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Nano- Electrospun Filter for Efficient Liberation & Encapsulation of acticides for water treatment in transportation applications

Final Report Summary - NEFELE (Nano- Electrospun Filter for Efficient Liberation & Encapsulation of acticides for water treatment in transportation applications)

Executive Summary:
The importance of water as a vector for infectious disease transmission on aircraft has been a cause for concern for some time. In recent years, aircraft water quality issues have gained momentum, generating negative media coverage and attracting the attention of industry regulators around the world. The US Environmental Protection Agency (EPA) is currently in the process of putting together new, tighter quality regulations for aircraft drinking water and other regulators are sure to follow the EPA’s example.

If the source of water used to replenish aircraft supplies is contaminated, and unless adequate precautions are taken, disease can be spread through the aircraft water. It is thus imperative that airports comply with Article 14.2 (Part III – Health Organization) of the International Health Regulations (1969) and be provided with potable drinking-water from a source approved by the appropriate regulatory agency (WHO, 1983). A potable supply is no use if the water is subsequently contaminated on transfer, storage or distribution inside the aircraft. Water may be transferred to aircraft by vehicles and bowsers. Transfer of water from the water carriers to the aircraft provides an opportunity for biological contamination which may come from micro-organisms that multiply inside the water tanks, lines and filters. This situation is made worse by air pressurized water systems that allow water to remain still in the tank and lines until a tap is opened. Bacteria thrive in such conditions, and bacterial regrowth is a certainty even after deep cleaning. For many operators, bottled water has been the answer, but it is expensive, heavy, and only partially addresses health concerns because on-board water is still used in galleys and lavatories. Also, in the aviation sector, the rapid aircraft turn-around time required by operators is a major factor in the design and mode of operation of water treatment systems. Typically, between 500 and 1,500 litres must be drawn on board and, ideally treated at the point of entry into the aircraft within 5 to 10 minutes. This requirement places an upper limit on the residence time of the water in the treatment unit. This in turn implies that the most important factor in the treatment system is the maximisation of available surface area for pathogen/acticide interaction. The consequence of not sterilising water at the point of entry into the aircraft is that it has to be treated at each and every point of use. This in turn means that the storage tank(s) and pipe network have to be regarded as contaminated – a far-from-desirable state of affairs.

The NEFELE technology provides a way of removing 100% of both viruses and microbes in water used in aircraft, whilst creating a business opportunity to produce a Nano- Electrospun Filter for Efficient Liberation & Encapsulation of acticides. Further onward development will see the NEFELE technology incorporated into more general water treatment applications and anti-pathogenic filtration applications.
The treatment system traps and destroy pathogens (viruses and bacteria), since the polymer nanofibres which form the matrix material are hollow, porous and cored with a biocidal material. The system will be a major contribution to the provision of safe drinking water regardless of source quality. This in turn will provide for overall cost savings in terms of the need to carry fresh water for the return leg of flights to destinations with substandard water and more efficient use of resources.

The NEFELE technology development delivers a system to meet the needs of aircraft manufacturers and service providers by providing a light-weight, retro-fittable, treatment unit that has a high-density polymer outer containment and replaceable matrix elements that will be available in refill packs.

The NEFELE technology provides a way of greatly enhancing the effectiveness and functionality of biocidal systems without affecting the taste of water but at the same time providing a measurable residual of biocide in the distribution system.

The treatment system is designed to be used by airline operators and their service providers without the need for any chemical dosing.

Project Context and Objectives:
The primary aim of the NEFELE project was to develop an efficient and high quality water filtration system to ensure potable water supply on-board aircraft. In doing so, the technological advantages of the NEFELE system are greatest for contexts where the conditions and constraints of time, opportunity for access and safety considerations and suit the aircraft market. There is also a real potential for onward development in disaster area’s and the marine sector.

The NEFELE consortium forms an integrated value chain that is able to penetrate the market within the EU and globally. The individual role of each of the partners in terms of the manufacture and distribution of the system is as follows:

Aerocare, an airline services company, will assemble the various components of the final NEFELE treatment system into an integrated whole. The company has traditionally been associated with providing water purification systems and cabin refit and refurbishment services to airlines.

Inovenso is anxious to commercialise the technology which has been formed in an academic setting and to supply both electro-spinning equipment and their expertise in the art to make available an even wider range of functionalised materials.

