SONIC METHOD AND APPARATUS FOR COSMETIC APPLICATIONS
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to sonic devices for medical and cosmetic
applications More particularly the invention is concerned with methods
and apparatus facilitating the use of sonic energy coupled to anatomical tissue to precondition the skin to allow the penetration of medical and
cosmetic compounds, and to drive these compounds into and through the
epidermis into the dermis These compounds may be generally referred
to as therapeutic agents
Description of Prior Art
Numerous attempts have been made in the past to deliver
medications and cosmetic compounds into the skin by chemical, electrical
and ultrasonic means The application of chemicals to modify the skin
structure to allow the penetration of drugs was found to be dangerous because while it provided access for drugs to penetrate, it left the body
unprotected against harmful environments The application of electrical
fields to create transient transport pathways by a method called electroporation, and the method to electrically charge drug molecules to increase their penetration through the skin called iontophoresis, have
both been proven ineffective to deliver therapeutically adequate dosage of medications through the skin Past applications of high frequency (0 5 to 3 megahertz) and high intensity (0 5 to 5 W/cm2) therapeutic
ultrasound, called sonophoresis, were found to be uncertain, inefficient,
and the method found limited applications
The efforts of the prior art of ultrasonically induced drug delivery (sonophoresis) which were focused on driving drug molecules through the skin by the applications of high (megahertz) frequency high energy
ultrasonic pressure waves particularly suffered from the disadvantage of
tissue heating and the associated modification and sometimes destruction of healthy cells Once adequate ultrasonic power is applied either in a
continuous wave ultrasonic modality, or maximum burst length that were practicable without adverse tissue heating effects to force cosmetic
compounds through the highly resistive outermost sealing layer of the
skin, the stratum corneum (SC), the cosmetic compounds will proceed
uncontrollably through the less resistive dermis into the blood system,
creating systemic absorption of the cosmetic compounds which is
undesirable in most cosmetic applications
What has occurred to date is that notwithstanding the teachings of
the prior art, the ability to deliver large molecular weight cosmetic
compounds, such as proteins, vitamins, moisturizers, etc , into the deeper layers of the skin remained unresolved SUMMARY OF THE INVENTION
Responding to the above described unresolved needs, the object
of this invention is to provide a method and apparatus for the pre¬
treatment of the skin to open up passage ways through the epidermis to
allow the penetration of therapeutic agents
Another object of the invention is to provide a method and apparatus to enhance the penetration of therapeutic agents into the deeper layers of the skin, past the stratum corneum
In the method of the invention, sonic pressure waves are applied
to the skin of sufficiently high intensity to cause sonic vibrations within the skin A therapeutic agent is applied to the skin either before or promptly
after the sonic pressure waves are applied to the skin
The apparatus of the invention includes a rigid handle portion and
a flexible applicator portion The handle portion supports means for
producing vibrations which cause the applicator portion to vibrate in a
linear manner so as to transmit sonic energy to the skin and cause sonic
vibrations within the skin
The depth of penetration of the therapeutic agent is controlled by
applying sonic pressure waves in repetitive burst type modality, and
ultrasonic pressure waves may be applied between the bursts of sonic
waves BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 shows a cross sectional view of the skin and the invention
designed for developing passage ways in the stratum corneum and to
enhance the penetration of therapeutic agents into the skin under the force of sonic pressure waves,
Fig 2 shows a perspective view of the invention,
Fig 3 shows the conversion of the rotational vibrations of the handle into linear vibrations of the flexible applicator tip, and the
separation of the resulting linear vibrations into vibration vectors
perpendicular and parallel to the skin, and
Fig 4 shows a modified form of the invention
DESCRIPTION OF THE PREFERRED METHODS AND EMBODIMENTS
Referring in detail to the drawings, the reference numerals herein
refer to the like numbered parts in the drawings In the following discussion, unless otherwise qualified, the term "sound" or "sonic waves"
refer to either continuous sound waves or a repetitive burst type or pulsed
sonic wave modality, and refer to audible frequency sound waves, typically at frequencies between 15 hertz to 25 kilohertz A sonic skin conditioning device 1, in accordance with the simplest
form of the present invention, is shown in FIG 1 The skin conditioning
device 1 comprises of a rigid handle 16 and a flexible applicator end 3 These components may be formed of plastic or metal and the like. The
handle contains an electric motor 13 with a weight 11 mounted
eccentrically on the rotatable output shaft 17 of the motor. The handle 16
has a removable end portion 22 which contains a replaceable battery 14.
The battery 14 is connected to the motor 13 via switch 15 and electrical
conductors including lines 23 and 24.
When the user energizes motor 13 by closing switch 15, the motor
13 will rotate the eccentrically mounted weight 1 f about the shaft 17,
generating rotary vibrations of the entire handle 16 about its central axis
X as shown by arrow 4. The flexible applicator end 3 is designed to
resonate between about 15 hertz and 25 kilohertz, coinciding with the
vibration frequency generated by the motor 13. The vibrating flexible
applicator end 3 acts as a transducer converting the rotary vibrations of
the body 16 indicated by curving arrow 4 into linear vibrations of the
applicator end 3 indicated by arrows 7 and 8.
