THERMAL CONTROL OF LIQUIDS FOR TRANSCUTANEOUS DELIVERY

Abstract

The invention provides a device for controlling the temperature of liquids delivered to the skin during cosmetic, diagnostic, or curative procedures. The invention further provides procedures for treating the skin, including an efficient procedure for removing pigments or tattoos, employing a liquid delivered to the skin with precisely controlled temperature and flowrate.

Claims

1. A device for controlling the temperature of a liquid to be delivered onto or into the skin of a subject, comprising i) a container for storing said liquid at a temperature between above its freezing temperature and ambient temperature; ii) a liquid pump, such as a peristaltic pump conferring a desired flowrate to said liquid; iii) a heat exchanger which heats or cools the liquid to a working temperature up to 60 C., usually between 5 C. and 40 C.; iv) a temperature sensor suitable to detect the temperature of the liquid at the outlet from said heat exchanger; v) a heat pump, such as a solid-state Peltier module in thermal contact with said heat exchanger on one side, and optionally with a fan and cooling heat sink on the other side; vi) a disposable or reusable tip suitable to be placed in contact with said skin and to irrigate the skin with said liquid; vii) a tubing suitable to deliver said liquid from said container to said tip; and viii) a microprocessor or a control system suitable for receiving a temperature reading from said sensor and the flow rate of said liquid pump and for activating said heat pump such that the liquid delivered to said tip is delivered at a desired temperature.

2. The device of claim 1, wherein said peristaltic pump is suitable to control said flowrate with an accuracy of at least 0.01 ml/sec, said tubing comprises a disposable silicone tube, said exchanger comprises aluminum plates provided with a coiled channel for accommodating said tubing and for controlling the liquid temperature with an accuracy of at least 0.3 C.

3. The device of claim 1, wherein said microprocessor is configured to calculate the heat loss along the tubing length, to process the liquid temperatures in said container and exchanger, and said working temperature, and to activate the Peltier module to cool or heat the exchanger.

4. The device of claim 1, further comprising a needles array for puncturing the skin, an actuator designed to repeatedly thrust the needles at a selected frequency into a selected depth of the skin, suction means for removing used liquid after its contact with epidermis and/or dermis, and sealing means preventing an escape or spill of the liquid outside the device.

5. The device of claim 4, further comprising an item selected from the group consisting of: means for eventual rinsing the needles with fresh liquid, means providing separation between the fresh and used liquid, a trigger activating the actuator and the peristaltic pump, an external or internal power source, disposal means for disposing of the used liquid, and a cylindrically or conically shaped disposable tip or delivery member in contact with the skin through which the liquid with precisely controlled temperature and flow rate can be delivered to the skin vicinity.

6. The device of claim 1, wherein its components are suitable for removing a tattoo or pigments from the skin.

7. A cosmetic or aesthetic procedure for treating the skin employing a liquid delivered to the skin with precisely controlled temperature and flowrate, comprising: i) providing a container for storing said liquid at a temperature between above its freezing temperature and ambient temperature; ii) providing a peristaltic pump conferring a desired flowrate to said liquid; iii) providing a heat exchanger which heats or cools the liquid to a working temperature of up to 60 C., usually between 5 C. and 40 C.; iv) sensing a liquid temperature, using a temperature sensor suitable to detect the temperature of the liquid at the outlet from said heat exchanger; v) placing a solid-state Peltier module in thermal contact with said heat exchanger on one side and with a fan and cooling heat sink on the other side; vi) placing a disposable tip in contact with said skin thereby to irrigate the skin with said liquid; vii) providing a tubing suitable to deliver said liquid from said container to said tip; and viii) activating said Peltier module such that the liquid delivered to said tip is delivered at a desired temperature, using a microprocessor suitable for receiving a temperature reading from said sensor and the flow rate of said peristaltic pump.

8. The procedure of claim 7, further comprising i) providing a needles array for puncturing the skin and repeatedly thrusting said needles at a selected frequency into a desired depth of the skin; and ii) sucking the liquid after its contact with epidermis and/or dermis and disposing of it.

