Abstract:
A cutting instrument including a metal blade has a recess formed therein and a semiconductor substrate affixed to the blade in the recess. The semiconductor substrate includes at least one sensor formed thereon. The sensor formed on the semiconductor substrate may comprise at least one or an array of a strain sensors, pressure sensors, nerve sensors, temperature sensors, density sensors, accelerometers, and gyroscopes. The cutting instrument may also further include a handle wherein the blade is affixed to the handle and the semiconductor substrate is electrically coupled to the handle. The handle may then be coupled, either physically or by wireless transmission, to a computer that is adapted to display information to a person using the cutting instrument based on signals generated by one or more of the sensors formed on the semiconductor substrate. The computer or handle may also be adapted to store data based on the signals generated by one or more of the sensors. A method of making said cutting instrument includes the steps of at least one sensor being formed on a semiconductor wafer and a layer of photoresist being applied on a top side of the semiconductor wafer according to a pattern that matches the defined shape of the semiconductor substrate. The portion of the semiconductor wafer not covered by the photoresist is removed and thereafter the photoresist is removed from the semiconductor wafer, thereby leaving the semiconductor substrate having a defined shape and at least one sensor formed thereon. The semiconductor substrate having a defined shape and at least one sensor formed thereon is then affixed to a metal blade in a recess formed in said blade.

Description:
This application is a divisional of Ser. No. 09/626,273, filed Jul. 25, 2000, now U.S. Pat. No. 6,494,882. 

   FIELD OF THE INVENTION 
   The present invention relates to a cutting instrument having a variety of sensors integrated therein. More particularly, the invention relates to a blade having a sensor or sensors formed thereon, wherein the sensors are mounted adjacent the cutting surface to allow measurement of the physical characteristics of the blade and a workpiece or tissue. 
   BACKGROUND OF THE INVENTION 
   Cutting instruments exist for a myriad of applications, ranging from very specialized applications such as surgical scalpels, to industrial applications and common consumer applications. 
   Surgery continues to be one of the most delicate and risky medical procedures. Before making an incision into tissue, surgeons are required to identify what type of tissue is being incised, such as fatty, muscular, vascular or nerve. This task is greatly complicated by the fact that human anatomy differs slightly from person to person. The failure to properly classify tissue before making an incision can have severe adverse consequences. For example, if a surgeon fails to properly classify a nerve and cuts it, then the patient can suffer effects ranging from a loss of feeling to loss of motor control. 
   Thus, it would be useful to surgeons to be able to sense during surgery, and more particularly during the actual cutting operation, certain characteristics that would help to identify and classify the substrate tissue. For example, by sensing the amount of force being applied with a blade, the resistance of the tissue can be measured and can be used to assist in the classification of the tissue. Sensing the different pressure characteristics of material surrounding a blade, for example in the surrounding fluid, can help to classify the type or types of tissue surrounding the blade or the regions of the body being cut by the blade. Sensing the density of the tissue in proximity with the blade can also be used to assist in the identification of that tissue. Finally, as noted above, sensing the presence of nerve tissue can prevent the inadvertent cutting thereof. Moreover, the ability to sense the type of tissue in proximity with or cut by a blade would not only be useful to provide real time feedback for surgeons during surgery, but would also be useful if recorded for later use for tracking purposes. 
   Temperature can also be used to monitor the usage of a blade. For example, by monitoring the time for which a blade is at approximately 98.6 degrees Fahrenheit, the length of time that the blade has been in use can be determined. Also, information relating to the extent and direction of movement of a blade can useful both while the blade is being used and afterward for monitoring purposes, such as to measure the amount of cutting done in a procedure. 
   The ability to sense one or more of the parameters just described would also be useful in non-medical/surgical applications. For example, in connection with a consumer blade such as a razor blade, measurement of one or more of these parameters may be used to give consumers information regarding the cutting force applied to the blade, the materials being cut, and to estimate the sharpness of the blade. Furthermore, the manufacturers that design consumer blades may use the measured parameters to assess the impact of cutting tool design changes. For example, a razor blade manufacturer could quantify the changes in applied force to a blade that are due to changes in the handle or blade configuration. Similarly, in connection with machining tools such as a saw blade and milling tools, measurement of one or more of these parameters can be used to determine or predict the sharpness and cutting performance of the tool. 
