A Glasgow University team has developed medical sensors powered by a porous foam of graphene and silver, an advance with potential applications in the wearable device market.
They used a commercially available graphene foam to make a layered structure with a silver-containing epoxy resin to form supercapacitors capable of storing three times as much power as any similar flexible supercapacitor.
Lithium-ion batteries may not be suitable for wearable devices because they are inflexible and heavy and their heat may cause injuries. Supercapacitors charge and discharge quickly may be better for wearables.
• Development of Flexible graphene foam-Ag-graphene sheet-based supercapacitor with capacitance GFSC 38 mF/cm2.
• Supercapacitor exhibited energy density 3.4 μWh/cm2 and 0.27 mW cm− 2 power density.
• Integration of supercapacitor with flexible solar cell and flexible CuO nanorod based pH sensor.
• Development of fully flexible self-charging power pack (FSPP) for flexible/wearable sensor system.
• Developed supercapacitor performed 25000 charge-discharge cycles.
Abstract – Flexible self-charging supercapacitor based on graphene-Ag-3D graphene foam electrodes
A flexible three-dimensional porous graphene foam-based supercapacitor (GFSC) is presented here for energy storage applications. With a novel layered structure of highly conductive electrodes (graphene-Ag conductive epoxy–graphene foam), forming an electrochemical double layer, the GFSC exhibits excellent electrochemical and supercapacitive performance. At a current density of 0.67 mA cm−2, the GFSCs show excellent performance with areal capacitance (38 mF cm−2) about three times higher than the values reported for flexible carbon-based SCs. The observed energy and power densities (3.4 µW h cm−2 and 0.27 mW cm−2 respectively) are better than the values reported for carbon-based SCs. Analyzed under static and dynamic bending conditions, the GFSCs are stable with up to 68% capacitance retention after 25000 charge–discharge cycles. The light-weight, cost-effective fabrication and no self-heating make the GFSCs a promising alternative to conventional source of energy in the broad power density ranging from few nW cm−2 to mW cm−2. In this regard, GFSC was integrated with a flexible photovoltaic cell resulting in a flexible self-charging power pack. This pack was successfully utilized to power continuously a wearable CuO nanorod based chemi-resistive pH sensor.
Rice had separate research for scalably making different shapes with graphene foam
They have built a prototype machine that lets us make graphene foam into 3D objects through automated successive layering and laser exposure. They do not need furnaces or metal catalysts and the process is easily scaled.
Rice scientists are making 3D laser-induced graphene (LIG) foam through an automated process that begins by turning the top layer of a polyimide (PI) sheet into graphene (top), stacking another layer on top (center) with ethylene glycol (EG) as a binder and then burning the top layer’s PI into graphene as well (bottom). The process is repeated as necessary.