Highly Stretchable and Sensitive Unidirectional Strain Sensor via

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Highly Stretchable and Sensitive Unidirectional Strain Sensor via Laser Carbonization Rahimi, Manuel Ochoa, Wuyang

Highly Stretchable and Sensitive Unidirectional Strain Sensor via Laser Carbonization Rahimi, Manuel Ochoa, Wuyang Yu, and Babak Ziaie* Feb, 16, 2015

Traditional metallic and semiconducting strain sensors are not suitable for stretchable applications. Because they

Traditional metallic and semiconducting strain sensors are not suitable for stretchable applications. Because they can only withstand very limited strain (<5%) before fracture. Today’s most common approaches for fabrication of highly stretchable piezoresistive and piezocapacitive strain sensors are based on two main techniques: (1) Conductive-liquid-filled elastomeric tubes or microchannels ; using mercury-filled elastomeric tubes to measure blood volume in the limbs (mercury-in-rubber plethysmograph). When strained, the tube was stretched and narrowed, resulting in an increased resistance. (2) Polymeric blends or composites prepared by embedding conductive nanomaterials within an elastomeric network. ; making elastomeric composites containing conductive nanomaterials (e. g. , carbon nanotubes, graphene, silver nanowiresthat are either embedded directly into the elastomeric material or deposited on the surface of a stretchable substrate using various methods such as contact transfer printing, screen printing, and inkjet printing.

Polyimide PDMS Carbon Bendable, Stretchable Strain

Polyimide PDMS Carbon Bendable, Stretchable Strain

Before After Carbonized pattern Porous structure Carbonized pattern + PDMS Enable the PDMS to

Before After Carbonized pattern Porous structure Carbonized pattern + PDMS Enable the PDMS to penetrate into the carbon patterns

Carbonized pattern High laser speed require high laser power to carbonization Slope(Energy density) :

Carbonized pattern High laser speed require high laser power to carbonization Slope(Energy density) : 62 000 J/m 2 = Threshold The Cause of the difference Incomplete transfer where residual amounts of carbon particles remain on the polyimide surface Carbonized pattern + PDMS Defect of carbon Graphite

Longitudinal Transverse Longitudinal 20 MΩ Transverse > 100Ω The particles in this patterns possess

Longitudinal Transverse Longitudinal 20 MΩ Transverse > 100Ω The particles in this patterns possess an anisotropic orientation due to the laser rastering process Gauge factors (G = (R / R 0) / (ΔL / L)) Graphene-based composites : 2~50 CNTs & Ag. NWs sensors : 1− 7 Typical strain sensor 9% overshoot and 100 s response time New strain sensor 7% overshoots and 25 s stabilization time

Bending angle (0− 145°) Sensors

Bending angle (0− 145°) Sensors

Conclusion • Carbonization pattern have high performance in mechanical sensor Bendable Hydrophobic Cost effective

Conclusion • Carbonization pattern have high performance in mechanical sensor Bendable Hydrophobic Cost effective Sensor

Q&A

Q&A