9. The procedure of claim 7, comprising removing large tattoos of any color.

10. The procedure of claim 7, further comprising providing an aqueous liquid with an active agent, and pumping it at a precisely controlled temperature and flowrate to the skin without perforating the skin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other characteristics and advantages of the invention will be more readily apparent through the following examples, and with reference to the appended drawings, wherein:

[0017] FIG. 1. is a scheme outlining a device and a system according to one embodiment of the invention; the numbers represent: 1tubing, 2tubing heat sink, 3thermocouple, 4inlet port, 5needles area, 6Peltier module, 7fan heat sink, 8fan, 9set point, 10comparator, 11PWM, 12H-bridge;

[0018] FIG. 2. schematically shows an equipment for removing a tattoo according to WO 2012/140643 with a device for controlling the temperature of the working liquid according to the present invention; the working liquid flows from a stock container located at ambient temperature to a precise peristaltic pump which delivers the working liquid with a high precision even at flow rates of 1-5 ml/min to a pistol-shaped apparatus provided with a temperature sensor, heat exchanger through which the working liquid flows via silicon tubing, and a solid-state Peltier module with a fan, the tubing delivering the working liquid with precisely adjusted temperature to the skin via a disposable tip;

[0019] FIG. 3. shows the pistol-shaped apparatus of FIG. 2 with an opened metal heat exchange part for accommodating a coiled tubing;

[0020] FIG. 4. is a perspective view (from above) of the pistol-shaped apparatus of FIG. 3;

[0021] FIG. 5. is a detail of the rear part of the pistol-shaped apparatus of FIG. 3 in a perspective view (from below), with tubing closed in the heat exchanger;

[0022] FIG. 6. is a detail of the rear part of the pistol-shaped apparatus of FIG. 3 in a perspective view (from above), with exploded view of the heat exchanger;

[0023] FIG. 7. is a rear view of the pistol-shaped apparatus of FIG. 3, with the fan for cooling the Peltier module; and

[0024] FIG. 8. is a detail of the peristaltic pump of the equipment in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0025] It has now been found that the temperature of active liquids used in tattoo removal or various aesthetic treatments, for example liquids delivered onto the skin by a pistol-shaped apparatus for tattoo removal disclosed in WO 2012/140643, can be efficiently controlled by a system comprising precise peristaltic pump connected with said apparatus, thermocouple for sensing temperature in the apparatus, and a solid-state Peltier module integrated in the apparatus, thereby improving the efficiency of the method.

[0026] In one aspect, the invention provides a system for aesthetic, cosmetic or curative delivery of liquids onto the skin, comprising a needles array and a delivery means which supplies the liquid in a predetermined flow rate (typically in a range of about 1-10 ml/min) and temperature (typically in a range of 5-40 C.). FIG. 1 and FIG. 2 show a system in some embodiments of the invention, the main elements being briefly described as follows: [0027] A small infusion bag (13) containing a liquid stock, substantially at room temperature, supplies the liquid to a hand-piece via tube (1). [0028] The delivery is controlled by a precise peristaltic pump (14) capable of metering the flow to an accuracy of typically 0.01 ml/sec and delivering a flow of approximately 0.05 ml/sec. [0029] A disposable silicone tube (1), typically 4 mm OD, which conveys the liquid from the pump through the heat exchanger (2) and then to the needle area (5), via port (4). [0030] A heat exchanger (2) which heats or cools the liquid to a desired temperature (typically in the 5-40 C. range). The heat exchanger is designed to enable quick replacement of the single use silicone tube between treatments and yet provide good thermal contact with the liquid. [0031] A solid-state Peltier module (6) in good thermal contact with the heat exchanger (2) on one side and with a fan (8) and cooling heat sink (7) on the other side. [0032] An assembly (5) consisting of the needles, suction shroud and actuator designed to oscillate the needles at a predetermined frequency, irrigate the skin in the vicinity of the needle and eject the spent solution plus skin fragments (used liquid) by vacuuming the shroud (sealed) space. [0033] A microprocessor receiving the temperature from thermocouple (3), calculating the heat loss between the thermocouple and the skin, and activating the Peltier module (6), whereby ensuring the final predetermined temperature of the liquid when it comes into contact with the skin. This includes a feedback control system consisting of said temperature sensor (3), typically thermocouple of type K or T, embedded in one of the metallic plates of (2), supplying an input signal to a controller and comparator (10) which also contains the set point (9). By proportional control, polarity changeover and PWM (pulse width modulation, 11) output to the voltage applied to the Peltier (6) via H-Bridge (12), the desired temperature is maintained (in both heating and cooling) to an accuracy of0.3 C.

[0034] The following thermal aspects are taken into consideration. The system is required to supply energy to bring the solution from RT to a maximum of 40 C. at a maximum flow rate of 0.05 ml/sec. This requires a heat input of approximately 3 W (Q=m*Cp*T, where Q is heat flowrate, m is mass flowrate, Cp is specific heat capacity, and T is temperature change). The 3 W heat input must be transferred to the liquid in a volume and weight which can be conveniently housed in a hand-piece and which enables simple and quick replacement of the fluid carrying duct. The hand-piece may acquire the pistol-shape of the skin puncturing apparatus for use in eradicating tattoos according to WO 2012/140643 of the same inventors. It is intended to perform this by means of two metallic plates (typically aluminum, 3-4 mm thick) which sandwich the silicone tube in a serpentine groove machined into the plates. One of the plates is heated or cooled by the Peltier element. In another embodiment, the serpentine part of the tube can be replaced by a small infusion bag which is trapped between the two metallic plates. The lower plate is heated or cooled by the Peltier and thus controls the temperature of the liquid. By employing sufficient contact area to minimize the thermal resistance between the plate and liquid, the desired liquid temperature can be held to an accuracy of typically0.3 C. using feedback control from the metallic plate temperature alone. The desired liquid working temperature at the work site, near the needles or the skin, will usually not be significantly different from the liquid temperature in the plate, as a result of the low level of heat transfer from the exposed part of the tube, as our tests showed, and calculations confirmed; however, any losses may be compensated for by slightly increasing the temperature in the hand-piece (indicated by thermocouple 3) relatively to the desired final working temperature (9) (experiments indicated typically not more than 0.1-0.2 W losses between 40 C. and 25 C.).

[0035] The device according to the invention may, in one embodiment, be employed within an apparatus for non-surgical eradication of a tattoo from an area of skin as disclosed in WO 2012/140643. The apparatus of said prior art may be shaped like a pistol comprising handle section and barrel section, wherein the elements of the instant device, as seen in

[0036] FIG. 1, nos. 2, 3, and 6-8 may be comprised in said handle section, and element no. 4 may be comprised in said barrel section of the pistol-shaped apparatus, for example such as member 15 in FIG. 2.

[0037] In one embodiment of the invention, the system for controlling the temperature of a liquid delivered to the skin is integrated with an apparatus for efficiently removing tattoos from the skin, possibly even a multi-color large tattoo, for example an apparatus according to WO 2012/140643. A system or a device according to the invention, integrated into various apparatuses, may comprise elements selected from the group consisting of [0038] a motor for moving a needles-array and the array of needles to be pushed through the outer layer of skin into the dermis and withdrawn from the skin, [0039] an external or internal power source, [0040] a means for pressing the liquid outlet against the skin so that a hermetic seal is created isolating the interior of the barrel section from the outside, [0041] a means for sucking the used liquid away from the skin (the term used liquid relates to the liquid containing cellular fluid and tattoo pigments), [0042] a means for eventual rinsing the needles with fresh liquid, [0043] a means providing separation between the clean and the used liquid, wherein the active liquid preferably comprises water, and further may comprise other solvents, salts, buffers, organic acids, complexing agents, reagents such as including oxidizers, enzymes such as hydrolases, naturally derived components such as plant extracts, and others, [0044] a trigger activating the motor of the prior art apparatus and the peristaltic pump of the invention, [0045] a disposable, cylindrically or conically shaped tip or delivery member in contact with the skin through which the liquid, with precisely controlled temperature and flow rate, is delivered onto and into the skin, [0046] a storage means of the fresh liquid, for example cooled or placed at ambient temperature, and [0047] a disposal means for disposing of the used liquid.

