The Chips Are Coming
by William Wells
Implanted biochips could be the tool of
Big Brother, but they are more likely to become the treatment
of choice for the physician of the 21st century.
Paranoid ranting is a staple on the internet,
and the topic of biochips is a particular favorite. Biochips -
any microprocessor chips that can be used in biology - mean
many things to many people. The web's preachers focus on
a simple idea: an implanted chip that identifies each person uniquely,
and can be used to track their location.
This wonderful idea - capable of locating
lost children, downed soldiers, and wandering Alzheimers patients
- sounds alarming even to many mild-mannered civil libertarians.
To Living Truth Ministries of Austin, TX, it is no less than "a
tremendous bonanza for the coming Antichrist!" Second Advent
Ministries of San Bernardino, Calif., warns us that the US social
security number will soon be replaced (at the orders of the "New
World Order United Nations-controlled world government",
no less) by a chip-encoded "18-digit numbering system [which]
will consist of THREE separate sets of SIX DIGITS each: 6-6-6!
Coincidental? No. Not if you believe Bible prophecy."
Reality is somewhat less alarming. A simple
ID chip is already walking around in tens of thousands of individuals,
but all of them are pets. Companies such as AVID (Norco, Calif.),
Electronic ID, Inc. (Cleburne, Tx.), and Electronic Identification
Devices, Ltd. (Santa Barbara, Calif.) sell both the chips and
the detectors. The chips are the size of an uncooked grain of
rice, small enough to be injected under the skin using a syringe
needle. They respond to a signal from the detector, held just
a few feet away, by transmitting out an identification number.
This number is then compared to database listings of registered
Daniel Man, a plastic surgeon in private practice
in Boca Raton, Fla., holds a patent on a more sinister device:
a chip that would enable lost humans to be tracked by satellite.
He has a large-scale model, but for miniaturization and regulatory
approval he will need a substantial amount of cash. "There
are some companies that are interested, but nothing is official,"
he says. "We're not giving up on it yet."
Chips to monitor your every footstep and
The civil liberties debate over biochips has
obscured their more ethically benign and medically useful applications.
Medical researchers have been working to integrate chips and people
for many years, often plucking devices from well-known electronic
appliances. Jeffrey Hausdorff of the Beth Israel Deaconess Medical
Center (Boston, Mass.) has used the type of pressure-sensitive
resistors found in the buttons of a microwave oven as stride timers.
He places one sensor in the heel of a shoe, and one in the toe,
and adds a computer to the ankle to calculate the duration of
"Young, healthy subjects can regulate
the duration of each step very accurately," he says. But
elderly patients prone to frequent falls have extremely variable
stride times, a flag that could indicate the need for more strengthening
exercises or a change in medication. Hausdorff is also using the
system to determine the success of a treatment for congestive
heart failure. By monitoring the numbers of strides that a person
takes, he can directly measure the patient's activity level,
bypassing the often flawed estimate made by the patient.
Hausdorff's chips are external, but
a chip proposed by Sensors for Medicine and Science, Inc. (S4MS;
Germantown, Md.) will be injected under the skin. The chip will
allow diabetics to easily monitor the level of the sugar glucose
in their blood. Diabetics currently use a skin prick and a hand-held
blood test, and then medicate themselves with insulin depending
on the result. The system is simple and works well, but the need
to draw blood means that most diabetics don't test themselves
as often as they should. Although they may get away with this
in the short term, in later life those who monitored infrequently
suffer from blindness, loss of circulation, and other complications.
The solution is more frequent testing, using
a less invasive method. Various companies are trying to extract
the required body fluid, using either an electric current (Cygnus,
Inc., Redwood City, Calif.) or a tiny pore induced by a laser
(SpectRx, Norcross, Ga.) or a small needle (Integ, St Paul, Minn.).
"All of these approaches ameliorate
the drawing of blood," says George Daniloff, Chief Scientific
Officer of S4MS, "but they still require manipulation of
skin, and the skin may be perturbed." The S4MS chip, however,
will sit underneath the skin, sense the glucose level, and send
the result back out by radio-frequency communication.
A light-emitting diode (LED) starts off the
detection process. The light that it produces hits a fluorescent
chemical: one that absorbs incoming light and re-emits it at a
longer wavelength. The longer wavelength of light is then detected,
and the result is sent to a control panel outside the body.
|The S4MS chip for sensing oxygen or glucose. Light generated by the light-emitting diode (LED) causes surrounding molecules to fluoresce. The
light that emerges has a new wavelength, and only this light passes through
the filter to be detected by the photodiode. The oxygen or glucose
decreases the fluorescence of the molecules in the top reservoir.
