Brookes co-invented and leads development of whole-head wearable OPM-MEG, using arrays of zero-field SERF optically pumped magnetometers placed directly on the scalp to image neuromagnetic fields with higher sensitivity, better spatial resolution and lifespan compliance than SQUID-MEG. His group develops the hardware, field-nulling, and analysis methods and applies them to epilepsy, schizophrenia, concussion and developmental neuroscience. This vapour-phase approach reaches femto-to-picotesla sensitivities complementary to NV-center diamond ensemble quantum sensors (DEER, nano-NMR, T1 relaxometry) that operate near the pT/sqrt(Hz) regime.