Abstract:
The present invention is directed to a surgical cutting device having a body, a piezoelectric actuator received within and secured to the body and a blade associated with and in communication with the actuator. The actuator is adapted for vibrating at a frequency to produce an oscillating displacement of the blade. A method of operating the surgical cutting device is also provided wherein the cutting device includes an actuator which is adapted for vibrating at a frequency to produce a sinusoidal displacement of the blade in the range of 250-500 μm.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/933,528 filed on Jun. 7, 2007. The subject matter of the prior application is incorporated in its entirety herein by reference thereto. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally pertains to surgical instruments, and more specifically to high-speed electrically driven surgical blades. The invention is applicable to the cutting of skin and other tissues or materials found within the body. 
         [0004]    Cataract surgery is the most common surgical procedure in the United States today with close to 2 million procedures performed annually. Ocular keratomes are used to create self-sealing incisions entering through the conjunctiva, scleara or cornea to form clear corneal incisions during cataract surgery. Self-sealing incisions may also be referred to as self-healing incisions as there is no need to cauterize tissue to prevent further tissue damage and bleeding. 
         [0005]    In general surgical applications, percutaneous access to tissues and vasculature as well as access through body-surface organ tissues like the conjunctiva and sclera is typically accomplished with non-vibrating cutting and shearing edges. Due in part to the variability of sharpness of conventional metal ophthalmic knife blades, the force required to create an incision into the eye tissue can cause significant tissue trauma, separating stromal layers and causing delamination of the Descemets membrane. As the surgeon applies force through the handle to a non-actuated blade, the point ruptures the surface membrane of the tissue and the edges cut and divide the tissue. Essentially, the blade is resisted by the force of the elastically deforming tissue. The blade is also resisted by the force required to divide the tissue at the cutting edges and the force created by the adhesive bonds between the blade and the tissue. 
         [0006]    Several advances have been attempted to reduce the force necessary to penetrate a blade through tissue. Most of these, such as U.S. Pat. No. 6,554,840 (Matsutani et al.) for example, simply reduce the cutting edge to blade thickness ratio to lower the penetration force. Others, such as U.S. Pat. No. 6,547,802 (Nallakrishnan et al.) seek to improve incisions to the eye by maximizing the surface area of the cut with a blade having a wide surface area comprised of two cutting edges disposed at an angle greater than 90°. Meanwhile, U.S. Pat. No. 6,056,764 (Smith) not only changes the blade tip angle, or angle between cutting edges on either side of a sharp tip, but also offers alternative blade materials such as diamond, sapphire, ruby, and cubic zirconia. Additionally, the &#39;764 patent teaches the use of coatings over stainless steel blades to add strength to the blade. Other conventional attempts also disclose applying a surface treatment in the form of a hydrophobic/hydrophilic coating to the blade. However, while some reduction of force may be attained by the aforementioned disclosures, they are limited to only reducing the bulk surface friction between the instrument surface and the tissue surface being cut, and changing the surface area of the blade or changing the coefficient of friction between the surfaces. 
         [0007]    One of the problems associated with surface treatment of surgical blades is that the blade sharpness is sacrificed for a lowering of mechanical friction. Also, an associated problem with changing the dimensions of the blade is faster dulling, further resulting in increased friction at the blade-tissue interface. These results only further promote cauterization and do not contribute to reducing the force necessary for penetration. 
         [0008]    Another approach to cutting and penetrating through tissue is to sonically or ultrasonically vibrate the cutting edges of a surgical blade. Because piezoelectric ceramics deform when exposed to an electrical input, a phenomenon known as the converse piezoelectric effect, current technologies utilize stacks of piezoelectric material such as lead-zirconate-titanate (PZT) to produce the mechanical, ultrasonic motion. For example, U.S. Pat. No. 4,587,958 (Noguchi) discloses an ultrasonic surgical device that focuses on the application of ultrasonic energy to shatter tissue. Unfortunately, it is apparent from the &#39;958 disclosure that the express purpose of the ultrasonic vibrations applied upon the device is to “exhibit a satisfactory tissue shattering capacity”. As a result, this type of tissue penetration does not minimize scarring, but instead creates a blunt incision by shattering the tissue. 
         [0009]    On the other hand, U.S. Pat. No. 5,935,143 (Hood) attempts to minimize the “thermal footprint” of an ultrasonic blade. This is done by using a Langevin or dumbbell type transducer to produce axial motion of the cutting blade, thereby providing tactile feedback and enhanced ergonomics to the surgeon using the blade. The combination of ultrasonic vibration coupled with sinusoidal axial motion of the &#39;143 blade perpendicular to the tissue surface plane also causes coagulation and cauterization of the tissue being incised and, therefore, does not increase the quality of the incision. 
         [0010]    While it&#39;s been shown in the art that ultrasonically vibrating a blade enhances its sharpness, U.S. Pat. No. 5,324,299 (Davison, et al.) teaches that without proper configuration and design, an ultrasonic blade&#39;s “sharpness” is not enhanced when cutting through relatively loose and unsupported tissues. Therefore, the &#39;299 reference teaches ultrasonically driven scalpel blades having a hook tip design which focuses some of the vibration in a particular direction, but does not actually increase the quality of the incision as it serves to enhance coagulation of the tissue being incised. Furthermore, a hooked tip prevents the blade from being optimally tuned for stab type incisions. 
         [0011]    Unfortunately, the focus of the improvements of vibrating blades found in the aforementioned prior-alt disclosures were made with little regard to secondary issues related to incising tissue. For example, secondary issues such as those aspects of surgical procedure beyond simply incising the tissue include minimizing the pain experienced by patients during tissue penetration, minimizing scarring and improving wound healing, all of which are the result of having created a high quality incision at a reduced force necessary for cutting, incising, penetrating and the like. 