The outermost skin layer, the stratum corneum 10, consists of flat
dead cells filled with keratin fibers that are surrounded by ordered lipid
bilayers. This ordered structure of the lipid bilayers normally provides an impermeable protection of the anatomy and prevents the entrance of
medical and cosmetic compounds into the deeper layers of the skin. The
linear vibration vector in the direction of arrow 7, in frequencies between
about 15 hertz and 25 kilohertz, creates corresponding frequency sonic wave vibrations indicated by lines 2 in the stratum corneum 10. The sonic
wave vibrations 2 create physical vibrations which separate and
disorganize the lipid bilayers. The disorganization of the lipid bilayers
temporarily eliminates the barrier properties of the skin, and provides
penetrable channels for medical and cosmetic compounds along paths
indicated by arrows 26 through the epidermis into the deeper layers of the
living skin and the underlying tissues. A body 20 of a therapeutic agent
is shown in Fig. 1 as being disposed between the outer surface of the skin
and the applicator portion of the skin conditioning device. Body 20 is
applied to the skin manually, and then is engaged by the applicator portion so that the sonic pressure waves are applied through the therapeutic agent into the skin. In another method of the invention, sonic
pressure waves are first applied to the skin to cause sonic frequency
vibrations within the skin. The pressure waves are then terminated and a therapeutic agent is promptly applied to the skin before the natural
function of the person's body decreases permeability of the skin.
Fig. 2 shows a perspective view of the invention to explain the
conversion of the rotary vibration pattern of the handle 16 along the
curved arrow 4 into the linear vibration pattems of the flexible applicator
end 3 along the arrows 5 and 6. The flexible applicator end 3 is designed
to have a wide relatively inflexible dimension in the direction of arrow 5
and a thin, flexible dimension in the direction of arrow 6. The thin section of the flexible applicator end 3 is designed such a way that its natural
resonant frequency coincides with the vibration frequency generated by
the motor 13 and the eccentrically mounted weight 11 shown in FIG 1
The vibration amplitude of the applicator end 3 is minimized in the
direction of the thick dimension indicated by arrow 5, and maximized in
the direction of the thin dimension indicated by arrow 6 It should be
understood that the flexibility of applicator end 3 must be such that is
capable of vibrating in the desired frequency range much in the same
manner as a tuning fork Fig 3 shows separation of the linear vibration of the flexible
applicator end 3 in direction 6 into vibration vectors in the direction of
arrow 7 perpendicular to the skin and the direction of arrow 8 parallel to
the skin The vibration vector perpendicular to the skin in direction 7
transfers the mechanical vibration into sound wave vibrations 2 in the
tissues to disorder the lipid bilayers within the stratum corneum 10 The
sound wave vibrations 2, sometimes called sonic pressure waves, also
act to drive the therapeutic medical or cosmetic compounds into the
deeper layers of the skin past the stratum corneum The vibration vector
parallel to the skin in direction 8 is utilized to spread the medical
therapeutic or cosmetic compounds on the outer surface of the stratum
corneum 10 Referring to Fig 4, a modified form of the skin conditioning device
includes an applicator portion 32 having an inner end portion 34 which
has a friction fit within a complementary recess within the handle This arrangement enables the applicator portion of the device to be readily removed for cleaning or replacement when desired
A method to control the penetration depth of therapeutic agents
under the influence of sonic pressure waves was discovered by applying sonic pressure waves in a burst type modality When the sonic pressure
waves are applied in such a modality, for example, for one-tenth of a
second, followed by a pause of nine-tenths of a second, the burst width is one-tenth of a second and the repetition time is one second Therefore, the duty cycle is ten percent The depth of penetration of therapeutic
agents for a particular application frequency is proportional to the burst
width of this frequency When a burst is terminated and the sonic
pressure waves are stopped, the molecules passing through the passageways will also stop When the next burst is applied, it tends to
introduce new molecules into the passage, finding channels which are still open rather than the partially blocked channels caused by the previously introduced molecules Therefore, to limit the penetration depth of the
therapeutic agents, very short, microseconds length bursts are applied
To deepen penetration, the burst width is increased, keeping molecules
introduced into the passageways moving The dosage delivered is proportional to the sum of the sonic energy applied Therefore, to deliver
a particular dosage into the top layer of the skin, a large number of very
short bursts are applied To deliver the same dosage deep into the skin
and into the underlying tissues, a smaller number but longer duration
bursts are applied
It was also discovered that high frequency ultrasonic waves in the
megahertz frequency range tend to help the body reestablish the order of the lipid bilayers This knowledge can be utilized to limit the penetration
depth of the therapeutic materials under the influence of sonic pressure
waves to the stratum corneum In this enhanced method, short burst
width pulsed modality sonic waves in the frequency range of 15 hertz to 25 kilohertz are applied to the skin to enhance the penetration of
therapeutic agents, followed by the application of megahertz frequency
low intensity noncavitating ultrasonic waves, instead of the pause
described in the previous method above The megahertz frequency range ultrasound produces gentle angstrom wavelength vibrations in the stratum corneum which tends to reorder the lipid bilayers, and contain the penetration of the therapeutic agents within the stratum corneum A
typical sequencing, for example, is one-tenth of a second low frequency
(15 hertz to 25 kilohertz) sound wave burst followed by a nine-tenths of a second high frequency (megahertz frequency range) ultrasonic wave
burst While the preceding description contains many specificities, these
should not be construed as limitations on the scope of the invention, but
rather as an exemplification of a preferred and additional embodiments
thereof Many other variations are possible The important element of the
method invented is the generation and application of linear vibrations perpendicular to the skin to generate sonic pressure waves toward the deeper layers of the skin past the stratum corneum These linear
vibrations can be generated by numerous ways other than conversion of
a rotary vibration into linear vibration For example, a piezoelectric transducer placed on the surface of the skin driven by a sonic frequency power supply could achieve the same result Skilled artisans will readily
be able to change dimensions, shapes and construction materials of the
various components described in the preferred embodiment and adapt the
invention to various types of applications Accordingly, the scope of the
invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents