turning to the figures , an applicator 10 is shown . applicator 10 includes a first housing 12 . housing 12 is typically two cooperating parts , top 12 a and bottom 12 b which snap together or more commonly are glued are fused into a single housing 12 during production of the application care . housing 12 has a first (“ front ”) end 14 and a second ( opposite or “ rear ”) end 16 . first end 14 terminates in a generally flat widened region 18 having a height “ h ” and a width “ w ”. as shown in fig5 , h and w are selected to provide an aspect ratio w : h of from about 2 : 1 to about 10 : 1 and especially from about 2 . 5 : 1 to about 8 : 1 and more especially from about 3 : 1 to about 6 : 1 . as shown most clearly in fig1 and 3 , region 18 is covered with a conforming thin layer 20 of foam . this is a liquid - permeable ( open celled ) foam ranging in thickness from about 0 . 25 mm to about 5 mm and especially from about 0 . 50 mm to about 3 mm . the layer of foam may be adhered to region 18 but can also be merely conformed to exterior contours of region 18 . the thin layer of foam can be molded to conform to region 18 or it can be a sheet of foam material drawn over the region 18 so as to conform to it . the layer 20 of foam may be held in place by retainer ring 21 which can also hold or assist in holding the two sections 12 a and 12 b of housing 12 together , if needed . retainer teeth 23 help grip the foam layer 20 and hold it in position covering the flat area 18 at the front end 14 of the applicator . region 18 is relatively rigid ( minimally deflectable ) and provides a firm backing for foam layer 20 . in view of this relative rigidity , in use region 18 does not deflect substantially , for example more than one mm or two mm under the pressure of routine application . the first end 14 of housing 12 and its region 18 are liquid - impermeable except for the end of region 18 which contains one or more apertures ( holes ) 22 in liquid communication between the interior 24 of housing 12 and the foam cover 20 . in fig2 and 3 , three holes 22 a , b and c are shown . any number of holes such as from 2 to 10 , for example , may be employed . however , it should be kept in mind that the number and size of these holes can have a flow rate - controlling effect and can control the amount of liquid passed to the foam layer 20 and applied with the applicator 10 . it is generally desirable to space the holes across the width “ w ” of region 18 to provide a uniform flow of liquid to the foam layer across the width of the applicator . alternatively and equivalently , a porous region at the 18 portion of the housing could provide the same liquid release function as long as the region 18 retains its relatively rigid foam - supporting properties . the applicator includes a second housing 26 which slidably engages the second end 16 of first housing 12 . as can be seen by comparing fig1 and fig3 , second housing 26 can move relative to first housing 12 from an “ open ” position ( fig3 ) to a “ closed ” position ( fig1 ) by sliding housing 26 in direction d ( see fig3 ) relative to housing 12 &# 39 ; s fixed position . although shown only generally in the drawings , the two housings 12 and 26 may , and in most cases will , contain various latches and detents to control their movement relative to one another . these latches and detents can serve to bias the housings into the fully open and fully closed positions so as to prevent housing 26 inadvertently separating completely from housing 12 , and to prevent housing 26 prematurely moving from a fully “ open ” position relative to housing 12 or returning to an “ open ” position after the applicator has been activated by moving housing 26 to the “ closed ” position . as shown in fig2 and 3 , housing 12 is sized to accommodate one or more liquid containers 30 a , 30 b and 30 c . these containers are constructed of a frangible liquid - impermeable material such as glass , brittle plastic , flexible plastic film or the like . three containers are shown in these figs . it will be appreciated that the present applicator will work with fewer ( one or two ) or more ( four , five or more ) containers . housing 26 includes a container - receiving region 32 into which the one or more liquid containers 30 are fitted . region 32 is depicted as pairs of opposing fingers 34 and 36 which grip the one or more frangible containers 30 and hold them in place relative to housing 26 . in operation , one or more containers 30 are mounted in region 32 of housing 26 . then housing 26 is slid into engagement with housing 12 . in the “ open ” position of fig4 a the containers 30 are intact . to release the liquid from containers 30 , housing 26 is moved in direction d , relative to housing 12 . this causes containers 30 or , more preferably , fingers 34 and 36 to come into contact with ramps 40 in housing 12 and apply a container - breaking force to a predetermined region of the containers 30 and housing 26 is pushed further into housing 12 as shown in fig4 b . the nature of the “ container breaking ” ( container rupturing ) will to at least some extent be a function of the material of construction of the containers . in the case of a glass or brittle plastic container , the container breaking will be a focused cracking or focused shattering of a predetermined area of the container . in the case of a flexible film container , the container breaking will be a focused puncturing or tearing or penetrating of a predetermined region of the container