Green function daily chemical product innovation center of South China Collaborative Innovation Research Institute,China

Deng Yanning

Dongguan Huagong Chuangwei Biotechnology Co.,Ltd.,China

Abstract In view of the fact that wet-cloth facial masks are complicated in components and low in utilization efficiency of active ingredients,an all-solid-state nanofiber facial mask was innovatively developed.In the paper,brief introductions were given to the formation mechanism,microstructure and structural features of the nanofiber facial mask.High-molecular polymer and active ingredients were directly turned into nano cellosilk and a piece of nanofiber membrane of micrometer thick was span onto the receiving base cloth.Compared with common wet-cloth facial mask,nanofiber facial mask has less additive ingredients but works more effectively.For example,it is easy to apply,good at water retention,excellent in loading capacity and biocompatibility.The paper ended with existing problems with materials of all-solid-state nanofiber facial mask,its development orientation and application prospect.

Key words nanofiber technology; facial mask; slow-release

Driven by market demand,the facial mask market in China has been expanding rapidly and has become the largest one around the world,with its average annual growth rate predicted to be about 15%in the next five years.In 2023,China’s facial mask market will exceed 30 billion yuan.[1]Facial mask is one of the important cosmetics for facial skin care.Today the mainstream and most used is the wet cloth mask,that is,to apply a facial mask containing various substrates supplemented with nutrients and drugs to the face,allowing the moisture and nutrients in the mask to penetrate into the stratum corneum of the skin in a short period of time to realizesome skin care effect.[2]Nowadays,the carrier materials for face-mounted facial masks sold on the market in China include biological fibers,silk fibers,hydrogels,bamboo charcoal fibers,viscose fibers,and so on.[3]Generally,non-woven fabric materials are adopted as the carrier for essence.Ordinary non-woven fabricshave poor skin affinity and commonplace air permeability.The non-woven fabrics,which consumes petroleum resources during the production process,is a disposable material and it is hard to be degraded in the environment.[4]What’s more,facial mask cosmetics usually contain preservatives,which may be allergens.Also,facial masks are also susceptible to external environmental factorslike temperature,air and light,probably generating some harmful microorganisms,which may cause deterioration of the mask and cause skin allergy reactions.

In this regard,we propose a new presentation form of facial mask: the polymer and active ingredients are spun directly on the receiving substrate with a electrospinning technique,so that the active ingredients are directly fibrillated,and a solid nanofiber mask is made.The production process of this type of nanofiber facial mask is green,environmentally friendly,and water-free,with no preservatives,emulsifiers,flavors or fragrances,except for carrier polymers and cosmetic active ingredients,the truly “minimalism” of ingredients.The safety evaluation confirms that this nanofiber mask has the advantages of being mild,safe,environmentally friendly,green and sustainable;In addition,it touches softer,applies closer to skin,with high porosity,stronger water holding capacity,and good biocompatibility.

Nanofiber technology

Nanofiber refers to the ultrafine fiber with the diameter of tens to hundreds of nanometers.The nanofiber molding technology is a technical means to process polymers of different properties and molecular weights and active ingredients into nanometer-scale fibers by the electrospinning process.Compared with ordinary fiber,nanofiber has the advantages of a large specific surface area,high porosity,a ultra-high aspect ratio,etc.,with broad application prospects in the fields of filtration[5],lithium battery separators,[6]tissue engineering scaffolds,[7]cosmetics,[8]etc.Professor Cheng Jianhua’s team first proposed the idea of applying the nanofiber technology to the field of cosmetics,that is,to directly spin the polymer and active ingredients into composite nanofibers,so that the active ingredients are uniformly attached to the interior and surface of the composite nanofibers,and form a solid nanofiber mask after being dried and solidified,i.e.masked essence.With this production principle,thousands of facial masks can be produced at one time,including key core technologies,industrial parameters,the combination of facial mask liquid and the preparation of key facial masks.Figure.1 shows the scanning electron microscope image of the nanofiber facial mask,from which it can be seen that the fiber diameter of the facial mask is about 100 nm.

Figure 1.Scanning electron microscopy of nanofiber mask

What’s more,through liquid chromatography detection and analysis,it is found that during the production process of nano-spinning facial mask,the functional ingredients will not be denatured,with activity dramatically maintained.Compared with traditional masks,nanofiber masks can achieve better skin care effects while reducing the amount of functional ingredients.

Features of nanofiber facial mask

The nanofiber facial mask (also called masked essence) has four major advantages over the ordinary non-woven facial mask or the freezedried facial mask: the nanofiber structure has a large specific surface area and excellent porosity,which significantly increases the loading capacity of active ingredients in the mask; the nanofiber has perfect adhesion and biocompatibility to the skin,so that the active ingredients can better contact the skin and penetrate into the skin quickly; the nanofiber shows excellent moisturizing and water-holding properties,so the nanofiber mask can effectively lock the moisture in the face; with different carrier polymers selected to control the dissolution rate of the mask,the nanofiber can be dissolved instantly once exposed to water,releasing functional molecules,and realizing providing a fast skin care experience in 5 s.Below the major functions were introduced.

High load rate

The nanofiber has a large specific surface area and shows obvious advantages in loading active substances in nanofiber masks.Additionally,the nanofiber mask can also achieve a slow-release effect on active substances.Ye Long[9]employed regenerated silk fibroin and polyethyloxazoline as raw materials,and directly encapsulated fragrance in the silk fibroin nanofibrous membrane of the core layer.The coaxial fragrance-carrying fibrous membrane has higher fragrance loading efficiency,and its fragrance releasing behavior shows noticeable slow-release characteristics.Zhao Huihui[10]prepared a multi-scale structure of PA6 nanofibrous membrane,which is composed of main fibers with a diameter of 50～120 nm and branch fibers with a diameter of 10～50 nm.Due to the appearance of branch fibers,the specific surface area of the nanofiberof a multi-scale structure is increased,which can provide more attachment sites for the loading of silver nanoparticles.Mary Haba Beclay[11]prepared a quercetin/hordein nanofibrous membrane system with different drug loadings,in hope of successfully developing a slow-release system for functional active substances.

Excellent adhesion

The base fabric used in the non-woven fabric mask is generally prepared with a spunlace technique,and its fiber is relatively coarse,about a dozen microns or so.Since this fiber has a small aspect ratio,high rigidity,and hard hand feeling,the nonwoven mask generally has a poor face-mounted feature.The fibrous diameter of the nanofiber mask is between tens of nanometers to hundreds of nanometers,and the diameter of the grooves on the human skin surface is basically 50～60 nm.Therefore,the nanofiber can smoothly penetrate into the skin grooves,greatly increasing the contact area of the nanofiber mask with the skin,and improving the adhesion of the skin to the nanofiber mask.[12]

Good biocompatibility

High polymers such as cellulose,protein,hyaluronic acid,etc.can be adopted to prepare nanofiber facial masks with marvelous biocompatibility.Cao Xiying[13]discussed the cellular compatibility of polycaprolactone nanofiber scaffolds with high porosity,and the study found that polycaprolactone nanofiber scaffolds with high porosity have no significant effect on cellular morphology,and the adhesion,proliferation and metabolic activity of seed cells on the new scaffold are better than the traditional one.Experiments have proved that the polycaprolactone nanofiber scaffold displays awful biocompatibility.Qian Yuqiang[14]discussed the biocompatibility of olfactory ensheathing cells and silk fibroin nanofibers,and it was confirmed that silk fibroin nanofibers have fantastic biocompatibility.This research provides a fantastic tissue engineering scaffold material for repairing spinal cord injuries.Tan Wuyuan[15]studied the effect of the gelatin/polycaprolactone composite nanofiber scaffold on the wound healing of rabbit skin defects and that on the adhesion and proliferation of mesenchymal stem cells in the marrows of the rabbit.The study found that the gelatin/polycaprolactone composite nanofiber scaffold also has singular biocompatibility.The main reason why the nanofiber hasremarkable biocompatibility is that the high porosity of nanofibrous membranes provides sufficient space for cellular proliferation and adhesion and exchange of nutrients and signals.The nanofiber has a guiding effect on cells.The nanofiber provides a larger surface area and a three-dimensional environment for the cellular growth,which can support the cellular growth for a longer period of time.In addition,the nanofiber mask with special effects can sterilize,reduce inflammation and repair the wounds on the skin.

Good moisture retention

When the mask is applied to the user’s face,the temperature of the face will rise,and the essence in the mask will gradually evaporate,so the mask should have somewhat moisture retention.Studies have found that the evaporation amount of the essence is directly related to the water vapor transmission rate of the mask substrate.Compared with the ordinary non-woven fabric mask,the nanofibrous membrane has a small pore size and high porosity,which is not conducive to the volatilization of water vapor.Therefore,the nanofiber mask can effectively lock the facial moisture.What’s more,the nanofiber mask also shows significantly better performance in water absorption than ordinary masks.Due to the high porosity of the nanofibrous structure,the nanofiber mask under the same weight can carry more essence.Therefore,the nanofiber mask is more waterretaining than ordinary masks.

Products of nanofiber facial mask

Based on the above-mentioned advantages of the nanofiber,our team employed it in facial mask products,and directly formed the functional ingredients of cosmetics into the soluble nanofiber,a high-tech allsolid instant nanofiber product.On the one hand,the nano-scale fiber has a large specific surface area,a high loading rate of functional ingredients,and high activity of functional ingredients.On the other hand,the nanoscale fiber is more applicable for the skin texture,and instantly dissolves in the spray solution,releasing functional molecules.The functional molecules can quickly penetrate into the skin and exert their effects.

The nanofiber molding technology is a platform technology that can customize nanofiber membranes with different functions in accordance with consumer demands.This new type of nanofiber mask product fully meets the demands of modern young women for skin care in a “fast”,“convenient”,“safe and effective” manner.It is a targeted,fast and efficient first-aid functional skin care product,suitable for all kinds of use demands.It can also realize zoned or partial careto realize precise skin care,for example,an eye mask that can be applied to the eye area to reduce wrinkles and improve dark circles/eye bags,acne patch,etc.So far,the team has successfully developed a variety of slow-release nanofiber masks for different purposes,instant nanofiber masks,and skin care patches with different functions.

