BACKGROUND OF THE INVENTION

The present invention generally relates to securing layers of differing density sponge material together to form a composite body and mechanically treating the composite sponge body to store mechanical energy in the body so that when it is hydrated it transfers the stored energy to a driving device or a work area.

There currently is a need to provide medical devices which can be inserted into the human body in one condition and when hydrated by the body fluids transfer stored mechanical energy to a work area thus turning a pulley, displacing an organ or tissue to a different position, or applying a mechanical function to accomplish a desired result.

It is often necessary during surgery to displace or temporarily relocate tissue or organs from their natural anatomical position. This is done to facilitate surgery at the site. Organs and tissue must be handled gently to prevent damage or to minimize the tendency to produce adhesions, post operatively.

A number of patents exist which show various devices which have been designed to change shape to provide a desired medical function or to impart a mechanical force for accomplishing a desired result.

In this area, U.S. Patent Number 5,149,332 discloses an absorbent product which is longitudinally compressed or microcreped to produce microroundulations by compressing the web in its own plane in the direction of its length with compressive forces exerted substantially parallel to a longitudinal direction of the material. The material can, alternatively, be confined in a small dimension treatment cavity to produce microroundulations. The product when compressed has at least 10 microroundulations per inch in the layer in the direction of treatment. The microroundulated layer is shape- retentive and has stored mechanical energy capable under an activating condition such as hydration to cause the product to expand. The product is envisioned to be used as superabsorbent assemblages, menstrual tampons, pads such as bandages, compresses, rolls and the like and liquid distributing articles.

A number of shaped polymeric compositions for surgical use which can absorb liquid and thereby expand or contract in one direction are shown by U.S. Patent Number 4,565,722. Examples of such different shaped memory devices are shown in the figures of the patent, the even numbers representing expanded devices. One shaped memory device is a triangular shaped endodontic point for insertion into a tooth after a nerve cavity has been removed. The axial length stays unchanged while the product swells radially. Another shaped memory device is initially in the form of a sheath and expands radially for

holding severed nerve ends, veins or arteries in close proximity so that the contracted ends of the sheath provide a soft and pliable grip on the nerve, vein or artery ends. Another shaped device is shown which swells in contact with body fluid to a dumbbell shape which can be used for providing a permanent but non-irritant

Fallopian tube closure. Still another shaped memory device is directed to a cylindrical blank which expands in diameter. Another shaped memory device expands in thickness only provided that d-,/d ₂ equals the linear expansion ratio of the material during hydration to give the expanded insert an arcuate outer surface for use as a breast implant.

U.S. Patent Number 4,159,719 discloses a dehydrated wick of tightly coiled cellular sponge like material which when hydrated uncurls and expands radially to snugly engage the inner peripheral wall of the ear canal. Likewise U.S. Patent Number 4,034,759 discloses a moisture expandable prosthesis constructed of a hollow cylindrical wick of dehydrated regenerated cellulose sponge material. The sponge material is tightly compressed so that it is rigid for insertion endwise into a body opening. When the wick is moistened, it expands radially to engage the inner peripheral walls of the opening and when used in association with an ear canal, provides an axial opening through which the expanded member permits sound waves to reach the ear drum.

U.S. Patent Number 4,979,947 discloses a resilient foam material collapsed into a small volume condition having a string or cord passing through the material which when introduced into an orifice absorbs moisture to expand at a predetermined size and shape for blockage. Traction on the string during withdrawal results in compression of the contained foam cube allowing comfortable withdrawal from the body orifice.

A muIti-layered tampon formed by folding over a single layer of absorbent batt is disclosed by U.S. Patent Number 4,327,728. Pockets containing hydrocolloid and introfying particles are placed so as to lie between the layers and project into each layer. The dry solid granules of hydrocolloid particles when wetted begin to swell expanding the pockets. As the pockets expand, the expanding walls push the adjacent fibers of the batt aside while keeping the hydrocolloid particles trapped within the pockets thus significantly increasing the total absorptive capacity of the structure.

U.S. Patent Number 4,019,498 discloses a vaginal device for urinary incontinence in the form of a cellular mushroom-shaped body which is precompressed and inserted in a plastic sleeve. After insertion into the vagina the sleeve is pierced allowing the introduction of air into the sponge-like cells of the device permitting it to expand and exert pressure on the urethra.

Medical sponges and dressings are generally used to absorb bodily fluids as blood, serum, spinal fluid, tissue fluid, urine, sweat, bile, digestive juices and other fluids. However, medical sponges are also used to displace organs or tissues and dam and hold organs and tissues. Because the sponge material is difficult to place in human body cavities after it has absorbed fluid and obtain the desired results and since pre-wetting will decrease the amount of fluid that can be adsorbed, many absorbent sponges and dressing are placed in human body cavities in a dry compressed form. The present invention takes this prior art one step further and obtains a mechanical action by the sponge material when it is placed in the human body cavity.

The present invention utilizes treatment of sponges which impart stored mechanical energy to dry rigid absorbent sponge materials which when hydrated, act to absorb fluids and perform a mechanical action.

