Drexel Design Futures, Bacterial Cellulose (and a world record, maybe?)

PJ and a number of other Hive members have been fortunate enough to participate in preparations for the Drexel Design Futures Lab “Projects 12/13” exhibition.  PJ was almost certainly the most involved Hive contributor — he helped with the development of a number of key software elements for several of the exhibits.

I had grown some fairly large sheets of bacterial cellulose in the past, and was interested in having an excuse to grow something even larger — so sign me up!  Tashia wanted a sheet that started out about 4’x8′ so that the final screen could be cropped to dimensions that were about the size of a slightly gigantic person.I wound up getting involved in the creation of a special display screen that was part of an interactive piece which allows people to “play” with a computer model of bacterial swarms.  This piece was part of Tashia Tucker’s exhibit, and she wanted an “organic looking” display surface. After some brainstorming that included condemnations of the high price of silicone etc., PJ suggested bacterial cellulose.  What!?  The idea of a movie screen made by real bacteria to show movies of simulated bacteria was too “meta” to pass up.

Yikes — this was literally a tall order.  Bacterial Cellulose (BC) is created by the same organisms that are used to ferment Kombucha — in fact, the “Shroom” or “Scoby” in a Kombucha culture is a big lump of cellulose.  So this was simple, in principle, but the scale of the piece left a lot of novel details that had to be worked out.

Bioreactor Vessel: I remembered talking to Scott Beibin a few years back about whether BC could be produced artisanally in large sheets.  BC sheets will generally grow to cover the entire surface of any container they inhabit.  In fact, Scott speculated that there was probably no limit to the size of sheets that could be grown, and suggested (flippantly, I suspect) that you could even use a kiddie pool.  $25 at Target, thank-you-very-much.

Nutrients: This is kombucha, right?  So one cup of sugar per gallon .. hmm .. and three inches of fluid * 8′ * 4′ makes, … um .. 8 cubic feet of water which is … lessee … about 60 gallons, so 60 cups of sugar is about 30 lbs.  And we need some tea, so let’s say 200 tea bags.  And we can toss in two gallons of vinegar and a half-cup of activated yeast to kick-start the fermentation.  All available at your neighborhood grocery store for $30 or $40 or so.

Grow Site: BC cultures can get pretty rank, and this grow was going to consume a lot of floor space, so an indoor location was out of the question.  It also had to be close enough to Drexel to allow for occasional visits in order to care for the culture.   My sister was kind enough to offer us a secluded spot in her back yard.

Shelter: The BC cultures are pretty robust, but we needed a way to protect the pool from the elements.  Target wins again.  Tent to fit our kiddie pool with a little room to spare?  $90.  Shoving the oversized, semi-inflated pool through the undersized door?  Priceless.

There were miscellaneous other items — baking soda to neutralize the incredibly strong acetic acid in the harvested BC, buckets for mixing etc., plastic sheets to spread the harvested cellulose out etc. etc.  And there was a day or two of panic when, two weeks into the grow, there was no evidence that we were growing anything but a fetid swamp in a kiddie pool (nothing special about that).   Then the BC started growing with a vengeance, and we harvested it about three weeks into the venture — just in time to dry it and mount it for the exhibition.

A week later, we managed to pull a second sheet out.  This second sheet was qualitatively different from the first — it was generally thinner and weaker, and it had a few holes — but it was more uniform in the sense that it had a single, well-defined layer.  By this time Tashia was a pro with the material.  She deftly cut a strip of BC from one edge of the sheet, sliced the strip into a few square patches and slapped a patch over every void in the sheet.  BC is miraculous that way.  Since it starts out as a hydrogel, you can repair defects by placing a patch of “good” gel over any holes.  The two sheets will fuse together at a molecular level as they dry,  resulting in a repair that is about as strong as the original sheet and nearly invisible.

We’re Gonna Need a Bigger Boat: At any rate, I’m going to claim, solely on the basis of “this is the biggest sheet of BC I have ever seen after scouring the Internet for big sheets”, that this may be a world record of sorts.  If there’s a larger sheet out there, I’m interested in learning about it (and will gladly relinquish the title).  Even if this actually is a “record”, it’s a title that we expect to lose at some point, since the key to a larger sheet is simply a larger pool (and more tea etc.).