Buckling assisted and lithographically micropatterned fully flexible sensors for conformal integration applications

Abstract

Development of flexible sensors/electronics over substrates thicker than 100 μm is of immense importance for its practical feasibility. However, unlike over ultrathin films, large bending stress hinders its flexibility. Here we have employed a novel technique of fabricating sensors over a non-planar ridge topology under pre-stretched condition which not only helps in spontaneous generation of large and uniform parallel buckles upon release, but also acts as stress reduction zones thereby preventing Poisson’s ratio induced lateral cracking. Further, we propose a complete lithography compatible process to realize flexible sensors over pre-stretched substrates thicker than 100 μm that are released through dissolution of a water soluble sacrificial layer of polyvinyl alcohol. These buckling assisted flexible sensors demonstrated superior performance along different flexible modalities. Based on the above concept, we also realized a micro thermal flow sensor, conformally wrapped around angiographic catheters to detect flow abnormalities for potential applications in interventional catheterization process.

Electroplating and Ablative Laser Structuring of Elastomer Composites for Stretchable Multi-Layer and Multi-Material Electronic and Sensor Systems

“…With the high electrical conductivity of an electroplated flexible and solderable metal layer, a wide variety of applications can be realized. Through additional wave- [ 2 ] or meander-shaped [ 6 ] structuring, which has already been demonstrated for other substrates, the metal layers can also be made pseudo-stretchable. The high electrical conductivity enables the realization of flexible and elastic power electronics such as heating elements, coils, antennas or conductive tracks to supply energy-intensive components such as radio modules.…”

“…To increase conductivity and improve solderability, in recent publications the method of physical vapor deposition (PVD) was used to coat non-conductive polymers with conductive material [ 2 ]. Among other things, this serves as a basis for subsequent electroplating [ 3 ].…”

Soft and Deformable Sensors Based on Liquid Metals

“…For example, solid-state metallic nanowires show irreversible conductivity recovery when they are relaxed from large strains and show hysteresis in repeated cycles [1,2,3,4]. While the meander [5], serpentine [6,7,8], or kirigami [9] structures, which are made of thin metallic conductors, improve the strain range up to 300% [8], they have a limited operating range and cannot withstand more extreme strain [10]. Since form factors of computing and communication devices are now rapidly changing from portable to wearable, it is very important to look for and study materials ideal for such a new trend.…”

Laser‐Assisted Strain Engineering of Thin Elastomer Films to Form Variable Wavy Substrates for Cell Culture

“…It is worth mentioning that apart of the cell growth control, the wrinkled morphologies are of essential interest in many other research fields such as the metrology of polymeric thin films, adhesion control, design of diffraction gratings, and stretchable electronics …”