Literature Review: Open Source Water Filter

Background[edit | edit source]

The goal of this literature review is to gather information on several different ways of creating an open-source water filter. This literature review will look at 3D printed filters, 3D printed porous filters, and centrifugal melt spinning.

Literature[edit | edit source]

Sediment Filter for Well Water and More[edit | edit source]

"Sediment Filter for Well Water and More," ca-espwaterproducts.glopalstore.com. [Online]. Available: https://ca-espwaterproducts.glopalstore.com/sediment-filter/?utm_campaign=oth_r&utm_source=https://www.espwaterproducts.com&utm_medium=wi_proxy&utm_content=en_US&utm_term=c. [Accessed: May 05, 2022]

• A sediment filter can remove suspended particulates fro water
• Micron rating: indicates the size of contaminates that can be filtered
  • Absolute: largest pore size
  • Nominal: average pore size
• a 10 μm filter can remove sediment and particles
• a 0.5 μm filter can remove cysts such as giardia

The Polyfloss Machine[edit | edit source]

"Technology," The Polyfloss Factory. [Online]. Available: https://www.thepolyflossfactory.com/tech. [Accessed: May 05, 2022]

A rotating metal head with holes heats and spins plastic and extrudes it usign centrifugal force. The heat, speed, and head design can be changed to alter the diameter of the spun plastic.

Comment: There is no information about the specifications of the device or the material manufactured available.

Low cost centrifugal melt spinning for distributed manufacturing of non-woven media[edit | edit source]

A. Molina et al., "Low cost centrifugal melt spinning for distributed manufacturing of non-woven media," PLOS ONE, vol. 17, no. 4, p. e0264933, Apr. 2022, doi: 10.1371/journal.pone.0264933.

Abstract: Here, we consider the production of the non-woven polypropylene filtration media used in face filtering respirators (FFRs). In this study, we present an alternative manufacturing strategy that allows us to move towards a more distributed manufacturing practice that is both scalable and robust. Specifically, we demonstrate that a fiber production technique known as centrifugal melt spinning can be implemented with modified, commercially-available cotton candy machines to produce nano- and microscale non-woven fibers. We evaluate several post processing strategies to transform the produced material into viable filtration media and then characterize these materials by measuring filtration efficiency and breathability, comparing them against equivalent materials used in commercially-available FFRs.

• ‌Fiber diameter required for masks is 0.1 -10 μm
• Processing Defects:
  • material at the outer circumference has a lower density
  • material at the inner circumference becomes fused together
• Applied an electric field to minimize microspheres
• Fibers produced from polypropylene resin (Melt Flow Index=12g/10min) had an average fiber diameter of 3.2 ± 3.0 μm
  • large distribution demonstrates that some fibers are larger to act as a support for smaller, fragile fibers
• Material was calendered and compacted to increase the density of the fibers
  • Compacting with heat increased density the most
• Comment: The application here is for face masks, the material may be too tightly woven for water (too slow of a flow rate)

Fluoride removal from water using a 3D printed calcium carbonate filter[edit | edit source]

P. Ghosal et al., "3D Printed Materials in Water Treatment Applications," Advanced Sustainable Systems, p. 2100282, Dec. 2021, doi: 10.1002/adsu.202100282.

Abstract: Calcium carbonate has been demonstrated to influence fluoride removal in several forms6. To make fluoride removal a cost-effective and user-friendly process, a study has been done to test the efficacy of a 3D printed water filter using E.P Smartfil Filament, composed of 30% calcium carbonate and 70% PLA. The influence of varying conditions concerning the removal of fluoride from water, such as the design of the filter, time spent in contact with the filter, and initial concentration of fluoride have been investigated.

• Calcium carbonate act as an adsorbent for fluoride
• Filament was created from 30% calcium carbonate and 70% Polyactic Acid
• Results:
  • 180 mL of water was needed to activate the system and 9.5 mL of solution was lost to the system
  • of 20 filter designs the best removed 0.048 mg of fluoride/g of calcium carbonate over 24 hours
  • Cross sectional analysis of the filters showed that the flow was limited to the center
    • coiled design helped to increase this surface area
  • No quantitative relationship between initial concentration of fluoride and the amount of fluoride removed
  • On average the filter removed 0.01 mg of fluoride/g of calcium carbonate over 2 cycles
  • While some removal occurred it would not be enough to decrease the likelihood of fluorosis

CLEARBLUE: The 3D Printed Portable Water Filter[edit | edit source]

