The conventional brain–machine interface (BMI) concept is based on an electrical circuit that includes electrodes for sensing and/or stimulation. In most cases, electrodes are in contact with biological tissue, while the electrical circuit can be positioned on the backside of electrodes or connected through a wireless link [1–3]. In both cases, a tremendous amount of work is done to design a high-sensitivity circuit to detect a few millivolts related to electrical signal propagation in the brain [4, 5].

With recent advances in microfabrication and processing, more advanced systems can be considered to build a BMI [6–8]. Following these major advances, the highly integrated lab-on-a-chip (LoC) emerged, which led to the design of compact LoC in the size range of a few millimeters [9, 10]. LoC has become attractive as an advanced brain–machine interface and a promising approach for future new brain discoveries.

Conventional brain–machine interfaces: deep brain electrode stimulation

There are two major operations that are handled by BMI, which are stimulation and sensing. Conventional BMIs are deep brain electrodes (DBE) or patch electrodes [11, 12] used to detect the electrical activity of the brain. In the stimulation mode, DBE applies voltages or currents to tissue to generate action potentials (AP). In the sensingmode electrodes are used to detect the propagation of AP and brain electrical activity.