UNDERSTANDING THE BENEFICIAL PROPERTIES
OF EARLY ELECTROTHERAPY LEADS TO A NEW
PRODUCT CALLED THE TESLA-BRUSH™
BY: BERNHARD RUDERT BSc Electr Eng
INTRODUCTION
Electrotherapy is nothing new. It was extensively used in the first half of the 20th century
claiming to cure all kinds of illnesses. While such claims had merrit specifically regarding
skin care, hair loss and pain in general,
manufacturers tried to exploit the situation by
claiming their equipment would practically cure
everything. Eventually the authorities intervened
and stopped this exaggeration with the result that
this kind of therapy gradually got classified as
quackery while the medical profession increasingly
relied on the prescription of pharmaceutical
products. Early electrotherapy equipment is still
used today in beauty spas and by other firm
believers in its therapeutic benefits.
An example of such a historic hand held device can be seen in Fig.1. To date I have not
found any scientific or technical investigation into the therapeutic benefits of this type of
outdated equipment and consider this to be the reason for the many unsubstantiated claims
regarding its functioning or efficacy. It is my intention to disperse some of these claims and
show that the operating principle employed is actually very much supported by our present
understanding of electrical stimulation of the physical body. It will also emerge that early
electrotherapy devices are in fact another form of today’s frequently used Micro-Current or
TENS equipment used for various ailments including pain, with some important superior
properties. The subject matter is viewed mainly from a technical perspective relating to the
equipment itself with pointers as to where biological or medical benefits could arise.
THE ELECTRICAL OPERATING PRINCIPLE
Unfortunately I have to use some technical language to lay the foundation for the discussion
to follow and trust that you will make sense of my simplified explanations. Fig.2 shows the
basic electrical circuit of an early electrotherapy unit. The
capacitor “C” is charged by the
electrical current source “I” until
the energy stored in it reaches a
predetermined value while switch
“S” is in the position shown.
Thereafter switch “S” is activated
and connects capacitor “C” across
the primary winding of the
transformer “T” until all the energy is dissipated. Capacitor “C”
together with the inductance of the transformer “T”, form a
partially damped oscillating circuit with a frequency usually
above 100 KHz. The resulting ringing voltage dies down to zero
after a few cycles and then switch “S” returns to the original
position. The process is repeated about every 10ms or 100 times per second, which means
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that at the output of transformer “T” we have very short bursts of a few high voltage peaks
separated by long periods of inactivity as shown in Fig.3. The bottom part of Fig.3 shows
the short high voltage peaks just as straight lines because the peaks are extremely short.
The top part of Fig.3 shows a time magnification of these pulses where you can see the
decaying oscillation of the high voltage. The units usually have means of controlling the
energy level to which the capacitor “C” is charged or change the repetition rate of the pulses
thus making it possible to adjust the output power. In practice the waveform is not always
as clean as shown in Fig.3 due to contact bounce in the mechanical switch “S” causing a
whole bundle of pulses to occur containing all kinds of harmonic frequencies.
The output of transformer “T” is held at ground potential on the one side while the other
side is connected to the electrode of a glass tube “N” filled with either neon or argon gas.
When the high voltage bursts occur the gas ignites and the glass tube becomes electrically
conductive on the inside. Where the glass tube touches the skin of the human body “HB” a
small capacitance is created by the electrically insulating glass barrier. Because the high
voltage bursts are of a high frequency nature, a small electrical current flows into the skin.
Since the body capacitance “BC” is much larger than the barrier capacitance between the
glass tube and the skin, the major potential drop occurs across this barrier, which causes
numerous tiny sparks to occur on the glass surface.
THE EFFECT ON THE SKIN
In order to make sense of it all we need to know something about the structure of the
human skin which consists of 3 major layers as shown in Fig.4. The outermost layer called
the epidermis is the body’s actual
protective layer. No blood vessels
or nerve endings are found in this
layer. It is nourished by the layer
below called the dermis. The newly
formed cells near the barrier
between the dermis and the
epidermis are pushing the older
cells towards the outer surface of
the latter while slowly dying until
finally they form a thin layer of
flattened dead cells called the
stratum corneum which is the
actual surface of the skin.
The dermis which is below the
epidermis is made up of 80%
water, elastin fibres and collagen. It
contains many blood vessels and
nerve endings and plays an
important part in temperature
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regulation and healing. The sweat glands are found in this layer as well as the hair follicles
with their arrector pili muscles and their oil glands.
Under the dermis we have the hypodermis, also called subcutaneous tissue. The hypodermis
consists primarily of loose connective tissue and lobules of fat. It contains larger blood
vessels and nerves than those found in the dermis. The blood supply to the hair follicles
originates from this layer.
