Archive for the ‘IMPLANTS’ Category

Tiny “Neural Dust” Sensors Could One Day Control Prostheses or Treat Disease

Friday, August 19th, 2016
These devices could last inside the human body indefinitely, monitoring and controlling nerve and muscle impulses

neural-dust-uc-berkeley-sensor-on-fingertip image

They’re tiny, wireless, battery-less sensors no larger than a piece of sand. But in the future, these “neural dust” sensors could be used to power prosthetics, monitor organ health and track the progression of tumors.

A team of engineers and neuroscientists at the University of California, Berkeley have been working on the technology for half a decade. They’ve now managed to implant the sensors inside rats, where they monitor nerve and muscle impulses via ultrasound. Their research appears in the journal Neuron.

“There’s a lot of exciting things that this opens the door to,” says Michel Maharbiz, a professor of engineering and one of the study’s two main authors.

The neural dust sensors developed by Maharbiz and his co-author, neuroscientist Jose Carmena, consist of a piezoelectric crystal (that produces a voltage in response to physical pressure) connected to a simple electronic circuit, all mounted on a tiny polymer board. A change in the nerve or muscle fiber surrounding the sensor changes the vibrations of the crystal. These fluctuations, which can be captured by ultrasound, give researchers a sense of what might be going on deep within the body.

diagram-uc-berkeley-sensor-nerves image

Building interfaces to record or stimulate the nervous system that will also last inside the body for decades has been a long-standing puzzle, Maharbiz says. Many implants degrade after a year or two. Some require wires that protrude from the skin. Others simply don’t work efficiently. Historically, scientists have used radio frequency to communicate with medical implants. This is fine for larger implants, says Maharbiz. But for tiny implants like the neural dust, radio waves are too large to work efficiently. So the team instead tried ultrasound, which turns out to work much better.

Moving forward, the team is experimenting with building neural dust sensors out of a variety of different materials safe for use in the human body. They’re also trying to make the sensors much smaller, small enough to actually fit inside nerves. So far, the sensors have been used in the peripheral nervous system and in muscles, but, if shrunken, they could potentially be implanted directly into the central nervous system or the brain.

rat-diagram-uc-berkeley sensor image

Neural dust implanted in a rat (UC Berkeley)

Minor surgery was needed to get the sensors inside the rats. The team is currently working with microsurgeons to see what kinds of laparoscopic or endoscopic technologies might be best for implanting the devices in a minimally invasive way.

It may be years before the technology is ready for human testing, Maharbiz says. But down the road, the neural dust has potential to be used to power prosthetics via nerve impulses. A paralyzed person could theoretically control a computer or an amputee could power a robot hand using the sensors. The neural dust could also be used to track health data, such as oxygen levels, pH or the presence of certain chemical compounds, or to monitor organ function. In cancer patients, sensors implanted near tumors could monitor their growth on an ongoing basis.

“It’s a new frontier,” Maharbiz says. “There’s just an amazing amount you can do.”

Henry Sapiecha

Video shows how Stretchable, Long-Term Neural Implant on the Spinal Cord Could Restore Walking

Tuesday, March 10th, 2015

So-called “surface implants” have reached a roadblock. They can’t be applied long-term to the spinal cord or brain, beneath the nervous system’s protective envelope (known as the dura mater), because when nerve tissues move or stretch, they rub against the rigid devices. Repeated friction causes inflammation, scar tissue buildup, and rejection. Scientists from the Swiss Federal Institute of Technology in Lausanne (EPFL) now introduce the e-Dura implant, which is designed specifically for implantation on the surface of the brain or spinal cord. The neural implant combines electrical and chemical stimulation and has successfully made paralyzed rats walk again. Soft and stretchable, it is the first of its kind that can be implanted directly on the spinal chord without damaging it. Its silicon substrate is covered with cracked gold electric conducting tracks, and the electrodes are made of an innovative composite of silicon and platinum microbeads. They can be deformed in any direction, while still ensuring optimal electrical conductivity. A fluidic microchannel enables the delivery of pharmacological substances that will reanimate the nerve cells beneath the injured tissue.
Henry Sapiecha


Wednesday, May 23rd, 2012


Age-related macular degeneration is the leading cause of blindness in North America, while retinitis pigmentosa causes approximately 1.5 million people worldwide to lose their sight every year. Individuals afflicted with retinal degenerative diseases such as these might someday be able to see again, however, thanks to a device being developed at California’s Stanford University. Scientists there are working on a retinal prosthesis, that uses what could almost be described as miniature solar panels to turn light signals into nerve impulses.

