Patent Publication Number: US-2022226567-A1

Title: Insertion device with linkage assembly

Description:
TECHNICAL FIELD 
     This disclosure relates generally to systems for the insertion of medical devices. 
     BACKGROUND 
     Certain diseases or conditions may be treated, according to modern medical techniques, by delivering a medication fluid or other substance to the body of a patient, either in a continuous manner or at particular times or time intervals within an overall time period. For example, diabetes is often treated by delivering defined amounts of insulin to the patient at appropriate times. Some modern systems employ programmable fluid infusion devices (e.g., insulin pumps) to deliver controlled amounts of insulin to a patient. Some modes of providing insulin therapy to a user include delivery of insulin through manually operated syringes and insulin pens. Some other modes employ programmable fluid infusion devices (e.g., insulin pumps) to deliver controlled amounts of insulin to a user. Moreover, in certain instances, it may be desirable for a user to receive feedback from a physiological characteristic monitor, such as a glucose monitor. In these instances, the physiological characteristic monitor and the infusion set are often separately coupled to the user&#39;s anatomy at different insertion sites. 
     BRIEF SUMMARY 
     The disclosure generally relates to a insertion device for implanting a first medical device and a second medical device within a user. The insertion device may be configured to be worn by the user, and may include a housing configured to contact the skin of the user. The insertion device includes a first insertion needle and a second insertion needle configured to implant the first medical device and the second medical device by extending from the housing and releasing the devices. The insertion device is configured to retract the first insertion needle and the second insertion needle back into the housing while the first medical device and the second medical device remain implanted. 
     In examples, the first medical device is a fluid delivery cannula configured to deliver a fluid (e.g., insulin) from a fluid reservoir to the user. In examples, the second medical device is an analyte sensor (e.g., a glucose sensor) configured to provide a signal indicative of a physiological characteristic of the user (e.g., a glucose level). The insertion device may include a fluid pump configured to cause the fluid delivery cannula to deliver the fluid, and may include processing circuitry configured to receive the signal indicative of the physiological characteristic and determine the physiological characteristic. In examples, the processing circuitry is configured to control the operation of the fluid pump based on the indicative signal. 
     In an example, an insertion device for insertion of a first medical device and a second medical device into a user comprises: a housing; a first insertion needle configured to pierce and withdraw from skin of the user, the first insertion needle configured to releasably carry the first medical device; a second insertion needle configured to pierce and withdraw from the skin, the second insertion needle configured to releasably carry the second medical device; a first linkage assembly within the housing; a second linkage assembly within the housing; and a driver within the housing configured to cause the first linkage assembly and the second linkage assembly to rotate relative to the housing, wherein the first linkage assembly is configured to cause the first insertion needle to extend in a first direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the driver causes the first linkage assembly to rotate relative to the housing, and wherein the second linkage assembly is configured to cause the second insertion needle to extend in a second direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the driver causes the second linkage assembly to rotate relative to the housing. 
     In an example, an insertion device for insertion of a first medical device and a second medical device into a user comprises: a housing; a first insertion needle configured to pierce and withdraw from skin of the user at a first location, the first insertion needle configured to releasably carry the first medical device; a second insertion needle configured to pierce and withdraw from skin of the user at a second location displaced from the first location, the second insertion needle configured to releasably carry the second medical device; a first linkage assembly within the housing; a second linkage assembly within the housing; and a driver configured to concurrently cause the first linkage assembly and the second linkage assembly to rotate relative to the housing, wherein: the first linkage assembly is configured to cause the first insertion needle to extend in a first direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the first linkage rotates relative to the housing, the first insertion needle is configured to release the first medical device when the first insertion needle retracts toward the housing, the second linkage assembly is configured to cause the second insertion needle to extend in a second direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the second linkage rotates relative to the housing, and the second insertion needle is configured to release the second medical device when the second insertion needle retracts toward the housing. 
     In an example, a technique includes: extending a first insertion needle of the insertion device in a first direction away from a housing to pierce skin using rotation of a first linkage assembly with respect to the housing, wherein the first insertion needle is configured to releasably carry a first medical device; extending a second insertion needle of the insertion device in a second direction away from the housing to pierce the skin using rotation of a second linkage assembly with respect to the housing, wherein the second insertion needle is configured to releasably carry a second medical device; retracting the first insertion needle toward the housing to withdraw from the skin using the rotation of the first linkage assembly; and retracting the second insertion needle toward the housing to withdraw from the skin using the rotation of the second linkage assembly. 
     The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view of an example of an insertion device. 
         FIG. 2  is a bottom perspective view of the insertion device of  FIG. 1 . 
         FIG. 3  is a schematic side view of a insertion device attached to the body of a user. 
         FIG. 4  is a simplified block diagram representation of a medical system. 
         FIG. 5A  is a schematic of an example insertion device in an undeployed configuration; 
         FIG. 5B  is a schematic of the insertion device of  FIG. 5A  in a deployed configuration. 
         FIG. 5C  is a schematic of the insertion device of  FIG. 5A  and  FIG. 5B  in a stowed configuration. 
         FIG. 6A  is a schematic of an example insertion device in an undeployed configuration; 
         FIG. 6B  is a schematic of the insertion device of  FIG. 6A  in a deployed configuration. 
         FIG. 6C  is a schematic of the insertion device of  FIG. 6A  and  FIG. 6B  in a stowed configuration. 
         FIG. 7  illustrates an example technique of using a medical system. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure describes a insertion device configured to implant a first medical device and a second medical device within a patient. The insertion device may be generally related to a fluid infusion device configured to provide a therapeutic fluid to a user and monitor a physiological characteristic of the user. For example, the first medical device may be a fluid delivery cannula configured to deliver a fluid (e.g., insulin) to the user. The second medical device may be an analyte sensor (e.g., a glucose sensor) configured to detect a physiological characteristic of the user (e.g., a glucose level). The insertion device may be configured to insert the first medical device and the second medical device in the user substantially concurrently. In examples, the insertion device is a portable device configured to be worn by the user. 
     The insertion device includes a housing configured to position the insertion device proximate to the skin of the user. In examples, the housing is configured to contact the skin of the user. The housing may be configured to substantially secure its location on the user in order to, for example, allow mobility to the user as the insertion device administers and monitors therapies delivered to the user. For example, the insertion device may be configured to allow a degree of user mobility as the insertion device delivers insulin to the user through a fluid delivery cannula (e.g., the first medical device) and monitors a glucose level of the user using an analyte sensor (e.g., the second medical device). The insertion device may be substantially secured to the user using any suitable arrangement. In some examples, the housing of the insertion device includes an adhesive element configured to removably secure the housing to the skin of the user. 
     In examples, the insertion device is configured such that, when positioned on the skin of the user, the user may initiate the implantation of the first medical device and the second medical device. For example, the user may initiate the implantation using a manually operated button on the housing, a wireless communication to the medical system, or some other user-controlled activation. The insertion device is configured to cause a first insertion needle and a second insertion needle to extend to implant the first and second medical devices, and configured to subsequently withdraw the insertion needles from the user as the first and second medical devices remain implanted within the user. In examples, the housing mechanically supports an insertion mechanism unit including the first and second insertion needles, and the housing may be detached from the insertion device following implantation in order to, for example, reduce an overall volume and/or profile of the insertion device to lessen burden on the user. 
     The first and second insertion needles are configured to pierce and withdraw from the skin of the user. Upon activation by the user, the insertion device causes the first insertion needle and the second insertion needle to extend from the housing to pierce the skin and to subsequently retract toward the housing to withdraw from the skin. The first insertion needle is configured to releasably carry the first medical device, such that the first insertion needle substantially implants the first medical device during its extension and leaves the first medical device implanted within the user during its retraction. The second insertion needle is configured to releasably carry the second medical device, such that the second insertion needle substantially implants the second medical device during its extension and leaves the second medical device implanted during its retraction. In examples, the insertion device is configured to cause the first and second insertion needles to cause implantation of the first medical device and second medical device substantially concurrently. The substantially concurrent insertion of the first insertion needle and the second insertion needle insert may, for example, limit discomfort to the user that might be caused by insertions separated by a user-discernable chronological time increment. In examples, the insertion device is configured to cause the first and second insertion needles to withdraw substantially concurrently in order to, for example, limit discomfort to the user that might be caused by withdrawals separated by a user-discernable chronological time increment. 
     The insertion device may be configured to cause the first insertion needle to extend in a first direction away from the housing and cause the second insertion needle to extend in a different, second direction away from the housing, in order to implant the first medical device at a location displaced from the second medical device. The displacement may reduce negative effects that may occur due to a proximity between the first medical device and the second medical devices once implanted. For example, the insertion device may be configured to implant a fluid delivery cannula at a first location and implant an analyte sensor at a second location displaced from the first location, such that readings reported by the analyte sensor (e.g., glucose levels) are not adversely impacted by delivery of a fluid (e.g., insulin) through the fluid delivery cannula. 
     The insertion device may include a variety of internal components configured to use the first medical device and the second medical device to provide therapy and monitor a physiological characteristic of the user. In examples, at least one of the first medical device or the second medical device is a fluid delivery cannula, and the insertion device includes a fluid pump (e.g., an insulin pump) configured to deliver a fluid (e.g., insulin) to the user from a fluid reservoir within the medical system. The fluid reservoir may be, for example, a volume defined by a detachable fluid cartridge configured to mechanically engage a housing of the insertion device to establish fluid communication with the fluid pump. In examples, the insertion device includes processing circuitry configured to control an operation of the fluid pump. For example, the processing circuitry may be configured to cause the fluid pump to commence, continue, and/or cease transporting fluid from the fluid reservoir through the fluid delivery cannula. In examples, at least one of the first medical device or the second medical device is an analyte sensor configured to generate a signal indicative of a physiological characteristic of the user (e.g., a glucose level), and the processing circuitry is configured to determine the physiological characteristic using the indicative signal. In some examples, the processing circuitry is configured to control an operation of the fluid pump based on the indicative signal reported by the analyte sensor. 
     The insertion device includes a first linkage assembly configured to control the motion of the first insertion needle and a second linkage assembly mechanism configured to control the motion of the second insertion needle. The insertion device includes a driver configured to cause a rotation of the first linkage assembly and the second linkage assembly relative to the housing to control the motion of the first insertion needle and second insertion needle respectively. The driver may be configured to cause the rotation of the first linkage assembly and the second linkage assembly substantially concurrently, such that the first insertion needle and the second insertion needle extend away from the housing and retract toward the housing substantially concurrently. 
     The first linkage assembly linkage assembly includes a first plurality of interconnected links (e.g., elongated bodies), including a first input link and a first output link. The first plurality of interconnected links defines a first kinematic chain, such that rotation of the first input link relative to the housing causes movement of the first output link relative to the housing and relative to the first input link. The rotation of the first linkage assembly (e.g., the input link) causes the first linkage assembly (e.g., a first output link) to extend and retract the first insertion needle. The first linkage assembly may include one or more floating links in the first kinematic chain defined by the first input link and the second output link. 
     In some examples, the first output link is configured to linearly translate (e.g., experience a sliding stroke) when the driver rotates the first input link. The first output link may be constrained to slide within a channel defined by the insertion device (e.g., defined by the housing). In examples, the first linkage assembly is configured such that a rotation of the first input link in a single direction causes the first output link to initially linearly translate in a first direction and subsequently linearly translate in a second direction opposite the first direction. The first output link is configured to cause the first insertion needle to implant the first medical device when moving in the first direction, and subsequently withdraw the first insertion needle when moving in the second direction. 
     The second linkage assembly may include a second plurality of links defining a second kinematic chain. The second plurality of links may be configured similarly to the first linkage assembly. For example, the second linkage assembly may include a second input link and a second output link, where a rotation of the second input link relative to the housing causes the second output link to linearly translate. The linear translation of the second output link may cause the second insertion needle to extend away from the housing to implant the second medical device and subsequently retract toward the housing. 
     The driver may be configured to cause the rotation of the first linkage assembly (e.g., the first input link) and second linkage assembly (e.g., the second input link) substantially concurrently when the user activates the insertion device for implantation. For example, the driver may include a wound torsion spring configured to substantially unwind when the user activates the medical system. In examples, the housing defines a central axis, and the driver is configured to cause the first input link of the first linkage assembly and the second input link of the second linkage assembly to rotate around the central axis and relative to the housing. In some examples, the torsion spring surrounds the central axis, and the first input link and the second input link are coupled to respective ends of the torsion spring such that an unwinding of the torsion spring causes the first input link and second input link to rotate relative to the housing in substantially opposite directions. In some examples, the driver includes a hub configured to rotate around the central axis, and the first input link and the second input link are coupled to the hub such that rotation of the hub causes the first input link and second input link to rotate relative to the housing in the same direction. The hub may rotate due to an unwinding of the torsion spring, or by the action of some other suitable mechanism configured to generate a torque on the hub. 
     Hence, the insertion device may be configured to position proximate the skin of a user and cause a first insertion needle and a second insertion needle to extend away from the housing to pierce the skin and retract toward the housing to withdraw from the skin. The first insertion needle may be configured to implant a first medical device in the user and the second insertion needle may be configured to implant a second medical device in the user. The insertion device may include a user input device configured to allow the user to control when the insertion device causes the implantation of the first medical device and the second medical device. In examples, the first medical device is a fluid delivery cannula and the second medical device is an analyte sensor. The insertion device may include a fluid pump (e.g., an insulin pump) configured to deliver a fluid (e.g., insulin) to the user, and may include processing circuitry configured to receive signals indicative of a physiological characteristic of the user (e.g., a glucose level) from the analyte sensor. The processing circuitry may be configured to control an operation of the fluid pump based on the indicative signals received from the analyte sensor. The insertion device may be utilized to administer a variety of medications to a user such as, but not limited to, disease treatments, drugs to treat pulmonary hypertension, iron chelation drugs, pain medications, anti-cancer treatments, medications, vitamins, hormones, or the like. 
       FIG. 1  is a top perspective view of an example of an insertion device  100  configured as a fluid infusion device. The fluid infusion device may be implemented as a patch pump device (e.g., worn on the stomach or on the arm).  FIG. 2  is a bottom perspective view of insertion device  100 .  FIG. 3  is a schematic side view of insertion device  100  contacting the body of a user.  FIGS. 1, 2, and 3  depict one possible configuration and form factor of insertion device  100 . Other designs and configurations can be utilized if so desired, and the particular design aspects shown and/or described in  FIGS. 1, 2, 3 , and elsewhere are not intended to limit or otherwise restrict the scope or application of the examples described herein. 
     Insertion device  100  includes a device housing  102  that may serve as a shell for a variety of internal components of insertion device  100 . For example, device housing  102  may mechanically support one or more internal components configured to monitor a physiological characteristic of a user and/or delivery therapy to the user. In examples, device housing  102  is configured to mechanically support one or more insertion needles configured to implant one or more medical devices into the user. Device housing  102  may mechanically support components configured to cause the one or more insertion needles to implant the medical devices in the user. In some examples, device housing  102  is configured to mechanically support internal components configured to utilize and/or communicate with the medical devices for monitoring of and/or delivering therapy to the user. For example, device housing  102  may mechanically support a first insertion needle configured to implant a fluid delivery cannula into the user, a second insertion needle configured to implant an analyte sensor into the user, a fluid pump configured to deliver a fluid from a fluid reservoir using the fluid delivery cannula, and processing circuitry configured to communicate with the analyte sensor and/or the fluid pump. Device housing  102  may be configured to position insertion device  100  proximate and/or in contact with the skin of the user. 
     In examples, device housing  102  may be configured to mechanically support a removable fluid cartridge  104  defining a fluid reservoir. Fluid cartridge  104  may be, for example, a disposable insulin cartridge. Device housing  102  may be suitably configured to receive, secure, and release fluid cartridge  104 . For example,  FIG. 1  and  FIG. 2  depict a fluid cartridge  104  installed on and substantially secured by device housing  102 . Device housing  102  may be configured such that, when fluid cartridge  104  is mechanically supported by (e.g., installed on) device housing  102 , a fluid pump mechanically supported by device housing  102  establishes fluid communication with the fluid reservoir defined by fluid cartridge  104 . Device housing  102  may include a suitably shaped, sized, and configured cavity configured to engage particular physical characteristics of fluid cartridge  104 . For example, the device housing  102  can include structural features that mate with or otherwise engage structural features of fluid cartridge  104 . 
     Fluid cartridge  104  may have any shape, size, and/or configuration sufficient to engage with device housing  102 . In examples, fluid cartridge  104  includes a cartridge retention mechanism  106  configured to secure fluid cartridge  104  in an installed and seated position within insertion device  100 . Retention mechanism  106  may mechanically engage device housing  102  to substantially lock the fluid cartridge  104  in place to maintain physical and fluid connections between the fluid cartridge  104  and insertion device  100 . Retention mechanism  106  may be configured to allow physical manipulation by the user to release and/or install fluid cartridge  104  on device housing  102  as needed. 
     Insertion device  100  includes at least one user input device  108  which may be actuated by the user as needed. User input device  108  may be a manually operated button on device housing  102 , a circuitry configured to receive a communication (e.g., a wireless communication) from a smart phone, tablet, or other device, or some other device configured for control by the user. In examples, user input device  108  (e.g., a button) is configured to cause insertion device  100  to implant a first medical device and/or second medical device into the user. However, the user input device  108  may be a multipurpose user interface configured to prompt multiple operations of insertion device  100 . For example, user input device  108  may be configured to cause one or more of the following functions, without limitation: waking up the processor and/or electronics of insertion device  100 ; triggering an insertion mechanism unit to implant a first medical device (e.g., a fluid delivery cannula) and/or a second medical device (e.g., an analyte sensor) into a subcutaneous space or similar region of the user; configuring one or more settings of insertion device  100 ; initiating delivery of medication fluid; initiating a fluid priming operation; disabling alerts or alarms generated by insertion device  100 ; and the like. In lieu of or in addition to a button, user input device  108  can employ a slider mechanism, a pin, a lever, a switch, a touch-sensitive element, or the like. 
     User input device  108  may be configured to receive a communication from a device remote from device housing  102  (e.g., a wireless communication) to initiate insertion device  100  to perform one or more of the described functions, or other functions. In examples, insertion device  100  includes more than one user input device  108  (e.g., more than one button) to initiate the various functions described. 
     In examples, insertion device  100  is a portable device. Insertion device  100  may be a wearable device configured to be worn by the user. As depicted in  FIG. 2 , insertion device  100  may include an adhesive element  110  or an adhesive material configured to substantially affix the device housing  102  to the body of the user. Adhesive element  110  may be configured to substantially secure insertion device  100  in a location proximate (e.g., contacting) the skin  118  ( FIG. 3 ) of the user. Adhesive element  110  may be located on a bottom surface of the device housing  102  such that the device housing  102  can be temporarily adhered to the skin of the user. The adhesive element  110  may cover substantially all of the lower surface (as depicted), or it can only partially cover the lower surface if so desired. Adhesive element  110  may be, for example, a piece of double sided adhesive tape that is cut into the desired shape and size. In some examples, insertion device  100  is manufactured with an adhesive liner overlying adhesive element  110 , and the adhesive liner is peeled away to expose the sticky surface of adhesive element  110 . 
     Device housing  102  may include a base surface  112  (which is covered by the adhesive element  110  in  FIG. 2 ). Base surface  112  may be configured to serve as the user-mounting structure of insertion device  100 . In examples, base surface  112  defines at least one hole forming an opening through device housing  102 . For example, as depicted at  FIG. 1 , device housing  102  may define a first hole  114  and/or a second hole  116 . Holes  114 ,  116  may further form an opening through adhesive element  110  when adhesive element  110  covers some portion of base surface  112 . 
     First hole  114  and/or second hole  116  may be defined to accommodate passage of an insertion needle and a medical device from a position within device housing  102  to a position at least partially outside of device housing  102 . In examples, first hole  114  is configured (e.g., shaped, sized, and/or located) to accommodate passage of a first insertion needle and a first medical device (e.g., a fluid delivery cannula) from a position within device housing  102  to a position at least partially outside of device housing  102 , and second hole  116  is configured (e.g., shaped, sized, and/or located) to accommodate passage of a second insertion needle and a second medical device (e.g., an analyte sensor) from another position within device housing  102  to another position at least partially outside of device housing  102 . First hole  114  and/or second hole  116  may be configured to accommodate retraction of the first insertion needle and the second insertion needle respectively from a position outside device housing  102  to a position within device housing  102 . In examples, first hole  114  and second hole  116  are located to allow sufficient spacing in or under the skin of the user to avoid interference between a fluid delivered through a fluid delivery cannula and an operation of an analyte sensor. For example, first hole  114  and second hole  116  may be defined at substantially opposite ends of base surface  112 . 
       FIG. 3  depicts insertion device  100  in schematic form. Insertion device  100  is depicted proximate to (e.g., in contact with) the skin  118  of a user. A first medical device  120  is implanted in the user and extends through first hole  114  from a position within device housing  102  to a position outside of device housing  102  (e.g., a first location under the skin  118 ). A second medical device  122  is implanted in the user and extends through second hole  116  from another position within device housing  102  to another position outside of device housing  102  (e.g., a second location under the skin  118 ). In examples, first medical device  120  is a fluid delivery cannula configured to deliver a fluid (e.g., insulin) to the first location and second medical device  122  is an analyte sensor and/or communication links engaged with the analyte sensor configured to sense a physiological characteristic (e.g., a glucose level) at the second location. Insertion device  100  is configured to implant first medical device  120  and second medical device  122  such that the first location and the second location are separated by a displacement D. In examples, insertion device  100  is configured to cause the implantation of first medical device  120  in a first direction S 1  (e.g., using first insertion needle  132  ( FIGS. 4, 5A-5C, 6A-6C )) and cause implantation of second medical device  122  in a second direction S 2  (e.g., using second insertion needle  134  ( FIGS. 4, 5A-5C, 6A-6C )) different from the first direction S 1 .  FIG. 3  further depicts adhesive element  110  configured to substantially secure the device housing  102  to the skin of the user. 
     As will be discussed, an insertion mechanism unit  124  may be configured to cause implantation of first medical device  120  and second medical device  122  within the user when, for example, the user actuates insertion mechanism unit  124  using user input device  108 . Insertion mechanism unit  124  may be configured to cause a first insertion needle (e.g., first insertion needle  132  ( FIGS. 4, 5A-5C, 6A-6C )) to extend through first hole  114  to implant first medical device  120  (e.g., a fluid delivery cannula), and configured to cause the first insertion needle to retract back through first hole  114  while first medical device  120  remains implanted. Insertion mechanism unit  124  may be configured to cause a second insertion needle (e.g., second insertion needle  134  ( FIG. 4, 5A, 5B )) to extend through second hole  116  to implant second medical device  122  (e.g., an analyte sensor), and configured to cause the second insertion needle to retract back through second hole  116  while second medical device  122  remains implanted. Insertion mechanism unit  124  may include a housing  126  (“mechanism housing  126 ”) configured to mechanically support components of insertion mechanism unit  124 . Mechanism housing  126  may be configured to couple with housing  102 , and may be configured to detach from device housing  102  as device housing  102  remains proximate to the skin  118  of the user. A fluid infusion system  128  may be configured to deliver a fluid (e.g., insulin) to the user. A sensor system  130  may be configured to monitor an physiological characteristic of the user (e.g., a glucose level). 
       FIG. 4  is an example simplified block diagram representation of insertion device  100  including device housing  102 , user input device  108 , first medical device  120 , second medical device  122 , insertion mechanism unit  124  including a first insertion needle  132  and a second insertion needle  134 , fluid infusion system  128  including a fluid pump  136  and a pump motor  138 , and sensor system  130 . First insertion needle  132  is configured to releasably engage first medical device  120 . Second insertion needle  134  is releasably engaged with second medical device  122 . Insertion device  100  is configured to cause first insertion needle  132  to move in the first distal direction D 1  to cause implantation of first medical device  120  in the user. Insertion device  100  is configured to cause second insertion needle  134  to move in the second distal direction D 2  to cause implantation of second medical device  122  in the user. Insertion device  100  is configured to retract first insertion needle  132  and second insertion needle  134  in the first proximal direction P 1  and the second proximal direction P 2  respectively while first medical device  120  and second medical device  122  remain implanted in the user. 
     Insertion device  100  may be configured to provide a fluid (e.g., insulin) to a user using, for example, first medical device  120 . Insertion device  100  may be configured to provide the fluid when first medical device  120  is implanted within the user ( FIG. 3 ). Insertion device  100  may be configured to monitor a physiological characteristic (e.g., a glucose level) of the user using, for example, second medical device  122 . Insertion device  100  may be configured to monitor the physiological characteristic when second medical device  122  is implanted within the user ( FIG. 3 ). Insertion mechanism unit  124  is configured to cause first insertion needle  132  and second insertion needle  134  to extend away from device housing  102  and/or mechanism housing  126  (“housing  102 ,  126 ”) to implant first medical device  120  and second medical device  122  respectively into the user, and configured to cause first insertion needle  132  and second insertion needle  134  to retract toward housing  102 ,  126  as first medical device  120  and second medical device  122  remain implanted. In examples, first insertion needle  132  is configured to implant first medical device  120  via first hole  114  and second insertion needle  134  is configured to implant second medical device  122  via second hole  116 . 
     Insertion mechanism unit  124  includes a first linkage assembly  142  and a second linkage assembly  144 . First linkage assembly  142  is configured to cause first insertion needle  132  to extend away from housing  102 ,  126  and retract towards housing  102 ,  126  when some portion of first linkage assembly  142  rotates with respect to housing  102 ,  126 . Second linkage assembly  144  is configured to cause second insertion needle  134  to extend away from housing  102 ,  126  and retract towards housing  102 ,  126  when some portion of second linkage assembly  144  rotates with respect to housing  102 ,  126 . First linkage assembly  142  may include an input link  146  (“first input link  146 ”) configured to rotate relative to housing  102 ,  126 . Second linkage assembly  144  may include an input link  148  (“second input link  148 ”) configured to rotate relative to housing  102 ,  126 . In examples, housing  102 ,  126  defines a central axis A, and first linkage assembly  142  (e.g., an end of first input link  146 ) and/or second linkage assembly  144  (e.g., an end of second input link  148 ) is configured to rotate substantially around central axis A. In  FIG. 4 , central axis A is shown perpendicular to the page. 
     Insertion mechanism unit  124  further includes a driver  150  configured to cause the rotation of first assembly  142  and second assembly  144 . Driver  150  may be configured to cause the rotation of first assembly  142  and the rotation second linkage assembly  144  substantially concurrently. In examples, user input device  108  is configured to cause driver  150  to rotate first linkage assembly  142  and second linkage assembly  144 , such that the user may control the implantation of first medical device  120  and second medical device  122 . In some examples, as will be discussed, driver  150  may include a spring configured to cause first assembly  142  and/or second assembly  144  to rotate relative to housing  102 ,  126 . In some examples, the spring is a torsion spring configured to release from a wound position to an unwound position to cause the rotations of first assembly  142  and/or second assembly  144 . 
     Insertion device  100  may be configured to define a first flow path  152  from a discharge of fluid pump  136  to first medical device  120 . In examples, first medical device  120  is a fluid delivery cannula defining an interior lumen  154 , and insertion device  100  is configured to provide a first flow path  152  from a discharge  153  of fluid pump  136  through lumen  154  of the fluid delivery cannula. In examples, insertion device  100  includes a first conduit  156  configured to define first flow path  152 . Insertion device  100  may further define a fluid reservoir  158  (e.g., with device housing  102  and/or fluid cartridge  104  ( FIGS. 1, 2 )) and be configured to define a second flow path  160  from reservoir  158  to a suction  161  of fluid pump  136 . In examples, insertion device  100  includes a second conduit  162  configured to define second flow path  160 . The fluid pump  136  may include a motor  138  configured to cause fluid pump  136  to create pressure to deliver fluid (e.g., via first flow path  152 ). Fluid infusion system  128  may include one or more of fluid pump  136 , motor  138 , first conduit  156 , fluid reservoir  163 , and/or second conduit  162 . 
     Insertion device  100  may include one or more of a processor device  166 ; a memory element  168  to store data, processor-readable program instructions, and the like; a battery  170  or other power source; and a sensor interface  173  configured to establish electrical connectivity with a medical device, such as second medical device  122 . Processor device  166 , memory element  168 , battery  170 , and/or sensor interface  173  may be included on an electronics assembly  172 . In examples, second medical device  122  is an analyte sensor configured to electrically couple to sensor interface  173  to establish electrical connectivity between conductors of the analyte sensor and conductors of the electronics assembly  172 . Electronics assembly  172  (or the components of electronics assembly  172 ) can be electrically coupled to other elements of insertion device  100  as needed to support the operation of insertion device  100 . For example, the electronics assembly  172  can be electrically coupled to at least the following, without limitation: the fluid pump  136 ; the sensor interface  173 ; the insertion mechanism unit  124 ; and the user input device  108 . It should be appreciated that electrical connections to the electronics assembly  172  can be direct or indirect if so desired. Moreover, one or more components of the electronics assembly  172  may support wireless data communication in some embodiments. 
     In examples, processor device  166  includes processing circuitry configured to control an operation of fluid pump  136 . For example, the processing circuitry may be configured to cause the fluid pump  136  to commence, continue, and/or cease transporting fluid from fluid reservoir  158  to first medical device  120  (e.g., a fluid delivery cannula). In examples, at least one of first medical device  120  or second medical device  122  is an analyte sensor configured to generate a signal indicative of a physiological characteristic of the user (e.g., a glucose level), and the processing circuitry is configured to determine the physiological characteristic using the indicative signal. In some examples, the processing circuitry is configured to control an operation of fluid pump  136  based on the indicative signal reported by the analyte sensor. Sensor system  130  may include one or more of sensor interface  173 , first medical device  120 , and/or second medical device  122 . 
     Device housing  102  is suitably shaped, sized, and configured to house or support the electronics assembly  172 , the fluid pump  136 , the fluid reservoir  158 , the sensor interface  173 , and the user interface device  108 . The fluid infusion system  128  depicted in  FIG. 3  may include at least the fluid pump  136 , the fluid reservoir  158 , first conduit  156 , and second conduit  162  shown in  FIG. 4 . The sensor system  130  depicted in  FIG. 3  may include at least the sensor interface  173  shown in  FIG. 4 . 
     As discussed, insertion device  100  may be configured to cause first insertion needle  132  and second insertion needle  134  to implant first medical device  120  and second medical device  122  substantially concurrently. Insertion device  100  may be configured to cause first insertion needle  132  extend in a first direction away from housing  102 ,  126  and cause second insertion needle  134  to extend in a different, second direction away from housing  102 ,  126 , in order to implant first medical device  120  at a location displaced from second medical device  122 . Insertion device  100  includes an insertion mechanism unit  124  which may be activated by the user and configured to cause the implantation of first medical device  120  and second medical device  122 . 
       FIG. 5A ,  FIG. 5B , and  FIG. 5C . Schematically illustrate an insertion mechanism unit  124  including driver  150 . Insertion mechanism unit  124  includes first linkage assembly  142  configured to cause first insertion needle  132  to extend and retract relative to housing  102 ,  126 . Insertion mechanism unit  124  includes second linkage assembly  144  configured to cause second insertion needle  134  to extend and retract relative to housing  102 ,  126 . Central axis A is included for reference. Driver  150  is configured to drive first linkage assembly  142  and second linkage assembly  144  from the configuration of  FIG. 5A  to the configuration of  FIG. 5B  to extend first insertion needle  132  and second insertion needle  134  in a direction away from housing  102 ,  126 , and to drive first linkage assembly  142  and second linkage assembly  144  from the configuration of  FIG. 5B  to the configuration of  FIG. 5C  to retract first insertion needle  132  and second insertion needle  134  in a direction toward housing  102 ,  126 . 
     In examples, driver  150  includes a spring  174  configured to drive first linkage assembly  142  and second linkage assembly  144 . Insertion device  100  may be configured such that spring  174  is in a wound and/or charged condition when the user positions insertion device  100  proximate to the skin. For example, insertion device  100  may be manufactured and/or assembled such that spring  174  is in a wound and/or charged condition when delivered to the user. The user may actuate user input device  108  to cause operation of a release mechanism unit configured to allow spring  174  to unwind and/or discharge to cause movement of first linkage assembly  142 , and/or second linkage assembly  144 . For example, the release mechanism unit may be a mechanical stop having a first position where the mechanical stop engages spring  174 , first linkage assembly  142 , and/or second linkage assembly  144  to substantially prevent motion of spring  174 , first linkage assembly  142 , and/or second linkage assembly  144 , such that spring  174  is prevented from unwinding and/or discharging. The mechanical stop may have a second position where the mechanical stop is substantially disengaged from spring  174 , first linkage assembly  142 , and/or second linkage assembly  144 , such that spring  174  is substantially free to unwind and/or discharge to cause motion of first linkage assembly  142  and/or second linkage assembly  144 . Insertion device  100  may be configured such that a user may cause the release mechanism unit to shift from the first position to the second position using user input device  108 . 
     In examples, driver  150  includes a spring  174  configured to cause a rotation of first linkage assembly  142  (e.g., first input link  146 ) and/or second linkage assembly  144  (e.g., second input link  148 ) relative to housing  102 ,  126 . Spring  174  may be configured to convert potential energy into kinetic energy to cause the rotation. For example, spring  174  may be in a charged condition having a first potential energy when insertion mechanism unit  124  is in the configuration of  FIG. 5A . Spring  174  may convert some portion of the first potential energy to kinetic energy to transition insertion mechanism unit  124  from the configuration of  FIG. 5A  to the configuration of  FIG. 5B , such that spring  174  is in a partially uncharged state having a second potential energy less than the first potential energy. Spring  174  may convert some portion of the second potential energy to kinetic energy to transition insertion mechanism unit  124  from the configuration of  FIG. 5B  to the configuration of  FIG. 5C , such that spring  174  is in a substantially relaxed state having a third potential energy less than the second potential energy. 
     In examples, spring  174  is a torsion spring having a first end  176  (“spring first end  176 ”) and a second end  178  (“spring second end  178 ”). The torsion spring may be configured to store potential energy by substantially winding (e.g., twisting around) a spring axis, and may be configured to cause movement of spring first end  176  and spring second end  178  as the torsion spring unwinds to expend the potential energy. In examples, the spring axis may be substantially parallel to and/or coincident with central axis A. Spring first end  176  may be configured to exert a first torque T 1  (e.g., around central axis A) on first linkage assembly  142  when spring  174  expends potential energy, and may be configured to exert a second torque T 2  (e.g., around central axis A) on second linkage assembly  144  when spring  174  expends potential energy. In examples, first torque T 1  and second torque T 2  have opposite rotational directions. 
     First input link  146  of first linkage assembly  142  is configured to rotate relative to housing  102 ,  126  when the first torque T 1  is exerted on first input link  146  by driver  150 . In examples, first input link  146  is configured such that a terminal end  180  of first input link  146  rotates substantially around central axis A when the first torque T 1  is exerted on first input link  146 . In some examples, first input link  146  is rotatably pinned to housing  102 ,  126  or another portion of insertion device  100  at a first end  182  opposite terminal end  180 , such that terminal end  180  is constrained to define a circular path substantially around first end  182  when the first torque T 1  is exerted on first input link  146 . 
     First linkage assembly  142  includes a plurality of links including first input link  146  and a first output link  184 . First input link  146  and first output link  184  define a first kinematic chain, such that a rotation of first input link  146  relative to housing  102 ,  126  causes motion of first output link  184  relative to first input link  146 , and relative to housing  102 ,  126 . For example, first input link  146  may define an input angle θ1 (e.g., a crank angle) relative to a portion of housing  102 ,  126 . First linkage assembly may define the first kinematic chain such that, as the input angle θ1 increases or decreases during rotation of first input link  146 , the first kinematic chain causes first output link  184  to move relative to first input link  146  and housing  102 ,  126 . 
     In examples, first output link  184  is a sliding member configured to linearly translate relative to housing  102 ,  126  when first input link  146  rotates relative to housing  102 ,  126 . First output link  184  may be configured to linearly translate within a first channel  186  defined by housing  102 ,  126 . For example, first linkage assembly  142  may be configured such that first output link  184  slidably translates within first channel  186  in the distal direction D 1  when first input link  146  initially increases the input angle θ1 (e.g., up to about 90 degrees ( FIG. 5B )), and may be configured such that first output link  184  slidably translates within first channel  186  in the proximal distal direction P 1  as first input link  146  further increases the input angle θ1 (e.g., beyond about 90 degrees ( FIG. 5C )). First output link  184  is mechanically engaged with first insertion needle  132 , such that translation of first output link  184  in the distal direction D 1  causes first insertion needle  132  to extend in a direction away from housing  102 ,  126 , and translation of first output link  184  in the proximal direction P 1  causes first insertion needle  132  to retract in a direction toward housing  102 ,  126 . 
     In examples, first linkage assembly  142  includes a medial link  188  (“first medial link  188 ”) rotatably engaged with terminal end  180  and first output link  184 . In examples, first medial link  188  is configured as a floating link in the first kinematic chain defined by first linkage assembly  142 . For example, first medial link  188  may be rotatably engaged with terminal end  180  by a joint  190  configured to allow relative rotation of first medial link  188  and first input link  146 . First medial link  188  may be rotatably engaged with first output link  184  by a joint  192  configured to allow relative rotation between first medial link  188  and first output link  184 . First linkage assembly  142  may include any number of floating links in the first kinematic chain defined by first input link  146  and first output link  184 . 
       FIG. 5B  illustrates first linkage assembly  142  with driver  150  (e.g., spring  174 ) having expended potential energy to exert the torque T 1  on first input link  146 . The torque T 1  has caused first input member  222  to rotate relative to housing  102 ,  126 , such that first input link  146  defines the input angle θ1 at about 90 degrees. The rotation of first input link  146  relative to housing  102 ,  126  has caused terminal end  180  to travel over the substantially circular path C 1  around first end  182  compared to  FIG. 5A , causing first linkage assembly  142  (e.g., first medial link  188 ) to drive first output link  184  and first insertion needle  132  over the substantially linear path L in a direction away from housing  102 ,  126  (e.g., in the distal direction D 1 ). Torsion spring  174  may continue to exert the torque T 1  on first input link  146  to further increase the input angle θ1 as spring  174  continues to unwind. 
       FIG. 5C  illustrates first linkage assembly  142  with torsion spring  174  having expended additional potential energy to rotate first input link  146  such that first input link  146  defines the input angle θ1 at greater than 90 degrees. The rotation of first input link  146  relative to housing  102 ,  126  has caused terminal end  180  to travel over the substantially circular path C 2  around first end  182  compared to  FIG. 5B , causing first linkage assembly  142  (e.g., first medial link  188 ) to drive first output link  184  and first insertion needle  132  over the substantially linear path L in a direction toward housing  102 ,  126  (e.g., in the proximal direction P 1 ). In examples, driver  150  (e.g., spring  174 ) has expended substantially all of its potential energy and is in a relaxed state when first insertion needle  132  has been retracted into housing  102 ,  126 , such that driver  150  no longer exerts the first torque T 1  on first linkage assembly  142 , although this is not required. 
     Insertion device  100  is configured to substantially maintain spring  174  in the charged state to prevent spring  174  from causing rotation of first linkage assembly  142  and/or second linkage assembly  144  until user input device  108  ( FIG. 1, 4 ) is actuated. For example, insertion mechanism unit  124  may include a release mechanism unit (e.g., mechanical stops  194 ,  196  discussed below) configured to engage spring  174 , first linkage assembly  142 , second linkage assembly  144 , and/or some other portion of insertion mechanism unit  124  to substantially constrain movement of insertion mechanism unit  124 , such that spring  174  is substantially prevented from expending potential energy to cause movement of insertion mechanism unit  124 . User input device  108  may be configured to cause the release mechanism unit to disengage from insertion mechanism unit  124 , such that insertion mechanism unit  124  is substantially free to move and spring  174  may expend potential energy to drive the movement. In some examples, the release mechanism unit is configured to engage first linkage assembly  142  such that first linkage assembly  142  is constrained from movement caused by the first input torque T 1  exerted by driver  150 . In some examples, the release mechanism unit is configured to mechanically engage driver  150  (e.g., spring  174 ) to substantially prevent driver  150  from exerting the first torque T 1  on first linkage assembly  142 . 
     For example, insertion device  100  may include a mechanical stop  194  configured to constrain movement of first linkage assembly  142  in a first position. Mechanical stop  194  is depicted in  FIG. 5A  as mechanically engaging first output link  184 , however mechanical stop  194  may have any orientation and engage any portion of first linkage assembly  142  in the first position. Mechanical stop  194  is configured to engage first linkage assembly  142  such that first linkage assembly  142  is constrained from movement caused by the first input torque T 1  exerted by driver  150 . Mechanical stop  194  may be configured to mechanically disengage from first linkage assembly  142  such that first torque T 1  causes a rotation of first linkage assembly  142  (e.g., first input link  146 ). In examples, mechanical stop  194  is configured to establish the first position (e.g.,  FIG. 5A ) wherein mechanical stop  194  mechanically engages first linkage assembly  142  and establish a second position (e.g.,  FIG. 5B  and/or  FIG. 5C ) wherein mechanical stop  194  is mechanically disengaged from first linkage assembly  142 . User input device  108  may be configured to cause mechanical stop  194  to transition from the first position to the second position. User input device  108  may be coupled with the mechanical stop  194  wirelessly, electrically, mechanically or in any other effective way. 
     In some examples, instead of or in addition to mechanical stop  194 , insertion device  100  may include a mechanical stop  196  configured to constrain movement spring  174  from exerting the first torque T 1  on first linkage assembly  142  in a first position. Mechanical stop  196  is depicted in  FIG. 5A  as mechanically engaging first spring end  176 , however mechanical stop  196  may have any orientation and engage any portion of driver  150  in the first position. Mechanical stop  196  is configured to engage driver  150  such that spring  174  is substantially prevented from exerting the first torque T 1  on first linkage assembly  142 . Mechanical stop  196  may be configured to mechanically disengage from driver  150  such that spring  174  exerts the first torque T 1  on first linkage assembly  142  (e.g., on first input link  146 ). In examples, mechanical stop  196  is configured to establish the first position (e.g.,  FIG. 5A ) wherein mechanical stop  196  mechanically engages driver  150  and establish a second position (e.g.,  FIG. 5B  and/or  FIG. 5C ) wherein mechanical stop  196  is mechanically disengaged from driver  150 . User input device  108  may be configured to cause mechanical stop  196  to transition from the first position to the second position. User input device  108  may be coupled with the mechanical stop  196  wirelessly, electrically, mechanically or in any other effective way. 
     Mechanical stops  194 ,  196  are examples of a release mechanism unit. Insertion device  100  may include any release mechanism unit configured to substantially maintain spring  174  in the charged state to prevent spring  174  from causing rotation of first linkage assembly  142  and/or second linkage assembly  144  until user input device  108  ( FIG. 1, 4 ) is actuated. 
     Driver  150  may use any elastic object configured to store mechanical energy as potential energy and configured to cause the rotation of first linkage assembly  142  and/or second linkage assembly  144  using an expenditure of the potential energy. Spring  174  may be any type of spring. For example, spring  174  may be torsion spring discussed above, a compression spring, a leaf spring, a spiral spring, a flat spring, a machined spring, a serpentine spring, a garter spring, or another type of spring configured to store potential energy. Spring  174  may be a constant force or variable force spring. Driver  150  may use any number of springs and any type of spring in any combination to cause the rotation of first linkage assembly  142  and second linkage assembly  144 . 
     Driver  150  including spring  174  is one example of a driver configured to cause rotation of first linkage assembly  142  and/or second linkage assembly  144 . Driver  150  may cause the rotation of first linkage assembly  142  and/or second linkage assembly  144  in any manner. In examples, driver  150  includes one or more motors configured to cause the rotation of first linkage assembly  142  and/or second linkage assembly  144 . The one or more motors may be, for example, a rotary motor configured to cause the rotation using a rotation of an output shaft, a linear motor configured to cause the rotation using translation of a slider, or other type of motors configured to produce an output motion (e.g., relative to a motor housing) and use the output motion to cause the rotation. The one or more motors may be constant or variable speed motors, and may be configured to cause the rotation of first linkage assembly  142  and/or second linkage assembly  144  at a constant rotational speed or a varying rotational speed. In examples, the one or more motors are be configured to receive power from a battery (e.g., battery  170 ) within insertion device  100 . Insertion device  100  may include processing circuitry configured to control the one or motors (e.g., configured to cause a motor to generate motion, to cease generating motion, to generate motion at a particular speed, etc.) In examples, user input device  108  is configured to actuate the one or more motors to cause the rotation of first linkage assembly  142  and/or second linkage assembly  144 . 
     Hence, first linkage assembly  142  is configured to cause first insertion needle  132  to extend in a first direction away from housing  102 ,  126  (e.g., the distal direction D 1 ) and subsequently withdraw in a direction toward housing  102 ,  126  (e.g., the proximal direction P 1 ) when first linkage assembly  142  (e.g., first input link  146 ) rotates relative to housing  102 ,  126 . In examples, first insertion needle  132  defines a distal end  198  (“first needle distal end”), and first linkage assembly  142  is configured to cause first insertion needle  132  to transition from a first undeployed position wherein first needle distal end  198  is within housing  102 ,  126  (e.g., within first channel  186  ( FIG. 5A )) to a first deployed position wherein first needle distal end  198  is outside housing  102 ,  126  (e.g., outside of first channel  186  ( FIG. 5B )). In examples, first linkage assembly  142  is configured to cause first insertion needle  132  to transition from the first deployed position ( FIG. 5B ) to a first stowage position wherein first needle distal end  198  is within housing  102 ,  126  (e.g., inside of first channel  186  ( FIG. 5C )). The first stowage position may be a different position that the first undeployed position, or may be substantially the same position as the first undeployed position. 
     Insertion mechanism unit  124  further includes second linkage assembly  144 , including second input link  148 , second output link  204 , and second medial link  206 , which may be configured similarly to and in relation to each other in the same manner as that described for first input link  146 , first output link  184 , and first medial link  188  respectively. For example, second linkage assembly  144  may be configured such that the torque T 2  exerted on second input link  148  by driver  150  (e.g., via spring second end  178 ) causes second output link  204  to translate within a second channel  208  defined by housing  102 ,  126  in a distal direction D 2  and subsequently in a proximal direction P 2 . Second output link  204  may be mechanically engaged with second insertion needle  134 , such that translation of second output link  204  causes second insertion needle  134  to extend in a direction away from housing  102 ,  126  and to retract in a direction toward housing  102 ,  126 . Second input link  148  may define an input angle θ2 (e.g., a crank angle) relative to a portion of housing  102 ,  126 . 
     In examples, second insertion needle  134  defines a distal end  210  (“second needle distal end”), and second linkage assembly  144  is configured to cause second insertion needle  134  to transition from a second undeployed position wherein second needle distal end  210  is within housing  102 ,  126  (e.g., within second channel  208  ( FIG. 5A )) to a second deployed position wherein second needle distal end  210  is outside housing  102 ,  126  (e.g., outside of second channel  208  ( FIG. 5B )). In examples, second linkage assembly  144  is configured to cause second insertion needle  134  to transition from the second deployed position ( FIG. 5B ) to a second stowage position wherein second needle distal end  210  is within housing  102 ,  126  (e.g., inside of second channel  208  ( FIG. 5C )). The second stowage position may be a different position that the second undeployed position, or may be substantially the same position as the second undeployed position. 
     Insertion device  100  may include a mechanical stop (not shown) configured relative to second linkage assembly  144  and user input device  108  in the same or similar manner as mechanical stop  194  is configured relative to first linkage assembly  142  and user input device  108 . Insertion device  100  may include a mechanical stop (not shown) configured relative to driver  150  (e.g., second spring end  178 ) and user input device  108  in the same or similar manner as mechanical stop  196  is configured relative to driver  150  (e.g., first spring end  176 ) and user input device  108 . 
     The rotation of first input link  146  and/or second input link  148  may be in one, continuous, direction. The continuous direction may be clockwise or counter-clockwise. Further, input angle θ1 and/or input angle θ2 may be any angle. In an example, insertion device  100  is configured to cause first input link  146  and/or second input link  148  to define input angle θ1 and/or input angle θ2 within some range between 0 degrees to 180 degrees (e.g., within a range from about 30 degrees to about 150 degrees, from about 45 degrees to about 135 degrees, or some other range defined between 0 degrees to 180 degrees). Additionally rotation of first input link  146  and second input link  148  may be substantially synchronized such that first input angle θ1 and second input angle θ2 describe substantially equal angles as driver  213  causes rotation of first input link  146  and second input link  148 , however this is not required. In some examples, first input link  146  and second input link  148  may be non-synchronized, such that first input angle θ1 and second input angle θ2 describe substantially unequal input angles as driver  213  causes rotation of first input link  146  and second input link  148 . In a non-synchronized implementation, the first input angle θ1 and second input angle θ2 during movement may differ, with respect to the same time, from one another. Additionally, the lengths of first input link  146 , first medial link  188 , first output link  184 , second input link  148 , second medial link  206 , second output link  204 , and/or other links within first linkage assembly  142  or second linkage assembly  144  may be varied to adjust rotational symmetry, timing, the insertion depths of first insertion needle  132  and/or second insertion needle  134 , or for other reasons. 
       FIG. 6A ,  FIG. 6B , and  FIG. 6C  schematically illustrate another example insertion mechanism unit  212  including driver  214 . Insertion mechanism unit  212  includes first linkage assembly  216  including first input link  218  and second linkage assembly  220  including second input link  222 . Driver  214  is configured to exert a torque T 3  on first linkage assembly  216  (e.g., first input link  218 ) and a torque T 4  on second linkage assembly  220  (e.g., second input link  222 ) to cause first insertion needle  132  and second insertion needle  134  to extend and retract relative to housing  102 ,  126 . Driver  214  is configured to exert torque T 3  on first linkage assembly  216  and torque T 4  on second linkage assembly  220  in the same rotational direction around central axis A. Insertion mechanism unit  212 , first linkage assembly  216 , first input link  218 , second linkage assembly  220 , and second input link  222  may be examples of insertion mechanism unit  124 , first linkage assembly  142 , first input link  146 , second linkage assembly  144 , and second input link  148  respectively. 
     Driver  214  includes a hub  224  configured to revolve around an axis defined by housing  102 ,  126 , such as central axis A. Hub  224  may be configured to revolve relative to housing  102 ,  126 . Driver  214  is configured to impart a torque TM on hub  224  to cause the revolution. Hub  224  may be configured to transmit some portion of the torque TM to first input link  218 , such that first input link  218  experiences the torque T 3  in the same direction as the torque TM. Hub  224  may be configured to transmit some portion of the torque TM to second input link  222 , such that second input link  218  experiences the torque T 4  in the same direction as the torque TM. In examples, first input link  218  and second input link  222  mechanically engage hub  224  such that the revolution of hub  224  (e.g., around central axis A) driven by torque TM causes a rotation of first input link  218  and second input link  222  relative to housing  102 ,  126 . For example, the revolution of hub  224  may cause a first terminal end  225  of first input link  218  to rotate around hub  224 , and may cause a second terminal end  227  of second input link  222  to rotate around hub  224 . 
     First input link  218  and first output link  184  define a kinematic chain, such that a rotation of first input link  218  relative to housing  102 ,  126  causes motion of first output link  184  relative to first input link  218  and relative to housing  102 ,  126 . The kinematic chain defined by first input link  218  and first output link  184  may be configured in the same or a similar manner to the first kinematic chain defined by first input link  146  ( FIGS. 4, 5A-5C ) and first output link  184 . Second input link  222  and second output link  204  define an additional kinematic chain, such that a rotation of second first input link  218  relative to housing  102 ,  126  causes motion of second output link  184  relative to second input link  222  and relative to housing  102 ,  126 . The additional kinematic chain defined by second input link  222  and second output link  204  may be configured in the same or a similar manner to the second kinematic chain defined by second input link  148  ( FIGS. 4, 5A-5C ) and second output link  204 . 
     Thus, first linkage assembly  216  is configured to cause first insertion needle  132  to transition from the first undeployed position ( FIGS. 5A, 6A ) wherein first needle distal end  210  is within housing  102 ,  126  to the first deployed position ( FIGS. 6A, 6B ) wherein first needle distal end  210  is outside housing  102 ,  126 , and configured to cause first insertion needle  132  to transition from the first deployed position to a first stowage position ( FIGS. 5C, 6C ) wherein first needle distal end  210  is within housing  102 ,  126 . Second linkage assembly  220  is configured to cause second insertion needle  134  to transition from the second undeployed position ( FIGS. 5A, 6A ) wherein second needle distal end  210  is within housing  102 ,  126  to the second deployed position ( FIGS. 5B, 6B ) wherein second needle distal end  210  is outside housing  102 ,  126 , and configured to cause second insertion needle  134  to transition from the second deployed position to the second stowage position ( FIGS. 5C, 6C ) wherein second needle distal end  210  is within housing  102 ,  126 . 
     Driver  214  may include a spring  226  configured to exert the torque TM on hub  224  to cause the revolution of hub  224  cause the revolution of hub  224  relative to housing  102 ,  126 . Spring  226  may be an example of spring  174 . Spring  226  may be configured to convert potential energy into kinetic energy to cause the revolution of hub  224 . For example, spring  226  may be in a charged condition having a primary potential energy when insertion mechanism unit  212  is the configuration of  FIG. 6A . Spring  226  may convert some portion of the primary potential energy to kinetic energy to transition insertion mechanism unit  212  from the configuration of  FIG. 6A  to the configuration of  FIG. 6B , such that spring  226  is in a partially uncharged state having a secondary potential energy less than the primary potential energy. Spring  226  may convert some portion of the secondary potential energy to kinetic energy to transition insertion mechanism unit  212  from the configuration of  FIG. 6B  to the configuration of  FIG. 6C , such that spring  226  is in a substantially relaxed state having a tertiary potential energy less than the secondary potential energy. 
     In examples, spring  226  is a torsion spring configured to store potential energy by substantially winding (e.g., twisting around) a spring axis. Spring  226  may be mechanically engaged with hub  224  to cause revolution of hub  224  as the spring  226  unwinds to expend the potential energy. In examples, the spring axis may be substantially parallel to and/or coincident with central axis A. Some portion of spring  240  (e.g., a portion of the spring coil or a spring end) may be configured to exert the torque TM on hub  224  when spring  226 , causing hub  224  to transmit the torque T 3  to first linkage assembly  216  and the torque T 4  to second linkage assembly  220 . In examples, torque T 3  and torque T 4  have the same rotational direction. 
     The rotation of first input link  218  and/or second input link  222  may be in one, continuous, direction. The continuous direction may be clockwise or counter-clockwise. Further, input angle θ1 and/or input angle θ2 may be any angle. In an example, insertion device  100  is configured to cause first input link  218  and/or second input link  222  to define input angle θ1 and/or input angle θ2 within some range between 0 degrees to 180 degrees (e.g., within a range from about 30 degrees to about 150 degrees, from about 45 degrees to about 135 degrees, or some other range defined between 0 degrees to 180 degrees). Additionally rotation of first input link  218  and second input link  222  may be substantially synchronized such that first input angle θ1 and second input angle θ2 describe substantially equal angles as driver  214  causes rotation of first input link  218  and second input link  222 , however this is not required. In some examples, first input link  218  and second input link  222  may be non-synchronized, such that first input angle θ1 and second input angle θ2 describe substantially unequal input angles as driver  214  causes rotation of first input link  218  and second input link  222 . In a non-synchronized implementation, the first input angle θ1 and second input angle θ2 during movement may differ, with respect to the same time, from one another. Additionally, the lengths of first input link  218 , first medial link  188 , first output link  184 , second input link  222 , second medial link  206 , second output link  204 , and/or other links within first linkage assembly  216  or second linkage assembly  220  may be varied to adjust rotational symmetry, timing, the insertion depths of first insertion needle  132  and/or second insertion needle  134 , or for other reasons. 
     First linkage assembly  142 ,  216  may be configured and/or supported within housing  102 ,  126  to cause the extension and retraction of first insertion needle  132  in any direction relative to housing  102 ,  126 . Second linkage assembly  144 ,  220  may be configured and/or supported within housing  102 ,  126  to cause the extension and retraction of second insertion needle  132  in any direction relative to housing  102 ,  126 . Housing  102 ,  126  may define first channel  186  and second channel  208  to cause output link  184  and output link  204  respectively to linearly translate in any direction relative to housing  102 ,  126 . Further, first input link  146 ,  218 , first output link  184 , medial link  188 , and/or other links within first linkage assembly  142 ,  216  may have any orientation relative to housing  102 ,  126  and each other sufficient to cause first output link  184  to translate for the extension and retraction of first insertion needle  132 . First input link  146 ,  218 , first output link  184 , medial link  188 , and/or other links within first linkage assembly  142 ,  216  may form a joint angle with an adjacent link in any orientation relative to housing  102 ,  126 . Second input link  148 ,  222  second output link  204 , medial link  206 , and/or other links within second linkage assembly  144 ,  220  may have any orientation relative to housing  102 ,  126  and each other sufficient to cause second output link  204  to translate for the extension and retraction of second insertion needle  134 . Second input link  148 ,  222 , second output link  204 , medial link  206 , and/or other links within second linkage assembly  144 ,  220  may form a joint angle with an adjacent link in any orientation relative to housing  102 ,  126 . 
     Insertion device  100  may be configured to cause the extension and retraction of first insertion needle  132  and second insertion needle  134 , and the implantation of first medical device  120  and second medical device  122 , at any angle relative to housing  102 ,  126  and/or relative to each other. Insertion device  100  may be configured to cause the extension and retraction of first insertion needle  132  and second insertion needle  134 , and the implantation of first medical device  120  and second medical device  122  at any angle relative to the user when insertion device  100  is proximate the skin  118  of the user. In examples, and as depicted at  FIG. 3 , insertion device  100  is configured to extend first insertion needle  132  and first medical device  120  toward the user and in a first direction (e.g., the first direction S 1 ), and extend second insertion needle  134  and second medical device  122  toward the user in a second direction (e.g., the second direction S 2 ) different than the first direction. Insertion device  100  may be configured to cause the retraction of first insertion needle  132  in a direction substantially opposite the first direction and the retraction of second insertion needle  134  in a direction substantially opposite the second direction. 
     As discussed, first insertion needle  132  is configured to releasably engage first medical device  120  to cause the implantation of first medical device  120  within the user. In examples, first medical device  120  is a fluid delivery cannula configured to deliver a fluid (e.g., insulin) to a user. First insertion needle  132  and the fluid delivery cannula may be cooperatively configured and arranged such that the first insertion needle  132  releasably carries at least the a portion (e.g., a distal portion) of the fluid delivery cannula as first insertion needle  132  is caused to extend away from housing  105 ,  155 . In some examples, first insertion needle  132  is configured to extend into lumen  154  of the fluid delivery cannula when first insertion needle  132  extends away from housing  102 ,  126 . First insertion needle  132  and/or the fluid delivery cannula may be configured such that first insertion needle  132  mechanically engages the fluid delivery cannula when first insertion needle  132  extends in the first distal direction D 1  and disengages from the fluid delivery cannula when first insertion needle retracts in the first proximal direction P 1  ( FIGS. 4, 5A-5C, 6A-6C ). 
     In examples, when first insertion needle  132  is in the first undeployed position wherein first needle distal end  198  is within first channel  186  ( FIG. 5A )), insertion device  100  may be configured to fluidly isolate first medical device  120  (e.g., the fluid delivery cannula) and first insertion needle  132 . For example, insertion device  100  may be configured to fluidly isolate first insertion needle  132  and first medical device  120  using a first septum  228  ( FIG. 4 ). First septum  228  may define a portion of first conduit  156 . Insertion device  100  may be configured such that, as first insertion needle  132  extends in the distal direction D 1 , insertion needle  132  (e.g., first distal end  198 ) punctures first septum  228  prior to engaging first medical device  120 . First septum  228  may be comprised of a self-sealing material, such that first septum  228  substantially closes around first insertion needle  132  to substantially maintain a fluid isolation between first conduit  156  and other components of insertion device  100 , such as driver  150 , first linkage assembly  142 , second linkage assembly  144 , processor  166  including processing circuitry, memory element  168 , and other portions of insertion device  100  which may be adversely impacted by contact with a fluid within first conduit  156 . 
     First insertion needle  132  may be configured to engage first medical device  120  to cause first medical device  120  to translate in the first distal direction D 1 . First insertion needle  132  may be configured to exert a force on first medical device  120  in the distal direction D 1  to cause the translation of first medical device  120 . For example, first insertion needle  132  and/or first medical device  120  may include a first structural feature configured to cause first insertion needle  132  to exert the force in the distal direction D 1  on first medical device  120  when first insertion needle  132  extends in the first distal direction D 1 . In examples, first insertion needle  132  is configured to enter lumen  154  to engage first medical device  120 . First insertion needle  132  may be configured to engage first medical device  120  to cause implantation of first medical device in the user as first insertion needle  132  extends in the distal direction D 1  into the user. First medical device  120  (e.g., a fluid delivery cannula) may be configured to extend from device housing  102  when first insertion needle  132  causes the implantation of first medical device  120  within the user. First insertion needle  132  may be configured to disengage from (e.g., release) first medical device  120  when first insertion needle  132  is subsequently retracted in the first proximal direction P 1  by insertion device  100 . For example, first insertion needle  132  and/or first medical device  120  may include a structural feature (the same as the first structural feature or a different structural feature) configured to allow first insertion needle  132  to move substantially independently of first medical device  120  when insertion device  100  retracts first insertion needle  132  in the first proximal direction P 1 . 
     In examples, first insertion needle  132  is configured to substantially mate with first medical device  120  when a first insertion needle  132  exerts the force in the first distal direction D 1  on first medical device  120 . First insertion needle  132  may be configured such that a subsequent force in the first proximal direction P 1  causes first insertion needle  132  to unmate (e.g., disengage) and move independently of first medical device  120 . In examples, first insertion needle  132  includes a bearing surface configured such that, when the force in the first distal direction D 1  is exerted on first insertion needle  132 , the bearing surface engages a portion of first medical device  120  and transmits some portion of the force to first medical device  120 , and when a force in the first proximal direction P 1  is exerted in first insertion needle  132 , the bearing surface displaces from first medical device  120 , such that first insertion needle  132  moves independently of first medical device  120 . Hence, insertion device  100  may be configured to retract first insertion needle  132  in the first proximal direction P 1  independently from first medical device  120 , such that first medical device  120  remains implanted as first insertion needle  132  retracts. 
     Insertion device  100  may be configured to retract first insertion needle  132  to the first stowage position, wherein first distal end  198  is within housing  102 ,  126 . Insertion device  100  may retract first insertion needle  132  such that first needle distal end  198  retracts through septum  228 . Septum  228  may be configured to self-seal during or once first needle distal end  198  retracts through septum  228 , in order to substantially maintain fluid isolation between first conduit  156  and other components of insertion device  100 , such as driver  150 , first linkage assembly  142 , second linkage assembly  144 , processor  166  including processing circuitry, memory element  168 , and other portions of insertion device  100  which may be adversely impacted by contact with a fluid within first conduit  156 . 
     As discussed, second insertion needle  134  is configured to releasably engage second medical device  122  to cause the implantation of second medical device  122  within the user. In examples, second medical device  122  is an analyte sensor configured to monitor a physiological characteristic (e.g., a glucose level) of the user. Second insertion needle  134  and the analyte sensor may be cooperatively configured and arranged such that the second insertion needle  132  releasably carries at least a portion (e.g., a distal portion) of the analyte sensor as second insertion needle  134  is caused to extend away (e.g., in the second distal direction D 2 ) from housing  105 ,  155 . In some examples, second insertion needle  134  configured to at least partially surround the analyte sensor to carry the analyte sensor as second insertion needle  134  extends away from housing  102 ,  126 . Second insertion needle  134  may be configured as a substantially hollow needle defining a void that accommodates the analyte sensor within the void. Second insertion needle  134  and/or the analyte sensor may be configured such that second insertion needle  134  mechanically engages the analyte sensor when second insertion needle  134  extends in the second distal direction D 2  and disengages from the analyte sensor when second insertion needle  134  retracts in the second proximal direction P 2 . 
     Second insertion needle  134  may be configured to engage second medical device  122  to cause second medical device  122  to translate in the second distal direction DS. Second insertion needle  134  may be configured to exert a force on second medical device  122  in the second distal direction D 2  to cause the translation of second medical device  122 . Second insertion needle  134  and/or second medical device  122  may include a second structural feature (e.g., the void defined by second insertion needle) configured to cause second insertion needle  134  to exert the force in the second distal direction D 2  on second medical device  122  when second insertion needle  134  extends in the second distal direction D 2 . Second insertion needle  134  may be configured to engage second medical device  122  to cause implantation of second medical device  122  in the user as second insertion needle  134  extends in the second distal direction D 2  into the user. Second medical device  122  (e.g., an analyte sensor) may be configured to extend from device housing  102  when second insertion needle  134  causes the implantation of second medical device  122  within the user. 
     Second insertion needle  134  may be configured to disengage from (e.g., release) second medical device  122  when second insertion needle  134  is subsequently retracted in the second proximal direction P 2  by insertion device  100 . For example, second insertion needle  134  and/or second medical device  122  may include a structural feature (the same as the second structural feature or a different structural feature) configured to allow second insertion needle  134  to move substantially independently of second medical device  122  when insertion device  100  retracts second insertion needle  134  in the second proximal direction P 2 . In some examples, second insertion needle  134  is configured such that body tissue within the user engages with second medical device  122  (e.g., the analyte sensor) when second insertion needle  134  retracts, such that second medical device  122  remains implanted in the user when second insertion needle  134  is withdrawn from the user. For example, second insertion needle  134  may include a portion (e.g., a distal portion) defining a longitudinal opening, such that a portion of the analyte sensor is exposed to body tissue when second insertion needle  134  and second medical device  122  are inserted in the user. The body tissue may act to grip (e.g., frictionally engage) the exposed portion of the analyte sensor as second insertion needle  134  is retracted, such that second insertion needle  134  may be retracted into housing  102 ,  126  as second medical device  122  remains implanted in the user. In examples, second medical device  122  (e.g., an analyte sensor) may include one or more structural features configured to assist the frictional engagement with the body tissue. In some examples, insertion device  100  may be configured to mechanically engage second medical device  122  to hold second medical device in place (e.g., within the user) when second insertion needle  132  is retracted in the second proximal direction P 2 . 
     In examples, insertion device  100  may be configured to fluidly isolate portions of insertion device  100  from second hole  116  defined by device housing  102  in order to, for example, fluidly isolate portions of insertion device  100  from the user. The portions of insertion device  100  may include driver  150 , first linkage assembly  142 , second linkage assembly  144 , processor  166  including processing circuitry, memory element  168 , and others portions of insertion device  100  which may be adversely impacted by contact with a fluid from the user. In examples, insertion device  100  includes second septum  230  ( FIG. 4 ) configured to fluidly isolate the portions of insertion device  100  and the second hole  116 . Insertion device  100  may be configured such that, as second insertion needle  134  extends in the second distal direction D 2 , second insertion needle  134  (e.g., second needle distal end  210 ) punctures second septum  230 . Second septum  230  may be comprised of a self-sealing material, such that second septum  230  substantially closes around second insertion needle  134  and/or second medical device  122  to substantially maintain a fluid isolation between the portions of insertion device  100  and the user. 
     Insertion device  100  may be configured to retract second insertion needle  134  to the second stowage position, wherein second distal end  210  is within housing  102 ,  126 . Insertion device  100  may retract second insertion needle  134  such that second needle distal end  210  retracts through second septum  230 . Second septum  230  may be configured to self-seal (e.g., around second medical device  122 ) during or once second needle distal end  210  retracts through second septum  230 , in order to substantially maintain fluid isolation between the components of insertion device  100  and the user. 
     Second medical device  122  may be fabricated using a flexible or pliable substrate or carrier. In examples, second medical device  122  (e.g., an analyte sensor) is initially provided in a folded, serpentine, coiled, or accordion shape to, for example, provide a desired amount of slack to accommodate extension of second medical device  122  while second medical device  122  is electrically coupled to insertion device  100  (e.g., to electronic assembly  172  ( FIG. 4 ). Second medical device  122  may be configured such that, as second insertion needle  134  carries second medical device  122  in the second distal direction D 2 , second medical device  122  extends without losing electrical contact with the electronics assembly  172 . In some examples, second medical device  122  is configured to establish electrical coupling (e.g., with electronics assembly  172 ) after insertion mechanism unit  124 ,  212  has been triggered. For example, second medical device  122  may include electrical contact pads configured to electrically connect with a one or more connectors of insertion device  100  as or when second insertion needle  132  implants second medical device  122  within the user. The one or more connectors may be, for example, one or more pogo pins or other electrical connector in electrical communication with electronics assembly  172 . 
     A technique for implanting a first medical device and a second medical device is illustrated in  FIG. 7 . Although the technique is described mainly with reference to insertion device  100  of  FIG. 1  through  FIG. 6C , the technique may be applied to other medical systems in other examples. 
     The technique includes contacting a housing  102 ,  126  of a insertion device  100  with the skin  118  of a user. The technique includes rotating a first linkage assembly  142 ,  216  and a second linkage assembly  144 ,  220  with respect to housing  102 ,  126  using a driver  213 ,  214  ( 240 ). The technique may include rotating first assembly  142 ,  216  using a first torque T 1 . The technique may include rotating second assembly  144 ,  220  using a second torque T 2 . In examples, driver  150  includes a spring  174 . The technique may include exerting first torque T 1  on first linkage assembly  142 ,  216  using spring  174 . The technique may include exerting second torque T 2  on second linkage assembly  144 ,  220  using spring  174 . In some examples, first torque T 1  and second torque T 2  have different rotational directions with respect to a central axis C defined by housing  102 ,  126 . In some examples, first torque T 1  and second torque T 2  have the same rotational direction with respect to central axis C defined by housing  102 ,  126 . 
     In examples, first linkage assembly  142 ,  216  includes a first input link  146 ,  218  rotatably connected to housing  102 ,  126 . In examples, second linkage assembly  144 ,  220  includes a second input link  148 ,  222  rotatably connected to housing  102 ,  126 . The technique may include rotating first input link  146 ,  218  using first torque T 1  and rotating second input link  148 ,  222  using second torque T 2 . 
     The technique includes extending a first insertion needle  132  using the rotation of first linkage assembly  142 ,  216  and extending a second insertion needle  134  using the rotation of the second linkage assembly  144 ,  220  ( 242 ). The technique may include extending the first insertion needle  132  and second insertion needle  134  in a direction away from housing  102 ,  126 . In examples, the technique includes extending first insertion needle  132  in a first direction away from housing  102 ,  126  and extending second insertion needle  134  in a second direction away from housing  102 ,  126 , where the first direction is different from the second direction. 
     The technique may include implanting a first medical device  120  in the user using the extension of first needle  132 , and implanting a second medical device  122  in the user using the extension of second insertion needle  134  ( 244 ). In examples, first medical device  120  is a fluid delivery cannula configured to the delivery of a medical fluid (e.g., insulin). In examples, second medical device  122  is an analyte sensor (e.g., a glucose sensor) configured to sense a physiological characteristic of the user (e.g., a glucose level). In examples, insertion device  100  is configured to cause the implantations such that first medical device  120  and second medical device  122  are separated by a displacement D when implanted in the user. 
     The technique may include extending first insertion needle  132  using a motion of a first output link  184  defining a first kinematic chain with first input link  146 ,  218 . In examples, first output link  184  is configured to linearly translate when driver  213 ,  214  causes the rotation of first input link  146 ,  218 . First output link  184  may be configured to linearly translate within a first channel  186  defined by housing  102 ,  126 . In examples, first linkage assembly  142 ,  216  includes one or more floating links in the first kinematic chain between first input link  146 ,  218  and first output link  184 . In examples, first linkage assembly  142 ,  216  includes a first medial link  188  rotatably coupled to first input link  146 ,  234  and first output link  184 . 
     The technique may include extending second insertion needle  134  using a motion of a second output link  204  defining a second kinematic chain with second input link  148 ,  222 . In examples, second output link  204  is configured to linearly translate when driver  213 ,  214  causes the rotation of second input link  148 ,  222 . Second output link  204  may be configured to linearly translate within a second channel  208  defined by housing  102 ,  126 . In examples, second linkage assembly  144 ,  220  includes one or more floating links in the second kinematic chain between second input link  148 ,  222  and second output link  204 . In examples, second linkage assembly  144 ,  220  includes a second medial link  206  rotatably coupled to second input link  148 ,  222  and second output link  204 . 
     The technique includes retracting first insertion needle  132  toward housing  102 ,  126  to withdraw first insertion needle  132  from the user using the rotation of first linkage assembly  142 ,  216 . In examples, the technique includes causing first insertion needle  132  to release first medical device  120  when first insertion needle  132  retracts toward housing  102 ,  126 . In examples, the technique includes retracting first insertion needle  132  using first output link  184 . The technique may include reversing a direction of the linear movement of first output link  184  to cause the retraction of first insertion needle  132  toward housing  102 ,  126 . The technique may include mechanically disengaging first insertion needle  132  from first medical device  120  such that first medical device  120  remains implanted in the user when first insertion needle  132  retracts toward housing  102 ,  126 . The technique may include causing first insertion needle  132  to move independently of first medical device  120  during the retraction of first insertion needle  132  such that first medical device  120  remains implanted in the user when first insertion needle  132  retracts toward housing  102 ,  126 . 
     The technique includes retracting second insertion needle  134  toward housing  102 ,  126  to withdraw second insertion needle  134  from the user using the rotation of second linkage assembly  144 ,  220 . In examples, the technique includes causing second insertion needle  134  to release second medical device  122  when second insertion needle  134  retracts toward housing  102 ,  126 . In examples, the technique includes retracting second insertion needle  134  using second output link  204 . The technique may include reversing a direction of the linear movement of second output link  204  to cause the retraction of second insertion needle  134  toward housing  102 ,  126 . The technique may include causing second insertion needle  134  to move independently of second medical device  122  during the retraction of second insertion needle  134  such that second medical device  122  remains implanted in the user when second insertion needle  134  retracts toward housing  102 ,  126 . 
     In examples, the technique includes actuating driver  150 ,  214  using user input device  108  to cause the implantation of first medical device  120  and second medical device  122 . In examples, user input device  108  is configured to cause driver  150 ,  214  to exert first torque T 1  on first linkage assembly  142 ,  216  and exert second torque T 2  on second linkage assembly  144 ,  220 . In some examples, the technique includes depressing a button on housing  102 ,  126  to cause user input device  108  to initiate the implantation of first medical device  120  and second medical device  122 . In some examples, the technique includes transmitting an electrical communication to user interface  112  (e.g., a wired or wireless communication) to initiate the implantation of first medical device  120  and second medical device  122 . 
     Mechanism housing  126  may be configured to support at least driver  150 ,  214 , first linkage assembly  142 ,  216 , second linkage assembly  144 ,  220 , first insertion needle  132 , and second insertion needle  134 . Mechanism housing  126  may be configured to engage (e.g., mechanically engage) device housing  102  of insertion device  100 . The technique may including positioning at least first insertion needle  132  and second insertion needle  134  proximate the skin  118  of the user by engaging mechanism housing  126  and housing  102 . The technique may include separating mechanism housing  126  and device housing  102  when first medical device  120  and second medical device  122  are implanted within the user. 
     The techniques and functionalities described in this disclosure, including those attributed to processor  166 , processing circuitry, sensors, and/or various constituent components, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various aspects of the techniques may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in any suitable device. Processing circuitry, control circuitry, and sensing circuitry, as well as other processors, controllers, and sensors described herein, may be implemented at least in part as, or include, one or more executable applications, application modules, libraries, classes, methods, objects, routines, subroutines, firmware, and/or embedded code, for example. In addition, analog circuits, components and circuit elements may be employed to construct one, some or all of the control circuitry and sensors, instead of or in addition to the partially or wholly digital hardware and/or software described herein. Accordingly, analog or digital hardware may be employed, or a combination of the two. 
     In one or more examples, the techniques and functionalities described in this disclosure may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may be an article of manufacture including a non-transitory computer-readable storage medium encoded with instructions. Instructions embedded or encoded in an article of manufacture including a non-transitory computer-readable storage medium encoded, may cause one or more programmable processors, or other processors, to implement one or more of the techniques described herein, such as when instructions included or encoded in the non-transitory computer-readable storage medium are executed by the one or more processors. Example non-transitory computer-readable storage media may include RAM, ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), electronically erasable programmable ROM (EEPROM), flash memory, a hard disk, a compact disc ROM (CD-ROM), a floppy disk, a cassette, magnetic media, optical media, or any other computer readable storage devices or tangible computer readable media. 
     In some examples, a computer-readable storage medium comprises non-transitory medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM or cache). 
     The functionality described herein may be provided within dedicated hardware and/or software modules. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components. Also, the techniques could be fully implemented in one or more circuits or logic elements 
     The present disclosure includes the following examples. 
     Example 1: An insertion device for insertion of a first medical device and a second medical device into a user, the insertion device comprising: a housing; a first insertion needle configured to pierce and withdraw from skin of the user, the first insertion needle configured to releasably carry the first medical device; a second insertion needle configured to pierce and withdraw from the skin, the second insertion needle configured to releasably carry the second medical device; a first linkage assembly within the housing; a second linkage assembly within the housing; and a driver within the housing configured to cause the first linkage assembly and the second linkage assembly to rotate relative to the housing, wherein the first linkage assembly is configured to cause the first insertion needle to extend in a first direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the driver causes the first linkage assembly to rotate relative to the housing, and wherein the second linkage assembly is configured to cause the second insertion needle to extend in a second direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the driver causes the second linkage assembly to rotate relative to the housing. 
     Example 2: The insertion device of example 1, wherein one of the first medical device or the second medical device is an analyte sensor and the other of the first medical device or the second medical device is a fluid delivery cannula. 
     Example 3: The insertion device of example 1 or 2, wherein the first insertion needle is configured to release the first medical device within the user when the first insertion needle retracts toward the housing and the second insertion needle is configured to release the second medical device within the user when the second insertion needle retracts toward the housing. 
     Example 4: The insertion device of any of examples 1-3, wherein at least one of the first linkage assembly or the second linkage assembly includes an input link mechanically engaged with the driver and an output link mechanically engaged with one of the first insertion needle or the second insertion needle, wherein the input link and the output link define a kinematic chain, wherein the driver is configured to cause the input link to rotate relative to the housing, and wherein the rotation of the input link causes the output link to extend the first insertion needle in the first direction away from the housing and subsequently retract toward the housing or extend the second insertion needle in the second direction away from the housing and subsequently retract toward the housing. 
     Example 5: The insertion device of example 4, wherein the output link is a sliding member, and wherein the sliding member is configured to linearly translate when the driver causes the input link to rotate relative to the housing. 
     Example 6: The insertion device of example 4 or 5, further comprising a medial link between the input link and the output link, wherein a first end of the medial link is coupled to the input link by a first rotatable joint and a second end of the medial link is coupled to the output link by a second rotatable joint. 
     Example 7: The insertion device of any of examples 1-6, wherein: the first insertion needle is configured to at least partially insert within a lumen defined by the first medical device when the first insertion needle extends in the first direction away from the housing, and the second insertion needle is configured to at least partially surround the second medical device when the first insertion needle extends in the first direction away from the housing. 
     Example 8: The insertion device of any of examples 1-7, wherein the first linkage assembly is configured to cause the first insertion needle to pierce the skin substantially concurrently with the second linkage assembly causing the second insertion needle to pierce the skin. 
     Example 9: The insertion device of any of examples 1-8, further comprising: a release mechanism unit configured to establish at least a first configuration and a second configuration, wherein in the first configuration, the release mechanism unit is configured to constrain the driver from causing at least one of the first linkage assembly or the second linkage assembly to rotate relative to the housing, and wherein in the second configuration, the release mechanism unit is configured to allow the driver to cause at least one of the first linkage assembly or the second linkage assembly to rotate relative to the housing; and a user input device configured to cause the release mechanism unit to transition from the first configuration to the second configuration. 
     Example 10: The insertion device of any of examples 1-9, further comprising: a fluid pump; a fluid reservoir, wherein the fluid pump is configured to deliver a fluid from a fluid reservoir to the first medical device; and processing circuitry, wherein the processing circuitry is configured to receive a signal indicative of a physiological characteristic of the user from the second medical device. 
     Example 11: The insertion device of any of examples 1-10, wherein the first insertion needle is configured to extend in the first direction to pierce the skin at a first location and the second insertion needle is configured to extend in the second direction to pierce the skin at a second location displaced from the first location. 
     Example 12: The insertion device of any of examples 1-11, wherein the housing defines a central axis, and wherein the driver is configured to impart a first torque around the central axis on the first linkage assembly and a second torque around the central axis on the second linkage assembly to cause the first linkage assembly and the second linkage assembly to rotate relative to the housing. 
     Example 13: The insertion device of any of examples 1-12, wherein the driver includes a spring configured to cause the driver to impart a first torque on the first linkage assembly and a second torque on the second linkage assembly. 
     Example 14: The insertion device of any of examples 1-13, wherein the housing is a mechanism housing mechanically engaged with the driver, and further comprising a device housing, wherein: the device housing is configured to contact the skin of the user, the mechanism housing is configured to mechanically engage the device housing to position the mechanism housing proximate the skin of the user, and the mechanism housing is configured to detach from the device housing. 
     Example 15: An insertion device for insertion of a first medical device and a second medical device into a user, the insertion device comprising: a housing; a first insertion needle configured to pierce and withdraw from skin of the user at a first location, the first insertion needle configured to releasably carry the first medical device; a second insertion needle configured to pierce and withdraw from skin of the user at a second location displaced from the first location, the second insertion needle configured to releasably carry the second medical device; a first linkage assembly within the housing; a second linkage assembly within the housing; and a driver configured to cause the first linkage assembly and the second linkage assembly to rotate relative to the housing, wherein: the first linkage assembly is configured to cause the first insertion needle to extend in a first direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the first linkage rotates relative to the housing, the first insertion needle is configured to release the first medical device when the first insertion needle retracts toward the housing, the second linkage assembly is configured to cause the second insertion needle to extend in a second direction away from the housing to pierce the skin and subsequently retract toward the housing to withdraw from the skin when the second linkage rotates relative to the housing, and the second insertion needle is configured to release the second medical device when the second insertion needle retracts toward the housing. 
     Example 16: The insertion device of example 15, further comprising: a fluid pump; a fluid reservoir, wherein the fluid pump is configured to deliver a fluid from a fluid reservoir to the first medical device; and processing circuitry, wherein the processing circuitry is configured to receive a signal indicative of a physiological characteristic of the user from the second medical device. 
     Example 17: The insertion device of example 15 or 16, wherein the driver includes a spring configured to cause the driver to impart a first torque on the first linkage assembly and a second torque on the second linkage assembly. 
     Example 18: The insertion device of any of examples 15-17, wherein at least one of the first linkage assembly or the second linkage assembly include an input link mechanically engaged with the driver and an output link mechanically engaged with one of the first insertion needle or the second insertion needle, wherein the input link and the output link define a kinematic chain, wherein the driver is configured to cause the input link to rotate relative to the housing, and wherein the rotation of the input link causes the output link to extend the first insertion needle in the first direction away from the housing and subsequently retract toward the housing or extend the second insertion needle in the second direction away from the housing and subsequently retract toward the housing. 
     Example 19: A method comprising: extending a first insertion needle of the insertion device in a first direction away from a housing to pierce skin using rotation of a first linkage assembly with respect to the housing, wherein the first insertion needle is configured to releasably carry a first medical device; extending a second insertion needle of the insertion device in a second direction away from the housing to pierce the skin using rotation of a second linkage assembly with respect to the housing, wherein the second insertion needle is configured to releasably carry a second medical device; retracting the first insertion needle toward the housing to withdraw from the skin using the rotation of the first linkage assembly; and retracting the second insertion needle toward the housing to withdraw from the skin using the rotation of the second linkage assembly. 
     Example 20: The method of example 20, further comprising: positioning the first medical device in the user by releasing the first medical device from the first insertion needle when the first insertion needle retracts toward the housing; and positioning the second medical device in the user by releasing the second medical device from the second insertion needle when the second insertion needle retracts toward the housing. 
     Various examples have been described. These are other examples are within the scope of the disclosure.