         [0012]    Advancements in the surgical arts have been attempted to address these secondary issues. For instance, it has been shown that oscillating the blade of a surgical tool laterally or parallel to the tissue surface, rather than axially or perpendicular to its surface, may reduce pain during incising. As is disclosed in U.S. Pat. No. 6,210,421 (Bocker, et al.), the lateral motion of the blade against the skin reduces the pressure waves that would otherwise be directed perpendicular to the skin in an axially driven blade, resulting in a smaller number of pain receptors being activated. The &#39;421 patent, however, is directed to a blood lancet which is not optimal for cutting tissue to a depth necessary as in ocular or minimally invasive surgery. 
         [0013]    In an attempt to optimize tissue incising, U.S. Pat. No. 6,254,622 (Hood) discloses an ultrasonically driven blade having an unsymmetrical cutting surface which causes an offset center of gravity that creates transverse movement of the blade, perpendicular to the longitudinal axis of the surgical device. The blade, having a low attack angle to form the asymmetric shape that gives the blade a sharp point, is able to then effectively cut both hydrogenous tissue and non-hydrogenous tissue without requiring tension on the cutting medium. The transverse movement of the blade provides an efficient means of transferring the ultrasonic energy directly into the tissue and also moves the blood away from the cutting edge, allowing for a more efficient transfer of ultrasonic energy to the tissue. Unfortunately, the &#39;622 patent relies on a driving frequency from 60,000-120,000 Hz, a frequency range that is generally too high for preserving the soft tissue as it usually causes thermal damage. 
         [0014]    In yet another attempt to transform the axial motion of a driving piezoelectric transducer into transverse motion of a surgical blade, U.S. Pat. No. 6,585,745 (Cimino) discloses a split-electrode configuration to drive a bolt-type or Langevin actuator  311 . The patent discloses the use of lower frequencies such as 10 kHz in an axial or longitudinal direction, causing a transverse motion of the blade perpendicular to the long axis of the device. While the &#39;745 patent attempts to disclose that the device produces improved cutting, it is inherently flawed as it depends on the split-electrode configuration, which is complex as compared to a single-phase pattern. Because the split-electrode configuration causes the piezoelectric transducers that drive the device to contract on one half and expand on the other, the device is vulnerable to induced stress and cracking, thereby reducing life and efficiency. 
         [0015]    Lateral motion of the blade in a surgical tool has also been combined with longitudinal motion, such as that which is described in U.S. Patent Application No. 2005/0234484 A1 (Houser, et al.). While the &#39;484 application discloses that longitudinal ultrasonic vibration of the blade generates motion and heat, thereby assisting in the coagulating of the tissue, the disclosure also recognizes that transverse ultrasonic vibration of the blade offers beneficial results. One such result is a total ultrasonic vibration having an amplitude that is larger and more uniform over a long distance of the blade as compared to surgical blades having only longitudinal vibrations. Yet, the invention relies solely on ultrasonic vibrations, which inherently limits the invention to incising specific tissues only, and not the wide range of tissues that are encountered during a surgical procedure. A weakness of all blades, which are solely ultrasonically driven, is that they atomize the surrounding fluids. Because fluids are broken into small droplets when they encounter a solid mass vibrating at ultrasonic frequencies, the fluids becomes a mobile “mist” of sorts. As droplets, which have a size inversely proportional to the vibrating frequency, the fluid “mist” is similar to that of room humidifiers and also to the droplets created by industrial spray nozzles. One negative aspect of creating a mobile mist during a surgical procedure is that these particles may contain viral or bacterial agents. By ultrasonically vibrating the moisture surrounding unhealthy tissue as it is being incised, it is possible to unknowingly transport the bacterial or viral agent to healthy tissue. It, therefore, is an inherent weakness of ultrasonically driven surgical blades that they increase the chance of spreading disease or infection. 
         [0016]    Therefore, a need exists for an improved surgical blade that is able to be vibrated sonically and ultrasonically, reducing the force required to penetrate tissue, and thereby reduces the amount of resulting tissue damage and scarring while also improving wound healing. 
       SUMMARY OF THE INVENTION 
       [0017]    Transducer technologies that rely on conventional, single or stacked piezoelectric ceramic assemblies for actuation are hindered by the maximum strain limit of the piezoelectric materials themselves. Because the maximum strain limit of conventional piezoelectric ceramics is about 0.1% for polycrystalline piezoelectric materials, such as ceramic lead zirconate titanate (PZT) and 0.5% for single crystal piezoelectric materials, it would require a large stack of cells to approach useful displacement or actuation of, for example, a handheld device usable for processes such as cutting, slicing, penetrating, incising and the like. However, using a large stack of cells to actuate components of a handpiece would also require the tool size to increase beyond usable biometric design for handheld instruments. 
         [0018]    Flextensional transducer assembly designs have been developed which provide amplification in piezoelectric material stack strain displacement. The flextensional designs comprise a piezoelectric material transducer driving cell disposed within a frame, platten, end-caps or housing. The geometry of the frame, platten, end caps or housing provides amplification of the transverse, axial, radial or longitudinal motions of the driver cell to obtain a larger displacement of the flextensional assembly in a particular direction. Essentially, the flextensional transducer assembly more efficiently converts strain in one direction into movement (or force) in a second direction. 
         [0019]    The present invention comprises a handheld device including a cutting, slicing, incising member which is actuated by a flextensional transducer assembly. For example, the flextensional transducer assembly may utilize flextensional cymbal transducer/actuator technology or amplified piezoelectric actuator (APA) transducer technology. The flextensional transducer assembly provides for improved amplification and improved performance which are above that of conventional handheld devices. For example, the amplification may be improved by up to about 50-fold. Additionally, the flextensional transducer assembly enables handpiece configurations to have a more simplified design and a smaller format. 
