A device comprising: monolithic substrates forming a chip including a wireless, battery-less monolithically-integrated neural interface (MINI) device configured to be implanted, the chip comprising: (i) an integrated circuit (IC) being embedded in a first monolithic substrate and comprising a plurality of amplifiers configured to amplify received neural signals from a monitored subject, and a radio data signal generator configured to process the amplified neural signals and generate a multiplexed digital signal; (ii) radio-frequency (RF) planar coils embedded in a second monolithic substrate, being electrically connected to the IC through the first monolithic substrate, being configured for wireless transmission of the multiplexed digital signal to a remote wireless device and being configured to receive wireless power signals to power the IC; and (iii) a plurality of on-chip electrodes configured to directly sense the neural signals of the subject and provide the neural signals to the plurality of amplifiers, wherein the plurality of on-chip electrodes comprises a pillar electrode array or a planar electrode array with the plurality of on-chip electrodes comprising 1000 or more electrodes. monolithic substrates forming a chip including a wireless, battery-less monolithically-integrated neural interface (MINI) device configured to be implanted, the chip comprising: (i) an integrated circuit (IC) being embedded in a first monolithic substrate and comprising a plurality of amplifiers configured to amplify received neural signals from a monitored subject, and a radio data signal generator configured to process the amplified neural signals and generate a multiplexed digital signal; (ii) radio-frequency (RF) planar coils embedded in a second monolithic substrate, being electrically connected to the IC through the first monolithic substrate, being configured for wireless transmission of the multiplexed digital signal to a remote wireless device and being configured to receive wireless power signals to power the IC; and (iii) a plurality of on-chip electrodes configured to directly sense the neural signals of the subject and provide the neural signals to the plurality of amplifiers, (i) an integrated circuit (IC) being embedded in a first monolithic substrate and comprising a plurality of amplifiers configured to amplify received neural signals from a monitored subject, and a radio data signal generator configured to process the amplified neural signals and generate a multiplexed digital signal; (ii) radio-frequency (RF) planar coils embedded in a second monolithic substrate, being electrically connected to the IC through the first monolithic substrate, being configured for wireless transmission of the multiplexed digital signal to a remote wireless device and being configured to receive wireless power signals to power the IC; and (iii) a plurality of on-chip electrodes configured to directly sense the neural signals of the subject and provide the neural signals to the plurality of amplifiers, wherein the plurality of on-chip electrodes comprises a pillar electrode array or a planar electrode array with the plurality of on-chip electrodes comprising 1000 or more electrodes. <EOS>