FIELD OF THE INVENTION

This invention relates to a skin cleaning device and method.

BACKGROUND OF THE INVENTION

There is a large market for skin care products and skin cleaning products. For example, there is particular interest in skin cleaning to overcome problems of oily skin.

The pores of the skin comprise a channel which leads to the sebaceous gland, where sebum is produced. Sebum is an oily substance which provides waterproofing and lubrication of the hair and skin. The sebum can give rise to an oily coating on the skin. Newly generated sebum is situated at the base of the pore at the sebaceous gland. The pore shaft contains stored sebum, and released sebum resides on the surface of the skin.

There are different approaches to skin cleaning, including surface cleaning, deep cleaning and manipulation of the sebaceous glands.

Surface cleaning products include brushes and blotting sheets (e.g., sebum absorbing sheets). The effect of surface cleaning only lasts only for several hours since only the superficial sebum is removed, not the sebum in the shaft or sebaceous gland.

Deep cleaning can be carried out using brushes, which can remove sebum in the pore shafts, as well as surface sebum. However, the effect is likely to be limited since the brush hairs move laterally across the pores and can thus not reach deep into the shafts because of the stroking motion. The effect does however last longer than just surface cleaning.

These two cleaning approaches are straightforward, safe and easy to implement as part of a daily skin care routine. However, the cleaning does have to be repeated at least several times per day to remain effective.

Manipulation of the sebaceous glands is also a known approach. For example, intense pulsed light, such as pulsed laser light, may be used to destroy the sebaceous gland using the mechanism of photothermo lysis. Photodynamic therapy has also been proposed to destroy the sebaceous gland based on the use of photosensitizers (e.g. aminolevulinic acid) which produce a photo-toxic effect. These are professional treatments used only for severe medical conditions such as acne and cancer, in which reduced sebum generation is believed to be desirable. However, these approaches are not suitable for home use. These approaches will however give longer term advantages. For example, the treatment can be carried out only once every few weeks or so. Excessive treatment can however cause dry and vulnerable skin, in addition to a risk to the eyes and/or skin caused by overexposure to intense light.

There are known devices which apply suction and heating to the skin for skin cleaning, for example as disclosed in US 5 295 982. This arrangement has a diaphragm which pulsates to create a miniature pumping action at the skin, and a cleaning cloth is then used to clean the skin. This means there are multiple stages to the cleaning process making it complicated for the user to perform each step optimally.

There is still a need for a long lasting skin cleaning approach which is safe and easy to carry out. SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to an aspect of the invention, there is provided a skin cleaning device, comprising a hand held unit, the hand held unit comprising:

a cleaning surface for application to the skin, the cleaning surface comprising an array of orifices; and

a force sensor configured to sense a force applied by the hand held unit against the skin and provide a feedback based on the sensed force.

The device is designed to be pressed against the skin. Each orifice forms a skin cleaning area, which enables the skin pores to be manipulated by the positive pressure applied to the skin as a whole by means of the walls around the orifices. The device provides effective manipulation of the skin with force feedback. The device is moved across the skin in use while maintaining the positive pressure to the overall hand held unit. The speed of movement may for example be in the mm/sec range. The manipulation of the skin then enables more effective cleaning while or after the mechanical operation is complete.

In an embodiment, the hand held unit further comprises a pump configured to provide suction to the orifices. In this way, the cleaning takes place simultaneously with the mechanical operation.

The orifices define cavities to which the suction can be applied. In this way, each orifice forms a skin cleaning area, which enables the skin pores to be manipulated by the combination of the suction within the cleaning area and the positive pressure applied to the skin as a whole by means of the walls around the orifices. The device in this preferred example thus combines positive force applied mechanically with suction applied

pneumatically to provide effective manipulation of the skin and removal of sebum.

Each orifice may be defined at the tip of a raised ridge. This ridge functions to provide a desired pressure to the skin, in response to a particular force applied to the overall device against the skin. The desired pressure causes manipulation of the skin to assist in removal of sebum from the pores.

The device may further comprise a heating unit for providing heating to the skin in the vicinity of the cleaning surface. The combination of heating and pressure application enables even more effective extraction of sebum from the skin pores using the pump.

The heating unit may comprise a near infrared light source. It may be adapted to generate an output temperature which gives rise to a temperature at the skin surface in the range 40 to 45 degrees Celsius.