         [0020]    The present invention relates generally to a minimally invasive surgical blade for the cutting and incising of various materials and tissues within a body. Specifically, the present invention is a handpiece comprising a body, at least one piezoelectric transducer driver disposed within the body, a motion transfer adaptor and a surgical blade for cutting, incising and penetrating. 
         [0021]    The invention is also a method for cutting, incising and penetrating tissues or other materials found within a patient&#39;s body using a handheld surgical tool comprising a body, at least one piezoelectric transducer disposed within the body, a motion transfer adaptor having at least a distal end and a proximal end, and a surgical blade. 
         [0022]    The method includes driving the at least one piezoelectric transducer disposed within a body of the handheld surgical tool sinusoidally in a frequency range of 10-1000 Hertz (Hz) and at an electric field in the range of about 300-500 V/mm. Specifically, the blade is driven sinusoidally at such a frequency and displacement so as to attain a peak velocity in the range of 0.9-2.5 m/s, more preferably in the range of 1.0-2.5 m/s and most preferably in the range of 1.5-2.0 m/s. The sinusoidal vibrations are transferred mechanically to the motion transfer adapter coupled at the proximal end to the at least one piezoelectric transducer. The vibrations are further transferred mechanically to the surgical blade attached to a proximal end of the motion transfer adaptor. The surgical blade is configured in such a manner so as to oscillate in a direction that comprises an in-plane motion. In particular, the in-plane motion comprises motion that is primarily in one plane. Most preferably, the surgical blade of the present invention is parallel to the surface of the tissue which is being incised, cut, penetrated or the like, by the blade. The in-plane motion is such a motion that is primarily perpendicular to the long axis of the device handle. In other words, the sinusoidal vibrations are an axial driving motion produced parallel to a hypothetical, centrally located axis which extends through a distal end and through a proximal end of a surgical tool&#39;s handle portion. The axial driving motion is transposed into lateral motion, perpendicular to the direction of the originating sinusoidal vibrations. It is an object of this invention to reduce tissue deformation, thereby giving superior shaped flap peripheries and flap or stromal bed apposition in ophthalmologic surgical procedures. 
         [0023]    In one embodiment, the piezoelectric transducer is a standard bimorph actuator or a variable thickness bimorph similar to but not limited to, those configurations which are described by Cappalleri, D. et al in “Design of a PZT Bimorph Actuator Using a Metamodel-Based Approach”, Transactions of the ASME, Vol. 124 June 2002 and is hereby incorporated by reference. 
         [0024]    In another embodiment, the piezoelectric transducer is a cymbal transducer/actuator similar to, but not limited to, that which is described in U.S. Pat. No. 5,729,077 (Newnham) and is hereby incorporated by reference. 
         [0025]    In one embodiment, the piezoelectric transducer is a Langevin or dumbbell type transducer similar to, but not limited to, that which is disclosed in U.S. Patent Publication No. 2007/0063618 A1 (Bromfield), which is hereby incorporated by reference. 
         [0026]    In yet another embodiment, the piezoelectric transducer is an APA transducer similar to, but not limited to, that which is described in U.S. Pat. No. 6,465,936 (Knowles et al.) and is hereby incorporated by reference. 
         [0027]    These and other features of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of this invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0028]    Exemplary embodiments of this invention will be described with reference to the accompanying figures. 
           [0029]      FIG. 1  is a graph illustrating the reduction of force response. 
           [0030]      FIG. 2  is a perspective view of a first embodiment of the handheld surgical device. 
           [0031]      FIG. 3A  is a cross sectional view of the piezoelectric bender-type actuator shown in  FIG. 2 . 
           [0032]      FIG. 3B  is a perspective view of the piezoelectric bender-type actuator shown in  FIG. 3A . 
           [0033]      FIG. 4  is a cross section view of a variable thickness unimorph type actuator. 
           [0034]      FIG. 5  is a visual representation of an example surgical blade of the present invention undergoing sinusoidal, lateral motion. 
           [0035]      FIG. 6  is a cross-sectional view of a second embodiment of the handheld surgical device. 
           [0036]      FIG. 7  is a cross-sectional view of a third embodiment of the handheld surgical device. 
           [0037]      FIG. 8  is a cross-sectional view of a fourth embodiment of the handheld surgical device. 