SUMMARY OF THE INVENTION The present invention is directed towards a mechanically treated layered medical sponge device with potential energy for performing mechanical work stored in composite absorbent layers of different densities. The sponge is compressed into a rigid and dry form with stored mechanical energy and is capable of the release of the mechanical energy by expanding when the device is hydrated. The sponge is constructed of polyvinyl acetal.

a material with high absorptive properties and immediate wicking and is twisted with one end optionally being secured to a drive mechanism. Upon hydration the sponge material untwists resulting in the ultimate release of stored mechanical energy rotating or driving a connected mechanism or engaged tissue or organ.

In another aspect of the invention a sponge device is constructed in the shape of a leaf spring. The leaf spring device is prefolded so that it expands along the fold or folds during hydration and the fold placement allows predetermined application of force by the arms of the device on any organ or tissues that the spring is placed against.

An important object of the invention resides with the layered device being shape-retentive when dry with stored mechanical energy, the layered device being capable of releasing mechanical energy when expanded by hydration to drive a mechanism or displace an organ or tissue.

In the accompanying drawings, there is shown an illustrative embodiment of the invention from which these and other of objectives, novel features and advantages will be readily apparent.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a base composite layered material of the hydration engine device prior to treatment;

Figure 2 is a perspective view of the hydration engine material twisted into a spiral shape device storing mechanical energy;

Figure 3 is a schematic view of the spiral shaped hydration engine device of Figure 2 connected to and driving a drive mechanism;

Figure 4 is a perspective view of a base composite layered material of an alternative spring leaf embodiment of the hydration engine prior to treatment;

Figure 5 is a perspective view of the hydration engine material of Figure 4 bent into a rigid leaf spring hydration engine device storing mechanical energy;

Figure 6 is a perspective view of the hydrated leaf spring hydration engine device shown in Figure 5 transmitting force;

Figure 7 is a perspective view of a hydration spring plate embodiment with the ends shown in relaxed orientation;

Figure 8 is a perspective view of the embodiment of Figure 7 prepositioned by raising one end to a vertical position;

Figure 9 is a perspective view of a laminated plate device embodiment; and

Figire 10 is a perspective view of the embodiment of Figure 10 prepositioned to add an increment of displacement force above that achieved with the device of Figure 6.

DETAILED DESCRIPTION OF THE DRAWINGS

The preferred embodiment and best mode of the invention is shown in Figures 1 and 2. As shown in the drawings, a flexible hydration engine sponge device 10 capable of transmitting stored mechanical energy is constructed of a layered body 12 of rigid absorbent polyvinyl acetal material. The layered body 12 has two layers of differing density sponge material; a low density sponge material 14 and a high density sponge material 16 which are secured together in one composite piece by ultrasonic welding, an adhesive or other suitable method known in the art. The sponge material is produced from polyvinyl acetal (PVAc) polymer by the methods described in U.S. Patent Number 4,098,728. The sponge material has the desirable medical properties of being highly absorbent to liquids, is very soft when wet and also has high wet strength. The polyvinyl acetal material has a controlled pore size uniformly distributed throughout the volume of each of the specific layers, the material being fast wicking and having a high liquid holding capacity. The sponge material has an instantaneous fluid wicking, absorptive capacity of up to 25 times its weight in fluids, and a retained fluid capacity of up to 25 times its own weight in fluids as measured by ASTM D-1117-80.

Being soft when wet allows the PVAc sponge to conform to the precise space of the cavity or site required for transmission of stored energy or to displace or move the organs and/or tissue without damaging same.

The PVAc sponge material is produced by Merocel

Inc. located in Mystic, Conn, in a variety of pore or cell sizes. These cell sizes can vary from MEROCEL sponge product designation CF 50 which has a pore size which ranges from 0.2mm to 1.2mm in diameter; CF 100 which has a pore size which ranges from 0.02mm to 0.6mm in diameter;

CF 150 which has a pore size which ranges from 0.01mm to

0.5mm in diameter; CF 200 which has a pore size which ranges from 0.004mm to 0.4mm in diameter; and CF 400 which has a pore size which ranges from 0.004mm to 0.2mm in diameter. The aforenoted grade designations CF 50, 100,

150, 200 and 400 have a respective average pore size of

.95mm, 0.45, 0.35mm and 0.20mm (0.205 for CF 200 and 0.190 for CF 400). The present invention uses the different swelling rates of layered PVAc sponges to achieve a controlled force against tissue.

The inventive sponge composition uses a compound sponge made of two or more layers or plates of PVAc sponge, preferably CF 50 as the base low density sponge layer and another greater density or smaller pore size sponge such as CF 100, CF 150, CF 200 or CF 400 as the other layer. The compound sponge has the property of curling or unfolding depending on its shape because of the differential in the swelling rates and the swelling potential of the two layers. Since the two layers or plates have a different equilibrium level of liquid absorption, it has been found that the curling or folding property is a permanent feature of the wet sponge as long

as it remains wet.

Other differentials which can be used are: (1) Percent expansion from full compression (CF50 is greater), overcompression (>10:0 ratio for CF50) will lead to delayed expansion, then a permanent set, and ultimately formation of a film layer; and (2) Percent expansion from dried volume (CF50 is greater).