To stimulate the skin electrically we need to overcome the often poorly conducting surface
formed by the stratum corneum on top of the epidermis. This layer which consists of mainly
dead organic matter, is a very poor electrical conductor especially if the skin is dry. For this
reason special conductive pads are used for modern electrotherapy treatment. However, if
bare metal probes are used as with some skin or hair treating products a moistening liquid
is necessary to ensure that electrical current flows into the skin under all circumstances. The
dermis and the hypodermis are electrically conductive. Their electrical resistance is a
nonlinear function of applied potential. Therefore, for effective stimulation the electrical
source requires proper attention.
With the instruments used in early electrotherapy the above problems are solved very
simply with repeatable results. The reason is that the electrical stimulus is transmitted via
the capacitive barrier formed by the glass wall of the electrode together with the insulating
properties of the stratum corneum. Because of the high voltage, combined with the high
impedance of the barrier capacitance, a reasonably defined electrical current source supplies
the dermis with the desired electrical stimulus. This means that the skin must be dry during
treatment obviating the need for a special cream to facilitate electrical conduction.
We know that the electrical stimulation decreases with the distance from the outer surface
of the skin. This means that we need adequate electrical stimulation to reach the
hypodermis because the dermis and the hair follicles receive their nourishment from this
layer. A much higher electrical stimulus would be required to affect a muscle situated below
the hypodermis.
It has been established that with a decreasing pulse width especially below 100
microseconds the intensity of the stimulus required to cause muscle contraction increases
rapidly. Early electrotherapy units can be considered as having stimulating pulses of less
than 5 microseconds and therefore even if they were to produce high currents they would
not reach the threshold where muscle contraction occurs.
Observing the scalp under a microscope after a few weeks of massaging it regularly once a
day for about 10 minutes with an electrotherapy device, small brown spots appear. Further
observation over a longer period seems to indicate that where those brown spots appear
small fluff starts to develop. My explanation is that the electrical stimulation causes
repeated contraction of the arrector pili muscles connected to the follicles thus massaging
the latter to clear the clogged pores of excess sebum which softens due to the elctric
current.
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After each massage the skin often gets a slightly rosy color, indicating improved blood flow
in the treated area. This suggests that the skin and the follicles are being nourished more
effectively.
I am not a biologist or dermatologist and therefore cannot explain exactly what happens
inside the cellular structure of the skin but I know from results that these early devices do
work and that further research in refining the generated wave shape and the construction of
the electrodes could prove useful. Some of these early devices cause very strong
stimulation, which to my mind is excessive, as I have repeatedly been made to understand
that for biological effects higher intensity is not always better. For example I have often
been puzzled by the positive effects on pain due to the administaration of minute electrical
fields. This may be due to the fact that the human body has its own very small electrical
fields which do not need much energy for stimulation. To say that the latter is caused by
localized heating is an oversimplification.
SOME MYTHS SURROUNDING EARLY ELECTROTHERAPY
In the early days nobody really knew the exact working mechanism of the electrotherapy
devices and therefore all kinds of special properties were attributed to them. Also numerous
different glass shapes were constructed with the perceived aim to facilitate the effectiveness
of the equipment for specific ailments. It is no wonder that today’s technologists categorize
early electrotherapy as quackery. The subsequent paragraphs are meant to demystify some
of these claims which are still upheld by many present day users.
The first myth to be unraveled is the classification of early electrotherapy as HIGHFREQUENCY treatment. If we were unfamiliar with the electrical operating principle
explained above we would probably assume that the unit puts out a continuous high
frequency signal. However, the above description shows that we are dealing with repeated
very short bursts of damped high frequency oscillations at a low repetition rate of about 100
times per second. To an engineer this looks more like a pulsed low frequency operation
which brings us straight into the domain of today’s popular ‘Micro-Current’ or TENS
equipment with well established therapeutic effects.
Then there is the notion that a specific high frequency is a critical element for the
effectiveness of the therapy. We immediately see the fallacy of this when we realize that the
damped high frequency bursts do not have an exact frequency due to big manufacturing
tolerances let alone the fact that when the glass tubes touch the skin, the frequency is
usually lowered by up to 30%. With modern technology the pulse repetition rate can be
controlled very accurately which is more likely to influence the therapeutic effect of the
equipment.
Some people claim that the effectiveness of the therapy is due to the OZONE produced by
the little arcs which are generated around the glass tubes. These can be considered as
miniature lightning strikes producing minute amounts of ozone. Since this gas is generated
along the entire length of the arcs being perpendicular to the skin, it immediately mixes
with the surrounding air whereby most of it is carried away from the surface of the skin. The
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minuscule amount that gets in touch with the skin could possibly have some beneficial
cleansing effect but to my mind is most certainly not a major explanation for the therapeutic
effect of the equipment.
There are claims that the arc formed when holding the electrode a few millimeters away
from the skin creates enough ozone to heal infected areas as for example acne. In my view
the small diameter of the arc causes a very high current density at the surface of the skin
which destroys bacteria in the area.