   Sensor technology that can be integrated into semiconductor materials for sensing characteristics such as strain, pressure, temperature, density, the presence of nerves and movement are well known in the art. A strain sensor or gauge can be constructed using a resistor made of a material such as polysilicon. The resistance of a material such as polysilicon changes as it is stretched, and by measuring the change in resistance, one can calculate the strain. A pressure sensor can be constructed by placing a strain sensor on top of a diaphragm made of a material such as silicon nitride or polysilicon. When the diaphragm moves due to surrounding pressure changes, the strain gauge can be used to measure the local pressure. Examples of such pressure sensors are described in S. Sugiyama et al., “Micro-diaphragm Pressure Sensor,” IEEE Int. Electron Devices Meeting, 1986, pp. 184–7, and H. Tanigawa et al., “MOS Integrated Silicon Pressure Sensor,” IEEE Trans. Electron Devices, Vol. ED-32, No. 7, pp. 1191–5, July 1985, the disclosures of which are incorporated herein by reference. 
   One example of a temperature sensor can be constructed in a manner similar to a strain sensor using a resistor made of a material such as polysilicon. Using this type of a sensor, temperature can be measured as a function of the change in the resistance of the material. Similarly, as described in A. S. Sedra and K. C. Smith, “Microelectronic Circuits,” 4 th  Ed., Oxford University Press, New York, p. 135, 1998, the disclosure of which is incorporated herein by reference, diodes have an easily measured temperature dependence and thus are also used in designing temperature sensors. 
   Piezoelectric ultrasonic sensors can be used to measure density. Such sensors vibrate at a high frequency and emit, in the direction of the object of interest, a high frequency signal. Density of the impinged object can then be measured based on the signal that is reflected back by that object. Examples of such sensors are described in White et al., U.S. Pat. No. 5,129,262, entitled “Plate-mode Ultrasonic Sensor,” White et al., U.S. Pat. No. 5,189,914, also entitled “Plate-mode Ultrasonic Sensor,” and S. W. Wenzel and R. M. White, “A Multisensor Employing an Ultrasonic Lamb-wave Oscillator,” IEEE Trans. Electron Devices, Vol. 35, No. 6, pp. 735–743, June 1988, the disclosures of which are incorporated herein by reference. It is well known to sense the presence of nerve tissue using an electrical contact, such as a gold electrode, which picks up and conducts electrical signals in proximity therewith. 
   Movement or motion can be detected using an accelerometer, which measures acceleration. The signal output of an accelerometer can be integrated to determine or predict the distance traveled by a reference object. An example of an accelerometer integrated into semiconductor materials is described in Sherman, S. J.; Tsang, W. K.; Core, T. A.; Quinn, D. E., “A low cost monolithic accelerometer,” 1992 Symposium on VLSI Circuits. Digest of Technical Papers, Seattle, Wash., USA, 4–6, June 1992, p. 34–5, the disclosure of which is incorporated herein by reference. This accelerometer operates by monitoring the deflection of a polysilicon structure, which can then be used to determine or predict acceleration, and is produced using the micromachining of layers of semiconductor materials using semiconductor processing techniques. Direction of movement or motion can be detected using a gyroscope. An example of a gyroscope that can be integrated into semiconductor materials described in Ayazi, F.; Najafi, K., “Design and fabrication of high-performance polysilicon vibrating ring gyroscope.” Proc. IEEE MEMS 98, p. 621–6, 1998, the disclosure of which is incorporated herein by reference. This gyroscope operates by monitoring the movement of a vibrating ring of silicon to infer change in direction, and is produced using the micromachining of layers of semiconductor materials using semiconductor processing techniques. 
   Surgical tools constructed entirely of semiconductor materials, such as silicon, having the ability to sense, for example, temperature or strain, are known, examples of which are described in Carr et al., U.S. Pat. No. 5,980,518, entitled “Microcautery Surgical Tool,” and Mehregany et al., U.S. Pat. No, 5,579,583, entitled “Microfabricated Blades.” Using only semiconductor materials to construct the surgical tools is a natural approach since semiconductor materials such as silicon can be made with the requisite degree of sharpness and will also allow for direct fabrication of circuitry. However, semiconductor materials such as silicon tend to be brittle and hence not well suited for use as the primary structural component in a cutting device for surgical, industrial, and many consumer applications. 
   SUMMARY OF THE INVENTION 
   Described is a cutting instrument including a rigid blade having a recess formed therein and a semiconductor substrate affixed to the blade in the recess. The blade is preferably constructed of metal. The semiconductor substrate includes at least one sensor formed thereon. The sensor formed on the semiconductor substrate may comprise one or more of a strain sensor, a pressure sensor, a nerve sensor, a temperature sensor, a density sensor, an accelerometer, and a gyroscope. The sensor formed on the semiconductor substrate may also comprise an array of two or more of each sensor. 
   The recess in the blade is preferably formed so as to follow at least a portion of the edge of the blade. The semiconductor substrate may then be affixed to the blade in the recess adjacent the edge of the blade. The semiconductor substrate may also include circuitry formed thereon that is coupled to the sensors. The circuitry preferably includes one or more amplifiers and/or logic circuits for multiplexing the signals generated by the sensors. 
   The cutting instrument may also further include a handle wherein the blade is affixed to the handle and the semiconductor substrate is electrically coupled to the handle. The handle may then be coupled to a computer that is adapted to display information to a person using the cutting instrument based on signals generated by one or more of the sensors formed on the semiconductor substrate. The handle may include an electrical connector that is physically connected to a compatible connector associated with the computer, or may preferably include a wireless transmitter coupled the semiconductor substrate that is in communication with a wireless receiver associated with the computer. The handle or separate computer may also be adapted to store data based on the signals generated by one or more of the sensors. 
   Also described is a method of making a cutting instrument, including a semiconductor substrate having a defined shape and at least one sensor formed thereon. According to the method, at least one sensor is formed on a semiconductor wafer and a layer of photoresist is applied on a top side of the semiconductor wafer according to a pattern that matches the defined shape of the semiconductor substrate. The portion of the semiconductor wafer not covered by the photoresist is removed and thereafter the photoresist is removed from the semiconductor wafer, thereby leaving the semiconductor substrate having a defined shape and at least one sensor formed thereon utilizing techniques well known in the art. The semiconductor substrate having a defined shape and at least one sensor formed thereon is then affixed to a metal blade in a recess formed in said blade. 
   The semiconductor wafer may comprise a silicon-on-insulator wafer including a top layer of silicon, a middle layer of insulating material, and a bottom layer of silicon. The method would then include removing the bottom layer of silicon after applying the photoresist. An etching process may be used to remove the portion of the semiconductor wafer not covered by the photoresist and the bottom layer of silicon. 
   The semiconductor wafer may also comprise a silicon wafer. The method may then include grinding the wafer down to a desired thickness before affixing the semiconductor substrate to the blade. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the present invention will be apparent upon consideration of the following detailed description of the present invention, taken in conjunction with the following drawings, in which like reference characters refer to like parts, and in which: 
       FIG. 1  is an isometric view of a blade having a recess according to an aspect of the present invention; 
       FIG. 2  is a top plan view of a sensor element according to an aspect of the present invention; 
       FIG. 3  is an isometric view of the blade of  FIG. 1 , having the sensor element of  FIG. 2  mounted therein; 
       FIG. 4  is an isometric view of a blade according to the present invention affixed to a handle; 
       FIG. 5  is an isometric view of the blade and handle of  FIG. 4  coupled to an interface and a computer; 
       FIGS. 6 and 7  are top and bottom isometric views, respectively, of a blade and handle according to an alternate embodiment of the present invention that include a structure for connecting and electrically coupling the blade to the handle; 
       FIGS. 8 and 9  are more detailed isometric views of a portion of  FIGS. 7 and 6 , respectively; 
       FIG. 10  is a more detailed isometric view showing a portion of the handle of  FIGS. 6 through 9 , and specifically a portion of the connecting and coupling structure of  FIGS. 6 through 9 ; 
       FIGS. 11   a  through  11   e  are cross-sectional views illustrating the steps of a method of making the sensor element of  FIG. 2 ; 
       FIG. 12  is an isometric view of an alternate embodiment of a blade having a sensor element mounted therein; 
       FIG. 13  is an isometric view of a blade according to a further alternate embodiment; 
       FIG. 14  is an isometric view of a blade affixed to a handle according to an aspect of the present invention wherein the handle is provided with a wireless transmitter that is in communication with a wireless receiver coupled to a computer; 
       FIG. 15  is an isometric view of an alternate embodiment of the present invention, partially in section, comprising a razor blade having a sensor element mounted therein affixed to a cartridge in turn affixed to a handle; 
       FIG. 16  is a more detailed isometric view, partially in section, of a portion of the razor blade having a sensor element mounted therein affixed to a cartridge in turn affixed to a handle shown in  FIG. 15 ; and 
       FIG. 17  is a top plan view of a further alternate embodiment of the present invention comprising a saw blade having a sensor element mounted thereon. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , blade  10 , preferably made of a metal such as stainless steel, includes sharp edge  15  and recess  20  formed therein. As shown in  FIG. 1 , the shape of recess  20  preferably follows the shape of edge  15  of blade  10  so as to maximize the ability to increase the density of the sensors located at or near edge  15 . Recess  20  can be formed in blade  10  by one of several well known methods including grinding, milling, chemical etching, water-jet machining, stamping, or electron discharge machining. Although only a single recess  20  is shown on a single side of blade  10  in  FIG. 1 , it should be understood that recess  20  may be formed on either one of the sides of blade  10 , or both sides of blade  10 . Additionally, multiple recesses of the same or different size and/or arrangement may be formed on one or both sides of blade  10 . 
   Referring to  FIG. 2 , a sensor element  30  is shown. Sensor element  30  includes semiconductor substrate  35 , preferably made of silicon. Formed on semiconductor substrate  35  are sensor  40  and sensor array  45 , comprising a plurality of individual sensors. Sensor  40  and the individual sensors forming sensor array  45  can be any one of the well known types of sensors described herein, for example, a strain sensor, a pressure sensor, a temperature sensor, a density sensor, a motion sensor, or any other sensing device that can be formed on semiconductor substrate  35 . Also formed on semiconductor substrate  35  are one or more electrodes  50 , which are preferably gold electrodes. Other materials can be used to make electrodes  50 , such as polysilicon, tungsten, platinum, titanium, aluminum, and palladium. As described above, electrodes  50  can be used to sense the presence of nerve or other types of tissue. Although one sensor  40 , one sensor array  45 , and three electrodes  50  are shown in  FIG. 2 , it will be apparent to one of skill in the art that any combination of one or more sensors  40 , one or more sensor arrays  45 , and/or one or more electrodes  50  may be formed on semiconductor substrate  35  without departing from the present invention. It is to be specifically understood that the elements, such as sensor  40 , sensor array  45  and electrodes  50 , may reside entirely on the surface of semiconductor substrate  35  and alternatively having least a portion, if not the entirety, of the element below the surface of semiconductor substrate  35  within the ambit of formation on the semiconductor substrate  35 . 
   Sensor  40 , sensor array  45  and electrodes  50  are coupled to circuitry  55  formed on semiconductor substrate  35  using electrical traces  52  made of a material such as aluminum, tungsten, or titanium. Circuitry  55  preferably comprises an amplifier coupled to each of sensor  40 , sensor array  45  and electrodes  50 . Circuitry  55  also preferably includes conventional logic circuitry coupled to the above described amplifiers for multiplexing the signals coming from sensor  40 , sensor array  45  and electrodes  50  such that a single signal is output by circuitry  55  and ultimately by sensor element  30 . Circuitry  55  could also be used as a mechanism to provide identification of the blade to the surgical system by having an embedded serial number. This serial number can then be used by the system to determine such parameters as the type of blade, the number of sensors, and the performance specifications of the sensors. Furthermore, the serial number could be compared to databases of used surgical tools to prevent the reuse, or in the case of non-disposable devices, prevent the overuse of the surgical tool. Circuitry  55  may be formed by well known CMOS or bi-polar device processing techniques. Circuitry  55  is coupled to electrical contacts  60 , which include a positive contact, a negative contact, and a signal contact. Electrical contacts  60  provide the means for the multiplexed signal output by circuitry  55  to be output by sensor element  30 . 
   In an alternative embodiment, rather than multiplexing the signals output by sensor  40 , sensor array  45  and electrodes  50  so that the multiplexed signal can be output through a single electrical contact  60 , each of the signals output by sensor  40 , sensor array  45  and electrical contact  50  could be coupled to its own associated electrical contact  60  for outputting its signal from sensor element  30 . 
   As shown in  FIG. 2 , semiconductor substrate  35  may include an enclosed fluid channel  58  for delivering a fluid to the cutting location of the blade, such as an anesthetic or medication. Alternatively, a lubricant or other fluid can be delivered in an industrial or consumer application. An example of a fabrication process that can be used to create fluid channel  58  is described in K. S. Lebouitz and A. P. Pisano, “Microneedles and Microlancets Fabricated Using SOI Wafers and Isotropic Etching,” Proceedings of the Electrochemical Society, Vol 98-14, pp. 235–244, 1998 and in L. Lin, A. P. Pisano, R. S. Muller, “Silicon Processed Microneedles,” 7 th  International Conference on Solid State Sensors and Actuators, Yokohama, Japan, June 7–10, 1993, pp. 237–240, the disclosure of which is incorporated herein by reference. Fluid channel  58  may be pre-filled with the fluid, which is then allowed to seep out during the cutting operation, or, alternatively, fluid channel  48  may be connected to a source of fluid, such as a pump, using an external tube, not shown. Alternatively, a microchip drug delivery device such as those described in Santini et al., U.S. Pat. No. 5,797,898, the disclosure of which is incorporated herein by reference, may be included as part of semiconductor substrate  35 . As an alternate application, fluid channel  58  may also be used to sample fluid from a patient or workpiece. 
   Referring to  FIG. 3 , sensor element  30 , as described above, is bonded into recess  20  of blade  10  using any one of a number of adhesives, such as epoxy or cyanoacrylate glue, or by using eutectic bonding. As will be apparent to one of skill in the art, various alternative methods of bonding the sensor element  30  into the recess  20  of blade  10  are available, and any will be applicable so long as the bond is strong enough to prevent sensor element  30  from being dislodged from blade  10 . Preferably, biocompatible materials are used in the bonding process. 
   Referring to  FIGS. 4 and 5 , according to an embodiment of the present invention, blade  10  with bonded sensor element  30  is mounted to handle  70  using any conventional mounting methods such as an adhesive or fasteners such as screws or clips. Wires  75  are attached to electrical contacts  60  by one of various well known wire bonding techniques. Wires  75  are in turn connected to interface unit  80 . Interface unit  80  provides any necessary electrical power and may provide signal conditioning, such as filtering and amplification. Also, interface unit  80  may provide analog to digital conversion to convert the typically analog signals from sensor  40 , sensor array  45 , and electrodes  50  to computer usable digital signals. Interface  80 , is in turn is coupled to computer  85 , such as a conventional personal computer. Computer  85  collects and analyzes the signals output by sensor element  30  and displays an output that will assist the surgeon using the cutting instrument. The analysis may include comparing the signals to a database of known tissue or workpiece parameters to identify the type of tissue or material being cut. Computer  85  may then display on the screen possible tissue or material types that match the analysis. Furthermore, Computer  85  may display the measured parameters such as temperature, force applied, density, and pressure. Computer  85  may also provide direct tactile, visual, or audible feedback to the surgeon or operator. For example, a surgeon can select a mode whereby the level of force applied to blade  10  is converted into a sound which, for example, could change in pitch with applied force. Also, computer  85  may store the collected signals for later use. 
     FIGS. 6 through 10  show an alternative embodiment of the present invention having an alternative structure for connecting and electrically coupling blade  10  having sensor element  30  affixed thereto to handle  90 . As can be seen in  FIGS. 6 ,  9  and  10 , handle  90  has located at a blade end  95  thereof fastener  100  having flange  105 . Also located at blade end  95  of handle  90  are connectors or contacts  110  that penetrate the thickness of handle  90  and are surrounded by an electrical insulator  115  such as ceramic or plastic. Connectors  110  preferably comprise short metal wires, and most preferably comprise short gold wires. 
   According to this embodiment, blade  10  includes cutout  120  shown in  FIGS. 6 through 9 . Cutout  120  is through the entire thickness of blade  10 , thus creating a hole in blade  10 , and is at least as large as fastener  110 . Blade  10  is affixed to handle  90  by first inserting fastener  110  of handle  90  through cutout  120  of blade  10 , and then sliding blade  10  toward the end of handle  90  opposite blade end  95  so that flange  105  extends over a solid portion of blade  10  adjacent cutout  120  and so that end portion  125  of cutout  120  abuts wall  130  of fastener  100  located below flange  105 . As will be apparent, it is necessary to perform this operation with the side of blade  10  having sensor element  30  bonded thereto facing the fastener  100 . By doing so, the connectors  110  will mate with electrical contacts  60  of sensor element  30 . A seal between handle  90  and blade  10  is provided by O-ring  135  shown in  FIGS. 6 ,  9  and  10 . As seen in  FIGS. 7 and 8 , handle  90  includes ribbon connector  140  located on a side opposite fastener  100 . Ribbon connector  140  is electrically coupled to connectors  110 , and leads to an electrical connector  145  located at the end of handle  90  opposite blade end  95 . Electrical connector  145  can be utilized to couple handle  90  having blade  10  affixed thereto to an interface and/or computer such as those described above. 
     FIGS. 11   a  through  11   e  illustrate a preferred method for manufacturing sensor element  30  that allows for the manufacture of sensor element  30  so that it can be shaped to fit in complex shaped recesses  20 , for example those that follow the curvature of a blade used in a surgical tool. As shown in  FIG. 11   a , the process begins with a silicon-on-insulator wafer  150  which is comprised of three layers: a top layer of silicon  155  that will form semiconductor substrate  35 , an insulating layer  160  made of, for example, silicon dioxide, and a bottom layer of silicon  165  that provides additional thickness to allow ease of handling during the manufacturing process.  FIG. 11   b  shows the silicon-on-insulator wafer  150  after sensor or sensors  40 , sensor array  45 , electrodes  50 , electrical traces  52 , electrical contacts  60  and circuitry  55  have been formed according to the known techniques described above. For illustration purposes, a typical transistor structure is shown in  FIG. 11   b  where there is a doped region  170 , a gate oxide layer  175 , a polysilicon gate  180 , and a passivation layer  185  made of, for example, silicon nitride. The shaping of the silicon-on-insulator wafer  150  begins, as shown in  FIG. 11   c , with the addition of a layer of photoresist  190  patterned to define the desired outline of semiconductor substrate  35 , for example the curvature of blade  10 . Preferably, photoresist  190  is patterned to match the shape of recess  20 . Photoresist  190  may be applied to silicon-on-insulator wafer  150  using an appropriately patterned mask and any commonly known technique, such as spinning. Then, as shown in  FIG. 11   d , preferably using a deep reactive ion etcher which has a much higher etch rate of silicon versus oxide, the lower layer of silicon  165  is removed. Next, as shown in  FIG. 11   e , a deep reactive ion etcher is used to remove the portions of passivation layer  185 , top layer of silicon  155  and insulating layer  160  that are not covered by photoresist  190 . Alternatively, as described in W. Kern and C. H. Deckert, “Chemical Etching,” in Thin Film Processes, ed. J. L. Vossen and W. Kern, New York, Academic Press, 1978, pp. 401–496, instead of using reactive ion etching, various wet etches may be used to etch these layers. Additionally, as described in H. F. Winters and J. W. Coburn, “The etching of silicon with XeF2 vapor,” Applied Physics Letters, vol. 34, no., 1, Jan. 1978, pp. 70–73, xenon difluoride may be used to remove any unwanted silicon. Finally, photoresist  190  is removed using an oxygen plasma or chemical solvent such as acetone, leaving behind what ultimately forms semiconductor substrate  35  having the various elements formed thereon. Insulating layer  160  may be removed, or may be left in place, in which case it would provide additional electrical isolation between sensor element  30  and blade  10 . As can be seen, by using the silicon-on-insulator method described above, which delays the removal of the bottom layer of silicon  165  to the terminal steps of the process, a thin semiconductor substrate  35 , on the order of 100 micrometers, can be made while still utilizing a much thicker working product during processing. A typical silicon-on-insulator wafer is on the order of 500 micrometers thick. 
   According to an alternate embodiment, after application of photoresist  190  as shown in  FIG. 11   c , a deep reactive ion etch step that stops on insulating layer  160  may be used. At that point, in a fashion similar to that described in K. S. Lebouitz and A. P. Pisano, “Microneedles and Microlancets Fabricated Using SOI Wafers and Isotropic Etching,” Proceedings of the Electrochemical Society, Vol. 98-14, pp. 235–244, 1998, the disclosure of which is incorporated herein by reference, insulating layer  160  may be etched with a chemical, such as hydrofluoric acid, to separate upper silicon layer  155  from lower layer of silicon  165 . The process would then continue as shown and described in connection with  FIG. 11   e . This alternate embodiment thus avoids the need to etch away lower layer of silicon  165 . 
   According to a further alternate embodiment, instead of using silicon-on-insulator wafer  150  during the manufacturing process, a standard silicon wafer, typically on the order of 500 micrometers, may be used. In this embodiment, rather than removing the bottom layer of silicon  165 , the standard silicon wafer is ground down to a desired thickness after the circuitry and sensors are formed thereon. According to still a further alternate embodiment, a thinned silicon wafer on the order of 250 micrometers or less may be used. In the embodiment, the entire fabrication process can be performed without the need to remove a bottom layer of silicon  165  or to grind the thinned silicon wafer down after processing. 
   Referring to  FIG. 12 , an alternate embodiment of the present invention is shown wherein blade  10  comprises what is known in the art as a half blade. A half blade is a blade that has been machined such that the sharp edge is located at the surface on one side of the blade rather than in the mid-section of the blade. In other words, rather than beveling both sides of the blade to form an edge that is sharp in the middle, only one side of the blade is beveled to form the sharp edge at the surface of the other side of the blade. Such a configuration allows recess  20 , and thus sensor element  30 , to be located even closer to the edge  15  of the blade. 
   According to still a further embodiment of the present invention, recess  20  can be machined in edge  15  of blade  10  which is of the half-blade variety as shown in  FIG. 13 . The recess  20  can be made to follow the entire curve of blade  10 , as is the case in  FIG. 13 , or simply a portion of the curve of blade  10 . Then, sensor element  30  can be shaped so as to fit into recess  20 , thus allowing a high sensor area at the cutting edge. Since the top layer of silicon  155  of silicon-on-insulator wafer  150  is thin, on the order of 100 micrometers, and flexible, sensor element  30  can be shaped to fit a curved surface. 
   Referring to  FIG. 14 , handle  90  may be provided with wireless transmitter  200 , coupled to ribbon connector  140 , that is in communication with wireless receiver  205  of computer  85 . Wireless transmitter  200  and wireless receiver  205  may, for example, employ RF or infrared transmission. A suitable example of wireless transmitter  200  is the model TX20B-S1 wireless transmitter sold by Omega Engineering, Inc. located in Stamford, Conn., and a suitable example of wireless receiver  205  is the model RX 22 wireless receiver also sold by Omega Engineering, Inc. Power is supplied to the handle and combination shown in  FIG. 14  by way of a battery, not shown. The configuration shown in  FIG. 14  thus enables data to be transmitted to computer  85  for analysis and display without the need for any physical wires or cables, which tend to restrict the movement of the user. Although wireless transmitter  200  and wireless receiver  205  are shown in  FIG. 14  in connection with the embodiment of handle  90  shown in  FIGS. 6–10 , wireless transmitter  200  and wireless receiver  205  may also be utilized in connection with the embodiment of handle  70  shown in  FIG. 4 , wherein sensor element  30  would be couple to wireless transmitter  200  through wires  75 . 
   Referring to  FIGS. 15 and 16 , the present invention may be used in connection with a consumer cutting blade such as a razor blade. Shown in  FIGS. 15 and 16  is a typical consumer razor blade system including a cartridge  220  having a one or more blades  225  mounted therein, and handle  230  to which cartridge  220  is affixed. At least one of blades  225  includes a recess into which sensor element  30  is affixed. Wires  75 , or, alternatively a ribbon connector, connect sensor element  30  to wireless transmitter  200 . 
   The present invention may also be used in connection with various industrial cutting applications. For example,  FIG. 17  shows a saw blade  250  having a plurality of cutting teeth  255 . At least one of the cutting teeth  255  includes a recess into which sensor element  30  is affixed. Wires  75 , or, alternatively a ribbon connector, connect sensor element  30  to wireless transmitter  200 . 
   The terms and expressions which have been employed herein are used as terms of description and not as limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that various modifications are possible within the scope of the invention claimed. Although particular embodiments of the present invention have been illustrated in the foregoing detailed description, it is to be further understood that the present invention is not to be limited to just the embodiments disclosed, but that they are capable of numerous rearrangements, modifications and substitutions. For example, although portions of the description herein have shown the present invention as part of a surgical knife or scalpel, it is to be understood that the invention could form part of other surgical tools, such as the blade of a scissor or microcutter or a part of a suturing device, a trocar or a laparoscopic mechanical cutting tool such as a laparoscopic scissor. It should also be understood that the present invention may be applied not only in traditional surgery, but also to minimally invasive surgery and to robotic surgery. Finally, the term cutting as used herein is intended to cover the act of penetrating or severing with a sharp edge, including, but not limited to, puncturing as with a needle or shearing.