Patent Publication Number: US-2020297536-A1

Title: Peristaltic micropump assemblies and associated devices, systems, and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/819,902, filed Mar. 18, 2019, the entirety of which is incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to devices and methods for pumping fluids from a patient and/or delivering pharmaceutical agents to a patient, including peristaltic pump assemblies implantable in a patient for relieving intraocular pressure. 
     BACKGROUND 
     Intraocular pressure (TOP) quantifies the pressure of the aqueous humor inside the eye. Many individuals suffer from disorders, such as glaucoma, that cause chronic heightened IOP. Over time, heightened IOP can cause damage to the optical nerve of the eye, leading to loss of vision. Presently, treatment of glaucoma mainly involves periodically administering pharmaceutical agents to the eye to decrease TOP. These drugs can be delivered by, for example, injection or eye drops. However, the effectiveness of pharmaceuticals can vary greatly from patient-to-patient. Furthermore, effective treatment of glaucoma requires adherence to rigid dosage schedules that can be difficult to follow for some patients. 
     Another way TOP can be reduced is by removing some of the fluid from inside the patient&#39;s eye. However, current devices are not suitable or practical for therapeutic use. For example, current devices do not simultaneously satisfy the desire for small size, low power, and a lifetime of many years before failure. Thus, there remains a need for wearable fluid displacement devices that meet requirements for safety and reliability while being as cost-effective as possible. 
     SUMMARY 
     The present disclosure advantageously describes micropump assemblies configured to pump fluid from a patient and/or deliver pharmaceutical agents to the patient. In some embodiments, a micropump assembly can include a compressing member and a round fluid chamber comprising an outer portion and a flexible membrane coupled to the outer portion. The compressing member is controlled by a motor to rotate along a circumference to compress the fluid chamber in a circular motion, thereby pumping a fluid through the fluid chamber. The assembly can fit within a housing that is sized and shaped to be implanted in the patient. For example, the micropump assembly can be inserted into the patient&#39;s ocular cavity and configured to displace fluid from the patient&#39;s eye. 
     In one embodiment of the present disclosure, a pump assembly includes a rotor configured to rotate about an axis and comprising a compressing member at an outer portion of the rotor such that the compressing member is configured to rotate along a circumference, and a fluid chamber positioned at least partially around the circumference, the fluid chamber comprising a round outer portion and a membrane attached to the round outer portion and opposing an inner face of the round outer portion, wherein the compressing member is configured to deform the membrane of the fluid chamber to compress the fluid chamber and move a fluid through the fluid chamber. 
     In one aspect, the pump assembly is implantable in a patient for relieving intraocular pressure (IOP). In some embodiments, the pump assembly further comprising an actuator configured to cause the rotor to rotate about the axis. The actuator can include an electrostatic motor. In some embodiments, the rotor comprises a gear concentric with the first axis, wherein the actuator is configured to cause the rotor to rotate about the first axis via the gear. In another aspect, the fluid chamber is positioned around the axis in a non-circular pattern. In another aspect, the round outer portion comprises a hard ring and the membrane comprises an elastomeric material. The hard ring can include a first groove on one side and a second groove on an opposing side, wherein the membrane is joined to the hard ring using the first groove and the second groove. In some embodiments, the hard ring includes at least one of a flat surface or a concave inner surface, and the membrane comprises a thin wall tube comprising a soft rubber material. According to a further aspect, the hard ring and the membrane are attached by at least one of an adhesive or a weld. 
     According to another embodiment of the present disclosure, a peristaltic pump implantable in a patient for relieving intraocular pressure (TOP) includes, an actuator, a drive shaft coupled to the actuator and configured to rotate about a first axis, a roller coupled to and radially extending from the drive shaft such that the actuator, via the drive shaft, is configured to rotate the roller about the first axis and along a circumference, and a fluid chamber disposed around a portion of the circumference, the fluid chamber comprising a hard outer ring and a flexible inner ring positioned over an inner surface of the outer ring, wherein the roller is configured to deform the inner ring of the fluid chamber to compress the fluid chamber and move a fluid through the fluid chamber. 
     In some embodiments, the outer ring comprises a first groove on one side and a second groove on an opposing side, wherein the membrane is joined to the outer ring using the first groove and the second groove, wherein the membrane comprises a first ridge portion and a second ridge portion, wherein the first ridge portion resides in the first groove, and wherein the second ridge portion resides in the second groove. In another embodiment, the drive shaft is rotatably coupled to the roller via a first ball bearing, wherein the roller comprises a second ball bearing, and wherein the roller is configured to rotate about a second axis of the ball bearing. 
     In yet another embodiment, the peristaltic pump further includes a gear assembly coupled to the actuator and the drive shaft, wherein the gear assembly is configured to convert a torque provided by the actuator to the drive shaft. In some embodiments, the peristaltic pump further comprises an application specific integrated circuit (ASIC) configured to activate the actuator, and a rotary encoder configured to indicate a rotational position of the roller to the ASIC, wherein the ASIC is configured to control rotation of the roller by the actuator based on the rotational position provided by the encoder. 
     According to another embodiment, the peristaltic pump includes a processor configured to control an output of the actuator, a battery configured to provide electrical power to the processor and the actuator, a wireless charging coil coupled to the processor and the battery, the wireless charging coil configured to receive wireless power to recharge the battery, and a housing sized and shaped to be implanted in an eye cavity of a patient, wherein the actuator, drive shaft, roller, fluid chamber, processor, battery, and wireless charging coil are coupled to and contained within the housing. In another embodiment, the fluid chamber comprises a circular section and a non-circular section, wherein the non-circular section is positioned with respect to the first axis such that a radius between the first axis and the non-circular section of the fluid chamber increases in a direction of the circumference. 
     According to another aspect of the present disclosure, a method for pumping a fluid from a patient&#39;s eye to relieve intraocular pressure comprises compressing, in a circular motion, a fluid chamber in fluid communication with the patient&#39;s eye using a compressing member to pump a fluid through the fluid chamber, wherein compressing the fluid chamber comprises rotating the compressing member along a circumference by activating a motor coupled to the compressing member, wherein the compressing member compresses the fluid chamber along a circumference to pump the fluid through the fluid chamber, wherein compressing the fluid chamber includes deforming a flexible inner ring against a hard outer ring. 
     In some embodiments, the method further includes receiving, at an application specific integrated circuit (ASIC) in communication with the motor, a signal from a rotary encoder indicating a rotational position of the compressing member, and adjusting, by the ASIC, a rotational position of the motor based on the received signal. In another embodiment, the method further includes receiving, at an application specific integrated circuit (ASIC) in communication with the motor, a signal from a pressure sensor indicating a fluid pressure, and adjusting, by the ASIC, an output of the motor based on the received signal. In yet another embodiment, the method further includes stopping the motor, and adjusting a fluid flow through the fluid chamber to a predetermined fluid flow, wherein adjusting the fluid flow comprises stopping the motor to position the compressing member at a location along a non-circular portion of the fluid chamber corresponding to the predetermined fluid flow. 
     Additional aspects, features, and advantages of the present disclosure will become apparent from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the present disclosure will be described with reference to the accompanying drawings, of which: 
         FIG. 1  is a diagrammatic view of a micropump system, according to an embodiment of the present disclosure. 
         FIG. 2  is a diagrammatic schematic view of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 3  is a perspective view of a driver assembly and fluid chamber of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 4  is a perspective view of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 5  is a cross-sectional perspective view of a fluid chamber of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 6  is a perspective view of a driver assembly of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 7  is a cross-sectional perspective view of the driver assembly of  FIG. 6 , according to an embodiment of the present disclosure. 
         FIG. 8  is a diagrammatic schematic view of a driver circuit and fluid chamber of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 9  is a diagrammatic schematic view of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 10  is a diagrammatic schematic view of a micropump assembly, according to an embodiment of the present disclosure. 
         FIG. 11  is a flow chart illustrating a method for pumping fluid from a patient&#39;s eye, according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. For example, while the therapeutic devices are described in terms of eye-mountable devices configured to pump fluid (e.g., aqueous humor) from a human eye, it is understood that it is not intended to be limited to this application. The devices and systems are equally well suited to any application requiring pumping of fluids. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately. 
     Presently, treatment of glaucoma mainly consists of periodically administering pharmaceutical agents to the eye to decrease TOP. These drugs can be delivered by, for example, injection or eye drops. However, the effectiveness of pharmaceuticals can greatly vary from patient-to-patient. Furthermore, effective treatment of glaucoma requires adherence to rigid dosage schedules that can be difficult to follow for some patients. 
     Another way to reduce TOP involves removing quantities of fluid from inside the patient&#39;s eye. However, current devices are not suitable or practical for therapeutic use. For example, devices to remove fluid from the eye need to be small enough to be implanted into the patient at a practical location, such as the patient&#39;s eye cavity. Due to the invasiveness of implanting such a device, the device should be able to operate independently for a period of time. Thus the device must be able to operate efficiently in a restricted space, and must be reliable enough to require little or no maintenance. 
     The present disclosure describes micropump assemblies that overcome the challenges described above. In that regard, the micropump assemblies described herein provide advantageous arrangements of components and features that allow the micropumps to reliably and efficiently pump fluid from a patient&#39;s eye while minimizing the profile of the devices such that they can be implanted and worn by patients for extended periods of time. 
       FIG. 1  is a diagrammatic view of a micropump system  100 , according to one embodiment. The system  100  includes an eye-mountable micropump  110  coupled to an eye  55  of a patient  50 , and a wireless transmission device  150  configured to wirelessly transmit electrical power  152  and/or electrical signals to the micropump  110 . The micropump  110  is sized and shaped to be permanently or semi-permanently attached to the patient&#39;s eye  55 . In particular, the micropump  110  is configured to be positioned within an ocular cavity proximate the eye  55 . In some embodiments, the micropump  110  can be positioned at different locations with respect to the patient&#39;s eye, such as below the eye  55 , above the eye  55 , inside the eye  55 , or inside any suitable anatomical structure that allows the micropump to pump fluid from the eye  55 . 
     Because the micropump  110  may not be easily accessible for charging or reprogramming, the micropump  110  is configured to wirelessly receive electrical power  152  and/or electrical signals from the wireless transmission device  150 . The wireless transmission device  150  includes circuitry and components to send electrical power, such as coils, transformers, power supplies, batteries, or other circuitry. Additionally, the wireless transmission device  150  can include wireless communication components to transmit and/or receive data in the form of wireless signals to/from the micropump  110 . As explained further below, the micropump  110  can also include wireless electronic components for receiving electrical power and/or electrical signals form the transmission device  150 . The micropump  110  can include a battery and a processing component that allow it to operate independently for a period of time (e.g., days, weeks, months) without receiving power or signals from the transmission device  150 . 
       FIG. 2  is a diagrammatic schematic view of a micropump assembly  110 , according to one embodiment of the present disclosure. The micropump assembly  110  includes a compressible fluid chamber  120  and a driver assembly  130  configured to compress the fluid chamber  120  to move fluid through the fluid chamber  120 . The driver assembly  130  is actuated and controlled by a plurality of electronic and mechanical components, such as an application-specific integrated circuit (ASIC)  112 , an actuator or motor  114 , a gear box  116 , and a power circuit  118 . The power circuit  118  includes a battery  117 , and a coil  119  configured to receive electrical power from a wireless source, such as the wireless transmission device  150  shown in  FIG. 1 . The power circuit  118  is configured to supply electrical power to the components of the micropump  110 , including the ASIC  112 , and the motor  114 . The power circuit  118  separately provides electrical power to the ASIC  112  and the motor  114 , in some embodiments. In other embodiments, the power circuit  118  provides electrical power to the ASIC  112 , which distributes the electrical power to the other components of the micropump assembly  110 , including the motor  114 . 
     The ASIC  112  is configured to control an output of the motor  114 , thereby controlling the performance (e.g., flow rate) of the micropump  110  assembly. The ASIC  112  operates according to a protocol, which comprises computer code instructions saved in a memory device of the ASIC  112 . The protocol is defined by one or more parameters, such as time, number of cycles, physiological measurements, battery life, etc. Thus, the ASIC  112  is configured to control operation of the micropump assembly  110  while the assembly  110  is implanted in the patient. It will be understood that, although the ASIC  112  is shown as a single component in  FIG. 2 , the micropump assembly  110  may comprise a plurality of individual integrated circuits or other circuitry that is configured to carry out the functions of the assembly  110 . 
     The power circuit  118  and/or the ASIC  112  provide electrical power to the motor  114 , which is configured to activate the driver assembly  130  via the gear box  116 . The gear box  116  is configured to modify or convert a torque provided by the motor  114 , and apply the modified torque to the driver assembly  130 . In that regard, the gear box  116  comprises one or more gears or stages of gears to increase or decrease the torque applied by the motor  114 . Thus, the gear box  116  can also be appropriate referred to as a torque converter. In an exemplary embodiment, the gear box  116  is configured to increase the torque applied by the motor  114 . The increased torque provided by the gear box  116  can help to overcome friction on the driver assembly  130  caused by, e.g., the roller  134  on the compressible fluid chamber  120 . 
     In an exemplary embodiment, the motor  114  is an electrostatic motor, such as the Silmach PowerMEMS® electrostatic motor. However, other motors are also contemplated by the present disclosure, including lavet-type motors, piezoelectric motors, step motors, brushless motors, or any other suitable type of motor. 
     The driver assembly  130  includes a drive shaft  132  configured to rotate about a first axis and a compressing member or roller  134  rotatably coupled to the drive shaft  132  by a rotor  136 . The rotor  136 , which can also be referred to as a crank, couples the roller  134  to the drive shaft  132  such that the roller  134  travels about the first axis of the drive shaft  132  along a circumference  131  or circular path when the drive shaft  132  is rotated by the motor  114  via the gear box  116 . The roller  134  is rotatably coupled to the rotor  136 , such that the roller can rotate about a second axis while traveling along the circumference  131 . As described further below, the drive shaft  132  and roller  134  can each comprise one or more ball bearings, such as the drive shaft bearing  138 , to reduce friction, and therefore reduce the amount of torque required to rotate the driver assembly  130 . 
     As the driver assembly  130  rotates the roller  134  along the circumference, the roller compresses the fluid chamber  120  in a circular motion around the circumference  131 . This circular compression causes the peristaltic pumping action that moves fluid into the fluid chamber  120  through an inlet  126 , through the fluid chamber  120  in the circumferential direction  131 , and out the fluid chamber  120  through an outlet  128 . As an example, when the micropump assembly  110  is implanted onto the patient&#39;s eye  55 , the inlet  126  can be coupled the eye  55  to receive the aqueous humor, and the outlet  128  can be positioned outside the eye  55 , for example, in the ocular cavity. When the micropump assembly  110  is activated, the micropump  110  draws the fluid from inside the eye  55 , and expels the fluid outside of the eye  55 , thereby reducing the patient&#39;s intraocular pressure (IOP). 
     The fluid chamber  120  can include a round outer portion, or ring  122 , and a flexible membrane  124  coupled to the hard outer ring  122  and opposing an inner surface of the outer ring  122 . The outer ring  122  can comprise a material that is relatively harder and/or more rigid than the flexible membrane, such as a plastic. As will be explained further below, compression of the fluid chamber  120  involves deforming the membrane  124  toward the outer ring  122  to close or restrict a channel formed between the outer ring  122  and the membrane  124 . As will be understood with reference to the embodiment of  FIG. 2 , the outer ring  122  is not necessarily circular. For example, in  FIG. 2 , the outer ring  122  includes a circular arc portion and a linear portion. In that regard, the outer ring  122  is not closed, but forms a U-shape. Thus, although the term “ring” is used with respect to the outer portion or ring  122 , this is in no way limiting to closed, circular shapes. 
     The components of the micropump assembly  110 , including the driver assembly  130 , fluid chamber  120 , ASIC  112 , motor  114 , gear box  116 , and power supply circuit  118  are coupled to and/or contained within a housing  140 . The housing  140  is sized and shaped to be implanted into an ocular cavity of the patient  50 . The housing  140  is configured to contain and protect the components of the micropump assembly  110  from physical and/or chemical damage. In some embodiments, the housing  140  provides a waterproof casing for one or more electrical components of the device, such as the ASIC  112 , the power circuit  118 , and the motor  114 . The housing  140  may also be configured to protect one or more components from chemical damage. In some embodiments, the housing  140  is configured to protect the mechanical components, such as the gear box  116  and the driver assembly  130  from foreign material that could interfere with or inhibit the mechanical performance of the micropump  110 . 
       FIG. 3  is a perspective view of a drive assembly and fluid chamber  120  of the micropump assembly  110 , according to one embodiment. As in the embodiment shown in  FIG. 2 , the embodiment of  FIG. 3  includes a drive shaft  132  and a roller  134  rotatably coupled to the drive shaft  132  by the rotor or crank  136 . The roller  134  is configured to travel in a circular motion about a first axis of the drive shaft  132 . The fluid chamber  120  includes a hard outer ring  122 , and a flexible membrane  124  opposing an inner face or surface of the outer ring  122 . An inlet  126  and an outlet  128  of the fluid chamber  120  are integrally formed with the outer ring  122  and are configured to direct ingress and egress of fluid through the fluid chamber  120 . However, in other embodiments, the inlet  126  and/or outlet  128  are not integrally formed with the outer ring  122 . For example, the inlet  126  and/or outlet  128  can be formed of the membrane  124 , or formed of both the membrane  124  and the outer ring  122 . In other embodiments the inlet  126  and/or outlet  128  can comprise physically separate components that are attached to the outer ring  122  and/or the membrane  124 . As described above, as the roller  134  rotates about the circumference  131 , the membrane  124  is deformed or pressed against the outer ring  122  to move fluid through the fluid chamber  120  in a peristaltic motion toward the outlet  128 . To reduce friction, the roller  134  is also configured to rotate or spin in a planetary motion about a second axis and around the first axis. 
       FIG. 4  is a perspective view of a micropump assembly  110 , according to an embodiment of the present disclosure. Similar to the assembly  110  shown in the  FIG. 2 ,  FIG. 4  shows a driver assembly  130  and a fluid chamber  120  contained within a housing  140 . In contrast to the embodiments shown in  FIGS. 2 and 3 , the rotor or crank  136  shown in  FIG. 4  has a circular shape and is positioned around the drive shaft  132 . The circular rotor  136  couples the roller  134  to the drive shaft  132  such that the roller  134  travels around the first axis along a circumference. 
     The assembly  110  includes a housing  140  that houses the components of the assembly  110 , including the driver assembly  130  and the fluid chamber  120 . Other components are also positioned within the housing, such as the ASIC  112 , motor  114 , gear box  116 , power circuit  118 , or any other suitable components. The housing  140  shown in  FIG. 4  includes multiple pieces, including a first piece  141  and a second piece  143 . The second piece  143  may act as a cover for one or more components such as the gear box  116  and the motor  114 . The housing  140  is configured to contain the components of the assembly  110  within a space small enough to be implanted into the patient. In that regard, the assembly  110  comprises a length  144 , a width  146 , and a height  148 . In an exemplary embodiment, the length  144  is about 9 mm, the width  146  is about 9 mm, and the height  148  is about 2 mm. However, the dimensions can be modified as appropriate for the application. For example, the length  144 , width  146 , and/or height  148  can range from less than 1 mm to more than 30 mm. In an exemplary embodiment, the height  148  can range between 1 mm and 5 mm. The length and width can vary between 5 mm and 30 mm. It will be understood that these dimensions are merely exemplary and can be modified as suitable for a particular application. 
       FIG. 5  is a perspective cross-sectional view of the fluid chamber  120  of the assembly  110 . The fluid chamber  120  includes an outer ring  122 , and a flexible membrane  124  coupled to the outer ring  122  to define a fluid channel  125 . The flexible membrane  124  comprises an elastomeric material such as silicone, while the outer ring  122  comprises a relatively harder material, such as a plastic. In some embodiments, the outer ring  122  can comprise one or more metallic materials, such as stainless steel and/or titanium, one or more plastic materials such as polyetheretherketone (PEEK) and/or polytetrafluoroethylene (PTFE), and rubber, such as a rubber having a Shore D hardness, or any other suitable material. The flexible membrane  124  or inner ring can comprise a relatively soft, flexible material, such as a soft rubber, silicone, polyethylene terephthalate (PET), PTFE, or any other suitable material. The membrane  124  is positioned over, or opposing, an inner surface  121  of the outer ring  122 . The inner surface  121  comprises a valley that partially defines the fluid channel  125 . The membrane  124  is attached to the outer ring  122  at a first groove  127   a  on a top side of the outer ring  122 , and a second groove  127   b  on an opposing bottom side of the outer ring  122 . A first ridge  129   a  of the membrane  124  is positioned within the first groove  127   a , and a second ridge  129   b  of the membrane  124  is positioned within the second groove  127   b . The first and second ridges  129   a ,  129   b  can be attached to the outer ring  122  by any suitable method, including a weld, thermal bond, adhesive, or a mechanical fit (e.g., interference fit). It will be understood that, in some embodiments, the first and second ridges  129   a ,  129   b , are formed of opposing edges of a rectangular membrane. 
     As explained above, the outer ring  122  may comprise a material that is relatively harder and/or more rigid than the membrane  124 . Accordingly, while the membrane  124  is configured to be deformed by the roller  134 , the outer ring  122  may be configured to retain its shape, even with applied pressure from the roller  134 . In a relaxed or undeformed state, the membrane  124  spans across the curved inner surface  121  of the outer ring  122  such that a space exists in the fluid channel  125  for a fluid to pass through. When the roller  134  passes over the membrane  124 , the membrane  124  is deformed toward the inner surface  121  of the outer ring  122  to reduce or close the space in the fluid channel  125 . The membrane  124  is thus deformed in a circular fashion around the circumference to create a peristaltic pumping action that moves a fluid through fluid chamber  120  toward the outlet  128 . 
     The fluid chamber  120  described above exhibits certain advantages to existing fluid chambers. For example, the coupling of the membrane  124  to the hard outer ring  122  can reduce the stress applied to the fluid chamber  120  when compressed by the driver assembly  130 . In that regard, as opposed to flexible tubes that are compressed by collapsing one side of the tube toward the other side of the tube, compressing the fluid chamber  120  shown in  FIG. 5  is accomplished by deforming the flexible membrane against the relatively hard or rigid outer ring  122 . Thus, when the membrane  124  is relaxed, the channel  125  of the fluid chamber  120  between the membrane and the outer ring  122  is relatively unrestricted. Compressing the membrane  124  against the outer ring  122  can be achieved with relatively little stress to any given portion of the flexible membrane  124 . Furthermore, because the outer ring  122  provides the structural integrity to define the channel  125 , the flexible membrane can be formed of a soft elastomeric material that can be more easily compressed. Furthermore, the smooth, round surface  121  can also reduce the amount of stress on the membrane  124  during compression. Thus, the fluid chamber  120  can be compressed with less resistance than what would be required with flexible tubing. Furthermore, because the membrane  124  undergoes relatively little stress, the durability and lifespan of the fluid chamber  120  can be increased. 
       FIGS. 6 and 7  depict a driver assembly  130  of the micropump assembly  110  shown in  FIG. 4 , according to one embodiment of the present disclosure. In particular,  FIG. 6  is a perspective view of the driver assembly  130 , and  FIG. 7  is a perspective cross-sectional view of the driver assembly  130  taken along the line  7 - 7 . As in  FIG. 4 , the driver assembly  130  includes a drive shaft  132  and a rotor or crank  136 , which comprises a top plate  136   a  and a bottom plate  136   b . The driver assembly  130  also includes a gear  138  fixedly coupled to the top plate  136   a  and bottom plate  136   b  of the rotor by a rotor pin  136   c . The gear  138  is positioned concentrically with the drive shaft  132  and the first axis. The pin  136   c  couples the gear to the rotor such that torque applied to the gear  138  rotates the rotor  136 , and therefore the roller  134 . The drive shaft  132  is concentrically coupled to a first bearing  137  to rotate about a first axis. Similarly, the roller  134  comprises a bearing concentrically coupled to a roller bearing pin  133  to rotate about a second axis. 
     Because it is desired that the entire micropump assembly  110  is sized and shaped to be implanted into a patient (e.g., inside the ocular cavity), the components of the driver assembly  130  can be low-profile. For example, in some embodiments, the ball bearings of the drive shaft  132  and the roller  134  have a diameter of less than 1 mm. In some embodiments, the ball bearings have an outer diameter of between 1.5 mm and 3 mm. 
       FIG. 8  is a top view of a driver assembly and a fluid chamber  120 , according to one embodiment of the present disclosure. The driver assembly  130  of  FIG. 8  may include similar or identical components as the assembly  130  shown in  FIGS. 2 and 3 , such as a drive shaft  132 , a crank  136 , and a roller  134 . The fluid chamber  120  includes a circular portion  120   a  and a non-circular portion or spiral portion  120   b . In that regard, the non-circular portion  120   b  is shaped and arranged such that a radius  123  between the drive shaft  132  and the fluid chamber increases in a clockwise direction of the fluid chamber  120 . Thus, with the configuration shown in  FIG. 8 , the micropump assembly  110  can function as a pump over the circular portion  120   a , and as a flow controller for the rest of the cycle over the non-circular portion  120   b . In that regard, as the roller  134  passes over the circular portion  120   a , the fluid chamber  120  is fully compressed, but when the roller  134  passes over the non-circular portion  120   b , the fluid chamber  120  is only partially compressed, thereby reducing the hydraulic resistance as the roller  134  rotates clockwise over the non-circular portion  120   b . When a positive pressure gradient exists across the micropump  110  (e.g., when the TOP is relatively high), fluid may flow from the inlet  126  to the outlet  128  even without pumping. In this case, pumping is mainly used for clearing and preventing clogs. When a stepper motor is used as the actuator or motor  114 , the motor  114  can be controlled to stop at any desired angular location. Thus, the stepper motor  114  can control the roller  134  to stop at a desired position along the non-circular portion  120   b . Because the compression of the fluid chamber  120  by the roller  134  gradually decreases as the roller  134  moves clockwise along the non-circular portion  120   b , the micropump  110  can act as a variable flow controller to adjust the flow of fluid through the micropump  110  that is caused by the positive pressure gradient. For example, if the motor  114  stops the roller  134  over the circular portion  120   a , the fluid chamber  120  is fully compressed such that flow through the fluid chamber  120  is effectively zero. By contrast, when the roller  134  is moved to a location along the non-circular portion  120   b  that is near the outlet  128 , the fluid chamber  120  may not be compressed at all, or only minimally compressed, such that fluid flow through the chamber  120  is effectively unrestricted. The motor  114  can also control the roller  134  to stop at a desired location along the non-circular portion  120   b  corresponding to a desired amount of compression of the fluid chamber  120 , and therefore adjusting the flow of fluid through the chamber  120  to a desired amount. 
       FIG. 9  is a diagrammatic schematic view of a micropump assembly  110 , according to another embodiment of the present disclosure. The micropump assembly  110  embodiment shown in  FIG. 9  can include similar or identical components as the embodiment shown in  FIG. 2 . For example, the embodiment shown in  FIG. 9  includes an ASIC  112 , a motor  114 , a gear box  116 , a power circuit  118 , a fluid chamber  120 , and a driver assembly  130 . Additionally, the micropump assembly  110  includes a rotary encoder  160  in communication with the motor  114 , a pressure sensor  170 , and a rotor spring  139 . The rotary encoder  160  is communicatively coupled to the motor  114  and configured to provide an indication or feedback to indicate the rotational position of the motor  114  to the ASIC  112  and/or motor  114 . The rotary encoder  160  can be used to control pumping of fluid through the micropump  110  with volumetric precision. For example, in some embodiments, the micropump assembly  110  can be used to deliver pharmaceutical agents to the patient. The rotary encoder  160  can be used to provide feedback to the ASIC  112  to control dosing of the pharmaceutical with nanoliter precision. 
     The pressure sensor  170  measures a pressure or pressure gradient across the micropump assembly  120 . The pressure sensor  170  is communicatively coupled to the inlet  126  of the fluid chamber  120  to measure a fluid pressure from a source, such as the IOP of the patient&#39;s eye  55 . The pressure sensor  170  provides signals to the ASIC  112  representative of a measured fluid pressure. The ASIC  112  adjusts performance of the micropump  110  based on the feedback provided by the pressure sensor  170 . For example, as IOP fluctuates throughout the day, the ASIC  112  may control the micropump  110  to pump relatively greater volumes of fluid during portions of the day when the IOP measured by the pressure sensor  170  is relatively high. By contrast, the ASIC  112  may control the micropump  110  to pump relatively smaller volumes of fluid, or cease pumping altogether, during portions of the day when the IOP measured by the pressure sensor  170  is relatively low. In this manner the pressure sensor  170  and the ASIC  112  function as a pressure controller. For example, the ASIC  112  can be programmed to maintain the IOP, as measured by the pressure sensor  170 , at a desired pressure. 
     The driver assembly  130  includes a rotor spring  139  positioned between the drive shaft  132  and the roller  134 . The spring  139  can be biased to push the roller  134  toward the fluid chamber  120 . In that regard, the spring  139  can regulate the force applied by the roller  134  on the membrane  124  of the fluid chamber  120 . The spring  139  of the rotor  136  may also exhibit a particular amount of travel, thereby adjusting the radius or distance between the roller and the drive shaft  132 . The spring  139  can comprise one or more of a variety of mechanisms to impart a spring force, including compression springs, membranes, magnets, leaf springs, torsion springs, coil springs, or any other suitable type of spring. The spring  139  can provide a number of advantages to the driver assembly  130 . For example, the spring  139  may allow the driver assembly  130  to impart a relatively constant compressing force to the membrane  124  of the fluid chamber  120 , even as the size and/or shape of the components of the driver assembly  130  vary within tolerances. By maintaining a relatively stable compressing force, it can be ensured that an optimal force is consistently applied to create an effective seal between the membrane  124  and the outer ring  122  of the fluid chamber  120 . Accordingly, the longevity of the fluid chamber  120  can be increased because the membrane  124  is not over-stressed. Additionally, maintaining a consistent compressing force can keep friction between the driver assembly  130  and the fluid chamber  120  constant so that the pump consumes less power. Additionally, when residue sticks to an inner surface of the fluid channel  125  within the fluid chamber  120 , the spring  139  can prevent jamming because it allows the rotor  136  to retract to pass over the residue. 
       FIG. 10  depicts another embodiment of the micropump assembly  110  that is used for delivering a pharmaceutical agents to the patient. The micropump assembly  110  includes a reservoir  119  containing the pharmaceutical agent, with the reservoir  119  in communication with the inlet  126  of the fluid chamber  120 . It will be understood that the driver assembly  130  of the embodiment in  FIG. 10  is shown rotating in a counter-clockwise fashion toward the outlet  128 . The outlet can be connected to or otherwise in fluid communication with an anatomical structure of the patient, such as an organ (e.g., the eye) or a tissue. The micropump assembly  110  shown in  FIG. 10  includes a rotary encoder  160  in communication with the ASIC  112  and the motor  114 . The rotary encoder  160  can be used as described above to precisely control the volumetric flow of the pharmaceutical agent into the patient via the outlet  128 . In some embodiments, the motor  114 , rotary encoder  160 , and ASIC  112  are configured to enable microdosing of the pharmaceutical agent with nanoliter precision. 
       FIG. 11  depicts a method  200  of pumping a fluid (e.g., aqueous humor) from a patient&#39;s eye in order to reduce and/or regulate the patient&#39;s intraocular pressure (IOP). One or more steps of the method described can be carried out by a micropump assembly  110  as described above. In step  210 , a motor of a micropump is activated to actuate a pump mechanism comprising a compressing member and a compressible fluid chamber. The motor rotates the compressing member about an axis in a circular motion, with the compressing member compressing a membrane of the fluid chamber against a hard outer ring. The fluid chamber is in communication with the patient&#39;s eye such that the micropump displaces fluid from inside the eye to the exterior of the eye. In step  220 , the motor continues to rotate to pump a quantity of fluid from inside the eye, thereby reducing the IOP. The micropump may be controlled by an ASIC configured to control the output of the motor. The ASIC may control the output of the motor to displace a predetermined amount of fluid from the eye, to pump fluid at a predetermined flow rate, to operate the motor at a rotational speed, or some combination of these parameters. 
     In step  230 , the ASIC receives feedback from a pressure sensor and/or a rotary encoder, and in step  240 , the ASIC adjusts output of the motor based on the received feedback. For example, the feedback from the pressure sensor may include an electrical signal indicating a pressure measurement. The pressure sensor can be in fluid communication with an inlet of the fluid chamber to measure the fluid pressure from a source of the micropump, such as the patient&#39;s eye. The ASIC receives the pressure measurement and adjusts motor output according to a protocol. For example, the ASIC may be configured to execute computer instructions to maintain IOP at a particular pressure. When the pressure sensor measures a pressure that exceeds a threshold, the ASIC controls the motor to pump a particular quantity of fluid from the patient&#39;s eye. If the pressure measurement falls below a threshold, the ASIC does not activate the motor, or decreases the output of the motor. 
     In another example, the ASIC executes instructions to deliver an amount of a pharmaceutical agent to the patient. The ASIC activates the motor to rotate and receives feedback signals from the rotary encoder indicating the rotational position of the motor and compressing member. The ASIC controls the motor to rotate until the rotary encoder indicates that the motor is at a predetermined rotational position corresponding to an amount of pharmaceutical agent delivered to the patient. 
     In another example, the fluid chamber includes a circular portion and a non-circular portion, as described above. When a positive pressure differential is present across the fluid chamber (e.g., when IOP is relatively high), fluid may flow freely through the fluid chamber even without pumping. The motor and compressing member can be used to control the flow rate of fluid by controlling the motor to position the compressing member at a location on the non-circular portion that corresponds to a particular flow rate. To allow fluid to freely flow through the fluid chamber, the ASIC controls the motor to position the compressing member at a location on the non-circular portion at which the fluid chamber is least compressed, or uncompressed. To halt flow of fluid through the fluid chamber, the ASIC controls the motor to position the compressing member at a position along the circular portion of the fluid chamber such that the fluid chamber is fully compressed by the compressing member, thereby restricting flow of fluid through the fluid chamber. 
     In another example, the ASIC can include instructions to periodically pump fluid through the fluid chamber in order to prevent or remove clogs within the fluid chamber. For example, even when the IOP is below a threshold amount, or when a positive pressure gradient exists across the fluid chamber such that fluid is freely flowing without pumping, the ASIC may periodically activate the motor to compress the fluid chamber along its circumference to dislodge build-up of material and remove clogs. 
     It will be understood that various modifications can be made to the embodiments described above without departing from the material of the present disclosure. For example, although an ASIC is described as controlling the operation of the micropump assembly, other components and/or circuitry can be used to control operation of the micropump. For example, the micropump could include analog circuitry configured to control aspects of the micropump. The analog circuitry could function alone, or in combination with one or more microprocessors, field-programmable gate arrays (FPGA&#39;s), or any other appropriate analog or digital circuitry. Additionally, aspects of the different embodiments described above can be combined, even if the combinations are not explicitly shown in the drawings. For example, a micropump assembly can include a drug reservoir  119  as in  FIG. 10  and a pressure sensor as in  FIG. 9 , in some embodiments. In another embodiment, a micropump assembly can include a spring-loaded rotor  136  as in  FIG. 9  along with the drug reservoir  119  shown in  FIG. 10 . Additionally, any of the micropump assemblies described above can include a non-circular fluid chamber, as shown in  FIG. 8 . 
     The ASIC can include one or more processing components and one or more memory components. The ASIC can be configured to execute computer code according to one or more programming protocols. In some example embodiments, one or more of the ASIC functions described above are executed by a computer program written in, for example, C, C Sharp, C++, Arena, HyperText Markup Language (HTML), Cascading Style Sheets (CSS), JavaScript, Extensible Markup Language (XML), asynchronous JavaScript and XML (Ajax), and/or any combination thereof. 
     Persons skilled in the art will recognize that the devices, systems, and methods described above can be modified in various ways not explicitly described or suggested above. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.