Patent Publication Number: US-2021169551-A1

Title: System and method for temporarily and permanently disabling electronics in a disposable surgical tool

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/945,951, filed on Dec. 10, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The disclosure relates to surgical instruments and, more particularly, to a safety cut-off circuit and a powered surgical tack applier instrument including a safety cut-off circuit. 
     BACKGROUND 
     Various surgical procedures require instruments capable of applying fasteners to tissue to form tissue connections or to secure objects to tissue. For example, during hernia repair it is often desirable to fasten a mesh to tissue. In certain hernias, such as direct or indirect inguinal hernias, a part of the intestine protrudes through a defect in the abdominal wall to form a hernial sac. The defect may be repaired using an open surgery procedure in which a relatively large incision is made and the hernia is closed outside the abdominal wall by suturing. The mesh is attached with sutures over the opening in the abdominal wall to provide reinforcement. However, this may also be accomplished through the use of minimally invasive surgical fasteners such as, e.g., surgical tacks. 
     Following the surgical procedure, some surgical instruments may be reprocessed for reuse, while others are disposable. 
     SUMMARY 
     The disclosure relates to surgical instruments and, more particularly, to a safety cut-off circuit and a powered surgical tack applier instrument including a safety cut-off circuit. 
     In accordance with an aspect, a safety cut-off circuit for a surgical instrument includes a positive terminal and a negative terminal, the negative terminal being grounded, a fuse coupled in series to the positive terminal of the power supply, a liquid detection circuit coupled in parallel to the fuse and the negative terminal of the power supply, and a voltage regulator operably coupled to the liquid detection circuit and the positive terminal of the power supply via the fuse. Power supplied to the voltage regulator is cut-off when liquid comes into contact with the liquid detection circuit. 
     The fuse is configured to blow when liquid contacts the liquid detection circuit. In an aspect, the fuse includes an amperage rating greater than an amperage rating required to operate the safety cut-off circuit. 
     In an aspect, the liquid detection circuit is coupled to the fuse via a first trace and to the voltage regulator via a second trace and the first trace is of a lower gauge relative to the second trace. 
     In an aspect, the liquid detection circuit includes water detection traces. In an aspect, the liquid detection circuit includes an interlaced comb structure. 
     In an aspect, the safety cut-off circuit includes a transistor coupled in parallel to the safety cut-off circuit and configured to be selectively triggered to create a short circuit and blow the fuse. An amperage capacity of the transistor may be higher than an amperage capacity of the fuse. In an aspect, the transistor includes a logic pin coupled to a microcontroller for selectively triggering the transistor to create the short circuit and blow the fuse. The transistor may be triggered to create the short circuit and blow the fuse when at least one of an end of useable life is detected, liquid is detected elsewhere in the surgical instrument remote from the liquid detection circuit, or erroneous behavior or signals are detected from at least one other electrical component of the surgical instrument. The at least one other electrical component may include a motor or a power source. 
     In an aspect, the safety cut-off circuit includes a resettable fuse coupled in series to the fuse, wherein an amperage rating of the resettable fuse is less than an amperage rating of the fuse. The safety cut-off circuit may further include a first transistor and a second transistor, wherein an amperage capacity of the first transistor is greater than an amperage capacity of the fuse and an amperage capacity of the second transistor is greater than an amperage capacity of the resettable fuse. In an aspect, the second transistor includes a logic pin coupled to a microcontroller for selectively triggering the second transistor to create a short circuit and blow the resettable fuse. 
     In another aspect of the disclosure, a safety cut-off circuit for a surgical instrument includes a power supply including a positive terminal and a negative terminal, the negative terminal being grounded, a fuse coupled in series to the positive terminal of the power supply, at least one of a liquid detection circuit or a transistor coupled in parallel to the fuse and the negative terminal of the power supply, a voltage regulator operably coupled to at least one of the liquid detection circuit or the transistor and the positive terminal of the power supply via the fuse. Power supplied to the voltage regulator is cut-off when at least one of liquid comes into contact with the liquid detection circuit or the transistor is caused to short circuit the safety cut-off circuit and blow the fuse. 
     In yet another aspect of the disclosure, a powered surgical instrument includes a handle assembly, an articulation lever assembly, an elongate member, and a safety cut-off circuit operably coupled to at least one of the handle assembly, the articulation lever assembly, or the elongate member. The handle assembly includes an actuation assembly including a motor, an actuation rod having a first end operatively coupled to an output shaft of the motor for concomitant rotation therewith, and an actuation switch configured to actuate the motor. The articulation lever assembly includes an articulation rod and an articulation lever operatively coupled with the articulation rod. The safety cut-off circuit includes a power supply including a positive terminal and a negative terminal, the negative terminal being grounded, a fuse coupled in series to the positive terminal of the power supply, a liquid detection circuit coupled in parallel to the fuse and the negative terminal of the power supply, and a voltage regulator operably coupled to the liquid detection circuit and the positive terminal of the power supply via the fuse. Power supplied to the voltage regulator is cut-off when liquid comes into contact with the liquid detection circuit. 
     The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Various aspects of the disclosure are described hereinbelow with reference to the drawings, which are incorporated and constitute a part of this specification, wherein: 
         FIG. 1  is a perspective view of a handle assembly of a powered surgical tack applier in accordance with an aspect of the disclosure; 
         FIG. 2  is a partial perspective view of an elongate member of the powered surgical tack applier; 
         FIG. 3  is a partial perspective view of a loading unit of the surgical tack applier of  FIG. 1 , illustrating a coil separated from an inner tube; 
         FIG. 4  is a longitudinal, cross-sectional view of a distal end of the powered surgical tack applier, illustrating implanting of a surgical tack into underlying tissue through a surgical mesh; 
         FIG. 5  is a perspective view of a surgical mesh for use with the powered surgical tack applier of  FIG. 1 , illustrating anchoring the surgical mesh to underlying tissue with a plurality of surgical tacks; 
         FIG. 6  is a side view of the handle assembly of  FIG. 1  with a half of a housing removed; 
         FIG. 7  is an exploded perspective view of the handle assembly of  FIG. 1  with parts separated; 
         FIG. 8  is a partial side view of the handle assembly of  FIG. 1 ; 
         FIG. 9  is a partial side view of the handle assembly of  FIG. 1  with a portion of the housing removed; 
         FIG. 10  is a partial perspective view of the handle assembly of  FIG. 1 , illustrating an actuation assembly; 
         FIG. 11  is a perspective view of a handle assembly for use with a powered surgical tack applier in accordance with another aspect of the disclosure; 
         FIG. 12  is a perspective view of the handle assembly of  FIG. 11  with a half of the housing removed; 
         FIG. 13  is a side view of the handle assembly of  FIG. 11 ; 
         FIG. 14  is a circuit diagram of a safety cut-off circuit for a powered surgical instrument in accordance with an aspect of the disclosure; 
         FIG. 15  is a circuit diagram of a safety cut-off circuit for a powered surgical instrument in accordance with an aspect of the disclosure; and 
         FIG. 16  is a circuit diagram of a safety cut-off circuit for a powered surgical instrument in accordance with an aspect of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the disclosed surgical instrument and its components are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein, the term “distal,” as is conventional, will refer to that portion of the instrument, apparatus, device, or component thereof which is farther from the user, while the term “proximal” will refer to that portion of the instrument, apparatus, device, or component thereof which is closer to the user. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. 
     In electrically powered laparoscopic surgical devices, there often is a need to permanently disable electronic components due to an event occurring during a product&#39;s life. Manufacturers may choose to permanently disable electronics as a means of mitigating patient and surgeon hazard in the event of liquid ingress or to ensure that devices are not used beyond their known safe useful life. In both instances disabling the electronic components would allow the device to “fail safe.” 
     Following the surgical procedure, some surgical instruments may be reprocessed for reuse, while others are disposed of. A need exists for disabling surgical instruments that are to be disposed of in order to inhibit their reuse beyond their useful life and for ensuring the safety of the clinician and patient in the event of a faulty condition. 
     This disclosure provides electronic solutions to address the above-noted concerns. Multiple aspects using either liquid detection circuits (e.g., interlaced comb circuits) or one or more transistors to create short circuits combined with board-mounted fuses are described. The use of passive components that fail due to liquid ingress or other fault conditions ensures that if the microcontroller logic of the surgical instrument or signals become compromised, the device will still safely be able to turn itself off. 
     With reference to  FIGS. 1-4 , a handle assembly for use with a surgical tack applier for applying a surgical tack  10  suitable for insertion through a surgical mesh “M” and tissue “T” is shown generally as a handle assembly  200 . The surgical tack applier generally includes the handle assembly  200 , an elongate member  50  having an articulation portion  60 , and a loading unit  30  selectably connectable to a distal end of the elongate member  50 . The loading unit  30  is electro-mechanically coupled to the handle assembly  200  and supports a plurality of surgical tacks  10 . 
     The loading unit  30  includes an outer tube  32  defining a lumen (not shown), a spiral or coil  36  fixedly disposed within the outer tube  32 , and an inner tube  38  rotatably disposed within the coil  36 . The inner tube  38  defines a lumen therethrough, and includes a first portion  38   a  and a splined second portion  38   b.  The second portion  38   b  of the inner tube  38  is slotted, defining a pair of tines  38   b   1  and a pair of channels  38   b   2 . The second portion  38   b  of the inner tube  38  is configured to support the plurality of surgical tacks  10  within the inner tube  38 . In particular, the surgical tacks  10  are loaded into the loading unit  30  such that the pair of opposing threaded sections  112   a  of the surgical tacks  10  extend through respective channels  38   b   2  of the second portion  38   b  of the inner tube  38  and are slidably disposed within the groove of the coil  36 , and the pair of tines  38   b   1  of the second portion  38   b  of the inner tube  38  are disposed within the pair of slotted sections  116   a  of the surgical tack  10 . In use, as the inner tube  38  is rotated about a longitudinal axis “X-X” thereof, relative to the coil  36 , the pair of tines  38   b   1  of the inner tube  38  transmits the rotation to the surgical tacks  10  and advance the surgical tacks  10  distally as the head threads  114   a  of the surgical tacks  10  engage with the coil  36 . 
     With particular respect to  FIG. 2 , the surgical tack applier includes an articulation portion  60  operatively coupled with an articulation lever assembly  300  ( FIG. 6 ) supported in the handle assembly  200 . The articulation portion  60  may include a drive assembly (not shown) having a slidable tube and an articulation arm pivotally coupled to the slidable tube. The articulation lever assembly  300  is coupled to the slidable tube so that when the articulation lever assembly  300  is actuated the slidable tube is displaced through the elongated member  50 . Longitudinal translation of the slidable tube moves the articulation arm to enable the loading unit  30  to articulate relative to the longitudinal axis “X-X” ( FIG. 3 ). 
     With reference now to  FIG. 6 , the handle assembly  200  includes a housing  202 , an articulation lever assembly  300  configured to articulate the articulation portion  60  ( FIG. 2 ) of the elongate member  50 , an actuation assembly  400  configured to eject the surgical tack  10  out of the loading unit  30  of the elongate member  50 , and a battery pack  440  removably attached to the housing  202 . The housing  202  includes an ergonomic structure providing comfort, ease of use, and intuitiveness such that when the housing  202  is gripped by a clinician, e.g., a thumb, may be positioned to slide the articulation lever assembly  300  and, e.g., an index finger, may be positioned to trigger an actuation switch  404  of the actuation assembly  400 . Actuation of the actuation assembly  400  ejects a surgical tack  10  ( FIG. 4 ) out of the loading unit  30  through mesh “M” ( FIG. 4 ) and into body tissue “T”. 
     With reference to  FIGS. 6 and 7 , the articulation lever assembly  300  includes an articulation rod  310  and articulation lever  360  operatively coupled with the articulation rod  310 . The articulation rod  310  is operatively coupled with the articulation portion  60  ( FIG. 2 ) of the elongate member  50  of the surgical tack applier. The articulation rod  310  is slidably supported on the housing  202  of the handle assembly  200  by a mounting plate  312  defining a channel  304  ( FIG. 8 ) configured to enable axial displacement of the articulation rod  310  therethrough, which, causes articulation of the articulation portion  60  ( FIG. 2 ) based on the axial position of the articulation rod  310 . In particular, the articulation rod  310  has an annular structure defining a channel  317  ( FIG. 8 ) dimensioned to receive the actuation rod  402  of the actuation assembly  400  therein. The articulation rod  310  further defines a transverse bore  314  dimensioned to receive an articulation drive pin  316  coupled with the articulation lever  360 . 
     With continued reference to  FIGS. 6 and 7 , the articulation lever  360  includes a housing portion  362  and an engaging portion  364  slidably engaging an engaging surface  204  of the housing  202 . The engaging surface  204  has an arcuate profile enabling the engaging portion  364  to travel in, e.g., an arc. The housing portion  362  is disposed within the housing  202  and is dimensioned to receive articulation pivot arms  366   a,    366   b  mated together to receive a biasing member  368  therebetween. Each articulation pivot arm  366   a,    366   b  defines a first bore  370   a,    370   b,  a second bore  372   a,    372   b,  and a slot  374   a,    374   b.  The first bores  370   a,    370   b  are dimensioned to receive an articulation pivot pin  378  ( FIG. 8 ) pivotably coupling the articulation pivot arms  366   a,    366   b  to the housing  202 . The second bores  372   a,    372   b  are dimensioned to receive the articulation drive pin  316  extending through the transverse bore  314  of the articulation rod  310 . Under such a configuration, when the articulation pivot arms  366   a,    366   b  are pivoted about the articulation pivot pin  378 , the articulation drive pin  316  causes axial displacement of the articulation rod  310 . The articulation drive pin  316  defines a transverse bore  380  dimensioned to receive the actuation rod  402  of the actuation assembly  400  therethrough. The slots  374   a,    374   b  of the articulation pivot arms  366   a,    366   b  are dimensioned to cammingly receive a cam pin  384  biased away from the articulation pivot pin  378  by a biasing member  368  interposed between the articulation pivot arms  366   a,    366   b.    
     With reference now to  FIGS. 7 and 8 , the housing portion  362  of the articulation lever  360  is dimensioned to receive the mated articulation pivot arms  366   a,    366   b.  The housing portion  362  defines a slot  363  dimensioned to cammingly receive the cam pin  384  which is cammingly slidable in the slots  374   a,    374   b  of the articulation pivot arms  366   a,    366   b.  In addition, the housing portion  362  includes a tooth  367  configured to engage a detent portion  208  of the housing  202  to inhibit movement of the articulation lever  360  relative to the housing  202 , thereby locking an axial position of the articulation rod  310 , which, in turn, locks the orientation of the articulation portion  60  ( FIG. 2 ) of the surgical tack applier. Under such a configuration, the articulation lever  360  is biased away from the articulation pivot pin  378  such that the tooth  367  of the housing portion  362  engages the detent portion  208 . When the engaging portion  364  of the articulation lever  360  is depressed towards the housing  202 , the tooth  367  is moved away from the detent portion  208  enabling the clinician to slidably move the engaging portion  364  on the engaging surface  204  ( FIG. 6 ) of the housing  202 , thereby enabling articulation of the articulation portion  60  of the surgical tack applier to a desired orientation. 
     With reference now to  FIG. 9  the articulation lever assembly  300  further includes a cam wedge  350  having first, second, and third portions  350   a,    350   b,    350   c  configured to cammingly engage the cam pin  384  which is cammingly slidable in the slots  374   a,    374   b  of the articulation pivot arms  366   a,    366   b  and the slot  363  of the articulation lever  360 . The first, second, and third portions  350   a,    350   b,    350   c  correspond to the respective detent sections  208   a,    208   b,    208   c  of the detent portion  208 . In this manner, articulation backlash is reduced as the cam pin  384  rides along the first, second, and third portions  350   a,    350   b,    350   c  of the cam wedge  350 . 
     With reference back to  FIGS. 6 and 7 , the actuation assembly  400  includes an actuation rod  402  operatively coupled with the loading unit  30  ( FIG. 2 ) of the surgical tack applier, a motor  420 , an actuation switch  404  configured to actuate the motor  420  to eject the surgical tacks  10  ( FIG. 4 ), a printed circuit board  430  including a microprocessor (not shown) to control the actuation assembly  400 , and a battery pack  440  removably attached to the housing  202  and electrically connected to the motor  420  and the printed circuit board  430 . A proximal end of the actuation rod  402  is operatively coupled with an output shaft of the motor  420  for concomitant rotation therewith such that when the actuation switch  404  is triggered by the clinician, the motor  420  is actuated to impart axial rotation to the actuation rod  402 . A distal end of the actuation rod  402  is operatively coupled with the inner tube  38  ( FIG. 3 ) of the loading unit  30  for concomitant rotation therewith. 
     With reference now to  FIG. 10 , the actuation assembly  400  may further include an encoder assembly  410  operatively connected to the actuation rod  402  and the processor of the printed circuit board  430 . The encoder assembly  410  may include, e.g., an optical, motor encoder  405  configured to keep an accurate count of turns of the motor output shaft or the actuation rod  402  to ensure a proper number of turns are made to insert the surgical tack  10  through, e.g., the mesh “M”, and into tissue “T” ( FIG. 4 ). In addition, the encoder assembly  410  may further include, e.g., a single notched, encoder wheel  407  configured to ensure correct clocking of a distal end of the actuation rod  402  relative to the loading unit  30  ( FIG. 2 ). The encoder assembly  410  may further include a light emitting diode (“LED”) indicator  409  to indicate status of the ejection of each surgical tack  10 . For example, a green light may indicate proper application of the surgical tack  10  through the mesh “M” and into tissue “T”, and a red light may indicate, e.g., improper application of the surgical tack  10 , due to an error signal from the optical motor encoder  405  or the single notched encoder wheel  407 . Alternatively, the encoder assembly  410  may further include a piezoelectric element  411  ( FIG. 6 ) for providing an audible tone for proper application of the surgical tack  10 . 
     With brief reference to  FIG. 6 , the handle assembly  200  may further include a release lever  450  slidably attached to the housing  202 . The release lever  450  is operatively coupled with the loading unit  30  ( FIG. 2 ) such that when the release lever  450  is pulled, the loading unit  30  is detached from the elongate member  50  ( FIG. 2 ) of the surgical tack applier. 
     In use, the loading unit  30  is operatively mounted to a distal end of the elongate member  50 . The loading unit  30  is introduced into a target surgical site while in the non-articulated condition. The clinician may remotely articulate loading unit  30  relative the longitudinal axis “X-X” to access the surgical site. Specifically, the clinician may slide the engaging portion  364  of the articulation lever  360  along the engaging surface  204  of the housing  202 . As the articulation rod  310  is displaced axially, the loading unit  30  is moved to an articulated orientation relative to the central longitudinal axis “X-X”. Furthermore, the clinician may position the surgical mesh “M” adjacent the surgical site. Once the surgical mesh “M” is properly positioned on the surgical site, the clinician may trigger the actuation switch  404  to eject a surgical tack  10  through the mesh “M” and into tissue “T”. While the articulation rod  310  is configured for axial displacement, it is further contemplated that an actuation rod  1310  may be rotatably supported by a rotor  1370  such that the actuation rod  1310  outputs an axial rotation which may be utilized by the loading unit  30  to effect articulation thereof, as can be appreciated with reference to  FIGS. 11-13 . It is further contemplated that the actuation assembly  400  may further include a transmission assembly to selectively impart rotation of the output shaft of the motor  420  to the actuation rod  1310 . 
     Aspects of safety cut-off circuits for use with powered surgical instruments such as the surgical tack applier described above are illustrated in  FIGS. 14-16  and described in detail below. It is contemplated that the safety cut-off circuits of the disclosure are incorporated into the housing of the powered surgical instruments and may utilize a shared power supply with that of the powered surgical instrument or may include its own independent power supply. Although the safety cut-off circuits are described as including certain components, it is understood that aspects of the safety cut-off circuits may include some or all of the components described, as needed for any specific implementation. In aspects, the safety cut-off circuits described below are configured to electrically couple to other electrical components of the powered surgical instrument, and additionally or alternatively, may be controlled by microprocessors of the powered surgical instrument. 
       FIG. 14  illustrates a safety cut-off circuit  1400  which provides power cut-off when liquid is detected in the circuit to protect the electrical components of the surgical instrument. Safety cut-off circuit  1400  includes a power supply  1401 , a fuse  1407 , a liquid detection circuit  1411 , and a voltage regulator  1409 . The power supply  1401  includes a positive terminal  1403  and a negative terminal  1405  with the negative terminal  1405  being grounded, for example, to a chassis of a surgical instrument. The fuse  1407  is coupled in series to the positive terminal  1403  of the power supply  1401 . The liquid detection circuit  1411  is coupled in parallel to the fuse  1407  and the negative terminal  1405  of the power supply  1401 . The voltage regulator  1409  is operably coupled to the liquid detection circuit  1411  and the positive terminal  1403  of the power supply  1401  via the fuse  1407 . 
     The fuse  1407  includes an amperage rating greater than an amperage rating required to operate the safety cut-off circuit  1400 . The liquid detection circuit  1411  may include water detection traces and/or an interlaced comb structure. 
     During operation, power supplied to the voltage regulator  1409  is cut off when liquid comes into contact with the liquid detection circuit  1411 . In particular, in the event of water or other liquid ingress into the surgical instrument that could corrupt the logic and signals of the microcontroller or other component of the surgical instrument, the power supply  1401  becomes short circuited due to detection of liquid by liquid detection circuit  1411 . This creates a very high current draw in excess of what is required to operate the surgical instrument or circuit normally and causes fuse  1407  to blow. In aspects, first trace  1413 , illustrated to the right of the liquid detection circuit  1411  in  FIG. 14 , is of a lower gauge value than second trace  1415 , illustrated to the left of liquid detection circuit  1411  in  FIG. 14 , such that the first trace  1413  is large enough to handle the required current to blow the fuse  1407 . As illustrated in  FIG. 14 , the liquid detection circuit  1411  is disposed upstream of any components required to establish logic on the board or in the surgical instrument. Disabling fuse  1407  cuts power to any microcontroller and all other circuitry components on the board or in the surgical instrument. 
       FIG. 15  illustrates a safety cut-off circuit  1500  similar to safety cut-off circuit  1400  and only the differences between the two will be described for brevity. While safety cut-off circuit  1400  is useful for preventing damage to the components of the surgical instrument when liquid is detected in the circuit, safety cut-off circuit  1500  is configured to cut-off the power supply  1501  upon the occurrence of other safety-related conditions. 
     Unlike safety cut-off circuit  1400 , the liquid detection circuit  1511  of safety cut-off circuit  1500  is optional and may be removed from the circuit. Additionally, safety cut-off circuit  1500  includes a transistor  1513  coupled in parallel to the safety cut-off circuit  1500  which is configured to be selectively triggered to create a short circuit and blow the fuse  1507 . The amperage capacity of the transistor  1513  is higher than an amperage capacity of the fuse  1507  to ensure that the fuse  1507  will blow before any damage is incurred on the transistor  1513  or any other components of the circuit and surgical instrument. 
     The transistor  1513  of the safety cut-off circuit  1500  includes a logic pin  1513   a  coupled to a microcontroller for selectively triggering the transistor  1513  to create the short circuit and blow the fuse  1507 . The transistor  1513  is triggered to create the short circuit and blow the fuse  1507  when an end of useable life of the surgical instrument is detected, for example, for single use devices, upon completion of use of the surgical instrument. In an aspect, transistor  1513  is triggered to create the short circuit when liquid is detected elsewhere in the surgical instrument, not local to the liquid detection circuit  1511 . Additionally or alternatively, when erroneous behavior or signals are detected from another component of the surgical instrument (e.g., another circuit in the surgical instrument, a motor, a power source, etc.), transistor  1513  may also be triggered by a microcontroller to blow fuse  1507 . 
       FIG. 16  illustrates another aspect of a safety cut-off circuit  1600  similar to safety cut-off circuit  1400  and safety cut-off circuit  1500  described above. Safety cut-off circuit  1600  provides power cut-off when liquid is detected in the circuit to protect the electrical components of the surgical instrument and also includes a first transistor  1613  and a second transistor  1615  for selectively cutting off portions of the circuit. 
     Safety cut-off circuit  1600  includes a power supply  1601 , a fuse  1607   a,  a resettable fuse  1607   b,  a liquid detection circuit  1611 , a first transistor  1613 , a second transistor  1615 , and a voltage regulator  1409 . The power supply  1601  includes a positive terminal  1603  and a negative terminal  1605  with the negative terminal  1605  being grounded, for example, to a chassis of a surgical instrument. The fuse  1607   a  is coupled in series to the positive terminal  1603  of the power supply  1601  and the resettable fuse  1607   b  is coupled in series with the fuse  1607   a.  The first transistor  1613  is coupled in parallel, between the fuse  1607   a  and the resettable fuse  1607   b.  The liquid detection circuit  1611  is coupled in parallel to the resettable fuse  1607   b  and the negative terminal  1605  of the power supply  1601 . The second transistor  1615  is coupled in parallel after the liquid detection circuit  1611 . The voltage regulator  1609  is operably coupled to the liquid detection circuit  1611  and the positive terminal  1603  of the power supply  1601  via the fuse  1607   a  and the resettable fuse  1607   b.    
     The liquid detection circuit  1411  may include water detection traces and/or an interlaced comb structure. The fuse  1607   a  and/or resettable fuse  1607   b  includes an amperage rating greater than an amperage rating required to operate the safety cut-off circuit  1600 . Additionally, an amperage rating of the resettable fuse  1607   b  is less than an amperage rating of the fuse  1607   a,  such that the resettable fuse  1607   b  will blow before the fuse  1607   a  blows, or without the fuse  1607   a  blowing at all. Additionally, an amperage capacity of the first transistor  1613  is greater than an amperage capacity of the fuse  1607   a  and an amperage capacity of the second transistor  1615  is greater than an amperage capacity of the resettable fuse  1607   b.    
     The first transistor  1613  includes a logic pin  1613   a  coupled to a microcontroller for selectively triggering the first transistor  1613  to create a short circuit and blow the fuse  1607   a.  Such an occurrence will permanently disable the safety cut-off circuit and protect the components of the surgical instrument. The second transistor  1615  includes a logic pin  1615   a  coupled to a microcontroller for selectively triggering the second transistor  1615  to create a short circuit and blow the resettable fuse  1607   b.  Such an occurrence of blowing the resettable fuse  1607   b  via the second transistor  1615  does not impact the fuse  1607   a,  and only temporarily disables the operation of the safety cut-off circuit  1600 . Upon resetting the resettable fuse  1607   b,  the safety cut-off circuit  1600  functions normally. 
     During operation, power supplied to the voltage regulator  1609  is cut off when liquid comes into contact with the liquid detection circuit  1611 , when first transistor  1613  is caused to blow fuse  1607   a,  or when second transistor  1615  is caused to blow resettable fuse  1607   b.  In particular, in the event of water or other liquid ingress into the surgical instrument that could corrupt the logic and signals of the microcontroller or other component of the surgical instrument, the power supply  1601  becomes short circuited due to detection of liquid by liquid detection circuit  1611 . This creates a very high current draw in excess of what is required to operate the surgical instrument or circuit normally and causes fuse  1607   a  and/or resettable fuse  1607   b  to blow. 
     Safety cut-off circuit includes two additional components for disabling power. As described above, microcontroller logic can selectively trigger a transistor (e.g., first transistor  1613  or second transistor  1615 ) on the board that creates a short circuit to blow resettable fuse  1607   b,  to temporarily remove power, or blow fuse  1607   a,  to permanently remove power. The microcontroller could be programmed to do this for any number of reasons. The first transistor  1613  or second transistor  1615  can be triggered by microcontroller to create the short circuit and blow the fuse  1607   a  and/or the resettable fuse  1607   b  when an end of useable life of the surgical instrument is detected, for example, for single use devices, upon completion of use of the surgical instrument. In an aspect, the first transistor  1613  and/or the second transistor  1615  is triggered to create the short circuit when liquid is detected elsewhere in the surgical instrument, not local to the liquid detection circuit  1611 . Additionally or alternatively, when erroneous behavior or signals are detected from another component of the surgical instrument (e.g., another circuit in the surgical instrument, a motor, a power source, etc.), the first transistor  1613  may also be triggered by a microcontroller to blow fuse  1607   a  and/or the second transistor  1615  may be triggered by a microcontroller to blow resettable fuse  1607   b.    
     Persons skilled in the art will understand that the structures and methods specifically described herein and shown in the accompanying figures are non-limiting exemplary aspects, and that the description, disclosure, and figures should be construed merely as exemplary of particular aspects. It is to be understood, therefore, that the disclosure is not limited to the precise aspects described, and that various other changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the disclosure. 
     Additionally, the elements and features shown or described in connection with certain aspects may be combined with the elements and features of certain other aspects without departing from the scope of the disclosure, and that such modifications and variations are also included within the scope of the disclosure. Accordingly, the subject matter of the disclosure is not limited by what has been particularly shown and described. 
     It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device. 
     In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer). 
     Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.