Slow-release nanofiber facial mask

The slow-release nanofiber facial mask,a composite nanofibrous membrane prepared through mixing functional ingredients and polymers with the nanofiber technology,is in a solid state and will gradually release the functional ingredients after contacting with water to achieve the purpose of being absorbed by the facial skin.The release rate of the functional ingredients of this slow-release nanofiber mask is affected by the diameter of the nanofibers and the amount of active substances added.Jiang Yanyan[16]employed the nanofiber technology to prepare drug-loaded PLA/SF composite nanofibers with the drugs aspirin,polylactic acid (PLA) and silk fibroin (SF).The results showed that the average diameter of the composite fiber reduces with the increase of the powder mass fraction,the release rate of the composite fiber is the largest when the SF mass fraction is 3%,and the drug release rate rises with the increase of the powder mass fraction.

Instant-dissolving nanofiber facial mask

The instant-dissolving nanofiber facial mask refers to a dry facial mask directly prepared with the nano-forming technology by using water-soluble polymers and active substances.The nanofibers of this dry mask can be dissolved instantly once exposed to water,which can achieve a skin care experience in 5 s.The use diagram is as shown in Figure 2.The Figure 2(a) shows that the instant nanofibers are uniformly attached to the surface of the lace cloth before use.After spraying a small amount of water,it can be seen from Figure 2(b) that the nanofibers attached to the surface of the lace cloth quickly dissolve.Nanofibers can carry a variety of cosmetic active ingredients,such as small molecule sodium hyaluronate,ultra-low molecular Dendrobium polysaccharide,okra polysaccharide,nicotinamide and other high-active ingredients,which are quickly released and absorbed by the skinwhen nanofibers contact water.

Figure 2.The use chart of instant nano fiber mask: (a)before use,(b) after use

The Chick embryo chorioallantoic membrane test (HET-CAM) is used to evaluate the eye irritation of the nanofiber mask.And the rabbit experimental is employed to evaluate the skin irritation of nanofibers.The human body closed patch test is used to evaluate the adverse effects of the human body.The experiments have confirmed that the nanofiber mask is safe and non-irritating,and the effects of nanofiber masks with different functions on the human body are objectively evaluated through instruments such as the moisture content test probe (CM825),the skin transdermal moisture loss probe (TM330),and the facial imager VISIA-CR,etc.

In order to enhance the skin barrier function and improve skin elasticity,volunteers use anti-wrinkle nanofiber facial masks.The local effects as shown in Figure 3.It can be clearly observed that the skin folds at the corners of the volunteers’ eyes become shorter and shallower ,after using the mask for 30 minutes.So the anti-wrinkle effect is impressing.

Figure 3.Local effect map of wrinkle resistant nano fiber mask before and after using 30 minutes

The anti-allergic nanofiber facial mask can effectively relieve skin sensitivity.With capsaicin emulsion as a stimulus source,a skin neuropathic tingling model is established,and a capsaicin stimulating test is performed on volunteers.The skin redness is as shown in Figure 4.After the volunteers use the anti-allergic nanofiber facial mask for 30 minutes,the skin redness area get smaller and the color turned lighter compared to using pure water for moisturizing.It shows that the anti-allergic nanofiber mask can well improve the skin barrier and effectively alleviate the redness of the user’s skin.

Figure 4.Skin redness physical map: (a) wetting 30 min with pure water,(b) using anti sensitive nanofiber mask 30 min

The whitening nanofiber mask can effectively alleviate the loss of skin moisture and enhance the barrier ability of the skin,with remarkable whitening effects.The skin whiteness ITA value increased by 4.17% after using the product for two weeks.The volunteers before and after using the whitening nanofiber mask are shown in Figure 5: the volunteers’facial skin become fair after using the whitening nanofiber mask for two weeks.

Figure 5.Whitening nano fiber mask before and after the use of two weeks of whitening and brightening effect picture

In addition,we employ cecropin A-melitin hybrid peptide,Copper Tripeptide-1,Oligopeptide-1,Quaternium-73,Bacopa Monniera Extract,Dendrobium polysaccharide to prepare acne mask.In a word,we can add different cosmetic efficacy ingredients to prepare facial masks with different efficacy by using the electrostatic spinning technology .

Summary and prospect

The nanofiber technology is a platform technology that makes different active ingredients uniformly attached to the interior and surface of composite nanofibers.This innovative composite nanofibrous membrane material can be used in many fields such as cosmetics,environmental protection,medical apparatus,and so on.As a new type of mask formulation,the nanofiber mask is an innovation of the nanofiber technology and cosmetics.In the large-scale preparation of functional nanofiber facial masks,functional ingredients with an excellent water solubility and high polymers are mainly added to form a nanofiber facial mask.Oily functional ingredients can also be added to the nanofiber mask through technical means of solubilization and blending.It’s believed that with the continuous development of the nanofiber technology and research on functional ingredients,the nanofiber facial maskwill definitely win a placein the highend facial mask product market by virtue ofgood applicability,high active ingredient loading,and remarkable biocompatibility.