When the tiny arcs ‘hit’ the skin, they create minute burn marks only visible under a
microscope. Since the effect is probably much less than our exposure to the environment
we can ignore this effect. However, these little arcs are the only physical sensation felt by
the human body. Because this sensation is originating from the surface of the skin, it can be
expected that the nerve endings just under the epidermis are stimulated. In addition to the
electrical pulse this could be the cause for the possible contraction of the arrector pili
muscles clearing the clogged follicle pores as suggested above. It was also observed that a
flat mushroom like electrode produced very little arcing, which again would point to the
major therapeutic effect of the electrical pulses and not the ozone.
Some of the old equipment is specified as having an OUTPUT VOLTAGE of up to 50 KiloVolts. The voltage specification is totally meaningless, because it is the electrical current
which flows into the skin that causes the therapeutic effect. Much lower peak output
voltages can be used by correctly constructing the glass electrode. I therefore conclude that
such high output voltages are required to compensate for a very inefficient device or that
the stimulation created is excessive.
The output voltage is generated by the high voltage transformer often referred to as the
Tesla Coil shown as “T” in Fig.2. There are those who believe that a special construction of
the coil according to Nicolas Tesla would have an important influence on the therapeutic
outcome, which is totally unacceptable to the rational mind of an engineer because any
transformer has clearly defined properties which can be calculated and verified by
measurements.
Finally I would like to approach the subject of LIGHT generated by the glass electrode.
When the glass touches the skin, the neon or argon gas in the glass tube begins to glow.
The light is generated only during the very short bursts of damped high frequency
oscillations. During that period the light is very bright and will penetrate deeply into the
skin. I know that some of the colours in the wide spectrum of light emitted could have a
therapeutic effect, provided the light energy is high enough. Since the latter is not the case
I consider it sensible to discard this effect. Initial experiments seem to confirm this. On the
other hand I do not know how the cells in the skin respond to the light pulses in
combination with the electrical stimulus and I may want to investigate this further. The light
spectrum for argon gas shows some UV components, while with neon this can be ignored.
Because of the low energy levels there is no danger of UV radiation.
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RELIABILITY ISSUES AND REGULATORY REQUIREMENTS
Early electrotherapy devices are highly inefficient causing the handle to get very hot after a
while. Furthermore, the high voltage transformer generates enough heat to self-destruct
over time mainly due to the melting of the candle wax used for insulation. And then there is
the mechanical intensity adjustment which is subject to considerable wear making the
devices even more unreliable.
Due to the construction, early traditional equipment and modern substitutes all have the
common problem of safety. The long glass tubes not only break easily, but when broken can
expose the user to dangerous electrical shocks. For this reason manufacturers or marketers
state that the intended use is either for experimental purposes only or need to be handled
by professionals. Since mandatory safety standards are generally not met the equipment
cannot be sold freely on the open market.
Another undesirable characteristic of the above equipment is the huge amount of radio
interference generated. In order to meet mandatory standards set by the FCC or CE the
equipment would become not only bulky but could lose its therapeutic effect if the problem
is not handled skillfully. Therefore, this further limits the equipment being sold freely on the
open market.
NEW TECHNOLOGY
With all the evidence of effectiveness of early electrotherapy it is interesting to note that
nobody has thought of making devices suitable for general household use, meeting modern
mandatory regulatory standards. The Internet offers numerous alternative devices powered
by some simple electronic circuits. Not only are these devices potentially unsafe and emit
excessive electrical interference they are not allowed in most countries. They are generally
unreliable because of the inadequate quality of the high voltage transformer, while the
fragile glass electrodes require frequent replacement. Third party liability could become very
expensive in case of an accident. To make sure that a device meets mandatory regulatory
standards, it is sensible to request copies of valid relevant compliant certificates from the
manufacturer prior to purchase.
Manufacturing an economic hand-held device meeting the
required specifications necessitates certain special electronic
components which were not available in the 20th century.
Using latest technology led me to develop a robust, long
lasting, hand-held battery operated device which can be used
anywhere while overcoming all the above mentioned
limitations. Since the product is software driven beneficial
massage modalities can be incorporated.
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CONCLUSION
From the above we conclude that early electrotherapy uses devices producing very short
fast decaying high frequency pulses at a low repetition rate. Due to the construction of its
electrical source, the stimulating pulses reliably reach the dermis, in spite of the insulating
properties of the stratum corneum, which is a great advantage over modern Micro-Current
and TENS equipment for certain applications. Furthermore the low intensity very short
stimulating pulses result in a comfortable form of therapy without any danger of muscle
contractions. While the therapeutic benefits of early electro therapy equipment is well
known, it cannot be marketed because it does not meet mandatory regulatory standards.
With modern electronic components it is possible to design an equivalent device with
outstanding reliability and performance meeting all required standards.
Bernhard S. Rudert BSc Eng.
Copyright © 2011 – 2012 Bernhard S. Rudert
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