Movable micromotor brain implants odontológico
BRAIN implants containing microelectrodes are used widely in the laboratory and clinic, both to stimulate nerve cells and to record their activity. Researchers routinely implant electrode arrays into the brains of rodents to investigate the neuronal activity associated with spatial navigation, or into monkeys’ brains to gain a better understanding of the mechanisms of motor control. As a result, we now have brain-computer interfaces that can help paralysed patients to communicate or control a prosthetic limb. Electrode arrays can also be used to assess vegetative patients, and to treat conditions such as Parkinson’s Disease and depression.
In most instances, keeping the electrodes in place for long periods of time is crucial. But this is difficult, for a number of reasons. In experiments involving freely moving rats, for example, the animal’s movements can cause the electrodes to be displaced, and when they do stay in place, the electrodes become gradually become ensheathed with glial cells, causing the signal to deteriorate with time. The devices have to be re-adjusted regularly, and their decoding algorithms recalibrated, to maintain the signal strength. Implants containing movable electrodes can potentially overcome these problems. The latest such device (described in a new paper in the journal Frontiers in Neuroengineering) is the most advanced yet. It uses microelectromechanical systems (MEMS) to move the electrodes up and down, and can record stably for up to 6 months.
Implants with movable microelectrodes have been in development since the early 1980s. The first generation movable implants contained thin wire microelectrodes that were moved manually. More recently, DC motors, piezoelectric motors and hydraulic motors have been used to move the electrodes, but all of the devices developed to date are still large and heavy. The new implant, developed in Jit Musuthwany’s Neural Microsystems Laboratory at Arizona State University, is the first use MEMS technology, and is the smallest and lightest yet.
Thedevice consists of an array of microelectrodes that are fabricated, along with a number of microscopic mechanical components, onto a silicon wafer. Each microelectrode is controlled by four microactuators, one each to deactivate a release-up lock and release-down lock, and one each to move the electrode up and down. The actuators work using electro-thermal strips and are coupled to a ratchet system that drives the centre shuttle of each electrode up or down.
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