One out of three people in the world is exposed to earthquakes, and the number of people living in seismic areas increased by 93% in the past 40 years - 2.7 billion in 2018. Cities face a growing pressure from global challenge on resilience of structures and infrastructures to catastrophic natural events.
Seismic isolation is the most used technology to mitigate vibrations to buildings. This technology uses rubber-steel composite interposed between the structure and the foundations to divert the energy of the earthquake and to minimize interstory drift and floor accelerations of the above structure. However, while steel is needed to reinforce the composite, its presence limits the use of base isolation technology to strategic buildings such as hospitals and civic centres. This is because the current steel-based technology is heavy and requires engineered machinery to manufacture and cut it in bespoke shape and specialized manpower to install. To extend the use of this technology to houses and commercial buildings on a global scale, new materials for reinforcing rubber are required which will result in highly efficient, ultra-lightweight and low-cost seismic isolation devices.
Graphene-Reinforced Elastomeric Isolators (GREI) is a new ground-breaking technology exploiting the mechanical properties of rubber and a few-layer graphene to enhance resilience of structures, crucial to survive devastating seismic events.
Recently developed techniques such as transferring graphene on bulk materials (rubber) by spry coating and 3D printing have opened the frontiers of new advanced functional materials. GREI is made of alternate layers of graphene and rubber; it is shorter and lighter than commonly used steel-reinforced elastomeric isolator (made of alternate layers of rubber and steel shims) and therefore easier to transport and install. In GREI graphene deposition on rubber is achieved by an isopropyl alcohol (IPA) assisted direct transfer method (IDT). Specifically, a graphene film consisting of a random network of nanosheets is first deposited on a filter membrane and then transferred onto rubber by IDT due to IPA evaporation. Such advanced composite material is currently non-existent, and its development and implementation will boost the manufacturing industry, by opening the frontiers of self-build seismic metamaterials, ultimately resulting in saving human lives.
GREI scaled prototypes have been designed, manufactured and tested. Their unparalleled mechanical properties will push the boundaries of vibration engineering, envisaging mass productions and application in 1) earthquake engineering: where GREIs are (retro)fitted between the structure and the foundations to mitigate earthquake-induced vibrations 2) bridge construction: GREIs are used to accommodate movements due to moving loads and material deformations; 3) the marine industry: GREIs are installed between the hull of a vessel and its modules to keep oil/gas modules safe from impact and damage due to adverse sea conditions.
Graphene and rubber are both maintenance-free materials. The cost of a currently used steel-reinforced elastomeric isolator is thousands of pounds; whereas the cost of GREIs is predicted to be much lower at a few hundred pounds and there will be further cost reduction once a production line is implemented (manufacturing using 3D printing, transporting, installing and maintaining).