The skin surface typically has a temperature about 34-35 degrees, and can tolerate temperatures up to around 45 degrees for a reasonably long time (e.g. 10 minutes) with only transient and very mild irritation, which ceases immediately after removal of the heating. The heating is thus preferably controlled to raise skin temperature to no higher than 45 degrees. A temperature range 40 to 45 degrees may achieve a desired decrease in sebum viscosity, to assist in removal of sebum from the skin surface and at least partially from the skin pores.

The device may comprise a handle part, and the force sensor can comprise a spring device between the cleaning surface and the handle part of the device. The spring device compresses in response to a force applied, and the degree of compression can be used to generate an output indicating the pressure being applied to the skin.

The spring device may reach a limit of compression at a limit force

corresponding to a maximum desired force to be applied. In this way, tactile feedback may be provided which informs a user when e.g. a desired force or a maximum force is reached.

An output device may be used to provide an output which is indicative of the force applied. This can be used to guide the user to apply a force which is in a suitable range for the most effective operation of the device. In particular, the force applied influences how the skin will be deformed locally within the skin cleaning areas formed by the orifices. The output may be an audible signal or a visual signal, or else tactile feedback may be used. The output may for example positively indicate when a threshold force level is exceeded, or it may positively indicate when the force is within a desired range.

The range of forces indicated to the user as appropriate may be selected to correspond to a pressure range of IMPa to 5MPa applied to the skin. IMPa may be considered to be a minimum pressing force for the function to take effect, whereas the user may start to feel pain at about 5MPa. The maximum pressure is therefore preferably less than 5MPa.

The array of orifices may comprise an array of elliptical openings or rounded rectangular openings. These shapes allow a compact arrangement of hollows with thin and all-curved (i.e. not presented sharp edges) ridges in between.

Each opening may have a long-axis dimension in the range 4mm to 6mm and a short axis dimension in the range 2mm to 4mm. For example, one preferred size of the opening is 3mm on the short axis and 5mm on the long axis. An opening too small leaves a hollow cavity space which is too small for skin to deform locally. An opening too large disperses the applied force thus diminishes the extrusion effect and also has difficulty adapting to the ups and downs in the skin contour.

The ridges between the orifices may have an average thickness between 0.2mm and 0.5mm. In some embodiments, the ridge might be as thin as possible but without presenting a sharp face, for example no thinner than 0.2mm. Ridges that are too thick shield pores beneath the ridge area from being pressed, and thus reduce efficiency.

The pump is for example connected to a suction duct having a hood which opens out to the array of orifices. A filter may be provided in the suction duct. This can be replaceable or cleanable to provide a device with a long lifetime.

The hood may comprise transparent or translucent portions and reflecting portions, wherein the heating unit is mounted outside the hood, and the heating unit output is directed to the skin in the vicinity of the cleaning surface through the transparent or translucent portions. This enables direction of the heating energy to the desired skin location.

Examples in accordance with another aspect of the invention provide a skin cleaning method, comprising:

applying a hand held unit against the skin, the unit having cleaning surface for application to the skin and which comprises an array of orifices;

sensing a force applied by the hand held unit against the skin; and providing a feedback based on the sensed force. Heating may also be applied to the skin in the vicinity of the cleaning surface, and suction may be applied to the orifices.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 shows a cross section through a skin pore;

Figure 2 shows a skin cleaning device in accordance with an embodiment of the invention;

Figure 3 shows one orifice area according to an embodiment of the invention;

Figure 4 shows one example of design of the orifices according to an embodiment of the invention;

Figure 5 shows the effect of heating on the sebum viscosity according to one publication; and

Figure 6 shows one implementation of force sensor using a spring.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention provides a skin cleaning device, comprising a hand held unit which has a cleaning surface for application to the skin, which comprises an array of orifices. Pressure is applied to the device in use, to manipulate the skin to assist in the removal of sebum. A force sensor is provided for sensing a force applied by the hand held unit against the skin so that a user can be given guidance as to the desired force to apply for optimum effectiveness of a cleaning function being applied or to be applied subsequently. In a preferred embodiment, suction is applied to the orifices to remove sebum.

Figure 1 shows a cross section through a skin pore 10. The sebaceous glands

12 are at the base of the pore shaft 14. Newly produced sebum 16 is at the very base of the pore shaft, and the shaft stores sebum for release to the surface of the skin 18. The surface sebum is shown as 19.

Figure 2 shows an example of skin cleaning device 20 in accordance with an embodiment of the invention.

The device is a hand held unit which has a cleaning surface 22 for application to the skin, which comprises an array of orifices 24. In the example of Figure 2, a pump 26 is used for applying suction to the orifices. A force sensor 28 is used for sensing a force applied by the hand held unit, more specifically, by the cleaning surface 22, against the skin. The cleaning surface 22 can be dome shaped or flat.

