• As I still lean towards the unpopular view that mask for everyone is ineffective [1], even the WHO/CDC guideline that wearing mask to prevent transmission to others has preliminary evidence against it [2] . More over, few advocates for mask for all among professionals[3] mistakenly weighs "natural" comparison which has too many variables above controlled experiment.[4] That leads me to believe, if I'd place a bet between them, I would bet 95% that the general public is simply wrong , despite I as a non-health professional also would intuitively think that mask would be effective against respiratory transmittable disease.
• However as Hongkong security guard and bus driver demanding mask of what they think is effective, because I'm not a believer of confronting frontline as they are just following orders as it's neither effective in changing people's mind nor action. If the goal is not to compete with health workers for PPEs and potentially be more environmentally friendly, while being socially acceptable, it makes sense to go with DIY masks, and there are several parameters I'm looking here.
  • Effectiveness is not considered important here as the main goal now is just to blend in society, but will still be considered
  • Ease of construction
  • Reusability
  • Waste produce
• First on material
  • Vacuum bag (HEPA), as vacuum bag has pretty good particle filtering qualities, not as good as N95 but sitll very effective.
    • Can filter 99.97% 0.3micron[5]
    • But hot, have resistance breathing
  • Tissue paper
    • Bio - degradable
    • Can stop large droplet
    • No protection
    • Needs to change more often
  • Cloth
    • No protection
    • Can stop large droplet
    • Reusable ( can be washed )
    • Bio - degradable
• Pattern (All rights belong to the authors)
  • A1 Origami style, easy to construct
    • Design by Dr. Jiangmei Wu: https://research.impact.iu.edu/coronavirus/origami-face-mask-pattern.html
      Use pattern with staples, easy to construct, original material HEPA
      
    • A2 Paper origami, hard: by PaperART 013
      https://www.youtube.com/watch?v=ja79rkcDHf4
      
    • A3 Paper origami, tissue: by Ness _Y
      https://www.youtube.com/watch?v=q20OWV8Oxrk
      
  • Sewed, mainly 3 categories
    • B1 Closely resembles surgical mask, has folds, some with double layers like
      https://www.youtube.com/watch?v=o8OyV15ua24 by Hobby Lobby
      
      Or single layered like:
      https://www.youtube.com/watch?v=N4boLMM4paQ by NS Creative Collections
      
    • B2 Two pieces
      Symmetrical left right: https://www.youtube.com/watch?v=6hpzLQTy-SA by Mimi G Style (and many variants)
      
      Updown ( Not cloth, but put in here because of the construction ): https://www.youtube.com/watch?v=1bP1Z3Ks7xA by The Oregonian
      
    • B3 3D mask style
      https://www.youtube.com/watch?v=8RCuL1mX7eg by Thoan Nguyễn Vlogs
      
  • Others:
    • C1 Antex http://www.antexmask.com/20844214963603935338.html 
      
      My version: https://www.thingiverse.com/thing:4172119
      ( But for this, security guards and bus drivers will intuitively *feel* that is less effective, but given the tests on surgical masks and cotton masks[2], using PC sheet to fully redirect airflow would hypothetically be more effective to protect the others, although I do not have the condition to test it)
    • C2 Tissue clip https://www.youtube.com/watch?v=pqOGlbY3bgM by FreeziMee
      Of course, no protection, but in certain countries, can prevent from getting arrested.
• My speculation:
  • For protection and easy construction, the origami A1 wins, as for B2 style, a lot of sewing work is required, if it's not reusable, of course B2 is good if there's enough labour who actually need to make those masks and donate to health professionals in places where PPE is scarce.
  • For reusablilty, all the cloth ones, B1 and B3 is easier to construct than B2 as there's no middle seam concern for aesthetics.
  • A1 has high reusability and easier to clean than cloth masks (can wipe and spray alcohol), however, can't pass preception test for security and bus drivers.
• So to combine the ease to construct and reusability, it's probably good to 3d print clipping device to save the sewing work of B1/B3
  • For they both only need clips on the side
  • Surgical style seems more easy to pull off
  • 3D mask needs a little more though on the pattern

Appendix:

[1] COMMENTARY: Masks-for-all for COVID-19 not based on sound data; Lisa M Brosseau, ScD, and Margaret Sietsema, PhD , Apr 01, 2020; https://www.cidrap.umn.edu/news-perspective/2020/04/commentary-masks-all-covid-19-not-based-sound-data

[2] Bae S, Kim M, Kim JY, et al. Effectiveness of Surgical and Cotton Masks in Blocking SARS–CoV-2: A Controlled Comparison in 4 Patients. Ann Intern Med. 2020; [Epub ahead of print 6 April 2020]. doi: https://doi.org/10.7326/M20-1342

[3] Masks for all? The science says yes; Professor Trisha Greenhalgh OBE and Jeremy Howard; 13 Apr 2020; https://www.fast.ai/2020/04/13/masks-summary/

[4] @fangshimin ;口罩党最近在疯传这篇文章和这张模拟图，认为全民戴口罩能防止新冠病毒传播已被科学证明了。我看了该文的证据，觉得很可笑。他们承认随机对照实验证明戴口罩没能起到预防传染病作用，但认为“自然实验”证明戴口罩有用，证据是某国全民戴口罩后疫情好转了。他们竟认为有无数变量的“自然实验”胜于对照实验[tweet];Apr 16, 2020;  https://twitter.com/fangshimin/status/1250554893552611328

[5] https://www.abatement.com/learning-center/patient-isolation/facts-about-hepa-filtration/