M. Patel and D. Smith, "CLEARBLUE: The 3-D Printed Portable Water Filter," 2016 [Online]. Available: http://libjournals.unca.edu/ncur/wp-content/uploads/2021/06/1890-Patel-Manisha-FINAL-1.pdf. [Accessed: May 06, 2022]

Abstract: This project introduces a device, ClearBlue, that can not only filter out the two toxic metals and various types of bacteria, but is also portable and light weight- allowing it to be utilized at any time anywhere when filtered water is needed immediately. ClearBlue consists of a small sized filter that utilizes activated alumina technology and a bio-sand filter to kill and trap all arsenic metals, bacteria, and dirt. The exterior part of the filter was designed via designing software and was produced completely by a 3D printer, utilizing PVP plastic as the material- which is sturdy and well durable. The interior part, the actual filter itself, was put together with two sections. One section consisting of activated alumina- in which the water would absorb all arsenic metals. The second section is the bio- sand filter, which consists of finite sand and gravel that can trap 95% of all commonly found bacteria and dirt. Through further field testing, we will be able to confirm the success of this filter in purifying contaminated water into safe drinkable water.

• Uses Activated Alumina (Al₂O₃) as an adsorbent for dissolved pollutants
• Biosand mechanically traps 99% of pollutants
  • a biological community exists in the sand that can remove pathogens
• Small gravel stops large particles
• Filter paper separate the activated alumina, sand, and gravel
• Straw design where the water is filtered as it is being drank
• Water flows even with light suction

Porous ceramic filters through 3D printing[edit | edit source]

A. Withell et al., "Porous ceramic filters through 3D printing," Innovative Developments in Virtual and Physical Prototyping, pp. 313–318, Sep. 2011, doi: 10.1201/b11341-50.

Abstract: This paper describes current and on-going work in adapting Z-Corp 3D printers to operate with low-cost ceramic materials. The components produced with these clay-based ceramic powders can be fired to produce strong, complex and lightweight ceramic parts. The final material properties, including the porosity of the parts, can be controlled through the part design and, potentially, through additives to the material that burn out during firing. The paper begins with a brief description of the 3D printing process and how it can be used with clay powders. It then introduces a factorial design experiment initiated to explore the effect of ingredient and parameter variations on the dimensional stability and material properties of green and fired ceramic parts. It then explores the porosity properties of fired ceramic parts for use in filter applications.

• Clay is naturally porous
• Green parts must be fired at a very high temperature
  • Green parts: saturated clay powder before firing
  • Firing: dries and sets the clay powder into ceramic
• The material can be influenced by composition, printing, and firing
• Powder is binding by a printing liquid
• Printing liquid is mostly water, but also contains isopropyl alcohol to reduce the surface tension
• Effects of 3D Printing Parameters:
  • High saturation resulted in strong green parts but during firing they shrank significantly and irregularly
  • Increasing layer thickness required saturation to be increased as well
• Porosity of the filters ranged from 21% to 31.4% using different settings
• 1 USD/Kg to manufacture

Recent advances in polymer-based 3D printing for wastewater treatment application: an overview[edit | edit source]

Abstract: The introduction of Industrial Revolution (IR) 4.0 has signalled a transformation of traditional manufacturing landscape to intelligent production systems and advanced technologies. Additive manufacturing (AM) is a vital element in this latest revolution due to its remarkable potential in providing a green fabrication alternative with advanced design flexibility that surpasses the traditional manufacturing methods. At present, polymer-based additive manufacturing has drawn considerable interest in wastewater research due to its notable design freedom in manufacturing of novel, geometrically complex, and porous structures used in membrane modules and spacers, adsorption, advanced oxidation process, bioreactor, and microfluidic technology. In this work, recent advances of additively manufactured polymeric materials and 3D printing techniques used for various wastewater research are reviewed. Furthermore, the challenges in the fabrication techniques are assessed, alongside with the discussion on future perspectives of polymer-based AM technologies to develop a versatile and sustainable wastewater treatment system at commercial scale.

• Membranes and spacers
  • porous membrane allows water to pass while catching solids
  • research aims to develop a membrane with high selectivity and permeability
    • most methods result in significant air and water pollution from solvent
  • candle soot (hydrophobic) coated polyamide-12 membrane was able to separate oil/water mixtures
    • preserved functionality under sonication, different concentrations of NaOH, and at higher temperatures
    • 99% separation efficiency of hexane/water mixtures
    • it's contact angle of 141° ± 3° was shown to be a better repellent to water
    • can be 3D printed easily
    • can be used to clean oil spills without damaging the environment

POROLAY / print porous & fibrous objects / foam, felt, jelly / a new 3D-Filament / 2013[edit | edit source]

"POROLAY / print porous & fibrous objects / foam, felt, jelly / a new 3D-Filament / 2013," www.youtube.com, Dec. 18, 2013. [Online]. Available: https://www.youtube.com/watch?v=Pkaus3DN2w0. [Accessed: May 06, 2022]

• Rubber-like substance blended with PVA
• When rinsed for 1-4 days the PVA dissolves leaving only the rubber like substance
• After the PVA has been dissolved material is very spongy and elastic
• Material looks as though it absorbs the water; nothing is passing through
  • Comment: might be too low porosity for water filtration
• Once rinsed, the material deforms easily under low stress
  • Comment: might deform under a fast flow of water

3D printed porous PEEK created via fused filament fabrication for osteoconductive orthopaedic surfaces[edit | edit source]

H. Spece et al., "3D printed porous PEEK created via fused filament fabrication for osteoconductive orthopaedic surfaces," Journal of the Mechanical Behavior of Biomedical Materials, vol. 109, p. 103850, Sep. 2020, doi: 10.1016/j.jmbbm.2020.103850.

Abstract: Due to its unique and advantageous material properties, polyetheretherketone (PEEK) is an attractive biomaterial for implantable devices. Though concerns exist regarding PEEK for orthopaedic implants due to its bioinertness, the creation of porous networks has shown promising results for interaction with surrounding tissue. In this study, we created porous PEEK via clinically-available fused filament fabrication (FFF, 3D printing) and assessed the pore structure morphology, mechanical properties, and biologic response. The designs of the porous structures were based on a simple rectilinear pattern as well as triply periodic minimal surfaces (TPMS), specifically gyroid and diamond types. The material characteristics, including porosity, yield strength, and roughness, were evaluated using μCT, static compression testing, and optical profilometry. The porous PEEK, along with 3D printed solid PEEK, was then seeded with MC3T3-E1 preosteoblast cells for evaluation of cell proliferation and alkaline phosphatase (ALP) activity. The samples were then imaged via scanning electron microscopy (SEM) to observe cell morphology. μCT imaging showed the porous networks to be open and interconnected, with porous sizes similar (p > 0.05) to the as-designed size of 600 μm. Average compressive properties ranged from 210 to 268 MPa for elastic modulus and 6.6–17.1 MPa for yield strength, with strength being greatest for TPMS constructs. SEM imaging revealed cells attaching to and bridging micro-topological features of the porous constructs, and cell activity was significantly greater for the porous PEEK compared to solid at multiple time points.

• Properties of polyetheretherketone (PEEK)
  • modulus of elasticity is similar to bone
  • high yield strength
  • fatigue resistance
• 3 porous constructs: rectilinear, gyroid, and diamond
  • theorized that each would have a pore size of 600 μm
    • based on pore size for bone growth
    • comment: could change this for water filtration
  • theoretical porosities: 70%, 74%, 72% respectively
• Results:
  • actual pore sizes: 545 ± 43 μm, 708 ± 64 μm, 596 ± 94 μm
  • actual porosities: 70 ± 1.5%, 68 ± 1.8%, 69 ± 6.2%
  • rectilinear and diamond constructs showed pore shrinkage from the design
  • gyroid construct showed larger pores than designed
  • a very low volume of disconnected pores occurred
  • main failure for each construct was successive layer collapse
• Comment: This method will create pores that are far too large to filter water

Chemically Active, Porous 3D-Printed Thermoplastic Composites[edit | edit source]

K. A. Evans et al., "Chemically Active, Porous 3D-Printed Thermoplastic Composites," ACS Applied Materials & Interfaces, vol. 10, no. 17, pp. 15112–15121, Jan. 2018, doi: 10.1021/acsami.7b17565.

Abstract: Metal–organic frameworks (MOFs) exhibit exceptional properties and are widely investigated because of their structural and functional versatility relevant to catalysis, separations, and sensing applications. However, their commercial or large-scale application is often limited by their powder forms which make integration into devices challenging. Here, we report the production of MOF–thermoplastic polymer composites in well-defined and customizable forms and with complex internal structural features accessed via a standard three-dimensional (3D) printer. MOFs (zeolitic imidazolate framework; ZIF-8) were incorporated homogeneously into both poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) matrices at high loadings (up to 50% by mass), extruded into filaments, and utilized for on-demand access to 3D structures by fused deposition modeling. Printed, rigid PLA/MOF composites display a large surface area (SAavg = 531 m2 g–1) and hierarchical pore features, whereas flexible TPU/MOF composites achieve a high surface area (SAavg = 706 m2 g–1) by employing a simple method developed to expose obstructed micropores postprinting. Critically, embedded particles in the plastic matrices retain their ability to participate in chemical interactions characteristic of the parent framework. The fabrication strategies were extended to other MOFs and illustrate the potential of 3D printing to create unique porous and high surface area chemically active structures

• Metal-organic frameworks (MOFs): organic-inorganic hybrid crystalline porous materials that consist of a regular array of positively charged metal ions surrounded by organic 'linker' molecules.
• ZIF-8 is the MOF used; consists of zinc metal (inorganic metal) and 2-methylimidazole (organic 'linker' molecules)
• PLA/ZIF-8 Composite
  • PLA pellets were dissolved in trichloromethane at room temperature to create a PLA stock solution
  • PLA stock and MOF mixture was stirred and then sonicated for 20 minutes
  • Dried at 75°C for 16 hours or more in a vacuum to create a thick film
• Filament Extrusion
  • composite films were cut and loaded into an extruder
  • When a temperature of 185°C was reached the material was pressed through a 1.56 mm die to form the filament
  • Filament created had an average diameter of 1.67 ± 0.05 mm
• Results:
  • 40% ZIF-8
  • No flaking/powdering of MOF; good adhesion to PLA
  • Was able to absorb dye

References[edit | edit source]

[1] "Sediment Filter for Well Water and More," ca-espwaterproducts.glopalstore.com. [Online]. Available: https://ca-espwaterproducts.glopalstore.com/sediment-filter/?utm_campaign=oth_r&utm_source=https://www.espwaterproducts.com&utm_medium=wi_proxy&utm_content=en_US&utm_term=c. [Accessed: May 05, 2022]

[2] "Technology," The Polyfloss Factory. [Online]. Available: https://www.thepolyflossfactory.com/tech. [Accessed: May 05, 2022]

[3] A. Molina et al., "Low cost centrifugal melt spinning for distributed manufacturing of non-woven media," PLOS ONE, vol. 17, no. 4, p. e0264933, Apr. 2022, doi: 10.1371/journal.pone.0264933.

[4] M. Patel and D. Smith, "CLEARBLUE: The 3-D Printed Portable Water Filter," 2016 [Online]. Available: http://libjournals.unca.edu/ncur/wp-content/uploads/2021/06/1890-Patel-Manisha-FINAL-1.pdf. [Accessed: May 06, 2022]

[5] A. Withell et al., "Porous ceramic filters through 3D printing," Innovative Developments in Virtual and Physical Prototyping, pp. 313–318, Sep. 2011, doi: 10.1201/b11341-50.

[6] N. H. Mohd Yusoff, L.-R. Irene Teo, S. J. Phang, V.-L. Wong, K. H. Cheah, and S.-S. Lim, "Recent Advances in Polymer-based 3D Printing for Wastewater Treatment Application: An Overview," Chemical Engineering Journal, vol. 429, p. 132311, Feb. 2022, doi: 10.1016/j.cej.2021.132311. [Online]. Available: https://reader.elsevier.com/reader/sd/pii/S1385894721038900?token=D1CFD4D5225100E2EAA5A9EF1D778ACAC6AE922DD608D2C1B585588EF60D4332D873329A4E8BEA6B89BD4FEDC23AA18F&originRegion=eu-west-1&originCreation=20211110005201. [Accessed: Nov. 10, 2021]

[7] "POROLAY / print porous & fibrous objects / foam, felt, jelly / a new 3D-Filament / 2013," www.youtube.com, Dec. 18, 2013. [Online]. Available: https://www.youtube.com/watch?v=Pkaus3DN2w0. [Accessed: May 06, 2022]

[8] H. Spece et al., "3D printed porous PEEK created via fused filament fabrication for osteoconductive orthopaedic surfaces," Journal of the Mechanical Behavior of Biomedical Materials, vol. 109, p. 103850, Sep. 2020, doi: 10.1016/j.jmbbm.2020.103850.

[9] J. Feng, J. Fu, X. Yao, and Y. He, "Triply periodic minimal surface (TPMS) porous structures: from multi-scale design, precise additive manufacturing to multidisciplinary applications," International Journal of Extreme Manufacturing, vol. 4, no. 2, p. 022001, Mar. 2022, doi: 10.1088/2631-7990/ac5be6.

[10] K. A. Evans et al., "Chemically Active, Porous 3D-Printed Thermoplastic Composites," ACS Applied Materials & Interfaces, vol. 10, no. 17, pp. 15112–15121, Jan. 2018, doi: 10.1021/acsami.7b17565.