The device 20 is designed to be pressed against the skin. The orifices define cavities, and in one set of examples, suction is applied to these orifices. In this way, each orifice forms a skin cleaning area, which enables the skin pores to be manipulated by the combination of the suction within the cleaning area and the positive pressure applied to the skin as a whole by means of the walls around the orifices. The device 20 then combines positive force applied mechanically with suction applied pneumatically to provide effective manipulation of the skin and removal of sebum. The device is moved across the skin in use while maintaining the positive pressure to the overall hand held unit. The speed of

movement may for example be in the mm/sec range.

In an embodiment, the device 20 combines a downward pressing force and an upward suction force from the pump 26 to exert an outward pressure gradient to the subsurface sebum. When the cleaning surface is pressed onto a skin area, the ridges around the orifices are pressed in tight contact with the skin surface. The skin located within the orifices is lifted by the ridges, forming a sealed cavity within the device. In particular, the pressing action alters the stress distribution in the skin tissue and enlarges the hair follicle openings. For entrapped follicular contents, including primarily sebum, and secondarily dirt particles, inflammatory products, dead cells and the mixture thereof, the enlarged orifices ease their outflow from the follicular duct and enhance their exposure to cleaning actions.

In consequence, more effective sebum removal from its reservoir beneath the skin surface becomes possible. The device avoids skin discomfort, and ensures no pain or only mild and transient pain. It can be used safely, repetitively and conveniently in essentially all environments, as long as certain sanitary measures are taken.

A low cost implementation of force sensor 28 can be a spring device sitting between the cleaning surface 22 and the device body 30. The device body 30 can extend over the spring device so that the spring is internal to the device. Those skilled in the art should appreciate that other types of force sensor that could detect the force applied by the cleaning surface to the skin are, if suitable, also covered by the scope of the present invention.

The relative positions of the device body and the cleaning surface can be used to indicate the force applied. For example a hood may slide in and out, and the hood edge can move against force markings. The hood edge is thus used to indicate the relative movement between the body and the cleaning surface. Two fixed markers can be used to indicate a lower force limit and an upper force limit, between which the pressing fierce should be applied effectively and safely.

In a most simple embodiment, the upper limit of the pressing force can be arranged to compress the spring to its shortest length, thus giving the user a haptic feedback.

Experiments show that a minimum pressing force of around IMPa is suitable to ensure some effective skin manipulation takes place. The skin can start to feel pain at about 5MPa pressure, so the maximum pressure is preferably no higher than 5MPa.

The pump applies negative suction pressure, which may for example in the range lOOkPa to 3MPa.

The output of the force sensor can be visual as in the example above, but it may be audible as well or instead.

Figure 2 shows that the pump 26 is connected to a suction duct 32 having a hood 34 which opens out to the array of orifices 24. Where the hood opens out, it has a conical shape. A sealed cavity is formed, defined by the suction duct, the hood, the skin closing the orifices and the pump. A filter 36 is provided in the suction duct. This can be replaceable or cleanable to provide a device with a long lifetime.

Figure 3 shows that each orifice 24 may be defined at the tip of a ridge 40.

This ridge 40 functions to provide a desired pressure to the skin, in response to a particular force applied to the overall device against the skin. The cleaning surface has a designed size and shape, and configuration of orifices to provide the desired skin manipulation. The ridges may be defined simply by having the orifices close together so that the space between them forms a thin ridge.

Figure 4 shows one example of design of the orifices according to an embodiment of the invention. As shown in Figure 4, the array of orifices 24 may comprise an array of elliptical openings or rounded rectangular openings or both. These shapes allow compact arrangement of hollows with thin and all-curved ridges in between.

Each opening may have a long-axis dimension in the range 4mm to 6mm and a short axis dimension in the range 2mm to 4mm. For example, one preferred size of the opening is 3mm on the short axis and 5mm on the long axis. An opening too small leaves a hollow cavity space which is too small for skin to deform locally. An opening too large disperses the applied force thus diminishes the extrusion effect and also has difficulty adapting to the ups and downs in the skin contour.

The ridges between the orifices may have an average thickness between

0.2mm and 0.5mm. The ridge should be as thin as possible but without presenting a sharp face, for example no thinner than 0.2mm. Ridges that are too thick shield pores beneath the ridge area from being pressed, thus reduce efficiency.

For improved performance, the device may optionally further comprise a heating unit as shown in Figure 2 as item 50. This provides heating to the skin in the vicinity of the cleaning surface. The combination of heating and pressure application enables even more effective extraction of sebum from the skin pores using the pump.

