Process for the Fabrication of Zn-O Graphene Based Flexible Strain and Pressure Sensor

A process for fabricating a flexible strain and pressure sensor based on ZnO nanoparticles-graphene nanoplatelets, the process comprising:

• (a) mixing a synergistic mixture of ZnO nanoparticles having a particle size distribution from 43.8 nm to 712 nm and graphene nanoplatelets having a particle size range from 50.7 nm to 220 nm with N-methyl-2-pyrrolidone and polyurethane in a solvent;
• (b) masking a glass substrate with tape and exposing a section of the glass substrate at a center of the glass substrate;
• (c) dispensing a ZnO nanoparticles-graphene nanoplatelets ink on the exposed section of the glass substrate with a micropipette;
• (d) spin coating and curing the ZnO nanoparticles-graphene nanoplatelets ink and repeating the spin coating and curing three times;
• (e) removing the tape from the glass substrate;
• (f) spin coating a polydimethyldisiloxane (PDMS) solution on the glass substrate containing the cured ZnO-graphene pattern and heating at 100° C. to form a cured PDMS layer;
• (g) peeling the cured PDMS layer from the glass substrate to obtain an embedded sensing layer;
• (h) flipping the cured PDMS layer and connecting copper terminals to the embedded sensing layer using silver epoxy;
• and
• (i) pouring a final passivation layer of PDMS on the embedded sensing layer, followed by curing at 80° C. for 10 minutes.

A process for fabricating a flexible strain and pressure sensor based on ZnO nanoparticles-graphene nanoplatelets, the process comprising:

• (a) mixing ZnO nanoparticles-graphene nanoplatelets in a weight ratio from 0.5:1 to 1:0.5 with polyurethane and subsequently sonicating 30 minutes to 60 minutes at room temperature to reach an optimum viscosity of 14.5 mPa-s;
• (b) masking a glass substrate having a size from 25 mm×25 mm to 75 mm×25 mm with tape and exposing a section of the glass substrate having a size from 15 mm×2 mm to 50 mm×5 mm at a center of the glass substrate;
• (c) dispensing from 20 μL to 100 μL of an ZnO nanoparticles-graphene nanoplatelets ink on the exposed section of the substrate with a micropipette;
• (d) spin coating at a speed of 250 rpm to 2500 rpm, and acceleration time of 30 s to 60, and a control time of 50 s to 60 s, followed by heating at 60° C. for 10 minutes to 20 minutes on a hot plate;
• (e) repeating the (d) three times;
• (f) removing the tape from the glass substrate and spin coating a polydimethylsiloxane (PDMS) solution over the ZnO nanoparticles-graphene nanoplatelets pattern at 100 rpm to 150 rpm, an acceleration time of 5 s to 8 s, and a control time of 300 s to 360 s to yield a PDMS layer of approximately 0.4 mm thickness, followed by heating at 100° C. to 120° C. for 2 minutes to 5 minutes;
• (g) curing a first layer of PDMS on the glass substrate;
• (h) peeling the PDMS layer from the glass substrate to obtain an embedded sensing layer;
• (i) fixing copper wire terminals to two ends of the embedded sensing thin film by silver paste for further electrical measurements;
• and
• (j) pouring a second layer of PDMS on the embedded ZnO nanoparticles-graphene nanoplatelets to obtain a sandwich structure of the flexible strain and pressure sensor and subsequently curing the second layer at 60° C. to 80° C. for 10 minutes to 15 min to act as a passivation layer.