Scientists have developed a rubber-based, flexible strain sensor that can detect very small deformations with exceptional sensitivity while remaining functional at much higher strains. This dynamic combination has been difficult to achieve in stretchable electronics.
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Flexible strain sensors are used in wearable electronics, soft robotics, and health monitoring. But many existing devices struggle to combine three things at once: high sensitivity, a wide working strain range, and a predictable, near-linear electrical response.
Crack-based sensors are one promising route because tiny structural cracks can produce large electrical changes under strain. The drawback is that those cracks can also become unstable.
In many designs, rigid conductive layers do not deform in step with the soft elastic substrates, leading to uncontrolled crack growth, delamination, and signal failure.
Previous efforts to improve this have often relied on two-dimensional interfacial bonding, mainly through van der Waals forces or hydrogen bonding. Those approaches can lose stability at high strain.
Some three-dimensional interface designs have improved adhesion, but uneven crack formation and inconsistent sensing response have remained major limitations.
How The Sensor Was Built
The team developed what it calls a microcracked super-interface, flexible sensor (MSFS).
It consists of three layers: a brittle polyacrylamide/carboxymethyl cellulose (PAM/CMC)-silver nanowire crack layer, a more ductile PAM/CMC-single-walled carbon nanotube transition layer, and a micro- and nano-textured carboxylated styrene-butadiene rubber (XSBR) substrate.
The design depends on a so-called 3D super-interface. In practice, that means combining surface roughness on the rubber substrate with hydrogen-bonding interactions between layers, so the conductive layer is both physically anchored and better chemically supported.
The XSBR surface was textured during latex film formation to increase roughness and create more bonding sites. The researchers then deposited the conductive slurry onto that surface.
They also adjusted the PAM/CMC ratio to tune the stiffness of the conductive layer and control crack shape, shifting it from more networked to more parallel patterns. According to the paper, the crack regulation was central to balancing sensitivity, linearity, and strain tolerance.
Microscopy and spectroscopy, including AFM, SEM, and FTIR, supported the presence of the roughened interface, hydrogen-bonding interactions, and stable layered architecture.
The Strain Performance
In the 0-10 % strain range, the sensor reached a gauge factor of 1.1 × 108, with a linear correlation coefficient of 0.98. In simple terms, that means the device produced an exceptionally large and still highly regular electrical response to relatively small deformation.
The paper describes the sensing behaviour in two stages. At low strain, microcrack propagation drives the very high sensitivity. At higher strain, the SWCNT-containing transition layer helps preserve conductive pathways and limit disorderly crack evolution.
The authors report continuous conductive behaviour above 50 % strain and stable strain responsiveness at 100 % strain. They also describe signal output under strains greater than 100 %, suggesting the interface helps the device avoid catastrophic electrical failure even under substantial deformation.
Durability was another key result. After 10,000 loading and unloading cycles at 4 % strain, the device maintained a consistent resistance response, with terminal error below 10 %. The vulcanized XSBR substrate appears to contribute to that mechanical resilience.
The researchers also report a response sensitivity of about 2.1 × 107 per second, indicating the sensor can register transient strain signals quickly.
Baseline resistance remained relatively stable across the tested humidity and temperature ranges, and the device continued to operate during bending and folding tests.
Battery Monitoring Demonstration
To show a practical use case, the team applied the sensor to monitor expansion in silicon-anode batteries. Silicon expands during charging, and excessive swelling can become a safety concern.
In the demonstration, the sensor detected an expansion as low as 2 %, resulting in a 22-fold change in resistance. The paper notes that silicon-anode expansion in this context was roughly 2-4 %, suggesting the device may be sensitive enough to distinguish routine behaviour from more concerning deformation.
Wider Potential
The study also included proof-of-concept demonstrations in human-motion and physiological-signal monitoring. Those results suggest broader potential in wearable sensing, although such uses remain at an experimental stage.
Overall, the work presents a flexible strain sensor that combines ultra-high small-strain sensitivity with broader strain tolerance through interface engineering and crack control.
The central advance is more than stronger adhesion; it is a layered design that stabilises crack behaviour while maintaining conductive pathways under strain.
That makes the study a notable step in the design of flexible sensors for applications such as battery safety monitoring, wearable devices, and soft robotic systems.
Journal Reference
Wang X., et al. (2026). A rubber-based sensor with over 100 million-level ultra-sensitivity (0–10% strain range) via 3D super-interface. Nature Communications. DOI: 10.1038/s41467-026-70434-y