The heating element irradiates energy to the skin region in contact simultaneously with the pressing action. The heating element is configured to selectively increase the temperature of sebum underneath the surface of the exposed skin area. The elevated temperature reduces viscosity and surface tension of sebum, leading to a decrease in the resistance to sebum flow to the skin surface.

The effect of heating on sebum excretion has been investigated by Burton J. L., in "The Physical Properties of Sebum in Acne Vulgaris" in Clinical Science 1970 vol. 39, pp. 757-767.

Figure 5 is taken from that publication and shows the effect temperature has on sebum viscosity measured at the forehead (solid line) and scalp (dotted line). The x-axis is temperature in degrees Celsius and the y-axis is the viscosity in Poise. It shows the significant reduction in viscosity which arises from an increase in temperature from room temperature (e.g., 20 degrees) to 40 degrees.

The heating unit may comprise a near infrared light source for example to provide a temperature at the skin surface in the range 40 to 45 degrees. The heating source is selected to have relatively high absorption coefficient for sebum in comparison with that of the surrounding tissue.

The heating element can comprise a monochromatic light source with a wavelength of about 1210nm, 1720nm or 1760nm, where sebum has been found to have absorption peaks. This means the heating source can selectively increase the temperature of sebum underneath the exposed skin surface. The increased temperature reduces viscosity and surface tension of sebum, and thus reduces the resistance to the emergence and removal of the sebum.

The hood 34 has transparent or translucent portions 52 and the heating unit 50 is mounted outside the hood facing these transparent parts. The heating unit output is directed to the skin in the vicinity of the cleaning surface through the transparent or translucent portions. This enables direction of the heating energy to the desired skin location. Reflecting portions can be used for the remaining part of the hood to contain the heating energy and redirect the heating to the skin.

The level of heating and the amount of suction applied by the pump may be correlated. For example when heating to above 40 degrees Celsius, a suction pressure near the low end of the range lOOkPa to 3MPa may be used, whereas a higher pressure may be need for if the temperature is nearer to normal skin temperature

None of the existing cosmetic devices employing mild or moderate energy either in rinsing, wiping, abrasion, or sucking actions, can achieve a long-lasting effect against facial oiliness. This is because, compared with surface sebum, a larger volume of sebum is stored beneath skin surface, i.e., in the ducts of sebaceous glands and follicular infundibulum, and continuously flows to skin surface. The technical obstacle in deep cleaning of sebum is that the semi-solid sebum with high viscosity has to overcome very high resistance when exiting through the thin follicular duct and tiny orifice. The narrow paths also limit the exposure of the sebum stored in follicular duct to the removing force applied onto the skin surface. The combination of heating, local skin manipulation under pressure and suction provides particularly improved sebum removal.

The suction (when used) can be combined with wiping, dabbing or other cleaning actions.

The device includes driver circuitry for operating the pump and heating source (if present) and driving a user interface. The device also preferably includes a battery although it may simply be mains operated. These components have not been shown for improved clarity of the drawings.

The force sensor has been described above as a purely mechanical device, which shows to the user the degree of compression of a spring.

Figure 6 shows one possible design in more detail. A top hand-held part 60 of the device housing has a recess which retains a spring 61. A projecting part of the bottom part 62 of the device projects into the recess, and the relative positions of the bottom part 62 and the hand-held part 60 determine the degree of spring compression. This can be read out in a simple manner using a scale 64. The degree of overlap between the two parts 60 and 62 can be read out and provides a force indication.

There are numerous force sensor designs other than the purely mechanical hooded spring arrangement shown. Essentially, a force-sensitive material or structure is provided within the device housing which for example converts force into an electric signal which then can easily be compared against thresholds. An electric pressure sensor can be used for this purpose. When a predefined range is exceeded, a light or sound indicator is triggered for the user.

The force sensor can function as a limiter. For example when the two parts 60,62 bottom out, this will be felt by the user and this information can be used to instruct the user to limit the force they apply. The force sensor can alternatively function as an indicator, for example using light, sound, a display panel or a mechanical representation as in Figure 6. These two functions of force indicating and force limiting can of course be combined.

Other force sensors may be used. They may be mounted at the cleaning head to detect the force as applied to the skin, or they may be mounted within the device in the same way as the spring described above and shown in Figure 6.

The force feedback may be applied to a device which does not use suction. In this case, the device performs a skin manipulation function to assist in subsequent cleaning, instead of proving simultaneous cleaning and skin manipulation operations.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.