Chemiresistors are electrochemical sensors that monitor the changes in the electrical resistance of a sensing layer in between two electrodes. Conducting polymers have come to the forefront of this technology as ideal sensing layers due to their numerous advantageous properties. However the sensing layer in between the electrodes is usually deposited as a thin film which reduces the sensitivity. Recently researchers in the surface nanoscience group, Dr Krishnan Murugappan and Professor Martin Castell have shown how the sensing layer can be grown electrochemically in-between the electrodes at the percolation threshold. The percolation threshold is the region where there are only a few ‘sensing bridges’ between the electrodes. This dramatically enhances the sensitivity of the sensor as a localised change can be measured compared to the bulk change at the thin film region. This work reported in Electrochemical Communications opens up new opportunities for the use of conducting polymers in ultra-sensitive gas sensing devices.