Negative poisson ratio piezoresistive sensor and method of manufacture

Abstract

The present invention includes scalable and cost-effective auxetic foam sensors (AFS) created through conformably coating a thin conductive nanomaterial-sensing layer on a porous substrate having a negative Poisson's ratio. In general, the auxetic foam sensors possess multimodal sensing capability, such as large deformation sensing, small pressure sensing, shear/torsion sensing and vibration sensing and excellent robustness in humidity environment.

1 .- 12 . (canceled) 
     
     
         13 . A method of manufacturing a sensor, the method comprising:
 providing a porous substrate comprising a negative Poisson ratio; and   forming a piezoresistive layer covering at least a portion of the porous substrate.   
     
     
         14 . The method of  claim 13 , wherein forming a piezoresistive layer covering at least a portion of the porous substrate further comprises:
 forming an aqueous dispersion of conductive nanomaterial; and   dip-coating the aqueous dispersion of conductive nanomaterial onto the porous substrate.   
     
     
         15 . The method of  claim 14 , wherein forming an aqueous dispersion of conductive nanomaterial further comprises:
 creating a suspension comprising conductive nanomaterial, deionized water and nonionic surfactant;   sonicating the suspension to form an aqueous dispersion of conductive nanomaterial.   
     
     
         16 . The method of  claim 13 , wherein the piezoresistive layer comprises carbon nanotubes. 
     
     
         17 . The method of  claim 13 , wherein the porous substrate is auxetic foam. 
     
     
         18 . The method of  claim 14 , wherein dip-coating the aqueous dispersion of conductive nanomaterial onto a porous substrate having a negative Poisson ratio, further comprises:
 dipping the porous substrate into the aqueous dispersion of conductive nanomaterial; and   drying the porous substrate after dipping the porous substrate into the aqueous dispersion of conductive nanomaterial to form a porous substrate coated with conductive nanomaterial.   
     
     
         19 . The method of  claim 18 , wherein dip-coating the aqueous dispersion of conductive nanomaterial onto a porous substrate having a negative Poisson ratio, further comprises:
 immersing the porous substrate coated with conductive nanomaterial in deionized water; and   drying the porous substrate coated with conductive nanomaterial after immersing the porous substrate coated with conductive nanomaterial in deionized water.   
     
     
         20 . The method of  claim 13 , wherein the piezoresistive layer is about wt 1% of the sensor.