U C Berkeley engineers have built the first dust-sized, wireless sensors that can be implanted in the body, bringing closer the day when a Fitbit-like device could monitor internal nerves, muscles or organs in real time.Because these batteryless sensors could also be used to stimulate nerves and muscles, the technology also opens the door to “electroceuticals” to treat disorders such as epilepsy or to stimulate the immune system or tamp down inflammation.
“The original goal of the neural dust project was to imagine the next generation of brain-machine interfaces, and to make it a viable clinical technology,” said neuroscience graduate student Ryan Neely. “If a paraplegic wants to control a computer or a robotic arm, you would just implant this electrode in the brain and it would last essentially a lifetime.”
Brain-computer interfaces are being applied in neuroprosthetics, through which paralyzed persons are able to control robotic arms, neurogaming where one can control keyboard, mouse etc using their thoughts and play games, neuroanalysis (psychology), and in defense to control robotic soldiers or fly planes with thoughts.
The sensors, which the researchers have already shrunk to a 1 millimeter cube – about the size of a large grain of sand – contain a piezoelectric crystal that converts ultrasound vibrations generated from transducer outside the body into electricity to power a tiny, on-board transistor that is in contact with a nerve or muscle fiber. As natural electrical activity in the nerve varies, it changes the current passing through the transistor, thus providing a read-out mechanism for the nerve’s signal.
To send the information back out of the body, the external transducer alternates between sending ultrasound vibrations to power the mote and listening for the returning echo as some of those vibrations bounce back. The changing current through the transistor alters the piezo crystal’s mechanical impedance, thereby modulating how much bounce back the transducer receives. The slight change, called backscatter, allows them to determine the voltage.
While the experiments so far have involved the peripheral nervous system and muscles, the neural dust motes could work equally well in the central nervous system and brain to control prosthetics, the researchers say. Today’s implantable electrodes degrade within 1 to 2 years, and all connect to wires that pass through holes in the skull. Wireless sensors – dozens to a hundred – could be sealed in, avoiding infection and unwanted movement of the electrodes. But the current neural dust mote is a very low-power device, drawing only 0.12 milliwatt. Chad Bouton, who heads the Center for Bioelectronic Medicine at the Feinstein Institute, in Manhasset, N.Y., says a stimulating mote will require more power.
In a paper published online in 2013, the researchers estimated that they could shrink the sensors down to a cube 50 microns on a side – about 2 thousandths of an inch, or half the width of a human hair. At that size, the motes could nestle up to just a few nerve axons and continually record their electrical activity.
“The beauty is that now, the sensors are small enough to have a good application in the peripheral nervous system, for bladder control or appetite suppression, for example,“ Carmena said. “The technology is not really there yet to get to the 50-micron target size, which we would need for the brain and central nervous system. Once it’s clinically proven, however, neural dust will just replace wire electrodes. This time, once you close up the brain, you’re done.“
The team is working now to miniaturize the device further, find more biocompatible materials and improve the surface transceiver that sends and receives the ultrasounds, ideally using beam-steering technology to focus the sounds waves on multiple motes. The engineers are also writing new signal processing algorithms to make sense of returning echoes from multiple sources. They are now building little backpacks for rats to hold the ultrasound transceiver that could be positioned over the implanted mote to keep the proper alignment.
They’re also working to expand the motes’ ability to detect non-electrical signals, such as oxygen or hormone levels. “The vision is to implant these neural dust motes anywhere in the body, and have a patch over the implanted site send ultrasonic waves to wake up and receive necessary information from the motes for the desired therapy you want,” said Dongjin Seo, a graduate student in electrical engineering and computer sciences. “Eventually you would use multiple implants and one patch that would ping each implant individually, or all simultaneously.”
University of Melbourne scientists develop BCI which gets implanted in the brain without surgery
Australian scientists funded by the US Defense Advanced Research Projects Agency (Darpa) have developed a tiny, matchstick-sized Brain Computer interface called a stentrode. This stentrode is flexible enough to be able to pass through the blood vessels and get implanted into the motor cortex, the brain’s control centre – bypassing the need for complex invasive brain surgery.
The device would capture and decode the brain signals and then wirelessly transmit appropriate commands through the skin to enable control of an exoskeleton attached to their limbs simply by thinking about it.
The stentrode could also benefit people with Parkinson’s disease, motor neurone disease, obsessive compulsive disorder and depression and could even predict and manage seizures in epileptic patients. The work is the result of close collaboration between the University of Melbourne, the Royal Melbourne Hospital and the Florey Institute of Neuroscience and Mental Health.
In late 2017, a select group of paralysed patients from the Royal Melbourne and Austin Hospitals in Australia will be chosen for the trial, where they will be implanted with the stentrode. If the trial succeeds, the technology could become commercially available in as little as six years.
The US military fund research into brain implants for treating depression, PTSD
In 2014, Defense Advanced Research Projects Agency, or DARPA, awarded two large contracts to Massachusetts General Hospital and the University of California, San Francisco, to create electrical brain implants capable of treating seven psychiatric conditions, including addiction, depression, and borderline personality disorder.
The project builds on expanding knowledge about how the brain works; the development of microlectronic systems that can fit in the body; and substantial evidence that thoughts and actions can be altered with well-placed electrical impulses to the brain.
The effort could lead to cures for brain-based illnesses and diseases like Alzheimer’s, epilepsy, autism and diseases that disproportionately affect troops, such as post-traumatic stress, brain injury and associated memory loss. The technology will use sensors to watch for unusual neural activity at multiple parts of the brain. If something’s wrong, the implants will use deep electrical stimulation to restore healthy activity — permanently, if possible.
Clinical trials for the implants aren’t expected until five years from now, and it’ll take longer still for a wide-scale deployment. DARPA and the Presidential Commission for the study of Bioethical Issues also will investigate the ethical, legal and societal concerns raised when scientists begin tinkering in peoples’ brains, according to administration officials.