Glucose is detected because the sugar reduces
the amount of light that the fluorescent chemical re-emits. The
more glucose there is, the less light that is detected. S4MS is
still developing the perfect fluorescent chemical, but the key
design innovation of the S4MS chip has been fully worked out.
The idea is simple: the LED is sitting in a sea of the fluorescent
molecules. In most detectors the light source is far away from
the fluorescent molecules, and the inefficiencies that come with
that mean more power and larger devices. The prototype S4MS chip
uses a 22µW LED, almost forty times less powerful than the
tiny power-on buttons on a computer keyboard. The low power requirements
mean that energy can be supplied from the outside, by a process
called induction. The fluorescent detection itself does not consume
any chemicals or proteins, so the device is self sustaining.
Daniloff has a working model of an oxygen sensor
that uses the same layout. With it's current circuitry
it is about the size of a large shirt-button, but the final silicon
wafer will be less than a millimeter square. "The scale
transition is not a challenge," says Daniloff. "The
challenge is to illustrate the principle." The oxygen sensor
will be useful not only to monitor breathing in intensive care
units, but also to check that packages of food, or containers
of semiconductors stored under nitrogen gas, remain airtight.
Tom Ferrell of the Oak Ridge National Laboratory
in Oak Ridge, Tenn., is also developing an oxygen-sensing chip,
but his version sends light pulses out into the body. The light
is absorbed to varying extents, depending on how much oxygen is
being carried in the blood, and Ferrell's chip detects
the light that is left. The rushes of blood pumped by the heart
are also detected, so the same chip is a pulse monitor. A number
of companies already make large-scale versions of such detectors,
and Ferrell says he has "collaborated with almost every
company in this area," although he will not name names.
Ferrell estimates that the oxygen chip is two
years away, but he has already reduced the dimensions of his temperature-sensing
chip to 3mm per side. The transition of certain semiconductors
to their conducting state is inherently sensitive to temperature,
so designing the sensor was simple enough. With some miniature
radio-frequency transmitters, and foam-rubber earplugs to hold
the chip in place, the device is complete. Ferrell sees applications
for anyone from sick children, to chemotherapy patients who can
be plagued by sudden rises in body temperature in response to
their anti-cancer drugs.
Brain surgery with an on-off switch
Sensing and measuring is one thing, but can
we switch the body on and off? Heart pacemakers use the crude
approach: large jolts of electricity to synchronize the pumping
of the heart. The electric pulses of the Activa implant, made
by Medtronic, Inc. (Minneapolis, Minn.), are directed not at the
heart but the brain. They turn off brain signals that cause the
uncontrolled movements, or tremors, associated with diseases such
Drug therapy for Parkinson's disease
aims to replace the brain messenger dopamine, a product of the
brain cells that are dying. But eventually the drug's effects
wear off, and the erratic movements come charging back. "I've
had patients tell me that they scare their grandkids because they
are flaying around like a fish," says Gary Heit, a neurosurgeon
at Stanford University Medical Center. "Imagine your whole
body twisted like a charleyhorse."
The next option is to remove a portion of the
thalamus, a brain structure that triggers the tremors. The implant,
cleared for use in the United States in August 1997, is a new
alternative that uses high-frequency electrical pulses to reversibly
shut off the thalamus. "It has the same benefits as thalamotomy
[the brain operation] without the risks," says Heit. The
implantation surgery is far less traumatic than thalamotomy, and
if there are any post-operative problems the stimulator can simply
be turned off.
|The Activa implant for Parkinson's disease tremors. Driven by a pulse
generator implanted in the chest, the implant delivers high frequency
stimulation to an area of the brain called the thalamus. Image courtesy of
Adding back the senses
The Activa implant interferes with aberrant
brain functioning. The most ambitious bioengineers are trying
to add back brain functions, restoring sight and sound where there
was darkness and silence.
The success story in this field is the cochlear
implant. Most hearing aids are glorified amplifiers, but the cochlear
implant is for patients who have lost the hair cells that detect
sound waves. For these individuals, no amount of amplification
|The Clarion cochlear implant. Sound is received by a microphone, processed
by a minicomputer (not shown), and the electric signals are transmitted to
the implant by radio-frequency communication. After decoding of the signal,
the multiple electrodes directly activate nerve cells that communicate
information about sound to the brain. Image courtesy of Advanced Bionics
The cochlear implant delivers electrical pulses
directly to the nerve cells in the cochlea, the spiral-shaped
structure that translates sound into nerve pulses. In normal hearing
individuals, sound waves set up vibrations in the walls of the
cochlea, and hair cells detect these vibrations. High frequency
noises (deep notes) vibrate the base of the cochlea, while low
frequency notes vibrate nearer the top of the spiral. The implant
mimics the job of the hair cells. It splits the frequencies of
incoming noises into a number of channels (typically eight), and
then stimulates the appropriate part of the cochlea.
