ENDURANCE: Graphene based coatings for durable wear resistance low cost position sensors

Developed by Prof. Choy, Aerosol Assisted Ion Deposition (AAID) is a novel, non-vacuum, cost effective and eco-friendly method for the non-line-of-sight deposition of both thin and thick coatings to 3D structure (non-conformal substrates) with control of structure and composition at the nanoscale. The fabrication of uniform graphene based nano-composite coatings, involves formulation of chemical precursors, which can be a solution or a suspension, and atomisation of the precursor to generate a finely charged aerosol. This allows control of the dynamics of droplets and their evaporation to form droplets consisting of polymeric ions, leading to the deposition of polymeric films incorporating with graphene based nanomaterials to form nanocomposite coatings with uniform and well-controlled structures in an open atmosphere.

Within the ENDURANCE project we will apply this technique for the development graphene based nanocomposite coatings on potentiometer wiper heads targeting excellent conductivity between 1 and 300 ohm/square and wear resistance.

Key challenges to be addressed in our research include:
(1) Graphene interfaces: Limited knowledge of wear properties for graphene to graphene material contacts - we will explore the relationships between graphene coating formulation, chemical / physical properties and the wear properties at graphene to graphene interfaces;
(2) Coating stability: Achieving complete polymerisation during cure thereby enabling long term coating stability - we will explore the relationships between graphene ink formulation and cure properties enabling optimisation of rapid and stable cure;
(3) Coating surfaces: Ensuring graphene is concentrated at the coating surface to enable the surface properties to be realized- we will assess the feasibility to utilise electrostatic (repulsion) and formulation density to promote surface aggregation of graphene;
(4) Coating adhesion: Graphene traditionally has poor adhesion to material surfaces thereby limited coating wear stability - we will explore coating formulations, substrate surface treatments and layer thickness to improve adhesion and wear performance; and
(5) Conductivity: High conductivity requires excellent connectivity between graphene layers which may be difficult to achieve - we will explore the addition of both conductive additives and surface treatments to promote coating conductivity.

Our research approach will follow three key phases (tasks):
Task 1. Formulation Screening: nano-composite ingredients will be screened (graphene, nano-tubes, surfactants, binders, cross linkers, solvents, lubricants etc...) using standard formulations to understand relationships between formulation, AAID processing, and coating properties and performance (adhesion, conduction, wear and cure)
Task 2. Coating formulation: different coating formulations will be investigated to achieve the target properties within the constraints of the material and processing requirements. A limited number of systems will be selected for further study.
Task 3. First generation ink development: selected coating formulations will undergo a number of development cycles to optimise consistency, reliability, wear, rheology, cure etc. Substrate chemical (etching) & physical surface modification strategies will be considered to improve coating adhesion. A tribometer test rig will be used to assess wear and coating adhesion.

We will also support investigation of graphene to graphene interface wear properties using statistical analysis methods (performance analysis) and analysis of wear samples to understand the wear mechanisms.

Scientific Impact: our group will create scientific impact in five key areas: i) we will better understand the factors influencing wear properties at graphene to graphene interfaces enabling the development of new materials capitalizing on the benefits of graphene; ii) we will better understand the factors that influence and improve the adhesion of graphene composite materials to substrates enabling their use as robust coatings; iii) we will better understand how to formulate wear resistant and conductive graphene based nano-composite materials thereby open new lines of applied research; and iv) we will better understand how to fully cure graphene based inks thereby enabling long term stability of the coating properties. This scientific knowledge will underpin key technology impacts.

Technology Impact: ENDURANCE will demonstrate feasibility for highly innovative graphene enabled Linear Sensors (potentiometer + wiper) and Encoder Sensors (Encoder Unit + Wiper). The sensor designs will incorporate wear resistant graphene based resistive, conductive and barrier coatings enabling breakthrough advancements in sensor design, manufacture and performance: Wiper: will utilise wear resistant conductive graphene based nanocomposite coatings enabling replacement of palladium based wiper heads and leading to significant cost savings for manufacture (>50%). Potentiometer: will utilise atomically smooth, chemically inert, mechanically durable and lubricating graphene based resistive track to achieve a breakthrough in durability and lifetime (>10 million cycles) and sensor accuracy (<0.5% uncorrelated linearity) whilst realising cost savings by enabling fully printed units (>25%). Encoder Unit: will utilise wear resistant conductive barrier coatings for replacement of existing gold and nickel materials thereby enabling fully printed units with exceptional resolution (from 6 to 40+ pulse sensors) and lower manufacturing costs (>26%).


The ENDURANCE sensors represent a highly disruptive technology for the position sensor market combining the exceptional accuracy and durability of contactless sensors with the low cost of contact based sensors; thereby exceeding all commercially available sensor designs and meeting all key user requirements. This technology will underpin key market impacts.

Market Impact: Having a performance comparable to non-contact devices and a cost lower than contact based systems, the technology will enable clearly differentiated and cost competitive solutions (even against suppliers from Asia). Lower device costs will also enable greater use throughout the car at minimal extra cost to the customer, satisfying the demand for intelligence as standard. Since the performance and cost advantages are enabled only through use of the highly innovative graphene based materials the technology will be difficult to imitate by foreign competitors. The simplicity of device design will enable rapid customisation for different applications and market sectors. Excellent performance features (and lifetime) will also reverse the trend to non-contact based systems.