices, which convert temperature gradients directly into electrical energy, have attracted widespread interest for their potential applications in powering wearable sensors, medical implants, and soft robotics. Traditionally, the brittleness and planar configuration of thermoelectric materials have imposed strict constraints on their integration into flexible platforms. Attempts to embed these materials into stretchable substrates typically result in compromised performance due to mechanical fractures and degraded conductivity. The team’s novel microfluidic strategy deftly circumvents these obstacles by engineering intricate 3D architectures that reconcile flexibility, stretchability, and thermoelectric functionality in a single, cohesive system.

At the heart of this breakthrough lies the ingenious exploitation of microfluidic channels—minuscule conduits capable of precisely directing and confining liquid phases within elastomeric matrices. The researchers utilized these microfluidic pathways to deposit thermoelectric materials in predefined, three-dimensional configurations that inherently accommodate volumetric strain. By embedding the thermoelectric elements within elastomers such as polydimethylsiloxane (PDMS), the resultant composites exhibit exceptional mechanical resilience, supporting stretching, twisting, and bending while preserving their core electrical and thermal transport properties.

The fabrication methodology employs advanced soft lithography paired with layer-by-layer assembly techniques, enabling meticulous control over channel geometry and material deposition. Such microfabrication tactics, borrowed and refined from the microelectronics and biomedical device fields, are instrumental in realizing the complex 3D layout envisioned by the authors. By strategically orienting thermoelectric legs in vertical arrays connected via compliant interconnects, they dramatically enhance the device’s three-dimensional flexibility without compromising pathway integrity or performance stability.

Thermoelectric performance, quantified by metrics such as the Seebeck coefficient, electrical conductivity, and thermal conductivity, traditionally degrades when materials are subjected to mechanical rigor. Remarkably, the microfluidic-enabled 3D architecture not only preserves but in some configurations enhances these properties due to optimized heat flow management and intrinsic strain adaptation. The coupling of microfluidic design with material science insights leads to unconventional geometries that exploit the interplay of thermal gradients and elastic deformation to maintain high energy conversion efficiency under stretch.

Beyond mechanical resilience, thermal management emerges as a critical advantage afforded by the microfluidic channels themselves. The liquid media used within these pathways can facilitate heat redistribution, effectively modulating thermal paths and mitigating hotspots that ordinarily induce performance bottlenecks. This active thermal control presents a unique lever for optimizing thermoelectric efficiency in wearable settings, where ambient temperature fluctuations and human motion regularly distort device operating conditions.

The authors further demonstrate the dynamic applicability of their invention through an array of functional prototypes. Devices integrated onto curved human skin segments undergo repeated stretch cycles beyond 50% strain, showcasing consistent voltage generation without signs of material fatigue or electrical failure. Such findings directly attest to the viability of these thermoelectric modules in diverse real-world applications where flexibility and resilience are paramount.

In exploring material choices, the research probes beyond conventional bismuth telluride and other brittle compounds prevalent in thermoelectrics. Innovative formulations featuring conductive polymers, nanocomposites, and hybrid organic-inorganic blends are investigated for compatibility with the microfluidic patterning processes. These materials offer tunable mechanical compliance alongside favorable thermoelectric parameters, synergizing with the 3D architecture to elevate overall device performance.

Underlying the achievements is a multidisciplinary confluence of microfluidics, polymer chemistry, thermodynamics, and electronic engineering. The design principles elucidated in this study underscore the profound potential unlocked when traditionally disparate scientific domains intersect. By tailoring microscale geometries and exploiting fluid dynamics within elastomeric hosts, the researchers chart a pathway toward stretchable electronics that dynamically integrate sensing, actuation, and energy harvesting functions.

Scaling implications are equally promising. The microfluidic fabrication approach can be adapted to roll-to-roll processing and other high-throughput manufacturing schemes, signaling a pathway for commercial viability. Unlike brittle semiconductor wafers, these stretchable thermoelectric devices invite integration onto textiles, wearable patches, or even bioresorbable implants, broadening the landscape of autonomous electronics powered harnessing human body heat or environmental gradients.

From an ecological standpoint, enhancing thermoelectric harvesting from low-grade thermal sources, such as body heat lost during metabolism, touches upon sustainability goals. Wearable devices enhanced by this technology could reduce dependence on bulky batteries and frequent charging cycles, promoting longer-lasting, maintenance-free electronics that mesh effortlessly with daily life. The non-invasive energy scavenge approach also aligns with emerging trends in personalized healthcare and real-time monitoring.

Technically, the research addresses several key challenges inherent to stretchable electronics: achieving reliable electrical contacts amidst strain, balancing mechanical deformation with thermal conductivity, and circumventing delamination or structural failure from cyclic use. Through clever microfluidic channel designs that permit fluidic encapsulation and mechanical decoupling, these issues are elegantly mitigated. The seamless interoperability between rigid thermoelectric semiconductors and soft elastomers is a hallmark outcome of their methodology.

Of particular note is the dynamic modulation capability observed when varying microfluidic channel parameters such as diameter, length, and filling medium. Devices exhibited tunable mechanical properties and thermal responses by virtue of fluid movement and channel deformation under stress conditions, opening avenues for responsive systems that adapt performance in real-time. Such adaptability is a common motif in biological systems and marks a transformative step toward biomimetic wearable electronics.

The research team concludes by envisioning a new generation of flexible thermoelectrics that do not merely survive mechanical perturbations but thrive because of them—leveraging strain-induced modifications to optimize functional output. This paradigm shift challenges conventional design dogmas and inspires future innovations where comfort, form factor, and sustainability coalesce without compromise.

As this research gains traction, interest is expected to surge in portable, self-powered electronic devices that users can wear as comfortably as clothing yet whose energy sourcing is as reliable as traditional rigid batteries. The melding of microfluidics with thermoelectric science presents a fertile terrain for intellectual exploration and commercial exploitation, foretelling a vibrant revolution in how we think about and deploy flexible energy systems.

In summary, the seminal work by Huang et al. sets a robust foundation for realizing stretchable thermoelectric devices that marry advanced fabrication technologies with cutting-edge materials science. Its implications resound across fields ranging from soft robotics to personal healthcare monitoring, signaling a compelling stride toward truly flexible, multifunctional electronics optimized for the dynamic human environment.

Subject of Research: Development of microfluidic-enabled three-dimensional stretchable thermoelectric devices for flexible and wearable electronics.

Article Title: Microfluidic-enabled three-dimensional stretchable thermoelectrics.

Article References:
Huang, Z., Chen, T., Jiang, Y. et al. Microfluidic-enabled three-dimensional stretchable thermoelectrics. npj Flex Electron 9, 52 (2025). https://doi.org/10.1038/s41528-025-00429-0

Image Credits: AI Generated