       
    
    
     REFERENCE LABELS 
       [0000]    
       
         
           
             A Static blade force curve 
             B Vibrating blade force curve 
             D 1  Displacement distance 
             D 2  Displacement distance 
             W Blade width 
             TCW Total Cut Width 
             BA Hypothetical Bender long axis 
             HLA Hypothetical Long Axis 
               100  Bender actuated surgical tool 
               110  Body 
               111  Bimorph piezoelectric transducer/actuator 
               111 ′ Variable Thickness unimorph piezoelectric actuator 
               112  Piezoelectric plate 
               113  Bender support bar 
               113 ′ First side surface 
               113 ″ second side surface 
               114  Bender motion constraint 
               115  Bolt through hole 
               115 ′ Bolt 
               116  Support Surface 
               117  Bender distal end 
               118  Bender proximal end 
               119  Blade 
               119 ′ first blade displacement position 
               119 ″ second blade displacement position 
               120  Blade collar 
               121  Collar Attachment node 
               122  first cutting edge 
               122 ′ first cutting edge displacement position 
               123  second cutting edge 
               123 ′ second cutting edge displacement position 
               124  blade tip 
               125  first blade ear 
               125 ′ first blade ear positive displacement position 
               125 ″ first blade ear negative displacement position 
               126  second blade ear 
               126 ′ second blade ear positive displacement position 
               126 ″ second blade ear negative displacement position 
               127  first piezoplate stack 
               127   a  first layer 
               127   a ′ first layer upper surface 
               127   a ″ first layer bottom surface 
               127   b  second layer 
               127   b ′ second layer upper surface 
               127   b ″ second layer bottom surface 
               127   c  third layer 
               127   c ′ third layer upper surface 
               127   c ″ third layer bottom surface 
               127   d  fourth layer 
               127   d ′ fourth layer upper surface 
               127   d ″ fourth layer bottom surface 
               128  second piezoplate stack 
               129  first conducting electrical plate 
               129 ′ second conducting electrical plate 
               129 ″ third conducting electrical plate 
               131  ground connector 
               132  positive connector 
               133  negative connector 
               134  body proximal end 
               135  body distal end 
               200  cymbal actuated surgical tool 
               210  body 
               211  cymbal actuator/actuator 
               212  piezoelectric ceramic disc 
               213  first end-cap 
               214  second end-cap 
               215  dual beveled angled slit blade 
               216  blade neck 
               217  attachment node 
               218  motion constraining neck yoke 
               219  set screw 
               220  hypothetical long axis 
               300  Langevin actuated surgical tool 
               310  body 
               311  Langevin actuator 
               312  Langevin support collar 
               313  Piezoelectric ceramic discs 
               314  backing portion 
               315  Horn portion 
               316  compression bolt 
               317  Attachment node 
               318  Motion transfer adaptor 
               319  blade 
               320  Hypothetical long axis 
               400  APA transducer driven surgical tool 
               410  Body 
               411  APA transducer 
               412  Piezoelectric cell 
               413  Frame 
               414  Frame top wall 
               415  frame bottom wall 
               416  spacing member 
               417  blade neck 
               418  Motion constraining yoke 
               419  Blade 
               420  Blade Neck 
           
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION  
       [0134]    The preferred embodiments of the present invention are illustrated in  FIGS. 1 through 8  with the numerals referring to like and corresponding parts. 
         [0135]    The effectiveness of the invention as described, for example, in the aforementioned preferred embodiments, relies on the reduction of force principle in order to optimize incising, cutting or penetrating through tissue or materials found within the body. Essentially, when tissue is incised, cut, penetrated or separated by the high-speed operation of the surgical blade of the present invention, the tissue is held in place purely by its own inertia. In other words, a reduction of force effect is observed when a knife blade, for example a slit knife blade, is vibrated with an in-plane motion during the incision process and enough mechanical energy is present to break adhesive bonds between tissue and blade. The threshold limits of energy can be reached in the sonic or ultrasonic frequency ranges if the necessary amount of blade displacement is present. 
         [0136]    To exploit the reduction of force effect, the surgical blade of the present invention is designed such that the blade attains a short travel distance or displacement, and vibrates sinusoidally with a high cutting frequency. Utilizing the various device configurations as described in the aforementioned embodiments, it has been determined that the sinusoidal motion of the blade must include at least a peak velocity in the range of 0.9-2.5 m/s, more preferably between 1.0-2.25 m/s and most preferably at a velocity of 1.5-2.0 m/s. For example,  FIG. 1  shows a graphical representation of the resisting force versus depth of a surgical blade penetrating into material. In  FIG. 1 , the curve labeled A represents data for a blade in an “off” or non-vibrating condition, and the curve labeled B represents data for a surgical tool having a blade that is vibrated at 450 Hz at and a displacement of 500 μm. As is apparent from  FIG. 1 , curve A shows that without being vibrated, the force necessary to penetrate into a material is much higher than that for a blade being vibrated, such as that represented by curve B. 
         [0137]    In a first embodiment of the present invention as shown in  FIG. 2 , a bender actuated surgical tool  100  comprises a body  110 , and a bimorph piezoelectric transducer/transducer/actuator  111  disposed within body  110 . The bimorph piezoelectric transducer/transducer/actuator  111  comprises at least one piezoelectric ceramic plate  112 , but preferably comprises more than one of piezoelectric ceramic plates  112  attached longitudinally upon at least one side of a bender support bar  113 . The bender support bar  113  comprises a distal end  117  and a proximal end  118 , with a bender motion constraint  114  at the distal end  117 . The bender motion constraint  114  attaches bender support bar  113  to surface  116  of the body  110 . In one embodiment, the bender motion constraint  114  of the present embodiment comprises at least one thru-hole  115  (not visible in this figure) and a bolt  115 ′ passing at least partly through the bender support bar  113  and into an attachment slot (not shown) formed on support surface  116 . The attachment slot may be, for example, a threaded hole or the like. The bender actuated surgical tool  100  further comprises a blade  119  having a collar  120 . The blade collar  120  is directly and mechanically attached to the proximal end  118  of bender support bar  113  at collar attachment node  121 . Blade  119  may preferably comprise first cutting edge  122 , second cutting edge  123 , blade tip  124 , first blade ear  125  and second blade ear  126 . Collar attachment node  121  may comprise a threaded slot, compression slot, ¼″—cam lock slot, or the like. The bender actuated surgical tool  100  of the present invention also comprises a hypothetical long axis BA which is oriented centrally to rim through a distal end  135  a proximal end  134  of body  110 , further passing through the centers of each of body  110 , piezoelectric transducer/actuator  111  and blade  119 . Blade tip  124  is located externally to body  110 . 
         [0138]    Now, with respect to  FIG. 3   a , a cross-section of the bimorph piezoelectric transducer/actuator  111  of the bender actuated surgical tool  100  of  FIG. 2  is described. Preferably, the bimorph transducer/actuator  111  comprises at least one layer of a plurality of piezoelectric plate  112  formed side by side, each plate being formed longitudinally on, against, and in direct physical and electrical contact to a first side surface  113 ′ of bender support bar  113 , thereby forming first piezoplate stack  127 . The bimorph piezoelectric transducer/actuator  111  may also comprise a second piezoplate stack  128  configured in a similar fashion as the first piezoplate stack  127  except each of ceramic plate  112  being formed on, against and in direct physical and electrical contact to a second side surface  113 ″ formed opposite to the first side surface  113 ′ of bender support bar  113 . 
         [0139]    With respect to  FIG. 3   b , a perspective view of an embodiment of the bimorph piezoelectric transducer/actuator  111  with the blade  119  of the bender actuated surgical tool  100  of  FIG. 2  is described. At least one, but preferably two or more of thru-hole  115  are located at distal end  117  of bender support bar  113 . A plurality of piezoelectric plates  112  formed side by side, each plate being formed longitudinally on, against and in direct physical and electrical contact to a first side surface  113 ′ of bender support bar  113 , thereby forming first piezoplate stack  127 . Again, the bimorph piezoelectric transducer/actuator  111  may also comprise a second piezoplate stack  128  configured in a similar fashion as the first piezoplate stack  127  except piezoelectric plate  112  being formed on, against and in direct physical and electrical contact to a second side surface  113 ″ formed opposite to the first side surface  113 ′ of bender support bar  113 . 
         [0140]    Returning to  FIG. 2 , electrical contact is made to each of piezoelectric plates  112  of either first piezoplate stack  127  or second piezoplate stack  128 , but more preferably both first piezoplate stack  127  and second piezoplate stack  128 , by contact leads (not shown) connected to an external circuit (also not shown) so as to actuate the bimorph piezoelectric transducer/actuator  111 , with a separate electrical lead attached to the bender bar  113  as a ground electrode. Upon electrical activation of either first piezoplate stack  127  or second piezoplate stack  128 , but more preferably upon activation of both first piezoplate stack  127  and second piezoplate stack  128 , by an externally applied alternating current, bender bar  113  experiences a compressive force at its first side surface and a tensional force on its second side surface as a result of compression and expansion of the first piezoplate stack  127  and second piezoplate stack  128 , respectively, during one cycle of the applied current. Bender bar  113  then experiences a tensional force at its first side surface and a compressive force on its second side surface as a result of expansion and compression of the first piezoplate stack  127  and second piezoplate stack  128 , respectively, during the opposite cycle of the applied current. Thereby because proximal end  118  of bimorph transducer/actuator  111  is fixedly attached to body  110  at support surface  116  by bender motion constraint  114 , therefore, most importantly, first blade ear  125  and second blade ear  126  are oriented opposite to one another on blade  119  so as to be formed on either side of the aforementioned hypothetical axis, corresponding to the first side surface  113 ′ and the second side surface  113 ″ of bender bar  113 , respectively. In this way, when the bimorph piezoelectric actuator oscillates upon application of an AC current to electrically activate the first piezoplate stack and second piezoplate stack, a hypothetical first tangential vector passing through first blade ear  125  and hypothetical second tangential vector passing through second blade ear  126  are both parallel at any given point in time to a third hypothetical tangential vector corresponding to a radius of curvature defined by the motion at the blade tip  124  with respect to a fixed position of proximal end  118  held in place by bender motion constraint  114 . 
         [0141]    While the actuator of the bender actuated surgical tool has been described with respect to a bimorph type actuator, a unimorph type actuator may easily replace the bimorph piezoelectric transducer  111 . In essence, when the bimorph piezoelectric transducer  111  comprises at least one layer of at least one of piezoelectric plate  112  formed side by side, each plate being formed longitudinally against and in direct physical contact to a first side surface  113 ′ of bender support bar  113  so as to form first piezoplate stack  127 , and second piezoplate stack  128  is not formed, the piezoelectric transducer is a unimorph piezoelectric transducer. Furthermore, as shown in  FIG. 4 , a unimorph piezoelectric transducer may be a variable thickness unimorph piezoelectric transducer  111 ′. Variable thickness unimorph piezoelectric transducer  111 ′ comprises a plurality of stacked layers, each formed of at least one of piezoelectric plate  112 . In the case that a layer comprises a plurality of piezoelectric plate  112 , each plate is formed side by side, and longitudinally along the length of a bender support bar  113 . The plurality of layers are further formed such that each additional layer is shorter in length than the previously stacked layer, usually by at least the length of one piezoelectric plate  112 , with a conductive plate being formed between each layer. For example, as shown in  FIG. 4 , first layer  127   a  having an upper surface  127   a ′, and a bottom surface  127   a ″ opposite upper surface  127   a ′, comprises four piezoelectric plates  112  formed side by side and longitudinally with respect to the length of bender support bar  113 , and with bottom surface  127   a ″ being in direct physical and electrical contact to first side surface  113 ′ of bender support bar  113 . A first conducting electric plate  129  is formed in direct physical and electrical contact to upper surface  127   a ′. A second layer  127   b  having an upper surface  127   b ′ and a lower surface  127   b ″ opposite upper surface  127   b ′, comprises three piezoelectric ceramic plates  112  formed side by side and longitudinally with respect to the length of bender support bar  113 , and with lower surface  127   b ″ being in direct physical and electrical contact to first electrical plate  129  at a surface opposite to the interface formed by  127   a ′/ 129 . A second conducting electrical plate  129 ′ is formed in direct physical and electrical contact to upper surface  127   b ′. A third layer  127   c  having an upper surface  127   c ′ and a lower surface  127   c ″ opposite to upper surface  127   c ′, comprises two piezoelectric ceramic plates  112  formed side by side and longitudinally with respect to the length of bender support bar  113 , and with lower surface  127   c ″ being in direct physical and electrical contact to second electrical plate  129 ′at a surface opposite to  127   b ′/ 129 ′. A third conducting electrical plate  129 ″ is formed in direct physical and electrical contact to upper surface  127   c ′. A fourth layer  127   d  having an upper surface  127   d ′ and a lower surface  127   d ″ opposite to upper surface  127   c ′, comprises one of piezoelectric plate  112  formed with lower surface  127   d ″ in direct physical and electrical contact third conducting electrical plate  129 ″ at a surface opposite to  127   c ′/ 129 ″. Additional features of the functional variable thickness unimorph transducer  111 ′ include electrical leads necessary for connecting the transducer to an external circuit. The electrical leads comprise a ground connector  131  electrically connecting the upper surface  127   d ′ of fourth layer  127   d  to second electrical plate  129 ′ and also to the bender support bar  113 . The electrical leads further comprise positive connector  132  which electrically connects an external circuit (not shown) to third electrical plate  129 ″ and first electrical plate  129 . A negative connector  133  electrically connects the external circuit to bender support bar  113 . 