The hydration engine sponge device 10 is manufactured by layering or stacking the two differing density sponge materials in layers, cutting and sealing both layers together with an ultrasonic device. The ultrasonic device seals the sponge layers together on their outside edges. If desired the sponge layers can be cut by any standard means and secured together with an adhesive such as Dow Corning 355 Medical Adhesive. The composite sponge material 12 is compressed, saline or distilled water is applied to the sponge material to swell the material up to expanded size, the same is twisted into a spiral shape with both ends restrained and then compressed and dried to ambient condition.

The sponge material is formed into a rigid twisted spiral shaped body 18 as seen in Figure 2 which can be used by itself to displace organs or tissues by restraining end 19 and engaging end 21 against an organ or connecting end 21 to a drive member 20. The drive member 20 is constructed in the form of a pulley, disc or cylinder and is secured to one end of the twisted body 18 to receive torque from twisted body 18. It should be

noted that while a pulley, disc, cylinder and the like have been identified, any other member which can make use of a rotary motion could be used in place of the same.

The pulley 20 can be used in connection with another member 22 such as a hook or clamp to pull the hook or clamp and its associated organ or tissue into a desired position by rotation of the pulley. The disc or cylinder can be used to drive another member or engage an organ or tissue. The dried and twisted sponge spiral body 18 will approximately return to its straight configuration when rehydrated. It becomes functionally untwisted when hydrated thereby imparting its stored mechanical energy in a predetermined selected direction, the torque causing the pulley or drive member to rotate a desired number of times. The contacting fluid initiates the release of substantial stored mechanical energy that has been set into the body to generate a torque which when exerted on a body, moves the body.

Another embodiment is shown in Figures 4 to 6. In this embodiment the leaf spring body 30 is formed of polyvinyl acetal material of the differing densities as previously noted.

These cell sizes can vary from MEROCEL sponge product designation CF 50 which has a pore size (diameter) which ranges 0.2mm to 1.2mm as determined by Scanning Election Microscopy at lOx magnification and an average pore diameter of 0.95mm; to CF 100 which has a pore size which ranges from 0.02mm to 0.6mm in diameter and an

average pore diameter of 0.45mm, to CF 150 which has a pore size which ranges from 0.01mm to 0.5mm in diameter and an average pore diameter of 0.35mm, to CF 200 which has a pore size which ranges from 0.004mm to 0.4mm in diameter and an average pore diameter of 0.20mm (0.205) and CF 400 which has a pore size which ranges from 0.004mm to 0.2mm in diameter and an average pore diameter of

0.19mm (0.190).

Each of these different sponges of differing pore size has a different rate of water absorption and consequently a differing rate of swelling or other differentials as previously noted. The material 32 is folded over at 34 to form a leaf spring shape 31. Arms 36 and 38 of the leaf spring expand outward in the direction of arrow A when hydrated releasing stored mechanical energy in a predetermined selected direction. Arm 38 is set against a restraining surface 40 allowing the organ or tissue to be transported in direction A. The leaf spring 31 could be placed between two organs or tissue to separate the same. This density differential allows differential swelling providing a controlled force on an organ or tissue to obtain organ or tissue displacement.

Additional envisioned designs include control over the amount and type of volumetric expansion exhibited by the device upon hydration as well as prepositioning of one sponge plate relative to another prior to laminating.

Simple mechanical compression of one or more dry sponge plates, or portions thereof, may be performed to remove or substantially decrease the void volume. This selective compression is fully recovered immediately upon fluid wicking and sponge plate hydration.

Control of the volumetric expansion is achieved by selectively compressing one or more of the sponge plates beyond the point where the initial void volume is nearly eliminated. "Controlled" compression beyond this point results in a delay of fluid wicking and sponge plate hydration and expansion. The "controlled" compression and resultant delay makes timed sequences of events possible to the device designer.

The CF-50 layer 40 of Figure 9 is fabricated with an extra thickness 42 at the top shown in phantom resembling the number "7". If this area is compressed mechanically to the point of imparting a delay in the natural fluid wicking properties, the device of Figures 6 and 10 could be used as a leaf spring or wedge where a delayed expansion would occur in the area noted "c". The device would be useful as an endoscopic wedge to position intestines out of the operative site. A slim version of the wedge would be useful during placement with optimum site visualization. Approximately five to 60 seconds (delay controlled by compression format) after placement, the added bulk at "c" would expand and provide additional holding power and damming capabilities for positioning the intestines (or bowel, etc.) out of the operative field.

Pre-laminating orientation is achieved by fixing or otherwising prepositioning one plate relative to the remaining plates prior to joining. The orientation creates further potential energy and options for complex, mechanized motion.

The judicious choice of sponge plate shape; thickness; density; pore size; type, location and extent of mechanical compression; and any pre-laminating orientation of one plate relative to the remaining plates enables a variety of possibilities of storing and transmitting energy with the invention.

In the foregoing description, the invention has been described with reference to a particular preferred embodiment, although it is to be understood that specific details shown are merely illustrative, and the invention may be carried out in other ways without departing from the true spirit and scope of the following claims: