CD81 and neoplasm: Generally, immuno‐based microfluidic and microarray technologies have utilised tetraspanins (CD9, CD81 and CD63) and tumour‐cell surface associated markers such as EpCAM, CA125, CD19, EGFR, EGFRvIII, podoplanin and PDGFR for on‐chip capture of tumour‐EV sub‐populations (Belov et al., 2016; Cavallaro et al., 2019; Daaboul et al., 2016; He et al., 2014; Reategui et al., 2018).