wall . the rupture of the containers 30 should be predirected to occur at the first end 14 of housing 12 such that the liquid released from containers 30 can conveniently and directly enter volume 24 and pass through holes 22 to foam layer 20 for delivery to the solid substrate . the rupturing of the containers at this position can be directed by applying a focused force to the containers at the desired position of rupture with a force - focusing sharp comer , ridge , pin or projection on the ramps 40 or on one or both of fingers 34 and 36 as previously described . the liquid released from the containers is contained within chamber 24 by walls 25 a and 25 b for passage through holes 22 . the bottom surface of chamber 24 slopes upward toward holes 22 to create a weir . liquid released from containers 30 passes up and over the weir . container shards are less likely to pass over the weir and are retained in chamber 24 . in addition , the flat surface of region 18 can be equipped with a series of barriers or pegs 27 which can pass liquid but hold back any shards and prevent them from being released inadvertently through holes 22 . it is always a good idea to not have liquid leaking out of chamber 24 between housings 12 and 26 . to that end , it is generally desirable to place a seal 42 between housing 12 and housing 26 as shown in fig3 to contain the liquid within the applicator and restrict its exit to the specific exit holes 22 . while the applicator of the invention can be used to apply consistent thickness layers of liquids in many applications , the preferred application for which it was created is the application of surgical sealants to form surgical incise drapes in situ . the liquid materials favored for forming such surgical incise drapes are liquids containing cyanoacrylate prepolymers . in situ polymerization of such cyanoacrylate compositions provides for an adherent polymeric film over the surgical incision site , which acts as a surgical incise drape during surgery . the adherence of the polymeric film to the skin surface is sufficiently strong to effectively preclude the possibility of lifting the drape from the skin during surgery . additionally , the cyanoacrylate composition can be applied as a liquid to the skin surface which permits formation of an adherent film over any skin contour , including but not limited to , elbows , knees , hips , and the like . an antimicrobially - effective amount of an antimicrobial iodophore or the like in the cyanoacrylate composition may provide significant enhancements in the effectiveness of the composition as well . since the polymeric film is naturally shed from the skin surface two to four days following application , there is no need to effect removal of the drape following surgery , therefore avoiding the skin trauma associated with conventional drape removal . moreover , the addition of antimicrobial agents to the cyanoacrylate composition results in the gradual release of antimicrobial from the polymerized cyanoacrylate composition , providing antimicrobial a level protection for post - surgical infection that is currently unavailable with conventional drapes . accordingly , the applicator can be used in this highly desirable application for forming a surgical incision drape at a surgical incision site of a patient as follows : ( b ) using the applicator of this invention to apply a layer of a liquid cyanoacrylate composition onto skin at the surgical incision site , which layer is consistent in thickness and of a thickness to cover the surgical incision site with the cyanoacrylate composition and ( c ) polymerizing this cyanoacrylate composition to form a flexible , waterproof , surgical incision drape which adheres to the surgical incision site where the cyanoacrylate composition was applied thereafter permitting the applied liquid layer to form an adherent solid surgical incise drape . the cyanoacrylate composition which finds preferred application using the applicator of this invention comprises a cyanoacrylate ester , which , in monomeric form , is represented by formula i : alkyl of 1 to 10 carbon atoms , alkenyl of 2 to 10 carbon atoms , cycloalkyl groups of from 5 to 8 carbon atoms , phenyl , 2 - ethoxyethyl , 3 - methoxybutyl , and a substituent of the formula : wherein each r ′ is independently selected from the group consisting of : hydrogen and methyl , and r ″ is selected from the group consisting of : alkyl of from 1 to 6 carbon atoms , alkenyl of from 2 to 6 carbon atoms , alkynyl of from 2 to 6 carbon atoms , cycloalkyl of from 3 to 8 carbon atoms , aralkyl selected from the group consisting of benzyl , methylbenzyl and phenylethyl , phenyl , and phenyl substituted with 1 to 3 substituents selected from the group consisting of hydroxy , chloro , bromo , nitro , alkyl of 1 to 4 carbon atoms , and alkoxy of from 1 to 4 carbon atoms . preferably , in the cyanoacrylate esters of formula i , r is alkyl of from 2 to 10 carbon atoms and more preferably alkyl of from 2 to 8 carbon atoms . even more preferably , r is butyl , pentyl or octyl or a mixture of butyl and octyl ( e . g ., 2 - ethylhexyl ) and most preferably r is n - butyl . in preferred embodiments , the cyanoacrylate composition may contain from about 0 . 01 to about 5 weight - percent antimicrobial . in preferred embodiments , the layer of liquid cyanoacrylate laid down by the applicator has a thickness of no more that about 1 millimeter and yields a polymerized cyanoacrylate composition layer that has a thickness of no more than about 1 millimeter . more preferably , the polymer layer and the liquid layer have a uniform thickness of from about 2 to about 500 μm . still more preferably , the layers have a thickness of from about 20 to about 100 μm . the cyanoacrylate adhesive compositions employed in the applicator of this invention may contain , in addition to a polymerizable cyanoacrylate component and the optional antimicrobial in an amount sufficient to provide effective antimicrobial activity as already described , polymerization inhibitors , in amounts sufficient to provide inhibition or retardation of polymerization prior to the use of the composition , and / or biocompatible plasticizer components , in an amount sufficient to provide enhanced flexibility for the resulting film coating formed by polymerization of the cyanoacrylate adhesive composition . ( b ) about 0 . 01 to about 5 weight percent antimicrobial based on the total weight of the composition ; ( d ) optionally from about 10 to about 30 weight percent based on the total weight of the composition of a biocompatible plasticizer . in preferred embodiments of the invention , the cyanoacrylate composition is applied onto the surface of intact skin and the incision is made subsequent to formation of the surgical incision drape . more preferably , the intact skin is further characterized as lacking pre - existing sites of infection , open wounds , scabs , sun damage , etc ., which would permit the polymer to penetrate from the surface of the epidermis to or beyond the dermal layer . notably , while these and other skin conditions may reduce the performance of the surgical drape of the instant invention , they do not necessarily preclude use of the surgical drape on such skin . the surgical protocol in which the applicator is used preferably involves skin preparation prior to in situ formation of the cyanoacrylate polymer surgical drape over the surgical incision site . in one embodiment of the invention , the skin is cleansed to remove dirt and oils . the patient &# 39 ; s skin may be cleansed and / or scrubbed with mild detergents , antimicrobial soaps , alcohol , or other compositions routinely used to clean wounds or prepare skin for surgery . other cleansing or sanitizing compositions may be used , with the proviso that the cleaning and / or scrubbing compositions do not interfere with polymerization of the cyanoacrylate composition , once applied . the skin surface will typically be dried after cleansing and / or scrubbing . the surgical incision site is optionally dried and then an adherent polymeric surgical incision drape is formed over this site by rupturing one or more containers of cyanoacrylate adhesive based sealant in an applicator of this invention and thereafter , using the applicator , applying the cyanoacrylate adhesive composition to the intact skin surface at the surgical incision site . the polymerizable cyanoacrylate prepolymers polymerize in situ to form a cyanoacrylate polymer film upon contact with the surface skin moisture , tissue protein , etc . polymerization occurs at ambient skin temperature while maintaining the skin surface under suitable conditions to allow polymerization to proceed . in general , the length of time required for polymerization will vary depending on factors such as the amount of adhesive composition applied , the temperature of the skin , the moisture content of the skin , the surface area of skin to which the adhesive was applied , and the like . however , polymerization is typically complete within about 10 to about 60 seconds , while the skin is maintained at ambient conditions . during this period , the patient is maintained in a position which permits the cyanoacrylate to polymerize and form a polymeric surgical incise drape , while minimizing patient movement that might dislodge the cyanoacrylate composition from that surgical incision site , or cause the cyanoacrylate composition to spread beyond the intended surgical incision site . after polymerization , the resulting polymeric film forms a surgical incision drape which strongly adheres to the skin , is flexible and waterproof . such strong adherence effectively eliminates the possibility that the surgical drape will lift away from the patient &# 39 ; s skin during surgery . however , notwithstanding such strong adherence , the polymeric film defining the surgical drape will adhere to the skin for a period of about two to four days , after which time it sloughs off . this occurs because the cyanoacrylate polymer adheres only to the uppermost portion of the epidermal layer , which is continuously in the process of being sloughed off and replaced by the underlying cells . accordingly , the cyanoacrylate surgical drape need not be removed in the manner of conventional surgical drapes , thereby eliminating the skin trauma associated with the removal of conventional surgical drapes . it will be appreciated that while specific embodiments of this application have been described in detail this is not to be construed as limiting the scope of the invention which as defined by the appended claims .
an applicator for dispensing uniform thickness layers of liquid to surfaces and especially surgical sealants to surgical sites to create , in situ , a surgical incise drape is disclosed . the applicator employs a supported thin layer of foam which achieves layer thickness which are substantially independent of the pressure applied to the applicator during use . methods of using the applicator are also disclosed .