A laser-programmed strategy to engineer the local stiffness and interfacial properties of textiles enables the direct assembly of standard electronic components onto textiles to create stretchable hybrid electronic systems.
(Nanowerk Spotlight) Permeable and durable textiles hold great promise for wearable electronics, with applications spanning displays, communications, energy management, and health monitoring. As these systems evolve toward higher functional complexity, an increasing number of silicon chips are required for comprehensive signal processing and computation.
Currently, these chips are typically mounted on conventional rigid circuit boards, which fundamentally conflict with the desired wearing comfort and conformability of textile electronic systems.
Achieving truly monolithic and comfortable textile electronics requires the seamless integration of silicon chips. On elastic textiles, these chips, together with ductile interconnects and solder materials, can form stretchable hybrid systems.
A key challenge, however, lies in the dynamic and non-uniform strain that occurs when elastic textiles are stretched. This strain creates a mechanical mismatch between the textile and the electronic components, often leading to device failure under repeated use.
A recent study in Nature Communications (“Laser-programmed stiffness and interfaces for textile hybrid electronics”) addresses this challenge directly. Researchers from Zhejiang University present a laser-programmed strategy to engineer the local stiffness and interfacial properties of textiles, enabling the direct assembly of standard electronic components onto textiles to create stretchable hybrid electronic systems (Movie 1).
Movie 1: Laser-programmed textiles for hybrid electronic systems. (Courtesy of the researchers)
First, selective laser irradiation is applied to a photo-curable polymer precursor within the textile. This process creates laser-programmed textiles (LPTs), featuring precisely tailored regions with a tunable modulus increase of 2.7 to 14.9 times, along with consistent interfacial affinity through hydrogen bonding sites.
Second, the authors strategically pattern these programmed regions on the LPTs that interface with double-layer liquid metal (LM) wires and chips, respectively. This design ensures that the LM wires remain electrically stable under stretching and pressure, while the chips are securely connected to the wires and mechanically isolated from strain (Figure 1).
Figure 1: Working mechanism of laser-programmed textiles at textile–electronics interfaces. (Image courtesy of the researchers)
Overall, this work provides a viable strategy to bridge the mechanical mismatch between elastic textiles and hybrid electronic components, enabling diverse applications in long-term and dynamic wearable electronics.
“The inherent waviness and uneven strain distribution in textiles have long undermined the stability of printed circuits and mounted chips.” says Prof. Kaichen Xu, corresponding author of this publication. “The mechanical design of textile substrates is intuitive to address these problems, and laser-induced polymerization is quite advantageous to prototype porous textiles with mechanical gradients.”
Before laser processing, liquid PP precursor (containing polyurethane acrylate) is infiltrated into textiles. The crosslinking density of this polymer is tuned by the laser fluence, thus determining the polymer’s modulus and the stiffness of the resulting LPTs. In addition, the polymerized PP on textile surfaces provides hydroxyl and amine groups, which form hydrogen bonds with the oxide layer of LM circuits.
By combining the inherent LM affinity and the customizable local stiffness, LM wires printed on the soft LPT region can be elongated to 100% strain. When applying a compressive stress of 3 MPa at the overlapping area of double-layer LM wires, the intermediate stiff LPT region effectively suppresses the expansion of textile pores, avoiding a cross-layer short circuit.
Moreover, the stiff regions surrounded by soft regions establish a stiffness gradient. This design allows the soft regions to dissipate the strain energy induced by stretching, so that the chip-LM interfaces on the stiff region are protected.
Movie 2: Monolithic and stretchable sensor systems on laser-programmed textiles. (Courtesy of the researchers)
Simultaneously, experiments demonstrate that the LPT retains comparable permeability and biocompatibility to the original textile, ensuring safety and comfort for on-skin use. The authors designed and fabricated a monolithic, multimodal sensor patch by integrating double-layer LM wires and chips onto the LPT. This patch can continuously track cardiac, acceleration, temperature, and humidity signals even under 50% strain (Movie 2).
Owing to its permeability and ductility, the patch maintains stable and accurate signal monitoring during dynamic exercise, which is superior to the performance of its counterpart fabricated on a commercial flexible printed circuit board.
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