Implantable Neural Probes with Monolithically Integrated CNTFET Arrays for Multimodal Monitoring

The long-term implantable neural probe for simultaneous recording of various brain signals is the key technology of neuro clinic applications that needs to be broken through. This paper introduces carbon nanotube field-effect transistor (CNTFET) into the neural science and demonstrated an implantable neural probe for multimodal recording of electrical and chemical brain signals under magnetic resonance imaging (MRI). The CNTFET source followers are monolithically integrated with the electrodes to enhance the signal-to-noise ratio (SNR) up to 40.34 dB across a wide acquisition bandwidth from 0.01-32 kHz. The neurotransmitter ion sensors constructed by CNTFET are also integrated for cocurrent detection of concentration of calcium ions (Ca²⁺) changing with a detection limit down to 0.46 nM. The MRI compatablity is verified under 7 Tsela scanner with reduced artifacts. The immunohistology confirms the excellent biocompatibility and the long-term effectiveness with a capability for continuous recording of electrical potentials and ion concentraions from a rat for 3 months without obvious brain inflammatory responses. Leveraging on our probes, changes in Ca²⁺ concentration can be observed to occur nearly concurrently with the epileptiform local field potential events in a rat model, suggesting a potential enhancement in epilepsy detection accuracy. Given the multimodal recording capability and MRI compatibility, together with easy integration schemes, our work provides a powerful scaffold for the the future brain study and holds great potentials for practical dignositc applications.