The system consists of a camera- and microprocessor-equipped pair of goggles, and a small photovoltaic chip that is implanted beneath the retina.

The output of the camera is displayed on a miniature LCD screen, located on the inside surface of the goggles. That screen is special, however – it emits pulses of infra-red laser light, that correspond to the images it’s displaying. Photodiodes on the chip register those pulses, and in turn stimulate retinal neurons. In theory, this firing of the neurons should produce visual images in the brain, as would occur if they had been stimulated by visible light.

“It works like the solar panels on your roof, converting light into electric current,” said Dr. Daniel Palanker, associate professor of ophthalmology. “But instead of the current flowing to your refrigerator, it flows into your retina.”

Palanker’s team has created a chip about the size of a pencil point, which is thinner than a human hair, and contains hundreds of the photodiodes. These were tested using retinas from both sighted rats, and rats that were blind in a fashion similar to human degenerative blindness – the retinal neurons were still present, but were generally inactive. While the chips in the blind retinas didn’t respond to visible light (unlike those in the sighted retinas), they did respond to the near-infrared light. “They didn’t respond to normal light, but they did to infrared,” said Palanker. “This way the sight is restored with our system.”

The photovoltaic chip is implanted under the retina in a blind rat (upper right corner) – it is comprised of an array of photodiodes (center and lower left) (Image: Palanker Laboratory/Stanford University)

The scientists are currently testing the technology on live rats, and state that it so far looks as if the electrical signals are indeed reaching the rats’ brains. They are now looking for a sponsor for human trials. Palanker notes that the system doesn’t allow for color vision, however, and that what vision is does provide would be “far from normal.”

While other retinal prostheses are also in development, these reportedly involve more in the way of hardware such as coils or antennas being implanted in the eye. Most of the technology used in the light-based Stanford system, by contrast, is located in the goggles.

A paper on the research was published this week, in the journal Nature Photonics

Sourced & published by Henry Sapiecha


Wednesday, May 2nd, 2012


Scoliosis is a lateral deformity of the spine, that most often shows up in young children and adolescents. Besides resulting in disfigurement, in some cases it can also cause breathing problems. In severe cases, if the child is still growing, telescoping steel rods are surgically implanted alongside the deformed section of the spine, in order to straighten it. Unfortunately, repeat surgeries are necessary every six months, in order to lengthen the rods as the child grows. Now, however, scientists from the University of Hong Kong are reporting success in the first human trials of a system that incorporates rods which can be lengthened using magnets instead of surgery.

As its name suggests, the magnetically-controlled growing rod (MCGR) system uses magnets held outside of the body to engage and then extend the ends of the implanted rods. This can be done relatively quickly in a non-invasive outpatient procedure. The surgery required for the lengthening of traditional rods (a process known as a “distraction”), by contrast, requires hospitalization and general anesthesia. Not only is this unpleasant for the children, but it also causes them to miss school, involves considerable medical expenses, and often also requires at least one parent to miss work while the child recuperates.

In the recent trials, MCGRs were implanted in five test subjects. Once every month since, those subjects have been going into a clinic to get those rods lengthened. Two of the patients are now at the 24 month-mark of their treatment. The mean degree of their spinal deformities was 67º before implantation, but is now down to 29º. Their spines have grown at a normal rate, and they have reported no pain or other problems throughout the process.

