Inexpensive cleanroom for microfabrication, microarray work, and other activities requiring protection from airborne contamination.

Microfabricated devices includingmicroarrays and microfluidic systemsare subjects of increasing interest in avariety of fields (1). The production ofthese devices requires protection fromairborne contamination. Ideally, suchwork is best carried out in a cleanroomfacility, but conventional cleanroomconstruction can cost several hundreddollars per square foot. A less expensivealternative is the “softwall” cleanroom.A softwall clean room is simply a metal-framed tent of heavy vinyl curtains thatis continuously supplied with filtered airat the top. The air exits at the bottom viaa gap between the curtains and the floor.This type of cleanroom is commerciallyavailable from several manufacturersand can be installed in almost any kindof open room space. Typically, the topsof these rooms consist of lighting mod-ules and high-efficiency particulate filtermodules. ISO class 100, 1000, and10000 rooms are available (the numberindicating the average particle count percubic foot of air), with more filter unitsused per square foot of floor area toachieve cleaner conditions. A lightedsoftwall cleanroom costs on the order of$100 per square foot.We present here a construction de-sign whereby we produced a softwallcleanroom ourselves at a materials costof approximately $10 per square foot(excluding labor) (2). Key to the lowcost was the use of existing room light-ing via transparent ceiling panels inplace of expensive cleanroom lightingfixtures and the use of a new consumerproduct air cleaner unit that has recent-ly become available for use in wood-working shops. This type of filter unitis specified to move 850 cubic feet perminute of air with up to 98% efficiencyin removing 5-µm particles and up to85% efficiency in removing 1-µm par-ticles (Delta International MachineryData Sheet for Model 50-860 AirCleaner, http://www. deltamachinery.com). As a consumer product, the costof these air cleaner units is much lowerthan the cost of conventional clean-room filter units. The relatively easyand inexpensive method described hereto produce a cleanroom environmentshould facilitate wider participation inthe recent expansion of research involv-ing microfabricated devices.Figure 1 shows a drawing of the 6 ×10-foot softwall cleanroom constructedin this laboratory. The frame was fabri-cated from locally purchased standardsteel material using 2 ×2 ×1/8-insquare tubing for the posts and 2 ×4 ×1/8-in rectangular tubing for the hori-zontal beams. The corner joints wereformed by attaching 10 ×10 ×1/8-inthick triangular steel plates to the postsand beams with 3/8-24 machine screwsvia threaded holes in the beams.The sides of the frame were coveredwith curtains of 0.04 in transparentpolyvinyl chloride (PVC, cut from 54-inwide roll material; AIN Plastics, Mariet-ta, CA, USA) attached to the beams with10–24 machine screws and washers. Thecurtains were overlapped 6 in at theedges (no sealing was required; the ma-terial “sticks” to itself), and a 6-in gapwas left between the bottom of the cur-tains and the floor. A 2 ×4-foot entrancevestibule (under the air cleaner unit inFigure 1) was formed in the corner ofthe enclosure with additional PVC cur-tains and fitted with a “sticky mat”(Fisher Scientific, Pittsburgh, PA, USA).Air was not supplied to this vestibule.Passages were provided in the ends ofthe vestibule as overlapped joints be-tween two curtain pieces. The entrancevestibule provides a place for the opera-tor to put on cleanroom apparel (haircover, frock, and shoe covers; KapplerUSA, Guntersville, AL, USA) beforeentering the cleanroom.The top of the enclosure was framedwith standard ceiling grid material(Armstrong World Industries, Lancast-er, PA, USA) screwed to the beams in apattern to accept 2 ×4-foot transparentacrylic ceiling panels (ICI Acrylics,Cordova, TN, USA), which were held