[0048] The system and the device of the invention preferably comprise a microprocessor activating a heat pump, such as a Peltier module, but also other heat exchanging arrangement can be conveniently applied by the user, such as a plastic bag similar to infusion bag which is sandwiched between two suitable plates, wherein the microprocessor comprises data characterizing the system, including the desired flow rate of the liquid to be delivered onto or into the skin, tubing length and diameter of all tubing sections, heat transfer parameters of the involved materials, desired temperature of the liquid on the skin (working temperature), etc., wherein the microprocessor receives also the sensor temperature (from the thermocouple) and the storage temperature of the liquid stock. Of course, when providing the data, a skilled person will employ known relations for heat transfer, as well as for temperature effects on diffusion, including Stokes-Einstein equation, based on the famous Einstein's work on Brownian motion from 1905.

[0049] The prior art liquid delivery apparatuses, particularly the apparatus for eradicating tattoos, lacked the system for controlling the temperature of a liquid being stored at ambient or storage temperature and preferably working on skin at a higher temperature such as 40 C. The invention provides the temperature control for the liquid delivered through a disposable tip or other delivery member by employing a suitable heat pump like Peltier element, with a precise pump, and a simple processor. The system advantageously combines low thermal inertia tubing, heater aluminum plate exhibiting very good thermal contact with the tubing, processor providing accurate calculations, and elements with rapid response and accurate control. The administration of the active solutions onto the skin and into the dermis under isothermal condition improves the biochemical reactivity of the agents and their bonding to the pigments particles, thereby allowing for their eventual transport to an extracellular ambience and removal from the skin. In another aspect, the temperature control leading to a significant reduction of the thermal excursion can have a positive repercussion on the inflammatory induced response. Controlling the temperature contributes to the efficiency of pigments removal and minimizes the potential side effects.

[0050] The invention will be further described and illustrated in the following examples.

EXAMPLES

[0051] Practically, tube wall heat transfer was assessed while using typical values for total resistance, heater plate to liquid, of about 3 C/W, the overall heat transfer being (T/total resistance=3.2 W) for a heating plate temperature of 40 C. and solution temp of 30 C. This heat load can conveniently be supplied by a Peltier element of approximately 3030 mm (such as Ferrotec 9501-127-030) operating at 8V, 3-4 A in contact with a heat-sink/fan assembly. Typical heat-sink thermal resistances are 0.2-0.4 C/W for a 4040 mm footprint. This is adequate to maintain the Peltier at its normal operating temperature. The needed parameters can be easily obtained, including film coefficient of heat transfer, utilizing Reynolds number, Nusselt number, etc., the latter being possibly about 3.6 under usual conditions, providing film coefficient of about 1000 W/(m.sup.2.Math. C.) and liquid side resistance of 1.49 C./W. Tube wall heat transfer is approximately proportional to the tube wall thickness divided by the product of the tube conductivity and the wetted area available for heat transfer; typical values yield a tube wall resistance of 1.59 C./W. An estimate of 0.001 C./W is made for tube to plate interfacial resistance, based on known parameters for soft rubber and assuming good contact. The total resistance may be assessed, for the sake of example, as 1.49+1.59+0.001=3 C/W. Overall heat transferred may be assessed as (TplateTliquid)/total resistance=3.2 W for a plate temperature of 40 C. and a solution temperature of 30 C. This heat load can conveniently be supplied by a Peltier element of approximately 3030 mm (e.g. Ferrotec 9501-127-030) operating at 8 V and 3-4 A in contact with a heat-sink/fan assembly. Typical heat-sink thermal resistance is about 0.2 C/W for a 4040 mm footprint. This is adequate to maintain the Peltier at its normal operating temperature.

[0052] While this invention has been described in terms of some specific examples, many modifications and variations are possible. It is therefore understood that within the scope of the appended claims, the invention may be realized otherwise than as specifically described.