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"Neural dust" sensors could lead to implantable wearables

"Neural dust" sensors could lead to implantable wearables

Tiny sensors the size of a grain of sand could enable the control of prostheses and implantable wearable technology through the brain-machine interface.

"Neural dust" refers to small sensors developed by the EECS division at UC Berkeley. In an article published this month, Berkeley researchers revealed that they recorded the first in vivo readings from implanted dust.

This research faces a long time ago. In 2013, the team published research detailing their research into using ultrasound with CMOS circuitry. In 2015 they published another paper that focused on theory, modeling, and scaling.

The resulting prototype in this recent announcement is a step towards sensors that can be safely implanted in the brain. It is also a step into a future where wearable technology can be implanted directly into the body.

The prototype of the neural dust device with a penny for the scales. Screenshot courtesy of UC Berkeley.

CMOS

The neural dust works using Complementary Metal-Oxide-Semiconductor (CMOS) technology. The CMOS component is required to convert piezoelectric AC signals into direct current via a full-wave bridge rectifier. In order to supply the CMOS with a consistent and safe DC voltage, regulators are required in addition to DC-coupled ADCs and modulators.

A simplified version of the neural dust scheme. Image courtesy Cornell University Library.

Tiny, batteryless sensors

One of the biggest challenges for any tiny sensor is performance. In this case, the task was to power a CMOS circuit small enough to measure in millimeters. In the case of neural dust, the prototype measures only 3 x 1 x 1 mm.

A neural dust "mote" on the tip of a finger. Image courtesy UC Berkeley.

In addition to the problems associated with making such small-scale circuits, the neural dust has the hugely important parameter that it does not generate any appreciable heat while sitting on a human brain.

The neural dust team dealt with the problem of force using ultrasound (PDF). Ultrasonic waves emitted from outside the body are converted into electricity using a piezocrystal that supplies the resulting energy to the transistor.

Graphic representation of the neural dust device. Image courtesy UC Berkeley.

Ultrasound is also useful for this particular project because it can be transmitted and received anywhere in the human body. Where RF has limits on how well it transmits within (and through) the human body, ultrasound is more robust. Ultrasound not only removes the power supply to the dust, but also enables the device to communicate with monitoring devices (the "interrogator") outside the body.

The directed ultrasound input (blue) and the recorded backscatter (orange). Image courtesy UC Berkeley.

Neural control for prosthetics

When the nerve dust attaches to nerve fibers, it can read electrical impulses between the neurons via electrodes. The ability to measure these impulses is critical to developing an electromechanical system that can respond to them and physically move a prosthesis.

The neural dust prototype on a nerve fiber in a rat. Image courtesy UC Berkeley.

The goal is to have nerve impulse impulses to a receiver, which in turn moves the mechanical part of a prosthesis. This would allow amputees to control a substitute limb by just thinking.

Implanted "wearables"

There are innumerable applications that these sensors could have in the medical field beyond the control of prosthetics. MEMS technology (Micro-Electro-Mechanical Systems) is currently a popular research subject. Recently, scientists from various fields have developed projects such as brain implant prototypes.

Of course, there are many commercial applications that neural dust could make possible. At some point in the future, we could see a generation of wearables implanted directly into the body. This could enable real-time organ health data, provide insight into system health and even provide an alert for heart attacks, strokes and other emergencies.

But in addition to the benefits of wearables, there is also the risk of security breaches. To that end, you may have heard of smart dust in the past, albeit possibly in a much more sensational context. In 2013, MIT Technology Review published an article entitled "How Smart Dust Could Spy On Your Brain". It suggests that the same properties that make neural dust attractive for medical purposes (mobile tracking, remote monitoring, etc.) are also attractive for data collection.

Therefore, the same security problems that wearable technologies threaten to threaten both hackers and marketers are likely to persist as wearables become "implantable" devices. Those concerns are probably still a long way off, however, as the team at UC Berkeley is still in the process of developing the neural dust design.

The Neural Dust program is led by the EECS program in Berkeley and funded in part by DARPA.

Find out more about the neural dust program here.