Laser-induced carbon nanostructures

An agricultural testing method comprising the steps of:

• (i) producing an agricultural testing sensor, using the steps of:
• (a) using a first laser beam configured to irradiate an encapsulated, sub-surface region of a carbon pre-cursor material below a surface of the carbon pre-cursor material, parameters of the first laser beam being selected to create carbon foam in that encapsulated, sub-surface region and a carbon-based material above the carbon foam;
• and
• (b) using a second laser beam configured to remove or ablate the carbon-based material sitting above the carbon foam, parameters of the second laser beam being selected to expose or alter at least some of the carbon foam, to produce a resultant carbon foam material;
• and
• (c) functionalising the resultant carbon foam material by adding a receptor or recognition element that is specific to a target or analyte to the resultant carbon foam material or a linker that is attached to the resultant carbon foam material;
• (d) providing the functionalised carbon foam material for use as a sensor electrode in an assay device, configured for agricultural testing;
• and then
• (ii) applying or adding a sample to the sensor electrode and the assay device taking measurements of the behaviour of the sensor electrode to indicate the presence or absence of the target or analyte in the sample.