Patent Description:
Microsystems are miniaturized functional systems incorporating microelectromechanical systems (MEMS), microelectronics, and packaging systems. Microsystems often include microfabricated systems (such as one or more sensing and/or actuation elements, controller(s), communication module(s), and power source(s)) disposed within an encapsulating package. Microfabricated systems may be configured to sense, record, and transmit data to an external monitoring system. For example, microsystems can be used in the instance of fluid transportation, storage, and processing to access the structural health and process conditions of pipes, reservoirs, reactor vessels, heat exchangers, and other fluidic infrastructure elements. In such instances, microsystems can provide diagnostic data while minimizing disruption to normal operations, such as commonly experienced during use of conventional devices (i.e., "Smart pigs") that travel within the interior of a pipe to perform cleaning and diagnostic function and generally occupy an entire diameter of the pipeline and are costly and complex to deploy.

Microsystems (e.g., environmental logging microsystems (ELMs)), however, need to be configured to withstand the environmental conditions into which the microsystem is deployed. For example, in the instance of downhole monitoring of wellbores, such as those employed during exploration and production of oil and natural gas, the exterior layer of the microsystem must be unreactive and impervious to the caustic wellbore fluid environment that may include hydrogen sulfide (H<NUM>S), raw natural gases and oils, and/or have high saline concentrations, while also permitting the transfer of pressure, temperature, magnetic, and inertial data to the sensing elements defining the microsystem. Further still, such wellbore environments often have areas subject to pressures up to about <NUM> MPa and temperatures commonly between about <NUM> and <NUM>. The microsystem must be capable of surviving within such environments, while also sensing and recording the environmental conditions with sufficient resolution. Accordingly, it would be desirable to develop autonomous microsystems and methods for operation of such within various environments.

Document <CIT> relates to an untethered apparatus for measuring properties along a subterranean well. According to at least one embodiment, the untethered apparatus includes a housing, and one or more sensors configured to measure data along the subterranean well. The data includes one or more physical, chemical, geological or structural properties in the subterranean well. The untethered apparatus further includes a processor configured to control the one or more sensors measuring the data and to store the measured data, and a transmitter configured to transmit the measured data to a receiver arranged external to the subterranean well. Further, the untethered appratus includes a controller configured to control the buoyancy or the drag of the untethered apparatus to control a position of the untethered apparatus in the subterranean well. The processor includes instructions definining measurement parameters for the one or more sensors of the untethered apparatus within the subterranean well.

Further autonomous microsystems are known form documents <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

In various aspects, the present disclosure provides an example autonomous microsystem for immersion into a fluid according to claim <NUM>. The autonomous microsystem includes electronics, a power source, and a packaging system that surrounds the electronics and the power source. The electronics is configured to sense and record one or more environmental conditions. The packaging system includes a deformable shell that defines an internal space and a plurality of filler particles disposed in the internal space and configured to control a density of the autonomous microsystem in relation to the fluid. The filler particles comprise a low-density material having a bulk density greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>,<NUM>/m<NUM> and have a packing density greater than or equal to about <NUM><NUM>/m<NUM> and less than or equal to about <NUM><NUM>/m<NUM>.

In one aspect, a flexible pouch may also be disposed within the internal space. The flexible pouch may be configured to house the electronics.

In one aspect, the flexible pouch may be filled with a dielectric fluid.

In one aspect, the electronics may include a wireless power transfer circuit that can be configured to receive electrical power wirelessly from an external power source and to supply power to the autonomous microsystem.

In one aspect, each of the deformable shell and the flexible pouch may have a substantially flat surface. The substantially flat surface of the deformable shell may be adjacent to and parallel with the substantially flat surface of the flexible pouch. The wireless power transfer circuit may include a coil that is disposed adjacent to and parallel with the substantially flat surface of the flexible pouch in which it is disposed.

In one aspect, the power source may be a battery, and a relay may be electrically coupled between the wireless power transfer circuit, the battery, and the electronics. The relay may be configured to switch between supplying wireless power or battery power to the electronics.

In one aspect, the battery may be a rechargeable battery, and the relay may be further configured to switch between distributing wireless power between the electronics and the rechargeable battery.

In one aspect, each of the filler particles of the plurality of filler particles are hollow particles may have an average diameter greater than or equal to about <NUM> and less than or equal to about <NUM>.

In one aspect, an epoxy having a bulk density greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>,<NUM>/m<NUM> may also be disposed with the plurality of filler particles in the internal space.

In one aspect, a getter material may also be disposed within the internal space.

In one aspect, the deformable shell may be a non-metallic polymeric shell having a Shore A Hardness between about <NUM> and about <NUM>.

In one aspect, the deformable shell may include first and second halves. The second half may be configured to receive the first half so as to form an enclosed structure that defines the deformable shell.

In one aspect, a structural support may be disposed on an interior-facing surface of the deformable shell adjacent to an overlap of the first and second halves of the deformable shell. The structural support may have a rigidity greater than the deformable shell.

In various aspects, the present disclosure provides another example autonomous microsystem for immersion into a fluid. The autonomous microsystem may include electronics configured to detect and record one or more environmental conditions and a packaging system that surrounds the electronics. The electronics may comprise a wireless power transfer circuit that is configured to receive electrical power wirelessly from an external power source and supply power to the electronics, and a battery that is also configured to supply power to the electronics. The packaging system comprises a deformable polymeric shell that defines an internal space, a flexible pouch disposed within the internal space and configured to house the electronics, and a plurality of hollow filler particles also disposed in the internal space and configured to control a density of the autonomous microsystem in response to the fluid. The deformable polymeric shell may have a first half and a second half. The second half may have a substantially flat surface and may be configured to receive the first half so as to form an enclosed structure that defines the deformable polymeric shell. The flexible pouch may include an insulating oil.

In one aspect, each of the deformable polymeric shell and the flexible pouch may have a substantially flat surface. The substantially flat surface of the deformable polymeric shell may be adjacent to and parallel with the substantially flat surface of the flexible pouch. The wireless power transfer circuit may include a coil that can be disposed adjacent to and parallel with the substantially flat surface of the flexible pouch in which it is disposed.

In one aspect, the power source may be a battery, and a relay may be electrically coupled between the wireless power transfer circuit, the battery, and the electronics. The relay can be configured to switch between supplying wireless power or battery power to the electronics.

In one aspect, the battery may be a rechargeable battery, and the relay can be further configured to switch between distributing wireless power between the electronics and the rechargeable battery.

In one aspect, the plurality of hollow filler particles may be cenospheres having a bulk density greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>,<NUM>/m<NUM> and have a packing density greater than or equal to about <NUM><NUM>/m<NUM> and less than or equal to about <NUM><NUM>/m<NUM>.

In one aspect, at least one of an epoxy having a bulk density greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>,<NUM>/m<NUM> and a getter material may also be disposed with the plurality of filler particles in the internal space.

In one aspect, the deformable polymeric shell may have a Shore A Hardness between about <NUM> and about <NUM>.

The present disclosure relates to small-scale recording devices-microsystems-for immersion into a fluid (for example, oil) and the logging of certain environmental conditions therewithin, such as pressure, temperature, acceleration, and magnetic field. An exemplary illustration of an autonomous microsystem <NUM> for immersion into a fluid and the logging of environmental conditions therewithin is shown in <FIG>. The microsystem <NUM> comprises electronics <NUM>, a power source <NUM>, and a packaging system <NUM> that surrounds and encompasses the electronics <NUM> and the power source <NUM>. The microsystem <NUM> has a system density of less than about <NUM>,<NUM>/m<NUM>. As illustrated, the microsystem <NUM> may have a first dimension (i.e., height) of about <NUM> and a second dimension (i.e., width) of about <NUM>, such that each dimension of the microsystem is less than about <NUM>.

The packaging system <NUM> provides protection to the electronics <NUM> and the power source <NUM> (e.g., chemical and abrasion resistance), while also permitting the transmission of all the sensed environmental parameters, as well as the transfer or transmission of programming parameters, input control commands, and/or sensed data relating to, for example, physical properties (such as, pressure and temperature), as well as electromagnetic signals (such as, magnetic fields for a magnetometer, wireless power transfer fields, and wireless commands for microsystem programming and data transfer). The packaging system <NUM> comprises a deformable shell <NUM> that defines an internal space <NUM> and a plurality of filler particles <NUM> disposed within the internal space <NUM>.

The deformable shell <NUM> may have a material thickness greater than or equal to about <NUM> to less than or equal to about <NUM>, and in certain aspects, optionally about <NUM>. The deformable shell <NUM> may be a non-metallic polymeric shell having sufficient flexibility so as to permit pressure transmission. For example, the deformable shell <NUM> may be a non-metallic polymeric shell having a Shore A Hardness between about <NUM> and about <NUM>. The deformable shell <NUM> can include a high-density polymeric material (e.g., about <NUM>,<NUM>/m<NUM>), which also resists brittleness after long-term heat exposure. For example, in the instance of oil applications, the deformable shell <NUM> may comprise, for example only, one or more fluoro-elastomers (such as VITON® Type A, Type B, or Type F) or perfluoro-elastomers (such as sold by KALREZ®). In other applications, the deformable shell <NUM> may include, for example only, a silicone rubber. Though not illustrated, one or more thin-film coatings may be disposed on one or more surfaces of the deformable shell <NUM>. The thin-film coatings may be used to provide additional modifications to the chemical, mechanical, transport, and electrical properties of the deformable shell <NUM>. For example, a thin-film coating on an interior-facing surface of the deformable shell <NUM> of an impervious material may be used to mitigate gas diffusion through the deformable shell <NUM>. In each instance, the deformable shell <NUM> includes a material that can be manufactured using standard commercial injection molding processes.

In certain instances, as illustrated, the deformable shell <NUM> includes first and second halves 152A, 152B. As best illustrated in <FIG>, the second half 152B may be configured to receive the first half 152A so as to form the enclosed structure that defines the deformable shell <NUM>. Such a two-part deformable shell structure may permit rapid assembly of the autonomous microsystem <NUM>. In certain instances, a sealant <NUM> may be used to seal the interface between the first and second halves of the deformable shell <NUM>. The sealant <NUM> must be capable of maintaining a low profile and withstanding the necessary chemical, thermal, and mechanical stresses imposed by environments in which the microsystem <NUM> may be deployed. In certain variations, the sealant <NUM> may be an epoxy sealant.

A structural support <NUM> may be disposed on or adjacent to an interior-facing surface <NUM> of the deformable shell <NUM>. For example, as illustrated, the structural support <NUM> may be disposed on or adjacent to an overlap or interface of the first and second halves 152A, 152B. The structural support <NUM> has a rigidity greater than the deformable shell <NUM>. The structural support <NUM> may comprise, for example only, one or more high-strength plastics, carbon fibers, ceramics, and/or metal alloys. The structural support <NUM> must be capable of supporting high-pressure environments in which the microsystem <NUM> may be deployed.

The plurality of filler particles <NUM>, for example, as illustrated in <FIG>, are configured to control the density of the microsystem <NUM> of the autonomous microsystem <NUM> in relation to a fluid in which the microsystem <NUM> is immersed. For example, by adjusting the density of the filler particles <NUM> the microsystem <NUM> is able to be designed so as to have a density (i.e., target density) consistent with the intended application-that is, to have density-matched buoyancy, such that the microsystem <NUM> is free-flowing within the submerging fluid. In certain aspects, the filler particles <NUM> are selected such that the microsystem <NUM> has a system density of less than about <NUM>,<NUM>/m<NUM>. For example, the filler particles <NUM> can comprise a low-density material having a bulk density greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>,<NUM>/m<NUM>, and in certain instances, optionally greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>/m<NUM>. The low-density material can also be a high-pressure compatible material, such that the filler particles <NUM> enable the transmission of pressure data by the microsystem <NUM>. For example, the filler particles <NUM> may have a packing density greater than or equal to about <NUM><NUM>/m<NUM> and less than or equal to about <NUM><NUM>/m<NUM>.

The filler particles <NUM> may be hollow particles having an average diameter greater than or equal to about <NUM> µm to less than or equal to about <NUM> µm. For example, the filler particles <NUM> may be cenospheres comprising silica and/or alumina. The miniature diameter and the high packing density of the filler particles <NUM> allow the filler particles <NUM> to transfer pressure. For example, the filler particles <NUM> may collectively act as an incompressible fluid.

An epoxy may be disposed with the filler particles <NUM> within the internal space <NUM>. The epoxy may be a low-density and low-hardness epoxy. For example, the epoxy may have a Shore A Hardness of less than about <NUM>. The epoxy may have a bulk density greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>,<NUM>/m<NUM>. The epoxy may provide further mechanical support to the deformable shell <NUM>, as well as reducing gas retention within the internal space <NUM> that may otherwise cause volume expansion as the exterior pressure and temperature are varied. For example, because the epoxy may adhere to the filler particles <NUM>, the epoxy may reduce displacement between the filler particles <NUM> while maintaining flexibility and pressure transfer capabilities of the filler particles <NUM>. The epoxy may reduce gas retention within the internal space <NUM> by filling interstitial spaces between the filler particles <NUM> such that smaller quantities of gas may become trapped in the package <NUM>.

In further variations, one or more non-evaporable getter materials for gas trapping may be disposed with the filler particles <NUM> (and/or epoxy) within the internal space <NUM>. The one or more getter materials may be alloys of zirconium and/or titanium incorporating iron, magnesium, nickel, and/or vanadium. Such materials may be used for trapping nitrogen, hydrogen, carbon dioxide, and other gases. In certain instances, the epoxy may act as a getter for volatile organic compounds. Less than or equal to about <NUM> gram of the one or more getter material may include in the internal space <NUM> with the filler particles <NUM> (and in certain aspects, epoxy).

In some embodiments, the packaging system <NUM> may further include a flexible pouch <NUM> also disposed within the internal space <NUM>. The flexible pouch <NUM> may be configured to house the electronics <NUM>. In this fashion, the flexible pouch <NUM> may form a barrier between the filler particles <NUM> and the electronics <NUM>. The flexible pouch <NUM> may allow for easy retrieval of the electronics <NUM>, permitting, for example only, rapid iteration and testing, replacement of damaged components, and/or replacement of a damaged exterior package (i.e., deformable shell <NUM> and/or filler particles <NUM>). Like the deformable shell <NUM>, the flexible pouch <NUM> may comprise a non-metallic polymer. The flexible pouch <NUM> may have a Shore A Hardness between about <NUM> and about <NUM>, for example, when the flexible pouch <NUM> includes materials similar to that of the exterior deformable shell <NUM>. The flexible pouch <NUM> may include VITON®, KALREZ®, KAPTON®, and/or nylon. The flexible pouch <NUM> may be filled with a dielectric fluid, such as mineral oil and/or silicone oil, by way of non-limiting example.

The electronics <NUM> are configured to sense and record one or more environmental conditions, such as pressure, temperature, acceleration, and magnetic field. For example, the electronics <NUM> may generally include a printed circuit board <NUM>, and one or more environmental sensors, for example a pressure sensor <NUM> and/or an acoustic sensor (not shown), as well as other sensors as would be recognized by the skilled artisan. As illustrated, an opening <NUM> in the printed circuit board <NUM> may allow the pressure sensor <NUM> to be exposed to the dielectric fluid of the flexible pouch <NUM> and in turn the exterior pressure. Preferably there are no rigid obstructions in the path along which the pressure is transmitted from the exterior of the package <NUM> to a diaphragm of the pressure sensor <NUM>.

The electronics <NUM> may also include a wireless power transfer circuit including a coil <NUM>. As illustrated, the wireless power transfer coil <NUM> may be disposed substantially parallel with the printed circuit board <NUM>. The wireless power transfer circuit is configured to receive electrical power wireless from an external power source (as shown in <FIG>) so as to supply power to the microsystem <NUM>. For example, the wireless power transfer circuit may be used to provide power to the microsystem <NUM> during high-power draw events, such as during device programming and data transfer prior to, or following, remote deployment.

In various instances, the wireless power transfer coil <NUM> may be a receiver coil positioned so as to be aligned with an external power transfer coil (not shown). More specifically, to achieve wireless power transfer, the two coils (e.g., the wireless power transfer coil <NUM> and an external power transfer coil) often need be brought within close proximity so as to become sufficiently coupled. For example, a Qi-certified commercial wireless power transfer standard may be utilized. In such instances, the maximum coil-to-coil separation distance over which such coils can support power transfer is primarily a function of coil size and alignment.

To achieve appropriate alignment, in certain instances, the deformable shell <NUM> (and in certain embodiments, the flexible pouch <NUM> contained therewithin) may have substantially flat surfaces <NUM>, <NUM>. For example, the deformable shell <NUM> may have a substantially flat surface <NUM>, and in embodiments including the flexible pouch <NUM>, the flexible pouch <NUM> may have a substantially flat surface <NUM>. The substantially flat surface <NUM> of the deformable shell <NUM> may be adjacent to and parallel with a substantially flat surface <NUM> of the flexible pouch <NUM>. The wireless power transfer coil <NUM> (and/or the other electronics <NUM>) may be disposed adjacent to and parallel with the substantially flat surface <NUM> of the deformable shell <NUM> and/or the substantially flat surface <NUM> of the flexible pouch <NUM>. The wireless power transfer coil <NUM> may have the largest size permitted by the packaging <NUM>, including the deformable shell <NUM> and/or the flexible pouch <NUM>.

In certain variations, the present disclosure provides various power management systems that are configured to increase an operational lifetime of the microsystem <NUM>, for example by reducing current draw by the power source <NUM> (for example, a rechargeable battery, or in another example, a primary (non-rechargeable) battery). For example, in a first instance, a first power management system may be configured to reduce the power budget of the microsystem <NUM>. In a second instance, a second power management system may be configured to reduce or substantially eliminate current draw from the power source <NUM> during wireless data transfer (as detailed above in the context of the wireless power transfer coil <NUM>).

The microsystem <NUM> may be configured to remain in low power (i.e., "sleep state" or "power-down state") when data is not actively collected. In this low-power state, all components are set to a minimum power consumption mode. Nonetheless, the current draw in this low-power state is not negligible, which can be problematic when primary batteries are used as the power source <NUM>. For example, some analog components cannot be digitally powered down and will continue to draw current. Further still, leakage current and current consumption of most electronic components will increase exponentially with temperature, even in a low-power state.

To reduce power use of the microsystem <NUM> in the low-power state, and especially at elevated temperatures, electronic relays, such as illustrated in <FIG>, are configured to disconnect all non-essential components (e.g., electronic sensors and sensor readout circuitry) from the power source <NUM>. Disconnection of the non-essential components while the microsystem <NUM> is in a low-power state can improve the operational lifetime of the microsystem <NUM>, especially when deployed in environments having elevated temperatures, as well as extending shelf-life when it is difficult to physically disconnect the power source <NUM> from the electronics <NUM>.

The electronic relays can be further configured to disconnect the power source <NUM> for storage and/or to switch the microsystem <NUM> so as to be powered by the wireless power transfer circuitry instead of the battery. The electronic relays can be configured such that switching between power sources does not depended on any active electronics having power or programming. As such, the microsystem <NUM> can still operate using wireless power, even if the power source <NUM> (i.e., battery) has been depleted. If wireless power is not available, the electronic relays can automatically switch to the power source <NUM>.

For example, a circuit schematic of an example relay <NUM> is illustrated in <FIG>. As illustrated, the example relay <NUM> (such as Model ADG819, manufactured by Analog Devices) includes five terminals. Terminal <NUM> may be a relay power terminal. Terminal <NUM> may correspond with an input A. Terminal <NUM> may correspond with an input B. Terminal <NUM> may be a control which controls which input (terminal <NUM> or <NUM>) is passed through to terminal <NUM>, which is an output. For example, when a low logic level is connected to terminal <NUM> ("control"), terminal <NUM> ("input A") is passed, when a high logic level is connected to terminal <NUM> ("control"), terminal <NUM> ("input B") is passed. When the relay is not powered, terminal <NUM> ("output") has a high impedance, effectively creating an open circuit at terminal <NUM> ("output"), passing neither terminal <NUM> ("input A") nor terminal <NUM> ("input B").

In the present instance, the microsystem power source (e.g., battery) <NUM> may be connected to terminal <NUM> ("relay power") and terminal <NUM> ("input A"); the output of the wireless power transfer circuity (e.g., circuitry incorporating the coil <NUM>) may connected to terminal <NUM> ("control") directly and to terminal <NUM> ("output") through a back-current limiting diode; the power bus of the microsystem <NUM> may connected to terminal <NUM> ("output"); and terminal <NUM> ("input B") may be left unconnected. In such instances, the microsystem <NUM> may have three scenarios in which it is receiving power: the first scenario may refer to instances where the battery <NUM> has sufficient charge to power the microsystem <NUM> and wireless power transfer is inactive; the second scenario may refer to instance where the battery <NUM> has sufficient charge to power the microsystem <NUM> and wireless power is active; and the third scenario may refer to instances where the battery <NUM> is depleted and wireless power is active.

In the first scenario, the relay is powered on and terminal <NUM> ("control") is at a logic low, permitting terminal <NUM> ("input A") to pass the battery power from terminal <NUM> ("input A") to terminal <NUM> ("output") and supply the microsystem. In the second scenario, the relay is powered on and terminal <NUM> ("control") is at a logic high, disconnecting the battery from the rest of the circuit and causing the open connection of terminal <NUM> ("input B") to pass to terminal <NUM> ("output"). In this case, the output of the wireless power circuitry will supply the microsystem <NUM>, as it is connected to terminal <NUM> ("output") through the back-current limiting diode, bypassing the relay. In the third scenario, the relay is not powered, causing terminal <NUM> ("output") to be a high impedance port regardless of the logic level on terminal <NUM> ("control"). In this case, the output of the wireless power circuitry will supply the microsystem, as it is connected to terminal <NUM> ("output") through the back-current limiting diode, bypassing the relay.

<FIG> provides a functional diagram of example electronics, communication, and power transfer for microsystem <NUM>. As illustrated, the internal electronics <NUM> may incorporate means for wireless communication, such as Bluetooth Low-Energy Master Control Unit (B-MCU), capacitance-to-digital converter (CDC) or other suitable circuit interface, for example for pressure sensor readouts, and inertial measurement unit (IMU), as well as wireless power transfer circuitry, wireless power transfer coil, and power source, as discussed above. External components may include, as illustrated, a Bluetooth enabled microcomputer for communication with the microsystem <NUM> and a wireless power transfer module.

An example application for microsystem <NUM> is within an oil well borehole. Conventional monitoring devices, such as cable slickline (wireline) devices and methods are relatively costly and risky. The use of free-flowing autonomous microsystems, such as microsystem <NUM>, can eliminate, for example, risks of a gauge or cable becoming stuck or fixed within the well, while also allowing for data collection outside a main channel of the wellbore and permitting measurements to be performed deep within the reservoir. By adjusting the density of the filler particles <NUM> the microsystem <NUM> can be designed so as to have a density (i.e., target density) consistent with the intended application (e.g., effluent of the well)-that is, to have density-matched buoyancy, such that the microsystem <NUM> is free-flowing within the submerging fluid. If the microsystem <NUM> is too light pumping the microsystem <NUM> into the well may be too challenging, and conversely, if the microsystem <NUM> is too heavy retrieving the microsystem <NUM> from the well may be too challenging.

To use a microsystem prepared in accordance with the current technology, such as microsystem <NUM>, within an oil well borehole <NUM>, the microsystem <NUM> may be injected through a kill line <NUM> in a wellhead of a dry tree well <NUM> using a conventional pump <NUM>, such as used for slickline operations, for example as illustrated in <FIG>. The well <NUM> may be stopped for a prescribed time interval so as to allow for static data acquisition. After the static data acquisition period, the well <NUM> may be restarted such that the microsystem <NUM> is transported to the wellhead <NUM> through a well tubing during a production phase. The microsystem <NUM> can then be extracted from the fluid path either at the wellhead level or in a sand trap system <NUM> located, for example, immediately downstream of a choke, for example as illustrated in <FIG>.

In other instances, a microsystem prepared in accordance with the current technology, such as microsystem <NUM>, may be mounted on a wireline/slickline for use within an oil well borehole. For example, a small basket that contains the microsystem <NUM> can be attached to the wireline. Mounting the microsystem <NUM> onto wirelines can add low-cost monitoring capabilities to various operations that may require a wireline/slickline for other reasons.

Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure which is defined by the appended claims.

It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure which is defined by the appended claims.

As used herein, the singular forms "a", "an", and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", "including", and "having", are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

When an element or layer is referred to as being "on", "engaged to", "connected to", or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on", "directly engaged to", "directly connected to", or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.).

Terms such as "first", "second", and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context.

Claim 1:
An autonomous microsystem (<NUM>) for immersion into a fluid, the autonomous microsystem comprising electronics (<NUM>), a power source (<NUM>), and a packaging system (<NUM>) that surrounds the electronics and the power source, wherein the electronics are configured to sense and record one or more environmental conditions, and wherein the packaging system (<NUM>) comprises:
a deformable shell (<NUM>) that defines an internal space (<NUM>); and
a plurality of filler particles (<NUM>) disposed in the internal space and configured to control a density of the autonomous microsystem (<NUM>) in relation to the fluid, wherein the filler particles comprise a low-density material having a bulk density greater than or equal to about <NUM>/m<NUM> and less than or equal to about <NUM>,<NUM>/m<NUM> and have a packing density greater than or equal to about <NUM><NUM>/m<NUM> and less than or equal to about <NUM><NUM>/m<NUM>.