A step forward in personalizing beauty: the effect of 3D-printed skincare masks

The cosmetic industry is currently witnessing a surge in the personalized skincare trend, providing an alternative to the conventional one-size- and one-treatment-fits-all skincare approaches  (1, 2). The concept of personalized beauty has been further revolutionized by exploring 3D printing technologies, which enables the creation of customized skincare products that cater to individual skin requirements and characteristics. In addition, 3D printing offers flexibility in adjusting bioactive dosages and release rates and allows printing different designs and geometries, making modifications to skincare products fast and efficient (2–5).

Indeed, 3D printing technologies are making inroads into several skincare areas, including the development of customized cleansers, makeup products, personalized packaging, and customized hydrogel-based facial masks (6). Focusing on hydrogel-based facial masks, which are one of the most popular mask types for sensitive skins due to its cooling and soothing effects (7), major advances have been made in terms of customizing this kind of skincare products.

In this scenario, different personalization approaches have been explored, from size and shape to skin needs. However, 3D printing can also be used to personalize the patches’ internal geometry, which can significantly impact the patch’s performance and applicability (2,8). Therefore, this work aimed to demonstrate the relevance of using printing settings as personalizing features to customize hydrogel-based skincare masks and study the effect of the internal design on hydration performance.

Inks and Gel Production: Gelatin-based hydrogels were prepared in a water-bath (Nahita International, UK) at 55 ˚C for 1 hour. A gel-based formulation was also prepared using a polymer with the following INCI: Hydroxyethyl Acrylate and Sodium Acryloyldimethyl Taurate Copolymer.

3D Printing Process: 3-layered gelatin-based patches (30 mm × 30 mm × 0.60 mm) were printed in an extrusion-based 3D printer (Allevi2, Allevi, USA) employing a 25G nozzle. Prior to printing, the design of the patches was personalized using the Allevi2 Online Slicer, resorting to a grid infill type (IT) with and infill distance (ID) of 1.3 mm.

Topical application: The protocol for the in vivo hydration efficacy was submitted and approved by the Ethical Committee of PhD Trials® (http://phdtrials.com/, Opinion nº 005/2012, 15th June 2012). Additionally, it was also ensured that the protocols followed the regulations of the Helsinki Declaration (compliance with good clinical practices) and the Agence Française de Securité Sanitaire des Produits de Santé (AFSSAPS) to guarantee that all technical questions were meticulously evaluated during the application of the products in humans. All the evaluations were performed in a fully controlled and acclimatized room (Controlled temperature: T = 21°C ± 2°C; Controlled relative humidity: RH = 55% ± 10%). Moreover, the volunteers were included after informed written consent.

A total of 10 healthy female volunteers participated in the study (age range 25-55, mean age 28.9 ± 9.3 years). Firstly, to evaluate the effect of the patch’s design on hydration performance, occlusive (Ocl_Patch) and porous (Por_Patch) patches were applied to the ventral side of the forearm of the included volunteers for 4h, under no-occlusion. Additionally, the impact of applying a gel (100 µL) between the skin and the patches was also tested (Ocl_Patch+Gel and Por_Patch+Gel). At t_0h and t_4h, a quantitative assessment of the hydration and transepidermal water loss (TEWL) was performed using Corneometer® CM 825 and Tewameter® TM 300 (Courage – Khazaka Electronic GmbH, Koln, Germany) devices, respectively.

A plastic occlusion stress test (POST) was also performed according to (9), and involved the application of the Ocl_Patch and Por_Patch during a 24 h period. The occlusion was induced by further applying a layer of cling film ‘sandwiched’ between Parafilm (Bemis™ Parafilm™ M Laboratory Wrapping Film) and covered with gauze, which was then applied to the skin using self-adhesive fabric (Mefix®, Molnlycke, Gothenburg, Sweden). After this period, the patches were removed and TEWL data points were continuously registered for 30 min. Ultimately, the POST data points recorded were adjusted to a validated bi-compartmental mathematical model using a specially modified simplex routine and software developed for Microsoft Office Excel.

The following parameters were analysed: (a) Khydr, which represents the constant of hydration rate related to the distribution of the water through both compartments (water changes); and, (b) Kevap, which describes the evaporation process to the exterior, and can be used to evaluate the barrier function. To simplify data interpretation, a transformation of this parameter was performed according to (1):

where, t1/2_evap represents the time needed by the system to reduce its water loss to half.

A schematic representation of the in vivo hydration performance tests conducted is displayed in Figure 1.

Statistical analysis: Regarding the inferential statistics, One-Way ANOVA was performed to determine whether there were any statistically significant differences between the means of Hydration and TEWL variation at t_0h and t_4h. This was followed by the post hoc Tukey multiple comparison test to analyse the differences between groups. Values of p<0.05 were considered statistically significant for all analyses. The collected data was organised and analysed with the IBM SPSS Statistics V.29 software (Armonk, NY, USA).

While some advances in the customization of hydrogel-based facial masks can already be seen, having a thorough understanding of print setting management and construction design is critical as print settings can also be used as tools for product customization. Specifically, adjusting features such as patches’ size/shape and internal geometry design (including pore size), can significantly impact the mask’s performance and applicability (8,10). It is therefore essential to understand the influence of the most relevant printing parameters, which can be used to quickly adjust the patches design to the customer’s needs.

