Patent Publication Number: US-2022233775-A1

Title: Wearable auto-injector devices and methods

Description:
FIELD OF THE INVENTION 
     This invention relates generally to injection devices for use in delivering medication to a user; more specifically to wearable auto-injectors and methods of using wearable auto-injectors. 
     BACKGROUND OF THE INVENTION 
     Auto-injectors are a tool used by many to deliver therapeutic medication to users suffering from critical medical events, such as delivery of epinephrine to arrest severe allergic reactions or anaphylaxis, or thrombolytic medications in case of heart attack. Auto-injectors are designed to support “auto-” or “self-” injection by making it easier for a user to administer the medication than using a traditional syringe. 
     Related to the field of allergy, approximately  1  in  5  people suffer from allergies in the U.S. today, and many of those affected struggle with severe allergies, for which an untreated allergic response can lead to anaphylaxis or even a swift death. Sufferers of moderate to severe allergies are instructed to carry a dosage of epinephrine on their person at all times. The most common device for epinephrine distribution is Mylan&#39;s auto-injector, the EpiPen®, of which 50 million units have been distributed over the past 25 years. 1  The EpiPen® uses a hand-grip design, in which for use, the user&#39;s hand fully surrounds the device, presses the device against the target tissue, and injects the epinephrine. Kaleo&#39;s Auvi-Q® employs a similar design.  1  https://www.epipen.com/personal-stories 
     While auto-injectors have been lifesaving tools for countless cases worldwide, current designs have several drawbacks. For one, the allergic patient must carry the device with them at all times, which is often impractical, due to the size and shape of the device. A 2018 study of epinephrine auto-injector (EAI) owners found that 45% of survey participants did not employ an epinephrine auto-injector at the time of severe reaction because an EAI was not available. Only 44% of participants claimed to carry an EAI on their person “all the time.” Indeed, 34% of children and adolescents reported even carrying an EAI on their person habitually. 2    2  Warren, C. M., Zaslaysky, J. M., Kan, K., Spergel, J. M., &amp; Gupta, R. S. (2018). Epinephrine auto-injector carriage and use practices among US children, adolescents, and adults. Annals of Allergy, Asthma &amp; Immunology. doi:10.1016/j.anai.2018.06.010. 
     Almost all prior art regarding traditional auto-injector designs describe mechanisms that would be highly non-obvious to decompose and redesign such that it is included in a wearable device. Most delivery systems, such as Mylan&#39;s EpiPen®, are highly elongated structures, in which the needle, needle safety, medication reservoir, plunger, dispensing mechanism, lockout mechanisms, and activation mechanisms are collinear along the longitudinal axis of the device and thus cause highly elongated device designs. The length of the device has been included as part of the delivery workflow, as the patient is expected to wrap their hand around the main body of the device (i.e. grasping the device with his/her hand in a ‘fist’ shape) and pushing the device into the target tissue. This has become the understood standard of care for auto-injectors. 
     While the concept of improving access to auto-injectors at time of critical medical event is underexplored, some have proposed solutions in this area. Students at Kent State University developed a solution in 2017 that integrated the delivery system into a smartphone case. 3  Others have proposed generic “wearable” solutions, but are silent on how these non-specific solutions would be worn on the body, and critically, make no mention of designing similarity to, mimicry of, attachability to, or inclusion of functions of accessories that are already worn or carried by patients, such as the timekeeping characteristics of a wristwatch. Patients are hesitant to add additional burden to their routine; this is evidenced by the poor compliance in keeping EAIs on one&#39;s person.  3  https://www.allergicliving.com/2017/08/22/student-inventors-create-smartphone-case-that-administers-epinephrine/ 
     In other proposals, the device is intended to deliver its medication in its wearable configuration, i.e. while being worn. This imposes challenges on the device design such as limiting the location of the wearable to specific locations on the body that do not support seamless integration into a user&#39;s lifestyle, and add concern for users that they may accidentally activate the device and inject themselves at an undesired time. As examples, US2017/0182242A1 and WO2016064266A2 make it clear that the delivery of the therapeutic is only performed in the wearable state. Another example is U.S. Pat. No. 9,180,244B2, which describes a wearable device intended to deliver medication (1) in a wearable state and (2) “by subcutaneous injection at slow, controlled injection rates”, the latter of which is ill suited for the delivery emergency therapeutics, such as epinephrine. 
     Other proposals have described concepts that are wearable on one&#39;s person and undergo a structural state change in the main housing in order to be able to deliver the medication. US2019/0209780A1 describes foldable components and hinges that enable significant elongation of the delivery assembly, in order to more closely mimic typical autoinjector designs (e.g. EpiPen®), which compromise the ability to blend into existing accessories and complicates the workflow for patient delivery. 
     SUMMARY OF THE INVENTION 
     This invention is directed to wearable auto-injector devices, systems and methods. A device for injecting a medication constructed in accordance with the invention includes a housing, an attachment component enabling the housing to be worn by a user, and a medication delivery system disposed within the housing. The delivery system includes a needle and a medication reservoir in fluid communication with the needle. An advancement system, disposed within the housing, is operative to advance the needle through a user&#39;s skin and cause the medication to flow from the reservoir and through the needle for injection of the medication. 
     The device manually transitions from a worn state, wherein the attachment component is fully secured to the housing, to an unworn state, wherein at least a portion of the attachment component is detached from the housing to facilitate administration of the medication. The medication may epinephrine, administered to treat allergic reactions. However, those of skill in the relevant art will appreciate that the devices, systems and methods disclosed herein are applicable to other medications used to treat other conditions. Other medications that may be delivered include, but are not limited to, antiarrhythmic medication (such as during a cardiac emergency, e.g. a heart attack), thrombolytic medication (such as during a vascular emergency, e.g. a stroke), drug overdose reversal medication (such as the use of naloxone or nalmefene during an opiate or other addictive-substance overdose), or during a toxic exposure event (such as during a chemical or biologic exposure event, e.g. nerve agent, organophostate, anthrax, or sarin). 
     In the preferred embodiments of the invention, the medication cannot be administered when the device is in the worn state. To accomplish this, the device may further include a mechanism disposed within the housing that prevents the medication from being administered in the worn state. Alternatively, or in conjunction with such a mechanism, it may be impossible or overtly impractical to physical orient or align the device to achieve injection in the worn state. 
     The attachment component may be a strap adapted to encircle a user&#39;s wrist or other body part. Other configurations include wearing the device around: one&#39;s waist, in which the device mimics the behavior and appearance of a belt, one&#39;s neck, in which the device mimics the behavior and appearance of a necklace, or ones ankle, in which the device mimics the behavior and appearance of an ankle bracelet. Regardless, the attachment component may be unsecured by separating at least a portion of the attachment component from the housing. 
     The advancement system may include one or more compressed springs that are released to advance the needle or cause the medication to flow. Alternatively, the advancement system may use a compressed gas to advance the needle or cause the medication to flow. As yet a further alternative, the advancement system may include a battery-operated motor or other electromechanical unit to advance the needle or cause the medication to flow. The advancement system uses a multi-step activation sequence, or may be triggered by urging the device against tissue or by way of manual manipulation of the device. 
     The device may further include at least one mechanism for preventing exposure of the needle until use. Such a mechanism, which may comprise a moveable shield, effectively prevents needle exposure in the worn state. The device may further include apparatus for limiting premature activation of the advancement system. Such apparatus may include a manually operated mechanism, or may operate in conjunction with a sensor for detecting a specific condition. The device may further comprise apparatus that places the device into a non-injectable state after activation of the advancement system. The reservoir may be refillable, with or without removing the reservoir from the housing, and one or more internal components may be removable and/or replaceable. 
     At least one visual, audible or tactile indicator may be included to inform a user as to an operational status of the device. The housing may further include a clock or other timekeeping element; physiological monitor(s); GPS geolocating, and/or sensor(s) operative to detect a biomarker. Apparatus for wired or wireless communication with an external or remote device may also be integrated into the device. The device may be configured to record sensor or operational data, events, and/or communicate with a smartphone and/or directly with emergency personnel for various reasons. The device may further comprising one or more visual, audible or tactile alerts to indicate if the medication will expire or become compromised due to environmental factors. 
     The device of claim  1 , wherein the attachment component is secured to an existing wrist, ankle or neck worn wearable accessory, and instructions for use of the device are located on the attachment component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a simplified block diagram used to illustrate fundamental components of the invention; 
         FIG. 1B  shows how components of  FIG. 1A  may be duplicated; 
         FIG. 1C  illustrates on form of component sharing within a common housing; 
         FIG. 1D  shows the way in which multiple reservoirs may share a common needle, advancement system and lock-out/retraction mechanism; 
         FIG. 1E  illustrates the use of a single reservoir with multiple chambers that may or may not be refillable; 
         FIG. 1F  is an isometric view of an embodiment of device  10  comprised of a housing and an attachment component; 
         FIG. 2  is a cross-sectional, top-down view of a preferred embodiment of the invention; 
         FIG. 3  is an exploded view with a top cover being shown as a separate component, which can be separated from the housing during normal use or limited to separation for assembly purposes; 
         FIG. 4  is a further isometric view wherein the top portion of the housing is hidden, thus exposing the internal components; 
         FIG. 5  is a diagram of optional surface features of the housing; 
         FIG. 6  shows a mechanism to put a device into a safe state after activation; 
         FIG. 7  shows how an electromechanical device may control the advancement of a plunger; 
         FIG. 8  shows how the movement of a shield may be governed by a rotary user input; 
         FIG. 9  is an isometric view of lateral and posterior device aspects; 
         FIG. 10  is an isometric view of a wearable auto-injector device, wherein instructions for use are located on an attachment component; 
         FIG. 11  is an isometric view of a wearable auto-injector device in conjunction with a conventional wristwatch; 
         FIG. 12  is an exploded view of a wearable device; 
         FIG. 13  illustrates a smartphone communicating with emergency personnel in conjunction with hardware and/or software integrated into any of the embodiments disclosed herein; 
         FIG. 14  is a workflow (or flowchart) applicable to embodiments of the invention wherein pressing a shield against target tissue causes exposure of the needle and enablement of an activation mechanism; 
         FIG. 15  is a workflow applicable to embodiments wherein squeezing the lateral aspect(s) of the housing allows the shield to translate relative to the needle; 
         FIG. 16  shows a workflow associated with the way in which the device may trigger a signal to the processor, which in turn interprets the signal and triggers communication with emergency personnel; 
         FIG. 17  illustrates a method of transitioning the device out of the worn configuration, locating the device at the target tissue, defeating one or more safety mechanisms, activating the device, and removing the device from the target tissue. 
         FIG. 18  is the workflow associated with detecting a temperature change in ambient environment; 
         FIG. 19  is a workflow wherein changes in the state of the device cause an indication to transition from invisible to a user to visible to a user; and 
         FIG. 20  is a workflow that shows reaching a predetermined end date. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     By way of introduction,  FIG. 1A  is a simplified block diagram that may be used to illustrate preferred embodiments of the invention. Device  10  includes an external housing  12  which contains a delivery system  14  that is comprised of a needle  16  for delivering a medication, a reservoir  18  connected to the needle which contains the medication, and an advancement system  20  for pushing the medication from the reservoir into the needle and into a patient. Multiple embodiments for the advancement system are described below. The device may optionally include a shield mechanism  22  for keeping the needle hidden when the device is not being used to deliver medication, but which allows the needle to deliver medication when desired, and a lock-out or retraction mechanism  24  which prevents re-deployment of the needle after the medication has been delivered. A fixed or removable attachment component  26  connects to the external housing, and is used to secure the wearable device to the user. 
     A user transitions the device from a ‘worn’ state, wherein the device is physically coupled to the user, to an ‘unworn’ state, wherein device is detached. In the ‘worn’ state, the device will have a limited ability to deliver the therapeutic medication. This limitation may be an explicit preventative measure built into the device, such as a lockout mechanism, or an implicit limitation, such as the difficulty in aligning and impaling the skin when the device is in a worn configuration. 
     In a preferred embodiment, the device  10  is worn on the wrist, similar to a conventional wristwatch. In this embodiment, the housing  12  may resemble the main body of a watch, with a strap similar to a watch strap. The device may also function as a watch or other body-worn device, powered by mechanical and/or electrical components and/or readouts. Such multi-functional characteristics of the device further increase the likelihood that users will keep it on their person at all times. As such, the device may include one or more of: the following features: timekeeping, heart-rate monitor, blood-pressure monitoring, pedometer, GPS, pulsometer, surface electromyography (EMG), other surface-based biomarker detection, or other features available on marketed smartwatches. In one embodiment, the device contains Bluetooth, RFID, or other near-field communication technology. In a sub-embodiment, this technology is used to communicate with a smartphone, and can be used to record and visualize the data being tracked by the sensors disclosed herein, including activation and/or delivery-of-medication events. 
     The advancement system  20  may be driven by springs that are released from a compressed or extended state. Alternatively, the advancement system  20  may be comprised of a mechanism to increase pressure in the reservoir  18 , thus causing advancement of the medication into the patient. For example, a plunger may be advanced into the reservoir, thus pushing the medication into the patient. The advancement mechanism  20  may release a compressed fluid into a cavity immediately proximal to a plunger, thereby advancing the plunger toward the patient. As a further alternative, the advancement system  20  may be electro-mechanically powered, such as by a motor and battery system enclosed in the housing  12 . In these and other embodiments, one of multiple mechanisms can be employed to “prime” or allow subsequent activation of the advancement system. This may be carried out by pressing the device against a target tissue, in which case a reaction force on the device causes activation. Activation may also be caused by input by a user&#39;s hand, such as pressing on a button or twisting a dial. 
     One or more safety mechanisms can be employed to prevent premature activation of the advancement system. As one example, activation may be mechanically prevented until the device is pressed against the target tissue. In another embodiment, activation may be mechanically prevented until an attachment component (e.g. strap) is separated from the housing by the user. In embodiments wherein the activation is performed by a motor, electrical signals may be used as a safety mechanism. In certain embodiments, the safety mechanism can be defeated by digital detection of the target tissue. That is, the device may prevent advancement of the needle or activation of the delivery system until the tissue is detected by one or more of: temperature, proximity, capacitance, optical and/or resistance sensors. For example, capacitive sensors on the surface of the device could signal contact with tissue and thereby allow for activation of the motor by the activation mechanisms described above. The device may use any type of sensor to identify presence or proximity of the tissue; the listed sensor types are intended to be illustrative and non-limiting. 
     Physical alignment, including rotational motion may be used for ensuring that the medication cannot be delivered prior to the intended time of delivery. For example, rotation of a user input mechanism on the housing could cause rotation of the reservoir so as to align the longitudinal axis of the needle and reservoir, and thereby allow communication between the two. Alternatively, rotation of a user input mechanism on the housing could cause rotation of a valve that governs communication between the reservoir and the needle and/or the reservoir and the activation mechanism. 
     If a shield mechanism  12  is provided, retraction thereof to keep the needle hidden until the user is ready to deliver the medication can be triggered by one or more of: the safety mechanisms described above or alternative mechanisms. Indeed, the device  10  may contain multiple safety mechanisms that must be defeated in order to advance the needle, deliver the medication, and/or retract the needle. These mechanisms may be dependent on one another. For example, the user may need to press the device against the target tissue before the user is able to squeeze a mechanical button, which in turn must be done before the user is able to press a button to trigger the activation mechanism. 
     The device  10  may include a mechanism to put the device into a safe state after the medication has been delivered. This may be caused by moving the needle or the needle and reservoir assembly away from the target tissue after completion of delivery. In mechanical embodiments, this may be effected by a compressed or extended spring that is held in place until the plunger can complete its full stroke (which corresponds with complete delivery of the medication). In embodiments where the delivery is activated by a motor, the retraction of the needle, needle and reservoir assembly, or needle and reservoir and plunger assembly may be effected by the motor. 
     Device re-usability is possible in accordance with the invention. The device  10  may be designed to be refilled by adding medication to the reservoir  18  after depletion. This may be accomplished using a separate port, conduit or syringe system to access the reservoir and inject the new medication. As an alternative, the device may be designed to support exchange of one or more parts of the delivery system, such as the needle, reservoir, and/or plunger. If the advancement mechanism  10  is powered by the release of compressed fluid, re-use could include replacement of the compressed fluid cartridge. 
     Ensuring proper use of the device is essential in life-threatening emergencies such as those that are targeted by this device. Providing clear instructions for use is critical in order to support reliable and repeatable use. Instructions for use may be located on the housing  12  or attachment component, such as a wrist strap. Clear communication to the user that the device is in a primed, activated, or completed state is important for correct use as well. An indicator on the device may change in response to the transition between states. For example, an indicator may change when the device transitions from a typical ‘worn’ state, to a ‘ready to deliver’ state, to a ‘delivering medication’ state, and/or to a ‘delivery complete’ state. The indicator may be visual, audible, or tactile. In embodiments in which the indicator is visual, this could include text, color change, or a mechanical change in the exterior housing. In embodiments where the indicator is audible, this could be caused by a mechanical trigger, such as an audible ‘click’, or electronic, such as with a battery and speaker system. In embodiments where the indicator is tactile, this could be caused by a mechanical trigger, such as a tactile ‘click’, or electronic, such as with a battery and haptic vibration system. 
     The device  10  may further be configured to automatically contact emergency personnel when it is activated via an integrated communication device. The device may accomplish this through wireless or wired connections, as via connection with a smartphone or other device. 
     Medication to be stored in the reservoir  18  typically has a limited duration of efficacy; after the expiration date, the medication is no longer certified for use. All medical devices of this type are required to have an expiration date listed on the packaging. The device  10  may therefore include one or more additional indicators to communicate that the contained medication is past its expiration date. The indicator(s) may be of any of the types of indicators listed throughout this application. 
     Medication to be stored in the reservoir  18 , such as epinephrine, is subject to accelerated degradation associated with environmental factors, such as temperature. This is critical information for users, as the concentration of the needed medication can decline substantially, such as when an epinephrine auto-injector is stored in a car during summer months. The device may therefore include an indicator to communicate that environmental factors may have compromised the therapeutic. A change in this indicator may be caused by the device being exposed to temperatures at or above (or at or below) a specific temperature for a duration of time. As a point of reference, some marketed autoinjectors for epinephrine have a maximum recommended storage temperature of 25° C. An example of this feature in this device could be a material that undergoes a color change when it is heated above 25° C. for a prolonged period of time. The indicator(s) may be of any of the types of indicators listed throughout this application. 
     All of the device characteristics described herein may also be applied to a device that attaches to an existing accessory, rather than being a standalone device. For example, the device  10  may be an attachment to a conventional wristwatch, in which the external housing and delivery system are affixed to the wristwatch, and utilize the existing attachment mechanism (e.g. wrist strap) to remain accessibly located on the patient. In this embodiment, the detachment of the housing and delivery system from the conventional wristwatch could serve similar safety functions to the detachment from the strap in the preferred embodiment (in which all aspects are integrated in a single device). Note that “wristwatch” should be taken to include “smart” watches, and “existing accessory” may be taken to include other body-worn objects such as necklaces and bands or straps that at least partially encircle extremities or other body parts. 
     Note further that internal components maybe duplicated in accordance with different embodiments of the invention.  FIGS. 1B through 1E  show alternate internal configurations of the invention, in which the device is configured to enable multiple deliveries of medication to a patient.  FIG. 1B  is a simplified block diagram to describe an alternate internal configuration of the invention, which contains multiple delivery systems. The device  10  is again shown with housing  12  and attachment component  26 , and has a first delivery system  14  and a second delivery system  28 . The first delivery system  14  is identical to as shown in  FIG. 1A . The second delivery system  28  mirrors the first delivery system  14 , comprising a second needle  30  for delivery a medication, a second reservoir  32  connected to the needle which contains the medication, a second advancement system  34  for pushing the medication from the reservoir into the needle and into a patient, and a second lockout or retraction mechanism  38 . In  FIG. 1B , the second delivery system  28  is shown with a second shield mechanism  36 , though shield mechanism  22  may keep both needles hidden, as opposed to having second shield  36 . 
       FIG. 1C  is a simplified block diagram of another alternate internal configuration, which contains a single delivery system  40 , comprising the components from the delivery system  14  as shown in  FIG. 1A  (needle  16 , reservoir  18 , advancement system  20 , and lockout or retraction mechanism  24 ), a second reservoir  32 , which is connected to needle  16 , and a second advancement system  34 . In this embodiment, the device  10  uses a single needle  16 , shield  22 , and lockout or retraction mechanism  24 , and needle  16  is in communication with one or more reservoirs. 
     In configurations with multiple advancement systems, such as those shown in  FIG. 1B and 1C , the second advancement system  34  may be configured to prevent advancement until the first advancement system  20  has been used.  FIG. 1D  is a simplified block diagram of another alternate internal configuration, which contains a single delivery system  42 , comprising the components from the original delivery system  14  (needle  16 , reservoir  18 , advancement system  20 , and lockout or retraction mechanism  24 ), a second reservoir  32 , which is connected to needle  16 , and is connected to advancement system  20 . In this embodiment, advancement system  20  is configured advance medication from the first reservoir  18  upon first activation, and to advance medication from the second reservoir  32  upon second activation. It is apparent by one skilled in the art that this single-advancement system configuration may also be used with a first and second needle, as is shown in  FIG. 1B . 
       FIG. 1E  is a simplified block diagram of another alternate internal configuration, which contains the delivery system  14 , shows a configuration comprising the components from the delivery system  14  as shown in  FIG. 1A  (needle  16 , reservoir  18 , advancement system  20 , and lockout or retraction mechanism  24 ), but where the delivery system is configured to deliver a portion of the medication contained in the reservoir as part of a first activation of advancement system  20 , and is configured to deliver another portion of the medication contained in the reservoir as part of a second activation of advancement system  20 . 
       FIG. 2  provides a cross-sectional top-down view of a preferred embodiment of the invention, depicted generally at  100 . For the purposes of this figure, the words upward, downward, and lateral will be used in reference to the orientation of the image, but it should be noted that the device does not necessarily need to be used in an orientation corresponding to upward and downward relative to gravity. The outer housing  101  is shown supporting a reservoir  104  and needle  102 . A shield  103  covers the needle. A plunger  105  is shown partially translated within the reservoir. The attachment component  136  and its rigid member  137  which connects to the housing are shown. 
     An activation button  129  is shown above plunger  105 , with two elongate members  130  on either side of the reservoir. A spring  134  is shown connected to the plunger  105 . This spring  134  constraints the distance between the activation button and the plunger  105 . In the embodiment shown, the elongate members  130  are biased inward, and are only forced to the outside of the reservoir due to the mechanical interference between the member  130  and the reservoir  104 . Without the presence of the reservoir, the members  130  would move inward toward the vertical longitudinal axis of the device. 
     When the device  100  is to be used, the user removes the strap  136  thus exposing the bottom aspect of the shield  103 . The bottom aspect of shield  103  is pressed against the target tissue when the device is to be used. Shield  103  translates upward along slots  111 , thereby exposing the needle  102 . Springs  135  resist this upward motion and ensure that the exposure of the needle is intentional. Shield  103  has two elongate members  133  as well. As the shield translates upward, the shield&#39;s elongate members  133  contact the activation button&#39;s elongate members  130 , forcing them upward. Once the members  130  are no longer forced outward by the lateral aspects of the reservoir  104 , they move inward and rest above the top of the plunger  105 . The user then presses down on the activation button  129 , causing a downward force on the plunger  105 , thus propelling the medication in reservoir  104  into the needle  102  and into the user. Other features shown in  FIG. 2  include a step-down component  131  on the activation button that prevents the button from moving inside the outside walls of the housing  101 , and a physical stopper  132  that prevents the button from sliding completely outside the housing as it is forced upward. 
       FIG. 3  shows an exploded view of device  100 . In this embodiment, the top cover  141  is shown as a separate component, which can be separated from the housing  101  during normal use or limited to separation for assembly only. The shield  103  is also shown as a separable component, with a top element  140  and a bottom element  103 . Alignment features are shown on  140  to ensure proper alignment between  140  and  103 , and should be assumed to be optionally present on any other components of the device in which external surfaces are aligned. Alignment features  142  are also shown between the rigid member of the strap  137  and the housing  101 . These features  142  may optionally prevent movement of the shield  103  or activation button  129  until they are separated from the housing  101 . Features such as alignment structure(s)  142  can be applied to any advancement and activation mechanism, including embodiments that are motorized or driven by compressed fluid. 
       FIG. 4  shows another isometric view of the device  100 . In this Figure, the top housing is hidden, thus exposing the internal components. In this figure, the top cover of the shield  140  is shown attached to the bottom of the shield  103 . 
       FIG. 5  is a diagram of optional surface features of the housing, including device  100 . More or fewer of these surface features may be present on any embodiment. A timekeeping element  119  is shown as the main indicator on the surface of the device. An LED  120  is shown, with wires  121  that can connect to elements internal to the device, such as a motor, computing processor, or battery. A visual indicator assembly  122  is shown, with a radial element  123  with distinct sections, and a window  124 , arranged such that the user may only see one section of the radial element  123  at a time. A set of gears  125  that optionally connect to the internal mechanisms of the device are shown. The radial element  123  may be moved by physical motion of internal components, including translation of the shield or activation button, pressure change such as the release of a compressed fluid, or by a motor and battery system. Rather than radial element  123  the window  124  may be moveable, due to one or more of the same physical motion changes. A digital display  126  is shown, and may be connected to a computing processor and battery. An unpowered visual indicator is shown in  127 , and can be used to communicate changes in environmental conditions. For example, the visual indicator  127  may be a thermochromic ink that changes color in response to exceeding a prespecified temperature for a certain amount of time, thus communicating that the medication may be compromised. In another embodiment, visual indicator  127  may change color after exposure to oxygen for a certain amount of time, thus communicating that the medication has expired. 
       FIG. 6  shows an embodiment of device  100  wherein the advancement of the plunger  105  is driven by the release of a compressed gas. A compressed fluid storage chamber  107  is shown, with a communication  108  between the chamber  107  and the plunger  105 . This figure also shows mechanical elements for squeezing  106  on the lateral aspects of the housing  101 . A mechanism  109  is shown wherein the user squeezes the lateral touchpoints  106  inward, thus moving a primary rail  109  inward, thereby aligning an opening in the rail  110  to align with the slot  111  on which the shield translates. Therefore, in this embodiment, a user needs to squeeze the lateral aspects of the device in order to expose the needle  102 . The safety mechanism afforded by  109  and  110  is only shown on one side of the device but can optionally be employed on both sides of the device. The safety mechanism may also be used to limit motion of the activation mechanism, such as the plunger  105  or an activation button as shown in other figures. 
       FIG. 6  also shows a mechanism to put the device  100  into a safe state after activation. A second chamber with a compressed fluid  112  is connected to the slot along with the shield  103  translates. Following activation of the device,  112  releases fluid into slot  111  via the physical communication  113 , thereby forcing the shield to re-cover the needle  102  and prevent reactivation of the device.  FIG. 6  also shows an area  143  that can house one or more elements, including a battery, speaker system, wireless communication system, or one or more secondary functional elements, such as a heart-rate monitor, pedometer, pulsometer, electromyography (EMG) sensor, Global Positioning System (GPS) sensor, and sensor to detect biomarkers on the skin. Depending on the content of area  143 , these elements may be connected to a computer processor within area  143  or a separate area of the device. In some embodiments, these elements may be triggered by mechanical motion of other aspects of the device, in which that motion allows for completion of a circuit thus triggering a function of one or more of the elements. For example, motion of the plunger  105  may trigger an electrical contact between two wires, thus completing a circuit between a battery and speaker system, so as to trigger an audible alert when the plunger  105  has moved. 
       FIG. 7  shows how the advancement of the plunger  105  may be controlled by an electromechanical device such as a linear actuator such as a solenoid or rotational drive such as a motor system, which may include stepper motors. In this figure, a motor  116  is shown connected to a main shaft  117 , which is connected to a main body  118  connected to the plunger  105 . The main shaft  117  has a gearing element on its distal tip, and the main body  118  has recipient teeth, such that upon spinning motion of the shaft  117  by the motor  116 , the main body  118  moves downward, propelling the medication out of the reservoir  104 , into the needle  102  and into the user. The area shown for the motor  116  may also include a battery and computer processing system, such as a microcontroller. This figure also shows a sensor  114  on the bottom aspect of the shield  103 , as well as a connection between the sensor and the motor assembly  115 . One or more sensors may be in the device; one is shown in this figure for illustrative purposes. Sensors may include, but are not limited to, temperature, proximity, capacitance, or resistance sensors. The area shown for the sensor  114  may also include a computer processor. Once the sensor  114  has detected certain conditions, the device may then trigger activation of the motor, thus triggering advancement of the medication. 
       FIG. 8  shows how the movement of the shield  103  may be governed by a rotary user input. This embodiment maintains a removable attachment component  136 , comprised of rigid member  137  and flexible member  138 . A rotary input dial  146  is shown on the lateral aspect of the housing. Rotation of this dial causes upward motion of a geared or toothed member  145  (located on shield  103 ), within slot  111 , along a matching rack interface  144 . The rigid member of the attachment component  137  can optionally be used to prevent rotation of the dial until it [rigid member  137 ] has been removed from the device. The rack and gear embodiment shown should be considered one of several possible rotary mechanisms, including screw mechanisms. The dial on the lateral face should be considered one of several possible locations, including on the top face of the device. 
       FIG. 9  is an isometric view of the lateral and posterior aspects of device  100 . A sensor array  147  is shown on the posterior aspect of the device, such that this sensor array would be in contact with the user&#39;s skin in the ‘worn’ configuration. This sensor array may be attached to housing  101  or attachment component (i.e., strap)  136 . 
       FIG. 10  is an isometric view of a wearable autoinjector device  100 , wherein instructions for use  148  are located on the attachment component. In this figure, they are shown on flexible member  138 . 
       FIG. 11  is an isometric view of a wearable autoinjector device  201  in conjunction with a conventional wristwatch  203 . The wearable device is shown connected at a junction between the main body of the wristwatch  204  and its strap  205  at a cylindrical interface  206 , via links  202  that extend from the main body of device  201 . It is to be noted that in this configuration, the device is not itself connected to the user via any attachment component; rather the attachment component (in this figure, shown by  202 ) is used to connect the device to a conventionally worn accessory, such as wristwatch  203 . 
       FIG. 12  shows an exploded view of the wearable device  201 . In this figure,  201  is shown as being comprised of a lower housing  207 , attachment component  202 , an upper housing  208 , a needle  209 , reservoir  210 , and plunger assembly  211 . Other internal components of the device as described for embodiments in which the device attaches to the user, rather than a worn accessory, (such as shield, slot, activation button, etc.) should be assumed to apply to device  201 . 
       FIG. 13  shows a smartphone  300  communicating with emergency personnel in conjunction with hardware and/or software integrated into any of the embodiments disclosed herein. For example, device  100  or  201  can automatically trigger a response from smartphone  300  upon relevant transition states. It can communicate with smartphone  300  via a communication component, such as that shown by area  143  in  FIG. 6 . 
       FIG. 14  shows a workflow applicable to embodiments wherein pressing the shield against target tissue causes exposure of the needle and enablement of the activation mechanism. 
       FIG. 15  shows a workflow applicable to embodiments wherein squeezing the lateral aspect of the housing allows the shield to translate relative to the needle. 
       FIG. 16  shows a workflow associated with the way in which the device may trigger a signal to the processor, which in turn interprets the signal and triggers communication with emergency personnel. 
       FIG. 17  illustrates a method of transitioning the device out of the worn configuration, locating the device at the target tissue, defeating one or more safety mechanisms, activating the device, and removing the device from the target tissue. 
       FIG. 18  shows the workflow associated with detecting a temperature change in the environment, wherein the temperature change compromises the integrity of the medication, in which the temperature change causes a state change in a material in or on the device, wherein that state change causes a visible color change, thus causing the user to dispose of the device. 
       FIG. 19  shows a workflow wherein changes in the state of the device cause an indication to transition from invisible to a user to visible to a user. 
       FIG. 20  shows a workflow of the device reaching a predetermined end date, at which time a timekeeping element triggers a state change, which is identified by the user, and thus causing the user to dispose of the device.