Roiplas expects to expand their market for plastic parts injection opening new markets thanks to the access to new typologies of products. They also have an objective in getting direct economical benefits through the sales of plastic parts for the manufacture of the developed product.

Currently, commercially available treatment systems cost around €5,000 - €15,000 with an estimated additional service cost of €500 per machine per year. It is estimated that the proposed NEFELE system will cost no more than €5,000 each once full commercialisation has been achieved. It is more effective and more reliable and offesr more flexibility and functionality than any current systems.

The project has three specific results which will be absorbed by the SME’s to validate and generate the relevant IP. The SME’s will exploit the results for their commercial and financial benefit. The results are:

Result 1 – Prototype microfluidic manifold.
Result 2 – Prototype porous nanofibre matrix material with biocidal core.
Result 3 – Fully integrated system:

At the end of the project, the output produced from the prototype system development was validated against the project objectives and against the relevant EC standards (where applicable). This validation will be undertaken by all of the SME partners working closely with the RTD partners who are able to undertake testing to standard. As a part of the exploitation phase, the device will be tested by an independent testing company and the relevant standard validation documentation will be achieved.

Objectives and Targets

The project had specific scientific, technological, societal, economic and innovation related objectives:

Scientific objectives:

1. Investigate the preparation of advanced pororous core/sheath polymer nanofibres to enable the development of an electrospun matrix material which will both encapsulate and liberate biocidal substances in water. We aim to achieve a lifetime of each matrix element of >4months.

2. Investigate the adoption and adaption of microfluidics to enable the development of a multiple spinneretmanifold which has sufficient degree of control to enable the simultaneous production of at least eight polymer nanofibres.

Tchnological objectives:

1. Develop a drinking water treatment system which will use user-friendly, user-changeable matrix cartridges which provide the ability to scale up the amount of water treatable by a single unit by simply inserting a greater number of cartridges into the containing vessel.
2. Have a flow rate of 1 litre per second or better.
3. Conform to BS6920 type approval.
4. Lead to the manufacture, distribustion and sale of the NEFELE device at an ex factory cost of less than €5000 (with intensive post project development) with a servce lifetime of at least 5 years.

Societal and policy objectives were to benefit the people of Europe and beyond by improving the quality of life of the tens of millions of individuals who travel by air in increasing numbers and with increasing frequency by:

1. Reducing specialist ground crew needs without reducing aircraft turnaround time therefore reducing training costs by at least 5%.

2. Slowing the currently predicted growth in the unemployment rates resulting from by 5% based on a European market penetration of 10%.

3. Reducing the number of cases of illness caused by poor quality drinking water on board aircraft at least 90% by dramatically increasing the functionality, flexibility and overall effectiveness.

Economic objectives:

1. Substitute into at least 10% of the European market of €105Mn for traditional products and 10% of the remaining global market by 2019.
2. Generate €0.12 Bn p.a of healthcare savings in Europe (water-borne pathogens cost the EU health authorities over €58Bn p.a).

Inovation-related objectives:

1. To formulate the project results into a protectable form and apply for patent protection on the NEFELE system.
2. To transfer knowledge from the RTD performers in the project to the SME participants through case study products and the creation of a generic design guide for product design and manufacturing process operation.
3. To relay the benefits of teh developed technology and knowledge beyond the consortium to potential user communities such as municalpalities, mercantile enterprises and healthcare providers.

Project Results:
1. New Scientific Knowledge

A literature review was conducted and detailed knowledge gained on the benefits of PDMS within microfluidic devices and their applications. PDM was found to be the most suitable material as it is inexpensive, flexible and is optically transparent. It is also impermeable to water and non-toxic to cells. In addition it is easy to fabricate. Typical applications in microfluidic applications were investigated and found to be devices for the detection of immunoassays, microfluidic chips used in the separation of proteins from DNA and sorting & manipulation of cells. An analysis of the swelling ratio’s of PDMS when presented to a range of solvents was undertaken and tabulated.
A further literature review resulted in five types of biocide that are used in current soa filtering systems being identified. These have good antimicrobial properties. These were compared against a product already used by the Coordinator (Aerocare) for which basic data was provided in order that comparisons could be made against other alternatives. The solutions provided by the Aerocare Water-Clean 1-03W system offers effective microbial control and offer the following features and benefits; has been chemically engineered using a technology designed to combine microscopic physical effect and chemical control functions, and as it is already approved to a range of industry approvals, was chosen as the candidate solution.
A literature review of polymeric materials used in electro-spinning was conducted which resulted in six candidate materials. The candidate materials were discussed amongst the consortium and three selected for further analysis, PVdF, PAN and PSU. These were selected for their good levels of porosity and compatibility with the biocide.
A review of the available types of electro-spinning processes was undertaken and data gathered on conventional co-electro-spinning, electro-spinning from a single nozzle and microfluidic channel networks. Production from a single nozzle is the preferred mechanism for the NEFELE technology.
A technical meeting was held to discuss and agree an initial specification for the NEFELE technology. In order to ease the resultant technology into the market place as quickly as possible it has been agreed that the NEFELE system will be integrated as far as is possible within the design parameters of the current filter housing currently supplied by Aerocare. Using this approach will speed up the approval processes and accreditations required by end-users whilst maintaining the novel concept that NEFELE is. The initial specification is as follows:
• Flow Rate: 35 litres per minute. • Fill Time: 7 – 8 mins.
• Filter / Membrane Material: PVdF / PAN / PSU.
• Biocide: 1-03W. • Filter Housing O/D: 5” Max. • Filter Cartridge Length: 10”.
• Service Life: 6 weeks minimum.
• Weight: 5kg Maximum.
• Pre-Filter: Yes
• Pressure Rating: 10 bar (internal pressure test).
• Operating Temperature: -1°C to 30°C.
• Housing Material: Stainless Steel / PTFE.

The relevant standards for potable water on aircraft were made known to all members of the consortium and the legislation has been reviewed to determine what bacterial strains and types need to be removed from potable water. The test protocol has been discussed in detail amongst the consortium. A test protocol has been established based upon the assumption that the NEFELE filter samples can be used as filter membranes, the protocol details the preparation and enumeration of cell suspension for testing, evaluation of the biocidal efficacy NEFELE filter membranes and viable cell retention tests.
An outline of the NEFELE test rig was produced. Consideration has been given to durability testing and how this should be performed. This phase of the research concluded with a table showing the standards for the testing which are:
• Biocidal Efficacy: >10(2) reduction in numbers.
• Viable Cell Retention: <10 CFU/ml (TVC 37°C).
• Durability: 2 to 6 months (dependant on water quality).

2. Development of micro-fluidic spinneret manifolds

Detailed literature reviews were undertaken to determine the best methods of manufacturing microfluidic devices, soft lithography and bonding were identified as the best options. An in depth analysis was undertaken to determine the methods required to manufacture a microfluidic device using soft lithography. A detailed study of the manufacturing processes involved in producing the manifold via soft lithography was undertaken ;6against a proposed manifold design.. The results of this study revealed three major constraints with microfluidic devices:

1. The high cost of individual components may pose a significant commercial barrier when scaling up the microfluidic device for multi-spinneret (<30 fibres) electro-spinning.
2. Lead times for the use of facilities and for materials can be extensive, ranging from 3 to 8 weeks, this would be an issue for scaling up the technology to the required commercial volumes.
3. Labourious processes and high labour expertise is required to obtain a manifold of the required quality.

Following these results, the consortium then agreed to develop a milli-fluidic device as the preferred option. Milli-fluidics is referred to as a system using flows in capillaries showing an internal cross section above 1 mm. The limit of milli-fluidics with conventional fluidics is when the Reynolds number approaches the value 1 where turbulences cannot be neglected. A design was made and proposed, refined and manufactured in stainless steel. The device is coaxial and allows the injection of biocide into a 17g needle and the polymer solution into a 21g needle. The device be stripped down and cleaned which is a huge benefit to the production efficiency of the membrane.
Following feedback from the initial electro-spinning trials the design of the milli-fluidic manifold was modified slightly to improve the flow of the polymer. A new batch of milli-fluidic devices we re-manufactured and supplied for use in the manufacture of the NEFELE membranes.
The work undertaken showed that the use of micro-fluidic devices is not a feasible solution for the NEFELE technology whereas the use of milli-fluidic devices is a lot less costly and it is possible to produce a nano-fibre that meets the functional requirements of the technology. Prototype manifolds have been produced and refined to obtain the optimum channel dimensions (diameter and length).