In this research work, the impact of the design on the hydration performance of the 3D printed patches was assessed. Overall, the in vivo hydration (Figure 2 A) data show that the Ocl_Patch application increased the moisture content by 108.85% (t_0h = 35.21 ± 6.25 and t_4h = 72.28 ± 10.81), whereas the Por_Patch showed an increase of 45.38% (t_0h = 35.42 ± 7.78 and t_4h = 51.37 ± 13.31). Regarding the impact of applying a gel under the patches, an increase in hydrating performance was observed regarding the patch design (Ocl_Patch+Gel: t_0h = 34.05 ± 4.18 and t_4h = 80.10 ± 15.11; Por_Patch+Gel: t_0h = 36.16 ± 8.05 and t_4h = 63.15 ± 11.10). Specifically, a statistically significant difference between samples was determined by one-way ANOVA (F(4,45) = 28.26, p=9.08E-12). A Tukey post hoc test revealed that the hydration variation (%) for Ocl_Patch was statistically significantly higher than Blank area (p<0.001) and Por_Patch+Gel (p<0.001); Ocl_Patch+Gel was statistically significantly higher than Por_Patch (p<0.001), Por_Patch+Gel (p<0.01), and Blank area (p<0.001); and, Por_Patch+Gel was statistically significantly higher than Blank area (p<0.001). The TEWL results (Figure 2 B) showed a higher variation for the occlusive patches (Ocl_Patch = 41.07% and Ocl_Patch+Gel = 25.93%) compared to the porous ones (Por_Patch = -9.96% and Por_Patch+Gel = -3.20%); indeed, for the porous patches a decrease in TEWL was observed after 4h, independent of the gel application. As determined by one-way ANOVA (F(4,45) = 28.26, p = 0.012), there was a statistically significant difference between samples. Additionally, Tukey’s test showed that TEWL induced by Por_Patch was statistically significantly lower than Ocl_Patch (p<0.05).

The data obtained showed that the application of occlusive patches ensures greater hydration of the site when compared to porous ones. The application of the polymeric gel between the patch and the skin does not seem to affect this tendency, although an increase in the effectiveness of hydration is observed, which may be due not only to the product application itself but also to the possibility of a certain degree of swelling of the patches. However, the hydric retention values suggest that porous patch application during 4h significantly reduces the TEWL values (without gel application). Overall, these data indicate that the masks’ internal geometry impacts the hydration performance, which can also be linked to the skin occlusion degree induced by the design.

Regarding POST analysis, the experimental TEWL decay curves – desorption (Figure 3 A) were used to estimate the evaporation half-life period (t1/2_evap) as presented in Figure 3 B; this parameter indicates the time taken by the skin barrier to recover after the occlusion stress-induced. Specifically, the Ocl_Patch (t1/2_evap = 1.87 min) showed a similar behaviour to the control site (without patch, Blank area) (t1/2_evap = 1.85 min), whereas the Por_Patch showed a slower decay in the TEWL (t1/2_evap = 2.40 min); a difference of 28.3%.

Following, the experimental TEWL decay curves – desorption, were used to estimate the evaporation half-life period (t1/2_evap); this parameter indicates the time taken by the skin barrier to recovering after the occlusion stress induced (9). The POST-derived parameters further suggest that after an application during 24h, the porous patches showed a slower decay in the TEWL desorption curves, suggesting that a higher amount of water was retained on the surface of the skin compared to the occlusive ones. These results can also be emphasized by comparing the AUC results, which reflect the total amount of water involved in the process: occlusive (AUC = 376.6) and porous (AUC = 466.1). Therefore, reducing the occlusion of the patches (which is related to the design – pore size) seems to be beneficial in terms of hydration performance, since the porous patches allowed for the retention of a greater amount of water in the stratum corneum.

The data obtained show that the masks’ internal geometry impacts the hydration performance. This can also be linked to the skin occlusion degree induced by the design. Overall, these results emphasize that it is possible to modulate the hydration rate and control the TEWL by adjusting the skincare mask’s internal geometry. Moreover, this work delivered insight into the practicality of 3D printing in producing personalized porous skincare masks that cater to the consumer’s skin needs, which could represent a considerable step forward in personalizing beauty.

This research was funded by the Fundação para a Ciência e Tecnologia, Portugal (UIDB/04138/2020 and UIDP/04138/2020 to iMed.ULisboa, CEECINST/00145/2018 to J Marto, and fellowship UI/BD/153624/2022 to S Bom).

All the authors declare no conflict of interest.

Figure 1. Schematic representation of the in vivo hydration performance tests. TEWL, Transepidermal Water Loss.

Figure 2. Impact of patch’ design on hydration performance. (A) Hydration variation (%). (B) TEWL variation (%). TEWL, Transepidermal Water Loss. All data are represented as mean ± SD (n=10 volunteers), and data sets with significant differences are identified with *p<0.05, **p<0.01 and ***p<0.001.

Figure 3. Evaporation half-life (t1/2_evap) in function of patches design. All data are represented as mean (n=10 volunteers). AUC, Area Under Curve.