The two most successful implants are the Clarion
(developed at the University of California at San Francisco (UCSF),
Research Triangle Institute, N.C., and Advanced Bionics Corporation
of Sylmar, Calif.) and the Nucleus (developed at the University
of Melbourne, Australia, and made by Cochlear of Sydney, Australia).
Upgrades largely focus on improving the speech processing software,
which is operated by a minicomputer worn on the patient's
belt. Theoretically, increasing the number of channels (and electrodes)
could improve sound perception. But speech is perceived in an
area of the cochlea only 14 mm long, and spacing the electrodes
too close to each other causes signals to bleed from one channel
The result is a broad-brush version of hearing.
While some recipients of the devices report speech-like sounds,
many characterize their new world as being populated with legions
of quacking ducks or banging garbage cans. But the success is
undeniable. "Currently two thirds to three quarters of
patients [with more recent models] can understand speech without
lip-reading," says Steve Rebscher, a member of the UCSF
team. "It's pretty amazing, and certainly better
than a lot of people anticipated these devices would do."
With the ear at least partially conquered,
the next logical target is the eye. Several groups are working
on implantable chips that mimic the action of photoreceptors,
the light-sensing cells at the back of the eye. Photoreceptors
are lost in both retinitis pigmentosa, a genetic disease, and
age-related macular degeneration, the most common cause of lost
sight in the developed world.
Joseph Rizzo of the Massachusetts Eye and Ear
Infirmary, and John Wyatt of the Massachusetts Institute of Technology
have made a twenty-electrode, 1mm-square chip, and implanted it
at the back of rabbits' eyes. The original chip, the thickness
of a human hair, put too much stress on the eye, so the new version
is ten times thinner. The final set-up will include a fancy camera
mounted on a pair of glasses. The camera will detect and encode
the scene, then send it into the eye as a laser pulse, with the
laser also providing the energy to drive the chip. Rizzo has confirmed
that his tiny array of light receivers (photodiodes) can generate
enough electricity to run the chip. He has also found that the
amount of electricity needed to fire a nerve cell into action
is ~100-fold lower in the eye than in the ear, so the currents
can be smaller, and the electrodes more closely spaced.
For now the power supply comes from a wire
inserted directly into the eye and, using this device, Rizzo has
detected signals reaching the brain. "We know we can get
visual information to the brain," he says, "but we
don't know what kind of vision that will result in."
Eugene de Juan of Johns Hopkins Wilmer Eye
Institute (Baltimore, Md.) is trying to answer that question by using human subjects.
His electrodes, inserted directly into the eye, are large and
somewhat crude. But his results have been startling. Completely
blind patients have seen well-defined flashes, which change in
position and brightness as de Juan changes the position of the
electrode or the amount of current. In his most recent experiments,
patients have identified simple shapes outlined by multiple electrodes.
With as little as an 8 x8 array, de Juan believes he could approximate
character recognition, and a 25 x 25 array might give a crude
The big money in eye implants is in Germany,
where the government has pledged ~$10 million to two projects.
One is similar to the US projects, in which chips are implanted
on the surface of the retina, the structure at the back of the
eye. The other project is putting its implants at the back of
the retina, where the photoreceptors are normally found. These
'subretinal' chips may block the transport of oxygen
and food to the overlying nerve cells, so Eberhart Zrenner of
the University of Tübingen, Germany, is developing 'chain
mail' electrode arrays, with plenty of holes for the delivery
The subretinal approach more closely mimics
the action of the lost photoreceptors. The chip delivers its message
at the source, before intervening layers of retinal nerve cells
do some complicated processing. Rizzo thinks that his chip's
hardware will be able to compensate for these computations, but
for now he has other things to worry about. "There are
all sorts of processes that go on that we're just going
to ignore initially," he says. As with the cochlear implant,
he says, "the biological tests will show you the best way
to stimulate. Ultimately the only thing that matters is what the
The first big test - showing that a
remotely powered device can give true visual signals -
is yet to be done. "We haven't got to first base
yet," says Rizzo, "but we're close."
With a working device many years away, Rizzo is a model of caution.
"It's always better to talk down the possibilities
than to talk them up, because there are many reasons why the implants
might fail," he says. "This is science fiction stuff."