SKIN APPEARANCE, IMAGING AND 3D PRINTING

Understanding human skin appearance is a subject of great interest in science, medicine and technology.  In medicine, skin appearance is a vital factor in surgical/prosthetic reconstruction, medical make-up/tattooing and disease diagnosis.  With the 3D printing of human skin now at the horizon,  the process involved in matching natural and manufactured skin samples has become essential; a robust, accurate and efficient imaging system is required that acquires the relevant skin information and predicts a good match and translates this information through this new and innovative manufacturing process.   A major problem with manufactured skin is that the match to the individual’s natural skin must hold not only be accurate under a particular ambient illumination but the match needs to be preserved when the individual is moving between different environments, e.g. when the individual moves from office or LED lighting into daylight. To achieve this illumination invariance, the physical properties of the skin need to be taken into account.

Two of our team members, Professor Yates (Manchester) and Dr. Xiao (Leeds), have pioneered the use of additive manufacture for prostheses (
www.wellcome.ac.uk/noses). With funding from the EPSRC we were able to refine their technology, with the following outcomes:

(i) Proof-of-concept for the acquisition and additive manufacture of skin using a 3dMD photogrammetry facial system (3dMD, Atlanta, GA, USA).and a powder-based 3D printing system (Zcorp Z510) [1,3,6]

(ii) Assessment of the skin measurement reliability of two instruments (PhotoResearch PR650 spectroradiometer; Konica Minolta CM700d spectrophotometer) [5]

(iii) An algorithm for the spectral reconstruction of full skin spectra from camera [2]

(iv) Publicly accessible data base characterising the variability of natural skin colour  [4]

(v) Appearance evaluation of natural and manufactured skin using spectral and perceptual error metrics [6,7]

Future challenges: Our previous manufacturing method relied on post-processing techniques (infiltration with silicone) to increase the flexibility and durability of the manufactured skin, which also leads to poorly controlled textures and highlights. While the colour accuracy (comparing real skin with additively manufactured skin) is not far from an acceptable range and is not strongly dependent on the spectral distribution of the light source, the overall appearance of the manufactured prosthesis is deficient due to poorly controlled glossiness/highlights. With recent developments in 3D printing, allowing direct deposition of photocurable polymers with layer thickness < 15 mm and material specification at voxel resolution, we can address these shortcomings to optimise the optical and biomechanical properties.

 

 Collaborators

Dr. T Chauhan, University of Toulouse

Dr. K Xiao, School of Design, University of Leeds

Prof. J Yates, Dental School, University of Manchester

Dr. Ali Sohaib, Engineering, Nottingham

Dr. R Akhtar , Engineering, University of Liverpool

Dr. K Amano, Electrical Engineering, University of Manchester

Prof Jeremy Smith, Engineering, University of Liverpool



Lab Equipmen
t

For 3D image acquisition, we use a  3-pod 3dMD photogrammetry system , in conjunction with a VeriVide ceiling lighting system allowing for controlled illumination.

For calibration purposes we use various measurement devices, including the PhotoResearch PR670 spectroradiometer  and the Konica Minolta CM-700d spectrophotometer (with the CM-SA skin analysis software).


 Publications

[1]       K. Xiao, A. Sohaib, P.-L. Sun, J. M. Yates, C. Li, and S. Wuerger, A colour image reproduction framework for 3D colour printing, Proc. SPIE, vol. 10153, no. 2, 2016.

[2]       K. Xiao, Y. Zhu, C. Li, D. Connah, J. M. Yates, and S. Wuerger, Improved method for skin reflectance reconstruction from camera images, Opt. Express , vol. 24, no. 13, pp. 1493414950, 2016

[3]       K. Xiao, S. Wuerger, F. Mostafa, A. Sohaib, and J. M. Yates, Colour Image Reproduction for 3D Printing Facial Prostheses, in New Trends in 3D Printing, 2016, pp. 89109.

[4]       K. Xiao et al., Characterising the variations in ethnic skin colours: A new calibrated data base for human skin, Ski. Res. Technol., 2016.  

[5]       M. Wang, K. Xiao, M. R. Luo, M. Pointer, V. Cheung, and S. Wuerger, An investigation into the variability of skin colour measurements, Color Res. Appl., 2018.

[6]       A. Sohaib, K. Amano, K. Xiao, J. M. Yates, C. Whitford, and S. Wuerger, Colour quality of facial prostheses in additive manufacturing, Int. J. Adv. Manuf. Technol., vol. 96, no. 14, 2018.

[7]       Chauhan, T., Xiao, K., & Wuerger, S. (2019). Chromatic and luminance sensitivity for skin and skinlike textures. Journal of Vision, 19(1), 13. https://doi.org/10.1167/19.1.13

 

 Data sets

  1. Colorimetric (LAB) skin values for four ethnicities (Caucasian, Chinese, Kurdish, Thai): (download [link to https://pcwww.liv.ac.uk/~sophiew/data/skindatabaseLAB.zip]).  Details in pub #4.
  1. Database containing skin spectra (download [link to https://pcwww.liv.ac.uk/~sophiew/data/skindatabaseSpectra.zip]. Details in pub #2.

Acknowledgement of support:

Engineering and Physical Sciences Research Council (EPSRC) EP/K040057/1 (2013-2017)

Royal Academy of Engineering (2015-16)

EPSRC IAA EP/K503952 (2016-2017)

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