         [0142]    The bimorph piezoelectric transducer  111  may also be of a variable thickness type, so long as in the case of either the first piezoplate stack  127  or second piezoplate stack  128  comprise more than one layer of piezoelectric ceramic plate  112 , with each additional layer being shorter in length than the previously stacked layer and a conductive plate being formed between each layer. In other words, a variable thickness bimorph piezoelectric transducer may be formed in a similar fashion as prescribed to unimorph piezoelectric transducer  111 ′ with the exception that the multiplicity of layers of piezoelectric ceramic plates is symmetrically formed on second side surface  113 ″ of bender support bar  113 . 
         [0143]    The functional performance of the surgical tool is driven by the piezoelectric elements section. Piezoelectric ceramic elements, such as each of one or more piezoelectric ceramic plate  112  are capable of precise, controlled displacement and can generate energy at a specific frequency. The piezoelectric ceramics expand when exposed to an electrical input, due to the asymmetry of the crystal structure, in a process known as the converse piezoelectric effect. Contraction is also possible with negative voltage. Piezoelectric strain is quantified through the piezoelectric coefficients d 33 , d 31 , and d 15 , multiplied by the electric field, E, to determine the strain, x, induced in the material. Ferroelectric polycrystalline ceramics, such as barium titanate (BT) and lead zirconate titanate (PZT), exhibit piezoelectricity when electrically poled. Simple devices composed of a disk or a multilayer type directly use the strain induced in a ceramic by the applied electric field. Acoustic and ultrasonic vibrations can be generated by an alternating field tuned at the mechanical resonance frequency of a piezoelectric device. Piezoelectric components can be fabricated in a wide range of shapes and sizes. A piezoelectric component may be 2-5 mm in diameter and 3-5 mm long, possibly composed of several stacked disks or plates. The exact dimensions of the piezoelectric component are performance dependent. 
         [0144]    The piezoelectric ceramic material may be comprised of at least one of lead zirconate titanate (PZT), multilayer PZT, polyvinylidene difluoride (PVDF), multilayer PVDF, lead magnesium niobate-lead titanate (PMNPT), multilayer PMN, electrostrictive PMN-PT, ferroelectric polymers, single crystal PMN-PT (lead zinc-titanate), and single crystal PZN-PT. 
         [0145]    Bender bar  113  may comprise a metal such as stainless steel, titanium, or another conductive material also having high rigidity. 
         [0146]    Returning to  FIG. 2 , upon application of an external AC current at a predetermined frequency to the first or second, or both the first and second piezoplate stacks, bimorph piezoelectric transducer/actuator  111  reactively changes shape in a sinusoidal fashion such that the relative position of blade  119  with respect to say, a fixed position of a point on distal end  117  held in place by bender motion constraint  114  changes by a predetermined displacement. Because the AC current is a sinusoidal signal, the result of activating the piezoelectric ceramic plates is a sinusoidal, back and forth motion of the piezoelectric actuator, and the blade  119 , with the blade achieving a peak velocity at a central location of the sinusoidal motion. 
         [0147]    As depicted in  FIG. 5 , blade  119  appears at a location defined by the dark solid line at a moment directly preceding the application of an external AC current to the surgical blade of the invention. Blade  119  also appears at the location defined by the dark solid line upon attaining a peak velocity once motion has reached steady state after application of an external AC current to the surgical blade of the present invention. Correspondingly, during the positive cycle of an externally applied sinusoidal AC current signal, blade  119  appears at a location defined by the dotted-dashed line as first blade displacement position  119 ′ while appearing at a location defined by the dashed line as second blade displacement position  119 ″ during the negative cycle. In other words, blade  119  is displaced by a distance D 1 , during a positive cycle of the applied AC current at a predetermined frequency to a location defined by blade displacement position  119 ′. Alternatively, blade  119  is displaced by distance D 2  during a negative cycle of the externally applied AC current at a predetermined frequency to a location defined by blade displacement position  119 ′. Moreover, during for example the positive cycle of an externally applied sinusoidal AC current signal at a predetermined frequency, first blade ear  125  and second blade ear  126  are displaced by distance D 1  to locations defined by first blade ear positive displacement position  125 ′ and second blade ear positive displacement position  126 ′, respectively. Correspondingly, during the negative cycle of the applied AC current signal, first blade ear  125  and second blade ear  126  are displaced by displacement distance D 2  to locations defined by first blade ear negative position  125 ″ and second blade ear negative displacement position  126 ″. Ideally, displacement D 1  and displacement D 2  are approximately equivalent and equal to a distance in the range of 500-750 micrometers. Because the distance between first blade ear  125  and second blade ear  126  across the width of blade  119  is length W, the total distance traveled during a complete cycle of the externally applied AC current signal is W+D 1 +D 2  corresponding to a total cut width TCW. 
         [0148]    In a second embodiment, the surgical tool of the present invention can be a cymbal actuated surgical tool  200  as shown in  FIG. 6 . Surgical tool  200  comprises a body  210  and a cymbal actuator  211  which further comprises a piezoelectric ceramic disc  212  stacked between a first end-cap  213  and a second end-cap  214 . The first end-cap  213  is fixedly attached to the body  210 . Additionally, surgical tool  200  comprises a blade such as a dual beveled angled slit split blade  215 . A blade neck  216  is coupled at one end to the second end-cap  214  at attachment node  217 , and the blade at an opposite end. A motion constraining yoke  218  is attached to the blade neck at a location between the blade and the attachment node. In one configuration, the motion constraining yoke  218  has a cylindrical shape having an outer diameter with a hollow center defining an inner diameter. The blade neck may be connected to the motion constraining yoke at the inner diameter while the outer diameter is attached to a proximal end of the body  210  such that it is fixedly held in place. For example, the blade neck  216  may be connected to the inner diameter of the motion constraining yoke and held in place by a threaded set screw  219  which passes through the yoke, from the outer diameter to the inner diameter. The set screw compresses at least a portion of the blade neck against at least a portion of the inner diameter surface of the yoke. A hypothetical long axis HLA runs longitudinally in a direction corresponding to the length of the device. 
         [0149]    As shown in  FIG. 6  the cymbal actuator  211  is a type of flextensional transducer assembly including a piezoelectric ceramic disc  212  disposed within end-caps  213  and  214 . The end-caps  213  and  214  enhance the mechanical response to an electrical input, or conversely, the electrical output generated by a mechanical load. Details of the flextensional cymbal transducer/actuator technology is described by Meyer Jr., R. J., et al., “Displacement amplification of electroactive materials using the cymbal flextensional transducer”, Sensors and Actuators A 87 (2001), 157-162. By way of example, a Class V flextensional cymbal transducer/actuator has a thickness of less than about 2 mm, weighs less than about 3 grams and resonates between about 1 and 100 kHz depending on geometry. With the low profile of the cymbal design, high frequency radial motions of the piezoelectric material are transformed into low frequency (about 20-50 kHz) displacement motions through the cap-covered cavity. An example of a cymbal transducer/actuator is described in U.S. Pat. No. 5,729,077 (Newnham et al.) and is hereby incorporated by reference. While the end-caps shown in the figures are round, they are not intended to be limited to only one shape or design. For example, a rectangular cymbal end-cap design is disclosed in Smith N. B., et al., “Rectangular cymbal arrays for improved ultrasonic transdermal insulin delivery”, J. Acoust. Soc. Am. Vol. 122, issue 4, October 2007. Cymbal transducer/actuators take advantage of the combined expansion in the piezoelectric charge coefficient d 33  (induced strain in direction 3 per unit field applied in direction 3) and contraction in the d 31  (induced strain in direction 1 per unit field applied in direction 3) of a piezoelectric material, along with the flextensional displacement of the end-caps  213  and  214 , which is illustrated in  FIG. 6 . The design of the end-caps  213  and  214  allows both the longitudinal and transverse responses to contribute to the strain in the desired direction, creating an effective piezoelectric charge constant (d eff ) according to the formula, d eff =d 33 +(−A*d 31 ). Since d 31  is negative, and the amplification factor (A) can be as high as 100 as the end-caps  213  and  214  bend, the increase in displacement generated by the cymbal compared to the piezoelectric material alone is significant. The end-caps  213  and  214  can be made of a variety of materials, such as brass, steel, or KOVAR®, a nickel-cobalt ferrous alloy compatible with the thermal expansion of borosilicate glass which allows direct mechanical connections over a range of temperatures, optimized for performance and application conditions, a registered trademark of Carpenter Technology Corporation. The end-caps  213  and  214  also provide additional mechanical stability, ensuring long lifetimes for the cymbal transducer/actuators. 
         [0150]    The cymbal transducer/actuator  211  drives the dual beveled angled slit split blade  215 . When activated by an AC current, the cymbal transducer/actuator  211  vibrates sinusoidally with respect to the current&#39;s frequency. Because end-cap  213  is fixed to an inner sidewall of body  210 , when transducer  211  is activated, end-cap  214  moves with respect to the body in a direction perpendicular to the hypothetical long axis HLA of the surgical tool. This motion of end-cap  214  is transferred at the attachment node  217  through blade neck  216  and finally to slit split blade  215  which is displaced in a lateral direction to longitudinal axis HLA. Further, the displacement of slit split blade  215  is amplified relative to the displacement originating at piezoelectric ceramic disc  212  when it compresses and expands during activation due in part to the amplification caused by the design of end-caps  213  and  214 . An amplification of the motion originating at the piezoelectric ceramic disc  212  and terminating with a displacement of split blade  215  can further be attributed to the combination of yoke  218  and blade neck  216  acting as a fulcrum and arm of a lever. For example, the piezoelectric ceramic disc  212  alone may only displace by about 1-2 microns, but attached to the end-caps  213  and  214 , the cymbal transducer/actuator  211  as a whole may generate up to about 1 kN (225 lb-f) of force and about 80 to 100 microns of displacement. This motion is further transferred through the blade neck  216  and yoke  218  as an amplified lateral displacement of split blade  215  of 100-300 microns. For cases requiring higher displacement, a plurality of cymbal transducer/actuators  211  can be stacked end-cap-to-end-cap to increase the total lateral displacement of the split blade  215 . 
         [0151]    Turning the attention over to  FIG. 7 , a third embodiment of the invention is shown as a Langevin actuated surgical tool  300 . Langevin style transducers have a stack of piezoelectric ceramic discs  313  as shown in  FIG. 7 . In this embodiment, the surgical tool  300  comprises a body  310  and a conventional Langevin actuator  311  disposed within the body and fixedly held in place at body support collar  312 . The Langevin actuator comprises at least one, but preferably more than one piezoelectric ceramic disc  313 , a backing portion  314 , a horn portion  315  and a compression bolt  316 . Horn portion  315  terminates at a proximal end of body  310 , and comprises an attachment node  317 , which allows a motion transfer adaptor  318  to be mechanically connected to the Langevin actuator. The motion transfer adaptor  318  at one end is functionally attached to attachment node  317  while a blade  319  is attached at another end. A hypothetical long axis HLA runs continuously through the center of each of a distal portion of body  310 , a center portion of backing portion  314 , compression bolt  316 , horn  315 , the proximal end of body  310  and at least the center of part of motion transfer adaptor  318 . Additionally, motion transfer adaptor comprises a bend having an angle of between 20-90°, which allows the vibrations caused by the activation of ceramic discs  313  to be transferred into a displacement of the blade  319  that is useful for cutting. 
         [0152]    In other words, again referring to  FIG. 7 , when an alternating electric current is applied through the piezoelectric ceramic discs  313 , the result is an alternating motion in a direction defined by the displacement of the ceramic discs  313  transferred through the horn  315  and terminating at the tip of the blade  319 . The alternating motion results in a reciprocating displacement of the blade  319  relative to the Langevin actuator  311  which is held in place by the body  310  at body support  312 . Essentially, with the Langevin actuator  311  fixed to the body  310 , the horn  315  communicates this motion to motion transfer adaptor member  318  which in turn communicates motion to the blade  319 . 
         [0153]    In a fourth embodiment of the present invention, an APA transducer driven surgical tool  400  is shown in  FIG. 8 . The APA transducer driven surgical tool  400  comprises a body  410 , an APA transducer  411 , a blade neck  417  attached to the APA transducer, a motion constraining yoke  418 , a blade  419  and a blade neck  420 . As shown in  FIG. 8 , the APA transducer  411  is a flextensional transducer assembly including a cell  412  housed within a flexible frame  413 . The transducer cell  412  may include a spacing member separating at least two stacks of piezoelectric material. The flextensional transducer cell expands and contracts in one direction to cause movement in the frame. The frame  413  may additionally include either an elbow at the intersection of walls or corrugated pattern along the top and bottom walls,  414  and  415  respectively, of the assembly frame. 
         [0154]    In operation, the cell  412  expands during the positive cycle of an AC voltage, which causes top wall  414  and bottom wall  415  of the frame  413  to move inward. Conversely, the transducer cell  412  moves inward during the negative AC cycle, resulting in an outward displacement of the top  414  and bottom  415  walls of the frame  413 . However, in the present embodiment, bottom wall  414  is fixedly attached to body  410  so that any movement in the cell will result in only a relative motion of top wall  415  with respect to the body  410  and bottom wall  414 . Furthermore, a blade neck  417  is coupled to the top wall  415  on one end, and coupled to a blade  419  at an opposite end. A motion constraining yoke  418  attached to the walls of an opening at a distal end of body  410  serves to constrain blade neck  417  in a similar fashion as the yoke described in  FIG. 6 . 
         [0155]    Two examples of applicable APA transducers are the non-hinged type, and the grooved or hinged type. Details of the mechanics, operation and design of an example hinged or grooved APA transducer are described in U.S. Pat. No. 6,465,936 (Knowles et al.), which is hereby incorporated by reference in its entirety. An example of a non-hinged APA transducer is the Cedrat APA50XS, sold by Cedrat Technologies, and described in the Cedrat Piezo Products Catalogue “Piezo Actuators &amp; Electronics” (Copyright ®Cedrat Technologies June 2005). 
         [0156]    While the above described embodiments of the present invention are made with respect to a handheld surgical device having a vibrating blade and utilizing a bender-type, cymbal type, Langevin type or APA type transducer assembly for actuation, the present invention is not limited to these transducer assemblies. Generally, any type of motor comprising a transducer assembly, further comprising a mass coupled to a piezoelectric material, the transducer assembly having a geometry which upon actuation amplifies the motion in a direction beyond the maximum strain of the piezoelectric material, would also fall within the spirit and scope of the invention. 
         [0157]    From the above description, it may be appreciated that the present invention provides significant benefits over conventional surgical tools. The configuration of the actuating means described above such as embodiments comprising a bender transducer actuator, cymbal transducer/actuator actuator, Langevin actuator  311  actuator or an APA transducer actuator accommodates the use of piezoelectric actuating members in a surgical instrument by enabling the displacement of the cutting member or blade to such velocities that cause a reduction of force needed for cutting, incising, or penetrating of tissue during surgical procedures. Electrical signal control facilitated by an electrically coupled feedback system could provide the capability of high cut rate actuation, control over cut width, and low traction force for these procedures. 
         [0158]    Now that exemplary embodiments of the present invention have been shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. While the foregoing embodiments may have dealt with the incision of an eyeball as an exemplary biological tissue, the present invention can undoubtedly ensure similar effects with other tissues commonly incised during surgery. For example there are multiplicities of other applications like restorative or reconstructive microsurgery, cardiology or neurology, to name a few, where embodiments disclosed herein comprising sonically or ultrasonically driven cutting edges may be used to precisely pierce or incise tissues other than that forming an eyeball. Furthermore, while the previous embodiments have relied heavily on examples in which the surgical blades are vibrated sinusoidally in a direction parallel to the surface of the tissue or material being incised, cut, divided or penetrated by the blade, they are not limited to such locomotion in such a relative direction. For example, the motion of the blades of the previously described embodiments may actually be sinusoidal and in a direction that is perpendicular to the surface of the tissue or material being incised, cut, divided or penetrated by the blade. Accordingly, the spirit and scope of the present invention is to be construed broadly and limited only by the appended claims, and not by the foregoing specification.