4. Integration

It was decided to utilise Aerocare’s stainless steel outer containment vessel used in their current water filtration system. This was due to the cost of producing an injection moulded part and the advantage thatAerocare will have in being able to demonstrate the technology to potential end-users by using the current system. A design was completed for the whole NEFELE assembly using Solid works CAD modelling and the drawings transferred to Roiplas for manufacturing feasibility and cost studies.
Following a technical design meeting a specification for a matrix holder was produced. Unlike the original concept, the holder is cylindrical as it can be used in both the existing and NEFELE water filtration systems. Holders for the membrane were Roiplas manufactured and used in the assembly and testing of the NEFELE technology.
The Matrix holder was then incorporated into a wider design for the whole of the NEFELE assembly. This assembly consists of a large pre-filter unit and a de-scaling unit. These are positioned ‘up-stream’ of the NEFELE technology but form part of the commercial solution. The design was drawn up in CAD and models generated for assessment and quotation. The larger design represents a larger commercial opportunity for one of the partners (Roiplas) as more injection moulded components are required.
Standard pre-filters were specified consisting of a non-woven polypropylene (240mm x 150mm). These were easily sourced as it is a readily available material.
A handling and assembly guide was produced for the assembly of the nano-fibrous membranes onto the cartridge. This is a very delicate operation due to the thickness of the membrane and the requirement to separate it from its backing paper which is there to protect it during transport. The membranes were made to dimensions to accurately fit round the outer diameter of the cartridge.
The membrane once wrapped around the cartridge was then protected by an outer layer of the pre-filter. Following this, silicone rubber end caps were moulded on to each end to produce the guide. The function of these guides is to ensure a good fit into the outer containment vessel and act a functional seal of the pre-filter and membrane.
The finalised assembly was fitted to the stainless steel outer containment vessel and a gasket placed between the seal and lid. The standard stainless steel outer containment vessel and accompying gasket was used. The NEFELE cartridges are easily interchangeable.

WP5 – Testing & Validation

A design for the test-rig has was drafted and approved by the relevant members of the consortium. The rig was designed to incorporate the stainless steel outer containment vessel used by Aerocare in its existing water filtration system. Aerocare provided a unit for use on the rig. An assessment of the relevant industry standards for potable water on-board aircraft was made and the maximum contamination level goals determined for the NEFELE system. Conditions that the NEFELE test rig needed to mimic were determined from the specifications produced earlier in the project and the flow rate requirements finalised at 10 litres per minute with a maximum volume of 60 litres. Each test thus tales 6 minutes to complete. Using this data suitable pumps and flow-meters were specified.
Data was obtained for flow-rate, timings and volumes of water required. Specific consideration was given to the required design of the NEFELE filter which needed to be designed to handle efficiently the flow-rate of water and volume to be passed through it without being destroyed. A basic design was proposed to the consortium which was adopted for use in the system.
A test programme was followed for fully assembled NEFELE filter membranes to determine biocide leakage and biocidal effect. Data was gathered for water contaminated with micro-organisms and then with solids. All tests were undertaken on short-term and long-term periods of time. For short term tests samples were taken at 30 sec, 2 min and 5 min. For long term tests samples were taken at 10, 20, 30, 40 and 50 minutes. Samples were analysed for:
• Total suspended solids.
• Particle size distribution.
• Microscopy inspection.
• Ecotoxicological effects.

Biocidal efficacy was tested and determined by exposing known cultures to the filter and by sampling of the filtrate.
A study was undertaken to determine how the NEFELE technology will be integrated into the aircraft industry. The required approvals were determined first of all and an assessment of which airline operators are likely to take-up the NEFELE technology. Costs for implementing a full manufacturing and inspection facility were determined as well as where the NEFELE technology will be manufactured

Potential Impact:
Aviation companies have a duty of care to provide passengers with safe potable water. Regulatory bodies are aware that microbial contamination is a risk. Due to the public health concerns, it is expected that regulations for aircraft water treatment will become more restrictive. The NEFELE technology addresses the urgent market need of the airline industry and provides a low maintenance technology that can provide safe potable water on board aircraft according to international aviation regulations.
List of Websites:

Contact: Mr David Hickson: