Self-similar design for stretchable wireless LC strain sensors

• The paper presents a large-area stretchable wireless LC strain sensor, based on the concept of self-similar design.
• The designed wireless sensors can be stretched up to 40%, as demonstrated by finite element modeling and experiment results.
• The wireless strain sensor with self-similar structured coil incorporating variable inductance has been implemented to monitor the strain of artificial skin.
• Strain response of the stretchable wireless sensor has been characterized by experiments, and demonstrates high strain responsivity about 33.7 MHz/10%.

Stretchable sensors provide a foundation for applications that exceed the scope of conventional device technologies due to their unique capacity to integrate with soft materials and curvilinear surfaces. This article presents the implementation and characterization of a large-area stretchable wireless RF strain sensor, operating at around 760 MHz, based on the concept of self-similar design. It has an electrical LC resonant circuit formed by a self-similar inductor coil and a capacitor to facilitate passive wireless sensor. The inductance of the wireless sensor varies with the elongation of the PDMS substrate, so is the resonance frequency of the sensor that is detected using an external coil linked to a vector network analyzer. Finite element modeling was used in combination with experimental verification to demonstrate that the wireless strain sensor with 300 μm width can be stretched up to 40%. Self-similar structured coil incorporating variable inductance has been implemented to monitor the strain of artificial skin. Strain response of the stretchable wireless sensor has been characterized by experiments, and demonstrates high strain responsivity about 33.7 MHz/10%, which confirms the feasibility of strain sensing for biomedical and wearable applications.