“Whether MCGR leads to significantly better outcomes than traditional growing rods is not yet known, but early results are positive and the avoidance of open distractions is a great improvement,” the scientists said in a report on their research. “Additionally, this new growing rod system has potentially widespread applications in other disorders that could benefit from a non-invasive procedure to correct abnormalities. MCGR could assist with correction of limb abnormalities, thoracic insufficiency syndrome, limb lengthening, limb salvage procedures, or any disorders or injuries in which slow, progressive change to bone structures is needed.”

Source: Lancet

Published by Henry Sapiecha


Sunday, March 4th, 2012


With the wait still on for a miniaturization ray to allow some Fantastic Voyage-style medical procedures by doctors in submarines, tiny electronic implants capable of traveling in the bloodstream show much more promise. While the miniaturization of electronic and mechanical components now makes such devices feasible, the lack of a comparable reduction in battery size has held things back. Now engineers at Stanford University have demonstrated a tiny, self-propelled medical device that would be wirelessly powered from outside the body, enabling devices small enough to move through the bloodstream.

While the benefits of medical implants have already been realized with devices such as artificial pacemakers and cochlear implants, which are stationary within the body, energy storage continues to limit such devices. With half of the volume of implants often consumed by the battery, the locations in which they can be placed are limited. Additionally, batteries also need to be periodically replaced, which generally requires a surgical procedure.

Developing implants capable of traveling through the bloodstream not only requires an energy source to power the device’s medical functions, but also its propulsion system – something that today’s batteries are unable to deliver in a form factor that is small enough to fit inside arteries.

The obvious approach would be to remove the battery from the device altogether and look to wireless electromagnetic power delivery. This is just what many scientists have been working on for fifty years. While such wireless power transmission technology has recently entered the mainstream through wireless chargers for consumer devices such as mobile phones, it wasn’t believed the technology could be made small enough to be compatible with tiny implantable devices.

The problem is that, according to mathematical models, high frequency waves that would require antennas small enough to be used in such devices were believed to dissipate quickly in human tissue, fading exponentially the deeper they go. At the same time, antennas to harness enough power from low-frequency signals, which are able to penetrate the human body well, would need to be a few centimeters in diameter, making them OK for larger devices, but too large to fit in all but the biggest arteries.

However, when electrical engineer Ada Poon looked at the models more closely she realized they were calculated assuming that human muscle, fat and bone were generally good conductors of electricity. Realizing that human tissue is actually a poor conductor of electricity but that radio waves could still move through it, Poon decided to redo the models with human tissue as a type of insulator called a dielectric. Her new calculations revealed that high-frequency waves travel much farther in human tissue than previously thought.

“When we extended things to higher frequencies using a simple model of tissue we realized that the optimal frequency for wireless powering is actually around one gigahertz,” said Poon, “about 100 times higher than previously thought.”

This meant that antennae inside the body could be 100 times smaller while delivering the same amount of power. This finding enabled Poon to create an antenna of coiled wire small enough to be placed inside the body and receive power from a radio transmitter outside the body. The transmitter and the antenna are magnetically coupled so that any change in current flow in the transmitter induces a voltage in the coiled wire.

Poon has created two types of wirelessly powered devices that are able to propel themselves through the bloodstream. One creates a directional force by driving an electrical current directly through the blood to push itself forward at a velocity of just over half a centimeter (0.2 inches) a second. The second type switches current back-and-forth in a wire loop to produce a swishing motion to propel the device forward.

Poon’s research could finally enable the development of medical implants capable of traveling through the bloodstream to deliver drugs to a specific area, perform analyses, and maybe even zap blood clots or remove plaque from arteries.

“There is considerable room for improvement and much work remains before these devices are ready for medical applications,” said Poon. “But for the first time in decades the possibility seems closer than ever.”

Poon recently demonstrated one of her tiny, wirelessly powered, self-propelled devices at the International Solid-State Circuits Conference (ISSCC). The animation below produced by Carlos Suarez at StrongBox3d shows how such a device might move through the bloodstream.

Source: Stanford University

Sourced & published by Henry Sapiecha