TECHNOLOGY AREAS: Materials/Processes

ACQUISITION PROGRAM: PM Infantry Combat Equipment

OBJECTIVE: Research and test a practical method for preventing damage to hollow fiber water filtration media subjected to freezing and thawing. A practical method must NOT make the resultant system so heavy and bulky as to negate the weight and size advantage of hollow fiber filtration media.

DESCRIPTION: Hollow fiber (HF) water filtration media is comprised of many small diameter thin walled polysulfone tubes with porous walls arranged in a housing. This allows packing a very large filter area in a very small and lightweight container. This filtration media is the first with a low enough pressure drop to allow a soldier to drink directly through a reasonably sized filter without undue effort.

Hollow fiber filtration media has a significant shortcoming: The current versions do not survive freezing and thawing consistently. Current research suggests that the mechanism of damage is not rupture due to the expansion of the water as it freezes but mechanical damage done by ice crystal growth. A practical method to prevent this damage must be found if the weight and size advantages of hollow fiber are to be realized.

The Marine Corps desires an individual water purifier (IWP) filter capable of withstanding freezing conditions and maintaining performance upon thawing.

The current Marine Corps IWP block I filter uses 1,150 0.5mm diameter x 0.1mm wall hollow fiber microfilter tubes packed into a 33mm diameter x 55mm long housing. The hollow fiber is looped and both ends of each fiber are potted into polyurethane. The flow is from the outside of the fiber to the inside of the fibers, then out at the potting. This configuration yields a flow rate of 1.0 (liter per minute,lpm)at a pressure drop of 1.0 psi with a pore size of 0.2 micron (microfilter). Total weight of the HF module including housing and potting is about 50 grams.

A "practical" filter system would not increase the weight and/or bulk by more than 50%. The solution could be anything from a stronger fiber to an active system to prevent the water from freezing. The most successful system will increase the weight and bulk the least and not require any additional consumables.

PHASE I: Evaluate the freeze behavior and confirm the failure mode of the hollow fibers. Identify and rank freeze/thaw alternatives.

PHASE II: For top three alternatives, manufacture freeze/thaw filter prototypes and test in the lab under freezing conditions. Thaw filters and verify microbiological performance.

PHASE III: Downselect and pick best candidate solution for freeze/thaw filter capability. Produce 300 to 400 filter samples and test under field conditions.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Civilain outdoor/camping activities as well as survial environments represent an extremely large market of theis capability.

KEYWORDS: Hollow fiber; filtration; filter; water filtration; water purifier; freeze/thaw alternatives.

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between April 21 and May 18, 2008, you may talk directly with the Topic Author(s) to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting May 19, 2008, when DoD begins accepting proposals for this solicitation.

However, proposers may still submit written questions about solicitation topics through the DoD's SBIR/STTR Interactive Topic Information System (SITIS), in which the questioner and respondent remain anonymous and all questions and answers are posted electronically for general viewing until the solicitation closes. All proposers are advised to monitor SITIS (08.2 Q&A) during the solicitation period for questions and answers, and other significant information, relevant to the SBIR 08.1 topic under which they are proposing.

If you have general questions about DoD SBIR program, please contact the DoD SBIR Help Desk at (866) 724-7457 or email weblink.