ROTARY SOLENOID MICRO ACTUATOR WITH DRIVE COIL

Disclosed are techniques, devices and systems that provide a rotary solenoid micro actuator that has a rotary solenoid core with dual magnetic drive coils and magnetic field focusing elements. One or more examples may also include a spring return and other examples may include two sets of drive coils to push and pull on at each magnetic gap. The magnetic field focusing elements are operable to increase the magnetic field. The rotary solenoid micro actuator is configured to cause a liquid drug to be expelled from a drug delivery device.

BACKGROUND

For wearable medical devices, physical size is a major driver of the overall impact of therapy on the patients using them. One of the largest elements in a complex medical device (such as an insulin pump) is the pumping actuator which provides the force needed to deliver drug therapy to the patient. To maintain a small device footprint, a design objective is to optimize actuator efficiency and performance while still delivering the necessary output.

As electromechanical actuators shrink in size, the relative proportion of active elements (magnets, coils, etc.) to packaging elements decreases leading to losses in both performance and efficiency.

A cause of performance and efficiency reduction can be attributed to the reduction of total magnetic flux due to size reductions in both the permanent magnets and magnetic coils employed. Since volume is a third order relationship (i.e., L×W×H), reducing each axis by half leads to a final volume equal to ⅛ of the starting volume. However, with less magnet volume, there is less magnetic flux to induce a force between permanent magnet and coil.

In many cases the required force/torque density required of pumps is fairly high. Commercially available DC micro-motors based on existing technology have little available torque and require mechanical advantage techniques (i.e., gear reduction) which adds size, cost, and complexity to actuator solutions. Rotary motors are also designed for continual rotation at fairly high speeds, whereas pumping mechanisms tend to be reciprocal in nature meaning additional conversion is required.

While some solenoids address the issue of reciprocal motion by having a bi-polar operation (on/off, push/pull, etc.) they tend to suffer from other challenges. To produce a large output force, large magnetic fields are required. Solenoids can use the attractive force of magnetic coils on a ferromagnetic plunger, but this is limited to the field strength of the coil (current) and the magnetic permeability of the plunger. In addition, in some implementation in which a permanent magnet is added to the plunger or a ferromagnetic plunger is used, the plunger's magnetic field can interact with external electromagnetic fields which may lead to inadvertent insulin delivery if/when the drug delivery device is exposed to an external magnetic field. This additional magnet may also increase the size of the drug delivery device by increasing a key dimension, for example, the outside diameter of the reservoir including the new coil.

Unfortunately, the typical arrangement of a linear solenoid puts the plunger within the center of a coil of wire producing a magnetic field within the coil. This arrangement suffers from an increase in coil diameter to accommodate larger permanent magnet volumes. In this way, the two elements are not complimentary and lead to additional inefficiencies.

When these challenges are viewed together, it is possible to arrive at a clear problem statement for the optimization of force output, actuator size (volume), and electrical output.

It would be helpful to have a small, low-cost, micro-actuator with reciprocal motion, and maximal output force for a given electrical input.

It would also be beneficial if there were a device or algorithm that took advantage of provided data to customize insulin pump settings or algorithm parameters for each individual.

BRIEF SUMMARY

According to an example of the disclosed subject matter, a micro actuator for a wearable drug delivery device may include a force transfer assembly, a drive coil, and a main structure. The force transfer assembly may include a first focusing element and a second focusing element, wherein the second focusing element includes a yoke. The drive coil may be operable to attract or repel the first focusing element and the second focusing element. The main structure may be configured to hold the force transfer assembly and the drive coil in alignment with one another.

In another example of a micro actuator, a micro actuator for a wearable drug delivery device is provided that includes a force transfer assembly, a first pair of drive coils, and a second pair of drive coils. The force transfer assembly includes a magnet between a first focusing element and a second focusing element. The second focusing element includes a yoke. Each drive coil of the first pair of drive coils is energized to a magnetic polarity that is opposite the other drive coil in order to attract or repel the first focusing element and the second focusing element in a first direction. Each drive coil of the second pair of drive coils is energized to a magnetic polarity that is opposite the other drive coil in order to attract or repel the first focusing element and the second focusing in a second direction opposite the first direction.

DETAILED DESCRIPTION

The following discussion provides a detailed discussion of a micro actuator. The micro actuator examples described herein may be rotary solenoid micro actuators that include one or more drive coils.

In an example, the micro actuator100may include a single magnet110that provides a static N-S (where N is red and S is green) magnetic field and two (or a pair of) focusing elements121and122. The two focusing elements121and122may be physically connected (e.g., directly) to the magnet and are configured or operable to focus the magnetic field to align with one or more drive coils131,132, e.g. a first drive coil and a second drive coil. In some examples, the magnet110and focusing elements121,122are configured to rotate on a spindle140. The spindle140may be operable to snap fit into a main structure115that is configured to the drive coils131and132. For example, the drive coils131,132may be retained in the main structure115and provide controllable magnetic fields to attract or repel the static magnetic field of the magnet110. In the example, each drive coil131and132may be individually controlled to attract or repel the static magnetic field of the magnet110causing rotation in either of the two rotational directions.

A yoke150(or similar feature) is configured to transmit the torque/force of the actuator100to a pump mechanism (not shown in this example). In more detail, the yoke150may include one or more yoke extensions153,155(or yoke arms). The yoke extensions may form a yoke bearing. The yoke extensions153,155may be coupled to or integrated with either the first focusing element121or the second focusing element122. Alternatively, the yoke extensions153,155may be coupled to or integrated with both the first focusing element121and the second focusing element122. While the yoke150is shown in a U-shape with the yoke extensions153and155forming the extended portions of the U-shape, other shapes are envisioned such as, for example, the yoke extensions153,155extending from the yoke150in a T-shape or a Y-shape.

The process for assembling the structure and order of the actuator may be described with reference toFIG.1B. The focusing elements121and122may sandwich the spindle140and magnet110to form a complete magnetic assembly160. In some embodiments, the first focusing element includes a first spindle opening and the second focusing element includes a second spindle opening, and the spindle is configured to protrude through the first spindle opening and the second spindle opening and couple to the main structure. The first spindle opening and second spindle opening may be positioned centrally within the first and second focusing element. The square keying features141and142(also referred to as keying structure(s) or interlocking feature(s)) disposed at opposite ends of the spindle140ensure alignment of upper and lower focusing elements121and122, respectively, to the spindle140. A heat staking operation or the like may be used to lock the focusing elements121,122and magnet110to the spindle140. The complete magnetic assembly160, once constructed, may be an inseparable assembly.

Snap features117or the like in a top portion and a bottom portion of the main structure115may be operable to allow the spindle140to snap into place within the main structure115and provide axial and radial bearing-like features for the spindle140. The snap features117may be elastic. Further, the snap features117may each comprise a bearing surface configured to be in contact with a part of the spindle140. In particular the snap features may each comprise a bearing surface having a circular arc shape. Accordingly, in some embodiments, the snap features are configured to receive the spindle and operable to provide axial and radial bearing-like features for the spindle. The drive coils131and132may press fit into pockets119of the main structure115to receive and locate the respective drive coils131and132in alignment with respect to the focusing elements121,122. The pocket119may function to maintain alignment and spacing of the respective drive coils131and132with or within a gap (shown in a later example) between the first focusing element121and the second focusing element122. In some embodiments, the drive coil(s) are disposed within the pockets119. In some embodiments, the first drive coil131and the second drive coil132are positioned on opposite sides of the force transfer assembly within the main structure

Ferrite cores133and134may be positioned in the respective drive coils131and132to help ensure the magnetic field lines (not shown in this example) exit the drive coils131and132in an optimized direction to interact with the permanent magnet field lines. The ferrite cores133and134in the respective drive coils133and134help improve the shape of the magnetic field to optimize the magnetic force between the magnet110and drive coils131and132.

FIG.2Ashows a side view of a complete magnetic assembly of a micro actuator.FIG.2Billustrates examples of magnetic field lines in fully assembled micro actuator according to an aspect of the disclosed subject matter.

The complete magnetic assembly200may include two focusing elements221and222that rotate with spindle240with the magnet210disposed between the two focusing elements221and222. The focusing element221may be a first focusing element and focusing element222may be a second focusing element. Each of the focusing elements221and222ofFIG.1may include magnetic field directing elements, e.g. elements comprising or consisting of magnetic material such as iron. The magnetic field directing elements may be distinct element or integrally formed with the focusing elements. The first focusing element may include an upper element and a lower element. InFIG.2A, the reference number221-1U indicates the upper magnetic field directing element (first upper magnetic field directing element) on a first side of the first focusing element221and the reference number220-2U indicates another upper magnetic field directing element (second upper magnetic field directing element) on a second side of a first focusing element. The reference number222-1L indicates the lower focusing element (first lower magnetic field directing element) on the first side of a second focusing element and222-2L indicates the lower focusing element (second lower magnetic field directing element) on the second side of the second focusing element.

As shown on the right side ofFIG.2A, the upper magnetic field directing element221-2U and the lower magnetic field directing element221-2L direct the magnetic field generated by the magnet210(shown by lines231) across the gap225. In some embodiments, the upper magnetic directing element221-2U and the lower magnetic directing element221-2L are configured to form a gap that separates the upper magnetic directing element221-2U from the lower magnetic directing element221-2L. Similarly, as shown on the left side ofFIG.2A, a gap226is present on the opposite side of the magnet210and opposite to the gap225. The magnetic field generated by the magnet210also crosses the gap226(as shown by magnetic field lines232).

As shown inFIG.2B, a drive coil230typically is positioned within the gap225substantially equidistant from upper focusing element221-2U and lower focusing element221-2L. The drive coil230may be held in position in a pocket of a main structure as shown inFIGS.1A and1B. The pocket (as shown in the earlier examples) may function to maintain alignment and spacing of the drive coil with or within the gap225between the first focusing element and the second focusing element. Although not shown in this example, a drive coil similar to drive coil230is disposed in gap226.

FIGS.3A and3Bshow a top view of the micro actuator to illustrate a theory of operation of the example of micro actuator as shown inFIGS.1A through2B.

In operation, the micro actuator300may be coupled to an electrical power source that is operable to energize the drive coils331and332to attract (or repel) the poles of the magnet (not shown in this example). For example, an electrical current may be applied to drive coil331that causes the generation of a magnetic field (in this case, N) by the drive coil331, which may interact with a magnet, which may be a permanent magnet that emits a magnetic field Nm. The combination of the magnetic field N generated by the drive coil331and the magnetic field Nm emitted by the magnet produces a force that repels the focusing element321away from the drive coil331in the direction indicated by arrow A. In addition, or alternatively, an electrical current may be applied to drive coil332that causes the generation of a magnetic field (in this case, S) by the drive coil332, which may interact with a magnet (e.g., a permanent magnet) that emits a magnetic field Nm. The combination of the magnetic field S generated by the drive coil332and the magnetic field Nm emitted by the magnet produces a force that attracts the focusing element322toward the drive coil332in the direction indicated by arrow B.

In response to the generated force that repels the focusing element321from the drive coil331and/or the generated force that attracts the focusing element322toward the drive coil332, the yoke350translates or rotates about the spindle in the direction indicated by arrow C. Reversal of the electrical current through the drive coil(s) changes the direction of translation/rotation of the yoke350.

Additional features may be added to the examples shown inFIGS.1A-3B. For example, an external spring may be added to provide bi-stable positioning of the actuator at the end of a stroke. Accordingly, only one direction of current need be applied since a spring can cause the yoke350to rotate back to its original position (i.e., the position before a current was applied). Similarly, detents can be added to the spindle to also provide bi-stable positioning of the actuator at the end of stroke. Moreover, both an external spring and detents in the spindle may be added to provide even further bi-stable positioning of the actuator at the end of stroke beyond the single use of either the external spring or the detents in the spindle.

In a control example, the drive coils may be energized simultaneously to provide the repulsive and attractive magnetic forces. Alternatively, the drive coils may be energized in a staggered or sequential order (e.g., the attractive drive coil may be energized first, and the repulsive drive coil may be energized second) which may improve electrical efficiency.

In a further example, when the drive coils are energized, energy may be stored in the drive coils for a period of time and may be harvested utilizing a capacitive circuit or the like. In an example, the drive coil may be treated as an inductor which stores energy and only discharges stored energy after it stops receiving a current input. This stored energy can either be used to shorten the duration that the drive coil is energized or be transferred into a capacitor or the like to be reused at a later time.

FIGS.4A and4Bshow top and side views of an example of force transfer assembly with a single drive coil that is part of a single drive coil rotary solenoid micro actuator.

A top view of the force transfer assembly405and single drive coil430are shown inFIG.4A. This top view of the force transfer assembly405and single drive coil430shows a spindle410, a keying feature415(also referred to keying structure or interlocking feature), a top focusing element421, the single drive coil430with a ferrite core445. The drive coil430may be energized via electrical connections433. As shown in a later example, the electrical connections433may be coupled to control circuitry. Also shown inFIG.4Ais a yoke450of a bottom focusing element that is hidden from view beneath the top focusing element421. The top focusing element421hides the magnet inFIG.4A. The force transfer assembly and single drive coil400differ from earlier examples by using a single gap and drive coil instead of splitting the magnetic field focusing between two drive coils.

The side view of the force transfer assembly405and single drive coil430shown inFIG.4Bincludes additional details such as the magnet425disposed between the top focusing element421and the bottom focusing element422. The side view also shows the ferrite core445extending through the single drive coil430. In this example, the ferrite core445extends above a top edge and below a bottom edge of the single drive coil430. The top focusing element421is configured in a manner similar to the focusing element221with an upper focusing element curving downward toward the drive coil430, and the bottom focusing element422being configured similar to the focusing element222with a lower focusing element curving upward toward the drive coil430.

FIGS.4C and4Dillustrate additional details of an example of a micro actuator that includes the rotary solenoid micro actuator with a single drive coil shown in the examples ofFIGS.4A and4B.FIGS.4C and4Dillustrate an example of a micro actuator400that includes a main structure465for supporting the force transfer assembly405and the single drive coil430. The drive coil430may be held within a pocket to ensure alignment of the drive coil430with the focusing elements421and422.

In an operational example of the micro actuator400described with reference toFIG.4C, the drive coil430may be energized to have a magnetic polarity that repels the magnetic field created by magnet425and directed toward the drive coil430by the focusing elements421and422. In response to the energizing of the drive coil430, the force transfer assembly405may rotate in the direction indicated by Arrow C. An example of a drive mechanism coupling455is shown inFIGS.4C and4D. The drive mechanism coupling455, in particular a coupling element thereof, may be in contact with the yoke. In particular, the drive mechanism coupling455, in particular a coupling element thereof, may be disposed between the yoke extensions. The drive mechanism coupling455is actuated by the yoke450in the focusing element422and responds to the rotation (in the direction of Arrow C) of the force transfer assembly405by moving in the direction indicated by Arrow CC. The motion of the drive mechanism coupling455in the direction indicated by Arrow CC may cause a pump to initiate transfer of a liquid drug or the like from a reservoir by using the reciprocating motion of the drive mechanism. In some embodiments, the yoke450actuates a drive mechanism to expel a first amount of a liquid drug from a wearable drug delivery device. In some embodiments, movement of the yoke550in a first direction actuates a drive mechanism to expel a first amount of a liquid drug from a wearable drug delivery device and movement of the yoke in a second direction actuates the drive mechanism to expel a second amount of a liquid drug from a wearable drug delivery device. The rotation of the force transfer assembly405in the direction of Arrow CC may be stopped in a variety of ways, such as by de-energizing drive coil430, energizing the drive coil430to produce an opposite magnetic polarity (i.e., the magnetic field attracts the focusing elements421and422), by a mechanical stop, or the like. As shown inFIG.4D, the drive coil430may be energized to have a magnetic polarity that attracts the magnetic field created by magnet425and directed toward the drive coil430by the focusing elements421and422. In response to the energizing of the drive coil430, the force transfer assembly405may rotate in the direction indicated by Arrow D. The drive mechanism coupling455is actuated by the yoke450in the focusing element422and responds to the rotation (in the direction of Arrow D) of the force transfer assembly405by moving in the direction indicated by Arrow DD. The motion of the drive mechanism coupling455in the direction indicated by Arrow DD may cause the pump to enter another stage (or the like) of the transfer of the liquid drug or the like from the reservoir.

The micro actuator400may also include a bias spring (not shown in this example) to ensure the yoke450returns to a starting position after each actuation of the yoke450. The biasing spring may allow for only using one direction of current applied to drive coil430, such that the magnetic field moves the yoke in one direction and the biasing spring moves the yoke in the opposite direction.

FIGS.5A-5Dshow another embodiment that is suitable to provide a quadruple drive coil rotary solenoid micro actuator.FIG.5Ashows a sketch of a force transfer assembly540configured to operate with four drive coils511,513,515and517. For example, the oval drive coils in the earlier examples, such as131and132ofFIG.1A, may be split into two oppositely wound coils511/513and515/517on respective sides of the force transfer assembly540. The two oppositely wound coils511/513may be referred to as a first pair of drive coils and the two oppositely wound coils515/517may be referred to as a second pair of drive coils. The two oppositely wound drive coils511/513and515/517on each side may provide additional initial driving force (as compared to the single drive coils131and132ofFIG.1A) and help position the yoke550. The force transfer assembly540and four drive coils511,513,515and517may be coupled to control circuitry and a drive mechanism of a wearable drug delivery system (both shown in a later example). In some embodiments, the main structure further comprises a pocket to receive and hold each respective drive coil of the first pair of drive coils and each respective drive coil of the second pair of drive coils, and wherein the pocket is configured to maintain alignment of each respective drive coil of the first pair of drive coils and each respective drive coil of the second pair of drive coils with a gap between the first focusing element and the second focusing element. In some embodiments, the main structure further comprises a plurality of pocket each comprising a respective drive coil of the first pair of drive coils and of the second pair of drive coils, and wherein the pocket is configured to maintain alignment of each respective drive coil of the first pair of drive coils and each respective drive coil of the second pair of drive coils with a gap between the first focusing element and the second focusing element.

FIG.5Bprovides a sketch showing the positioning of the focusing elements521and522with respect to drive coil511that has been energized to attract the focusing elements521and522. The two oppositely wound drive coils on each side (e.g.,511and513,515and517) of the force transfer assembly540may be wound from the same wire (a first coil wound in a first direction and the second coil wound in a second direction opposite the first direction of the wire wound around the first coil), such as electrical connection533and electrical connection534, to simplify the manufacturing process. In an operational example explained with reference to bothFIGS.5A and5B, a control circuit (shown in another example) may energize drive coils513and515to cause the drive coils511and517to have a magnetic polarity that attracts the focusing elements521and522, while drive coils513and515are energized to have a magnetic polarity that repels the focusing elements521and522. The magnet510assists with the attractive forces generated by the respective drive coils511and517and with the repelling forces generated by the respective drive coils513and515. In this first state, the yoke550is moved in the direction of Arrow AA.FIGS.5A and5Bshow the yoke550after it has moved in the direction of Arrow AA. The yoke550may interact with a drive mechanism that causes a first amount of a liquid drug to be expelled from a wearable drug delivery device.

Conversely, as shown inFIGS.5C and5D, the control circuit (shown in another example) may energize drive coils513and515to cause the drive coils515and513to generate a magnetic polarity that attracts the focusing elements521and522, while drive coils511and517are energized to generate a magnetic polarity that repels the focusing elements521and522. The magnet510assists with the attractive forces generated by the respective drive coils513and515and with the repelling forces generated by the respective drive coils511and517. In this second state, the yoke550is moved in the direction of Arrow BB.FIGS.5C and5Dshow the yoke550after it has moved in the direction of Arrow BB. The movement of the yoke550in the direction of Arrow BB may also cause a drive mechanism of a wearable drug delivery device to cause a second amount of the liquid drug to be expelled from a reservoir of the wearable drug delivery device. In some embodiments, micro actuator further comprises a spindle, wherein the magnet has an opening through which the spindle passes, the first focusing element includes a first spindle opening and the second focusing element includes a second spindle opening, and the spindle is configured to protrude through the first spindle opening and the second spindle opening, in particular wherein the spindle includes at least one, in particular two, keying structure(s) configured to interlock with the first spindle opening and/or the second spindle opening

FIGS.6A-6Dshow a dual drive coil example similar to the example ofFIGS.4A and4B.

In this example as shown inFIG.6A(on the right), one pair of oppositely wound drive coils611and613on one side of the force transfer assembly640may provide the directional control and positional setup of a yoke660required if the output torque generated by the drive coils611and613and magnet610(shown inFIG.6B) is sufficient to drive a drive mechanism of a wearable drug delivery device. The two oppositely wound drive coils611and613may provide additional initial driving force and help position the yoke660. The force transfer assembly640and two drive coils611and613may be coupled to control circuitry and a drive mechanism of a wearable drug delivery system.

The two oppositely wound drive coils (e.g.,611and613) of the force transfer assembly640may be wound from the same wire (a first coil wound in a first direction and the second coil wound in a second direction opposite the first) to simplify the manufacturing process.FIG.6Bprovides a sketch showing the positioning of the focusing elements621and622with respect to drive coil613that has been energized to attract the focusing elements621and622as well as magnet610. In an operational example explained with reference to bothFIGS.6A and6B, a control circuit (shown in another example) may energize drive coil613to cause the drive coil613to attract the focusing elements621and622, while drive coil611may be energized to repel the focusing elements621and622. The magnet610may assist with the attractive forces generated by the drive coil613and with the repelling forces generated by the respective drive coil611. In this first state, the yoke660is moved in the direction of Arrow AAA.FIGS.6A and6Bshow the yoke660after it has moved in the direction of Arrow AAA. The yoke660may interact with a drive mechanism that causes a first amount of a liquid drug to be expelled from a wearable drug delivery device.

Conversely, as shown inFIGS.6C and6D, the control circuit (shown in another example) may energize drive coil611to cause the drive coil611to attract the focusing elements621and622, while drive coil613may be energized to repel the focusing elements621and622. The magnet610may assist with the attractive forces generated by the drive coil611and with the repelling forces generated by the respective drive coil513. In this second state, the yoke660is moved in the direction of Arrow BBB.FIGS.6C and6Dshow the yoke660after it has moved in the direction of Arrow BBB. The movement of the yoke660in the direction of Arrow BBB may also cause the drive mechanism to cause a second amount of the liquid drug to be expelled from the wearable drug delivery device.

The force transfer assembly640and drive coils611and613may be held in a structure similar to the main structure115ofFIGS.1A and1B. The micro actuators described herein may be used in conjunction with a computer controls, e.g. medication delivery algorithms.

A type of medication delivery algorithm (MDA) may include an “artificial pancreas” algorithm-based system, or more generally, an artificial pancreas (AP) application. For ease of discussion, the computer programs and computer applications that implement the medication delivery algorithms or applications may be referred to herein as an “AP application.” An AP application may be configured to provide automatic delivery of insulin based on an analyte sensor input, such as signals received from an analyte sensor, such as a continuous blood glucose monitor, ketone sensor, or the like. The signals from the analyte sensor may contain blood glucose measurement values, timestamps, or the like.

In addition, or alternatively, while the disclosed examples may have been described with reference to a closed loop algorithmic implementation, variations of the disclosed examples may be implemented to enable open loop use. The open loop implementations allow for use of different modalities of delivery of insulin such as smart pen, syringe or the like. For example, the disclosed AP application and algorithms may be operable to perform various functions related to open loop operations, such as the generation of prompts requesting the input of information such as diabetes type, weight or age. Similarly, a dosage amount of insulin may be received by the AP application or algorithm from a user via a user interface. Other open-loop actions may also be implemented by adjusting user settings or the like in an AP application or algorithm.

FIG.7illustrates an example of a wearable drug delivery system that may incorporate the example micro actuators described herein.

The wearable drug delivery system700may include control circuitry710, a power supply720, a micro actuator730, a drive mechanism740and a reservoir750. The wearable drug delivery device700may be a wearable device that is worn on the body of the user. The wearable drug delivery device700may be directly coupled to a user (e.g., directly attached to a body part and/or skin of the user via an adhesive, or the like). In an example, a surface of the wearable drug delivery device700may include an adhesive to facilitate attachment to the skin of a user.

The micro actuator730may be similar to the micro actuators with the force transfer assembly and drive coil configurations shown in the earlier examples ofFIGS.1A-6D. The reservoir750may store a liquid drug. Examples of a liquid drug may be or include any drug in liquid form capable of being administered by a drug delivery device via a subcutaneous cannula, including, for example, insulin, glucagon-like peptide-1 (GLP-1), pramlintide, glucagon, co-formulations of two or more of GLP-1, pramlintide, and insulin; as well as pain relief drugs, such as opioids or narcotics (e.g., morphine, or the like), methadone, arthritis drugs, hormones, such as estrogen and testosterone, blood pressure medicines, chemotherapy drugs, fertility drugs, or the like.

The micro actuator730may be physically coupled to the drive mechanism740via a coupling733. The coupling733may be a mechanical structure separate from the drive mechanism740that couples the yoke (shown in other examples) of the micro actuator730to the drive mechanism740or may be a mechanical structure that is an integrated part of the drive mechanism740. The coupling733may extend the motion of the yoke of the micro actuator to the drive mechanism or may translate the motion of the yoke to motion in a different plane or from linear motion to rotary motion or the like. Alternatively, the coupling733may be omitted and the yoke of the micro actuator730may couple directly to the drive mechanism740.

The drive mechanism740may include a number of mechanical elements such as gears, gear trains and the like, that convert the linear motion of the yoke into motion in another form, such as a rotary motion of the like. The drive mechanism740may also include an elongated shaft that couples to a first interface (i.e., a plunger) or another interface of the reservoir750.

A drive coupling743may couple the drive mechanism740to the reservoir750. The drive coupling743may have the structural elements that enable an amount of a liquid drug stored in the reservoir750to be expelled from the reservoir750via a fluid pathway760.

The power supply720may be an electrical power source, such as a battery, a super capacitor, an energy harvesting circuit or the like. The power supply720may be configured to last several hours, several days or the like. The power supply720may be replaceable and/or rechargeable via wired connections or wireless connections.

The wearable drug delivery device700may include control circuitry710that may be implemented in hardware, software, or any combination thereof. The control circuitry710may, for example, be a microprocessor, a logic circuit, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC) or a microprocessor coupled to a memory. The control circuitry710may be operable to perform a number of functions, such as executing a control application stored in the memory (not shown). In the present examples, the control circuitry710is operable to execute logic that causes a control signal in the form of a voltage or a current to be applied to the micro actuator730to energize via electrical connections (shown in earlier examples) one or more drive coils as described with reference to the examples ofFIGS.1A-6D.

Certain examples of the present disclosure were described above. It is, however, expressly noted that the present disclosure is not limited to those examples, but rather the intention is that additions and modifications to what was expressly described herein are also included within the scope of the disclosed examples. Moreover, it is to be understood that the features of the various examples described herein were not mutually exclusive and may exist in various combinations and permutations, even if such combinations or permutations were not made express herein, without departing from the spirit and scope of the disclosed examples. In fact, variations, modifications, and other implementations of what was described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the disclosed examples. As such, the disclosed examples are not to be defined only by the preceding illustrative description.

Although the present invention is defined in the attached claims, it should be understood that the present invention can also (alternatively) be defined in accordance with the following embodiments:1. A micro actuator for a wearable drug delivery device, comprising:a force transfer assembly including a first focusing element and a second focusing element, wherein the second focusing element includes a yoke;a drive coil, wherein the drive coil is operable to attract or repel the first focusing element and the second focusing element; anda main structure configured to hold the force transfer assembly and the drive coil in alignment with one another.2. The micro actuator of claim1, further comprising:a spindle, wherein the first focusing element includes a first spindle opening and the second focusing element includes a second spindle opening, and the spindle is configured to protrude through the first spindle opening and the second spindle opening and couple to the main structure.3. The micro actuator of claim1, further comprising:a magnet disposed between the first focusing element and the second focusing element.4. The micro actuator of claim1, wherein the main structure further comprises:snap features configured to receive the spindle and operable to provide axial and radial bearing-like features for the spindle.5. The micro actuator of claim1, wherein the main structure further comprises:a pocket to receive and hold the drive coil.6. The micro actuator of claim1, wherein the pocket is further operable to:maintain alignment of the drive coil within a gap between the first focusing element and the second focusing element.7. The micro actuator of claim1, wherein the drive coil comprises:a first drive coil and a second drive coil,wherein the first drive coil and the second drive coil are positioned on opposite sides of the force transfer assembly within the main structure.8. The micro actuator of claim1, wherein the first focusing element comprises:a first upper magnetic directing element and a second upper magnetic directing element disposed across from one another on opposite sides of the first focusing element.9. The micro actuator of claim1, wherein:the first focusing element includes:an upper magnetic field directing element disposed on a side of the first focusing element; andthe second focusing element includes:a lower magnetic directing element disposed on a side of the second focusing element beneath the upper magnetic field directing element,wherein the upper magnetic directing element and the lower magnetic directing element are configured to form a gap that separates the upper magnetic directing element from the lower magnetic directing element.10. The micro actuator of claim1, wherein the yoke comprises:yoke extensions operable to interact with a drive mechanism of the wearable drug delivery device.11. The micro actuator of claim1, wherein the yoke comprises:yoke extensions extending from either the first focusing element or the second focusing element, wherein the yoke extensions cause the yoke to have a T-shape, a U-shape, or a Y-shape.12. A micro actuator for a wearable drug delivery device, comprising:a force transfer assembly including a magnet between a first focusing element and a second focusing element, wherein the second focusing element includes a yoke;a first pair of drive coils; anda second pair of drive coils,wherein each drive coil of the first pair of drive coils is energized to a magnetic polarity that is opposite the other drive coil in order to attract or repel the first focusing element and the second focusing element in a first direction, andeach drive coil of the second pair of drive coils is energized to a magnetic polarity that is opposite the other drive coil in order to attract or repel the first focusing element and the second focusing in a second direction opposite the first direction.13. A micro actuator of claim12, comprising:a main structure configured to hold the force transfer assembly, each drive coil of the first pair of drive coils, and each drive coil of the second pair of drive coils in alignment to enable rotation of the force transfer element.14. The micro actuator of claim13, wherein the main structure further comprises:snap features configured to receive the spindle and operable to provide axial and radial bearing-like features for the spindle.15. The micro actuator of claim13, wherein the main structure further comprises:a pocket to receive and hold each respective drive coil of the first pair of drive coils and each respective drive coil of the second pair of drive coils, andwherein the pocket is configured to maintain alignment of each respective drive coil of the first pair of drive coils and each respective drive coil of the second pair of drive coils with a gap between the first focusing element and the second focusing element.16. The micro actuator of claim12, wherein each drive coil of the first pair of drive coils is wound from the same piece of wire, wherein the wire is wound in a first direction for a first respective drive coil of the first pair of drive coils and in a second and opposite direction for a second respective drive coil of the first pair of drive coils.17. The micro actuator of claim12, wherein the yoke comprises:yoke extensions operable to interact with a drive mechanism of the wearable drug delivery device.18. The micro actuator of claim12, wherein the yoke comprises:yoke extensions extending from either the first focusing element or the second focusing element in which the yoke has a T-shape, a U-shape, or a Y-shape.19. The micro actuator of claim12, further comprising:a spindle,wherein:the magnet has an opening through which the spindle passes,the first focusing element includes a first spindle opening and the second focusing element includes a second spindle opening, andthe spindle is configured to protrude through the first spindle opening and the second spindle opening.20. The micro actuator of claim19, wherein:the spindle includes a keying structure configured to interlock with the first spindle opening and the second spindle opening.