Therapeutic sleeve apparatus for reducing lymphedema

Abstract

A therapeutic sleeve apparatus for reducing lymphedema is described. The apparatus comprises a flexible sleeve body adapted to be worn around a limb extremity, an operational layer integrated within the sleeve body, and a plurality of piezoelectric elements disposed within the operational layer. The piezoelectric elements are operable to generate ultrasound waves within a frequency range of 0.9 MHz to 3.2 MHz. A controller regulates the elements in a dual-level regimen, selectively operating at 0.9–1.1 MHz for deeper tissue regions and 2.8–3.2 MHz for superficial tissue regions, and sequencing between these modes during a treatment cycle. The configuration permits therapeutic ultrasound delivery across multiple tissue depths while being embodied in a wearable format suitable for patient use.

Description

Therapeutic Sleeve Apparatus for Reducing LymphedemaField of the Invention

[0001] The disclosure relates generally to medical devices and, more specifically, to wearable therapeutic apparatus configured to reduce lymphedema by delivering controlled ultrasound energy to limb extremities.Background of the Invention

[0002] Lymphedema is a chronic medical condition characterised by the accumulation of lymphatic fluid in tissue, most commonly in the limbs. The condition results from impaired lymphatic drainage, which may occur due to congenital malformation, surgery, radiation therapy, infection, or trauma. Clinical manifestations include swelling, discomfort, and reduced mobility, and if left untreated, secondary complications such as fibrosis and infection may develop. A variety of management strategies are employed, including manual lymphatic drainage by trained professionals, compression garments or bandaging, pneumatic compression pumps, and physical exercise. While such measures can alleviate symptoms, they often require significant clinical input, specialised equipment, or sustained patient compliance.

[0003] A number of technical approaches have been disclosed in prior art documents that aim to provide wearable therapeutic devices. US 2023 / 0181415 A1 (University of Arkansas), published on 15 June 2023, describes a limb-worn apparatus incorporating multiple piezoelectric elements for therapeutic use.

[0004] WO 2023 / 003891 A1 (Carilion Clinic), published on 26 January 2023, discloses a garment or wrap incorporating actuators configured to apply vibratory and compressive stimuli within a frequency range below that typically considered ultrasonic.

[0005] WO 2024 / 013267 A1 (Cortery AB), published on 18 January 2024, describes a general-purpose wearable therapy device comprising an array of ultrasound transducers and associated control electronics.

[0006] KR 20100079448 A (Netblue Co Ltd), published on 8 July 2010, sets out a band-type structure in which piezoelectric components are integrated into a textile substrate and powered by a connected battery.

[0007] US 2022 / 0313547 A1 (Taket LLC), published on 6 October 2022, describes a layered flexible band structure incorporating piezoelectric material and configured to transmit vibratory energy to the user.

[0008] These examples illustrate prior attempts to apply wearable technologies to therapeutic contexts involving fluid management or tissue stimulation. Despite these developments, challenges remain in providing systems that are both technically effective and practical for routine, long-term use by patients outside of specialised clinical environments.

[0009] The present invention seeks to provide a way to overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative. It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.Summary of the Disclosure

[0010] The present disclosure relates to a therapeutic sleeve apparatus configured to reduce lymphedema by delivering controlled ultrasound energy to a limb extremity. The apparatus comprises a flexible sleeve body adapted to be worn around a limb, and an operational layer integrated within the sleeve. The operational layer contains an array of piezoelectric elements operable to generate ultrasound waves across a controlled frequency range. The apparatus further includes a controller configured to drive the piezoelectric elements according to a defined regimen.

[0011] In one implementation, the controller is arranged to operate the piezoelectric elements selectively in two distinct modes corresponding to different frequency ranges. A first mode operates in a lower megahertz range suitable for interacting with deeper tissue regions, while a second mode operates in a higher megahertz range suited to more superficial tissue structures. By switching between these two modeswithin a programmed cycle, the apparatus provides acoustic energy tailored to both deep and superficial levels of tissue in a coordinated manner.

[0012] This approach allows fluid that is present in different tissue depths to be addressed during a single treatment session, ensuring that regions closer to the dermis as well as deeper interstitial areas are both acted upon in turn. The ability to transition between frequency ranges within a unified cycle provides a more comprehensive engagement with the tissue than devices configured to operate in only one band or to deliver only surface-level vibratory stimuli. At the same time, embedding the piezoelectric elements directly into the sleeve ensures consistent acoustic coupling across the limb, while the programmable controller enables precise adjustment of cycle parameters to suit individual therapeutic needs.

[0013] The treatment cycle may begin with operation in the lower frequency range so that deeper interstitial tissues are acted upon first, with a subsequent transition to higher frequencies addressing more superficial tissues. Commencing in this order can ensure that mobilised fluid from deeper regions is encouraged to progress before attention is given to surface-level structures.

[0014] In some configurations, it is preferable for the lower frequency phase to be sustained for a longer interval than the higher frequency phase. By allocating greater duration to the deeper mode, sufficient energy can penetrate into underlying tissue before applying shorter superficial phases.

[0015] In other implementations, the cycle may be programmed to alternate repeatedly between the two frequency ranges within the same session. Alternating in this manner enables both superficial and deeper compartments to be addressed iteratively, which can contribute to a more uniform therapeutic outcome across tissue depths.

[0016] The operational layer may be sandwiched between an inner mesh layer and an outer mesh layer, each formed from a breathable textile. These layers can permit dissipation of heat generated by the piezoelectric array while maintaining acoustic coupling with the skin.

[0017] One of the mesh layers may be formed with a defined porosity to encourage airflow across the operational layer, thereby supporting convective cooling during extended sessions. Alternatively, thermally conductive fibres may be incorporated into the mesh to distribute heat laterally away from localised regions of higher intensity.

[0018] For hygiene and convenience, the inner or outer mesh layer may be attached in a removable fashion. A low-profile fastening system such as hook-and-loop strips can be used to permit the layer to be detached for washing or replacement while leaving the operational layer intact within the sleeve body.

[0019] The controller may be arranged to vary the activation timing of neighbouring piezoelectric elements so as to establish a wavefront travelling longitudinally along the sleeve. By setting the propagation velocity of this wavefront, the device can deliver ultrasound in a directional manner consistent with natural proximal fluid transport.

[0020] In some examples, the activation sequence is not fixed but defined by control instructions received wirelessly. A transceiver coupled to the controller can accept remote input from a handheld device, permitting clinicians or users to adjust propagation timing parameters externally.

[0021] Directionality of wavefront propagation may also be adjustable under software control. The ability to reverse or alter the path of activation can be useful for calibration or for specialised treatment patterns where a bidirectional effect is desirable.

[0022] The piezoelectric elements may be arranged in a distributed matrix across the operational layer. Such a configuration ensures that the limb surface is covered evenly, avoiding local concentration of energy while maintaining uniform contact.

[0023] The sleeve itself can be elasticised so that it conforms to the contour of the limb. Incorporating flexible conductive traces and resilient encapsulation around the piezoelectric elements allows the operational layer to elongate and contract without loss of electrical connectivity or mechanical stability.

[0024] Treatment profiles may be adjusted according to time-of-day settings, recognising that fluid accumulation varies diurnally. Evening cycles, for instance, may be longer or deeper-focused, while morning cycles may be shorter and less intensive.

[0025] Similarly, treatment parameters may be adapted to patient demographic data. Age, body mass, or comorbidities may be used by the controller to adjust output levels, thereby tailoring therapy to patient-specific tolerance.

[0026] Temperature monitoring may be incorporated through sensors positioned near the operational layer, enabling the controller to respond to excessive heating by reducing power or suspending operation.

[0027] Bioimpedance measurement may also be used, where impedance values detected at the limb surface inform the controller of tissue state and allow adjustment of ultrasound frequency or drive characteristics.

[0028] The system may further operate in a pulsed mode, delivering bursts of ultrasound separated by intervals of rest. The duty cycle of pulsed operation may be configurable between wide limits, permitting energy delivery to be balanced against heating considerations.

[0029] The operational layer can be divided into zones, each independently driven. Sequential activation of zones from distal to proximal regions of the limb can establish a controlled progression of therapy along the sleeve.

[0030] Power for the system may be replenished wirelessly via an inductive charging coil integrated into the sleeve, avoiding the need for exposed connectors.

[0031] Operational data may be logged by the controller into memory. Information such as frequency settings, cycle counts and durations can be transmitted wirelessly to external devices for compliance monitoring or clinical review.

[0032] Proper placement of the sleeve may be verified through a contact sensor embedded on its inner surface, preventing activation unless adequate skin contact is confirmed.

[0033] Finally, a maximum continuous treatment period may be enforced in software, with the controller suspending operation once a preset time threshold has been reached to ensure user safety.

[0034] Other aspects of the invention are also disclosed.Brief Description of the Drawings

[0035] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0036] Figure 1 illustrates a block-level system diagram of a therapeutic sleeve apparatus.

[0037] Figure 2 illustrates a flow diagram of an exemplary method of operating the therapeutic sleeve apparatus.Description of Embodiments

[0038] Referring now to Figure 1 , there is shown a therapeutic sleeve apparatus 100 configured for reducing lymphedema. The apparatus 100 includes a sleeve body 101 that is dimensioned to conform around a limb extremity such as a lower leg or arm. The sleeve body 101 is flexible and may be fabricated from an elastic textile composite that permits close contact with the skin while accommodating movement of the underlying musculature.

[0039] Integrated within the sleeve body 101 is an operational layer 102. The operational layer 102 houses a plurality of piezoelectric elements 103, which are configured to generate ultrasound waves when electrically driven. In one embodiment, the piezoelectric elements 103 are lead zirconate titanate (PZT) ceramics encapsulated within a biocompatible polymer matrix. In other embodiments, the elements may comprise polymer-based piezoelectric films, such as polyvinylidene fluoride (PVDF), to enhance flexibility. The distribution and encapsulation of the elements 103 within the operational layer 102 ensures continuous contact with the limb surface for efficient acoustic coupling.

[0040] The piezoelectric elements 103 are electrically coupled to a controller 104, which may comprise a microcontroller unit or a digital signal processor configured with firmware to regulate frequency generation, drive voltage, and duty cycle. The controller 104 is preferably operable to implement a dual-level regimen, selectivelydriving the elements 103 at a first mode frequency in the range of 0.9 MHz to 1.1 MHz and at a second mode frequency in the range of 2.8 MHz to 3.2 MHz. These frequency ranges are chosen to interact with tissue at different depths: the lower range propagates several centimetres into deeper interstitial regions, while the higher range is confined to more superficial layers where lymphatic capillaries are located close to the dermis.

[0041] When operated in the lower frequency range, the ultrasound wavelength of approximately 1.5 to 1.7 millimetres in soft tissue generates microstreaming and oscillatory shear forces within interstitial fluid, reducing stagnation and displacing fluid toward deeper lymphatic collectors. Cyclic mechanical stresses at this depth can also deform the walls of lymphatic vessels, enhancing the contractile activity of lymphangions and improving the opening and closing of their valves, which in turn propels fluid proximally toward regional lymph nodes.

[0042] At the higher frequency of 2.8-3.2 MHz, the ultrasound wavelength shortens to about 0.5 millimetres, concentrating acoustic energy in the upper dermal region. In this zone, oscillatory pressure acts on anchoring filaments that tether lymphatic capillaries to the extracellular matrix, with repeated stretching and relaxation of the filaments increasing the opening of primary endothelial junctions. This facilitates fluid entry into initial lymphatic vessels situated just beneath the dermis, complementing the deeper fluid mobilisation achieved at the lower frequency.

[0043] The controller 104 may sequence the two modes within a treatment cycle, either sequentially or in alternating intervals, so that both deep and superficial tissue layers are acted upon within a single session. In deeper regions, lymphatic vessels are prompted to contract and move fluid proximally, while in superficial layers capillaries are assisted in admitting interstitial fluid into the lymphatic system. The combined regimen reinforces proximal lymphatic flow across multiple tissue levels, providing a coordinated therapeutic effect.

[0044] By integrating the piezoelectric elements 103 within the operational layer 102 of the sleeve body 101 and driving them under precise control of the controller 104, the sleeve apparatus 100 delivers dual-frequency ultrasound tailored to tissue depth.This arrangement provides a wearable therapeutic system capable of repeated use without the need for direct professional intervention.

[0045] In some embodiments, and referring still to Figure 1 , the controller 104 may be configured such that the treatment cycle commences with operation of the piezoelectric elements 103 in the first mode. By initially applying ultrasound in the frequency range of 0.9 MHz to 1.1 MHz, the apparatus 100 may mobilise lymphatic fluid from deeper interstitial tissues and collectors. Following this initial phase, the controller 104 may then switch to the second mode in the frequency range of 2.8 MHz to 3.2 MHz, which may further act upon superficial lymphatic vessels situated nearer to the dermis, thereby complementing the earlier mobilisation of deeper fluid.

[0046] In other embodiments, the treatment cycle may be configured so that the first mode is maintained for a longer duration than the second mode. As the deeper tissue regions generally require more time for acoustic penetration and mobilisation of interstitial fluid, it may be preferable that the controller 104 sustains emission at 0.9- 1.1 MHz for an extended period before applying the shorter high-frequency phase at 2.8-3.2 MHz. The relative durations of each mode can be pre-programmed within the firmware of the controller 104 or adjusted by user input via a remote device as will be described later.

[0047] In yet other embodiments, the controller 104 may be configured to alternate repeatedly between the first mode and the second mode during a single treatment session. By alternating between the 0.9-1.1 MHz range and the 2.8-3.2 MHz range in repeated cycles, lymphatic fluid present in both deeper interstitial tissues and superficial tissues may be progressively mobilised and directed into corresponding lymphatic vessels for proximal drainage. This alternating cycle can be defined by programmable parameters, such as equal or unequal time intervals between modes, and may be tailored to suit patient-specific therapeutic requirements.

[0048] With reference to Figure 1 , in some embodiments the operational layer 102 is positioned between an inner breathable mesh layer 111 and an outer breathable mesh layer 112. The provision of mesh layers 111 , 112 allows the apparatus 100 to maintain effective acoustic coupling between the piezoelectric elements 103 and the skin ofthe user, while also dissipating heat generated during prolonged operation. The breathable construction of layers 111 , 112 may further allow perspiration and moisture to escape, thereby maintaining comfort and preventing degradation of coupling efficiency.

[0049] In certain embodiments, at least one of the mesh layers 111 , 112 may be formed with a defined porosity configured to enhance airflow across the operational layer 102. The porosity may be specified in terms of open area percentage or mesh aperture size, and is preferably selected so as to permit convective airflow while retaining sufficient structural integrity to support the operational layer 102 against the limb surface. Such an arrangement may assist in maintaining the temperature of the operational layer 102 within a safe operating range during repeated cycles of ultrasound emission.

[0050] In alternative embodiments, one or both of the mesh layers 111 , 112 may incorporate thermally conductive fibres. For example, fibres comprising graphite, carbon, or metallic filaments embedded within a polymer matrix may be woven into the mesh to facilitate conduction of heat away from the operational layer 102. The thermally conductive fibres may then disperse heat laterally across the mesh surface before dissipating it into the environment, reducing the risk of localised hotspots overlying the piezoelectric elements 103.

[0051] In further embodiments, at least one of the mesh layers 111 , 112 may be removably attached to the sleeve body 101 , for example using a hook-and-loop fastening system 113. This configuration allows the inner layer 111 or outer layer 112 to be detached for cleaning or replacement, while leaving the operational layer 102 and the piezoelectric elements 103 undisturbed within the sleeve body 101. The use of a hook-and-loop fastening system 113 provides a low-profile attachment mechanism that is flexible, durable under repeated use, and easily manipulated by patients or carers without specialist tools.

[0052] Turning again to Figure 1 , the controller 104 may be configured to vary the activation timing of adjacent piezoelectric elements 103 within the operational layer 102. By staggering the drive signals, the controller 104 can generate a controlledwavefront propagation velocity along the limb. In a preferred arrangement, the wavefront is directed proximally, thereby mimicking the natural peristaltic pumping action of lymphangions and encouraging fluid flow toward regional lymph nodes. The velocity of the wavefront can be set in software, allowing it to be tuned to approximate physiological contraction rates.

[0053] In some cases, the activation timing parameters are not fixed in the apparatus 100 itself but are provided wirelessly. The wireless transceiver 105 may be coupled to the controller 104 and configured to receive control instructions from a remote device, such as a smartphone or tablet. These control instructions can define the timing offsets between neighbouring piezoelectric elements 103, effectively allowing the user or clinician to specify the speed of propagation along the sleeve body 101. This feature enables external tailoring of treatment cycles to individual patient requirements without modifying the embedded firmware of the controller 104.

[0054] The same control logic can also be extended to directionality. The controller 104 may, under user or software command, reverse the order of element activation such that the wavefront is directed distally rather than proximally. Although proximal flow is typically desirable for lymphedema management, the ability to adjust directionality can be useful for calibration, diagnostic testing of the piezoelectric array, or for specialised therapeutic regimes. The option to alternate or switch direction under wireless command offers a degree of programmability that enhances the versatility of the apparatus 100.

[0055] The piezoelectric elements 103 may be arranged in a substantially uniform matrix across the operational layer 102. A grid-like distribution ensures that ultrasound energy is delivered evenly across the surface of the sleeve body 101 , minimising untreated regions and preventing localised concentration of acoustic intensity. The density of the matrix may be defined according to the size of the limb extremity, with closer spacing for smaller sleeves and wider spacing for larger circumferences, so that acoustic coverage is maintained consistently. Electrical interconnections between the elements 103 can be routed via flexible conductive traces 114 integrated into the operational layer 102.

[0056] The sleeve body 101 may be elasticised so that it conforms closely to the contour of the limb. To achieve this, the operational layer 102 may employ resilient encapsulation around each piezoelectric element 103, for instance using silicone elastomer or thermoplastic polyurethane. Such encapsulation provides mechanical isolation between the rigid piezoelectric structures and the surrounding flexible textile, enabling the sleeve 101 to stretch and contract with the wearer’s movements without damaging the elements 103. The conductive traces 114 may be patterned in serpentine or meandered geometries, allowing them to elongate under tensile strain while maintaining electrical continuity. In this way, the apparatus 100 can deliver therapeutic ultrasound effectively while remaining comfortable and durable during extended wear.

[0057] The controller 104 may also be programmed to adapt the treatment cycle according to time-of-day settings. Lymphedema symptoms often vary diurnally, with greater fluid accumulation occurring toward the end of the day due to gravitational effects. To account for this, the firmware of the controller 104 can include a clock function or receive synchronisation signals via the wireless transceiver 105. Using this information, the apparatus 100 may alter operational parameters, for example extending the duration of the first mode at 0.9-1.1 MHz in evening sessions to address deeper tissue accumulation, or reducing session time in the morning when oedema is less pronounced.

[0058] In addition to temporal adjustments, the controller 104 can be configured to tailor treatment intensity based on patient demographic data. Parameters such as age, body mass index, or the presence of comorbid conditions like diabetes or vascular insufficiency may be stored in the control software module 115. These values can be entered during device setup or transmitted from a clinical database. The controller 104 may then select appropriate output limits for the piezoelectric elements 103, for example lowering drive amplitude for elderly patients with fragile tissue or increasing the cycle count for patients with higher limb volume. Such tailoring ensures that the apparatus 100 provides safe and effective treatment across a wide patient population.

[0059] With further reference to Figure 1 , the therapeutic sleeve apparatus 100 may incorporate a range of sensors to ensure safe and adaptive operation. A temperature sensor 108 may be positioned adjacent to the operational layer 102, for example embedded within the encapsulation material surrounding the piezoelectric elements 103. The temperature sensor 108 may comprise a thermistor, resistance temperature detector, or solid-state digital sensor. Its output is monitored continuously by the controller 104 to determine the thermal load generated during operation. If the sensed temperature approaches a preset threshold, the controller 104 can reduce the drive amplitude or suspend emission from the piezoelectric elements 103 until acceptable conditions are restored, thereby preventing overheating of tissue or device components.

[0060] The apparatus 100 may also include a bioimpedance sensor 109 integrated into the sleeve body 101. Electrodes associated with the bioimpedance sensor 109 may be positioned on the inner surface of the sleeve in contact with the skin. By injecting a small alternating current and measuring voltage response, the sensor 109 can estimate tissue impedance, which correlates with fluid content in the underlying limb. The controller 104 may use this information to adapt the drive frequency or treatment cycle parameters in real time. For instance, if elevated impedance values indicate reduced coupling efficiency or changes in tissue fluid levels, the controller 104 can adjust drive settings to maintain consistent acoustic delivery.

[0061] Through the integration of sensors 108 and 109 with the controller 104, the apparatus 100 is able to perform closed-loop control. This arrangement allows the ultrasound emission to be adapted dynamically to tissue conditions, supporting consistent operation across a variety of users and physiological states.

[0062] The controller 104 may be configured to drive the piezoelectric elements 103 in a pulsed rather than continuous mode. In this arrangement, ultrasound bursts are emitted in intervals separated by defined periods of non-operation. Pulsed driving reduces continuous thermal loading on the operational layer 102 and the skin surface, while still achieving effective acoustic stimulation of tissue. The duty cycle, defined as the ratio of active emission time to the total cycle time, may be adjustable withina range from 10% to 90%. Such adjustability enables the clinician or user to select an operating profile appropriate to individual tolerance levels and therapeutic requirements.

[0063] In some configurations, the operational layer 102 may be divided into independently addressable zones, each containing a subset of the piezoelectric elements 103. Electrical separation between the zones can be achieved by arranging discrete drive circuits within the controller 104 and routing connections through the flexible conductive traces 114. This arrangement allows selective activation of zones in a sequence extending from the distal region of the limb toward the proximal region. By energising zones in this order, the apparatus 100 can generate a directed progression of ultrasound-induced fluid mobilisation along the length of the sleeve body 101. Sequential activation may be carried out in conjunction with the wavefront propagation functionality previously described, or as a standalone treatment mode.

[0064] Power for the apparatus 100 may be maintained through an inductive charging coil 107 electrically connected to the power supply 106. The inductive coil 107 allows the rechargeable energy storage within the sleeve body 101 to be replenished without requiring an exposed charging port. In one implementation, the inductive charging coil 107 is embedded within the outer breathable mesh layer 112, permitting the sleeve to be placed onto a charging pad between treatment sessions. This arrangement reduces ingress points for moisture and simplifies handling for patients with reduced dexterity.

[0065] The controller 104 may also be configured to record treatment session data. Parameters such as selected frequencies, mode durations, duty cycles, and number of cycles completed may be stored in a non-volatile memory associated with the control software module 115. Session data may be time-stamped, providing a record of treatment adherence and usage patterns. The wireless transceiver 105 can be used to transmit the stored data to an external computing device, such as a smartphone, clinician terminal, or cloud-based monitoring platform. This functionality allows longterm tracking of therapy without requiring manual logging by the user.

[0066] To ensure proper positioning, the sleeve body 101 may incorporate a contact sensor 110 disposed on its inner surface. The contact sensor 110 may be a capacitive, resistive, or pressure-sensitive switch that confirms when the sleeve is fitted securely to the limb. The controller 104 may be programmed to permit activation of the piezoelectric elements 103 only upon confirmation of adequate contact detected by the sensor 110, thereby preventing operation when the apparatus is loose or incorrectly positioned.

[0067] For safety management, the controller 104 may be further programmed to enforce a maximum continuous treatment duration. A timing function within the controller 104 may suspend operation of the piezoelectric elements 103 once a preset limit, for example 60 minutes, has elapsed. This safeguard prevents excessive exposure and reduces the risk of tissue irritation or user misuse.

[0068] The therapeutic sleeve apparatus 100 may be realised using an elastic textile sleeve body 101 , which may preferably be formed of a nylon-spandex blend to provide flexibility and compression. Integrated within the sleeve body 101 may be an operational layer 102 comprising a flexible printed circuit board (FPCB) substrate fabricated from polyimide. The operational layer 102 may house a plurality of piezoelectric elements 103. In one example, each element 103 may be a lead zirconate titanate (PZT-5A) disc transducer, approximately 10 mm in diameter and 0.5 mm thick, surface-mounted onto the FPCB using conductive epoxy. An array of twenty such elements may be distributed around the circumference of a lower-leg sleeve, arranged in a 4 x 5 matrix to provide uniform coverage.

[0069] Electrical drive to the piezoelectric elements 103 may be provided by the controller 104, which may comprise a Texas Instruments MSP430 microcontroller paired with an ultrasound driver circuit. The driver circuit may include a high- frequency amplifier such as the Analog Devices AD8331 variable gain amplifier, followed by a push-pull output stage that may be built using NXP BSS138 MOSFETs and capable of producing sinusoidal drive voltages up to around 50 Vpp. The controller 104 may be programmed to generate square-wave signals through its timerperipherals, with conversion into sinusoidal waveforms achieved by a digital-to- analog converter and low-pass filter stage.

[0070] For wireless communication, the controller 104 may include a Nordic Semiconductor nRF52840 Bluetooth Low Energy (BLE) module forming the wireless transceiver 105. Such a module may allow bidirectional communication with a smartphone or tablet application, from which treatment parameters such as cycle duration, frequency selection, and propagation timing can be set.

[0071] Power may be supplied by a lithium-polymer (Li-Po) battery 106, for example rated at 7.4 V and 2000 mAh, housed externally in a padded enclosure. The battery may be rechargeable via an inductive charging coil 107, such as a Wurth Elektronik 760308102142 coil operating at 100-205 kHz, used in combination with a Qi-standard receiver IC such as the Texas Instruments BQ51013B. This configuration may allow the device to be recharged wirelessly when placed on a compatible charging pad.

