Fig. 7 State-of-the-art developments in electrochemical biosensors for pathogens. a) Low-cost, flexible, disposable screen-printed carbon electrodes (Afonso et al. 2016). b) Free-standing graphene electrodes (Wang et al. 2013). c) Paper-based substrates for pathogen detection using electrochemical methods (Bhardwaj et al. 2017). d) Wearable wireless bacterial biosensor for tooth enamel (Mannoor et al. 2012). e) Smartphone-enabled signal processing for field-based environmental monitoring (Jiang et al. 2014).