[0072] Thermal monitoring may be provided by a digital temperature sensor 108, such as the Maxim Integrated DS18B20, which may be mounted directly on the FPCB adjacent to the central piezoelectric element 103. The sensor 108 may communicate with the controller 104 via a one-wire interface. Where the sensed temperature exceeds a programmed threshold (for instance 42 °C), the controller 104 may reduce drive amplitude or suspend operation.

[0073] Tissue condition may be monitored using a bioimpedance sensor 109. Two stainless-steel dry electrodes may be integrated into the inner surface of the sleeve body 101 and coupled to an Analog Devices AD5933 impedance converter IC. The AD5933 may inject a small alternating current in the tens of microampere range into the tissue and measure the response, producing impedance values across a sweep of 1 kHz to 100 kHz. These values may be transmitted to the controller 104 via l2C, and the controller may adapt ultrasound drive parameters dynamically in response.

[0074] The inner breathable mesh layer 111 and outer breathable mesh layer 112 may be formed from polyester mesh fabric with a pore size of approximately 1 mm. The outer mesh layer 112 may additionally incorporate woven carbon fibre filaments to conduct heat laterally across the surface. The inner layer 111 may be detachablysecured by hook-and-loop fastener 113 strips stitched along a seam, permitting the layer to be removed for washing or replacement.

[0075] The flexible conductive traces 114 that connect the piezoelectric elements 103 to the controller 104 may be patterned in a serpentine geometry on the FPCB, allowing the operational layer 102 to stretch with the textile sleeve without compromising electrical continuity. Each piezoelectric element 103 may also be encapsulated in medical-grade silicone elastomer, such as Shin-Etsu KE-45, forming resilient pockets that can deform with limb motion.

[0076] A contact sensor 110 may be provided on the inner surface of the sleeve body 101 , for instance a thin-film capacitive touch sensor such as the Azoteq IQS333. The contact sensor 110 may detect when the sleeve 101 is correctly fitted against the limb, with the controller 104 configured to enable ultrasound emission only when the capacitive load measured falls within an acceptable threshold range.

[0077] All subsystems may be coordinated by firmware executing on the controller 104. The firmware may perform a closed-loop algorithm that confirms sleeve placement through the contact sensor 110 before activation, then continuously monitors temperature conditions through the sensor 108, adjusting drive power or halting output if a threshold is exceeded. In parallel, impedance data from the bioimpedance sensor 109 may be assessed to guide adjustments in frequency or duty cycle. Using these inputs, the controller 104 may generate drive signals for the piezoelectric array 103 in accordance with programmed cycles, regulating timing, frequency, and sequencing. Treatment parameters such as frequency, duty cycle, and duration may be logged into non-volatile flash memory for subsequent retrieval. Wireless access through the transceiver 105 may allow these parameters to be updated or exported, enabling remote monitoring and adjustment by a clinician or user.

[0078] Referring now to Figure 2, an exemplary method of using the therapeutic sleeve apparatus 100 for reducing lymphedema is described. This example is provided to illustrate the functionality of the system and should not be considered limiting.

[0079] At the outset of a treatment session, the process begins at step 200, where the user prepares the therapeutic sleeve apparatus 100 by ensuring that it is adequately charged via the inductive charging coil 107. Once charged, the sleeve body 101 is fitted around the lower leg of the patient. At step 201 , the contact sensor 110 located on the inner surface of the sleeve body 101 detects proper placement and confirms that secure skin contact has been achieved. The controller 104 receives this signal and permits activation only after correct fitting is verified.

[0080] At step 202, the controller 104 initialises its operating parameters. These parameters may include the time of day, retrieved either from an internal clock or through wireless synchronisation via the transceiver 105. In this example, the patient has been instructed to conduct treatment in the evening when oedema is most pronounced. The control software module 115 therefore selects a cycle profile optimised for evening use, with extended deep-frequency operation. The patient’s demographic data, previously stored in the system, are also retrieved to tailor treatment intensity according to their age and presence of comorbidities.

[0081] At step 203, the controller 104 drives the piezoelectric elements 103 in the first mode, producing ultrasound at 0.9-1.1 MHz. This frequency penetrates more deeply into the limb tissues, mobilising lymphatic fluid from interstitial compartments and encouraging uptake by deeper lymphatic collectors. The duration of this step may be set longer than subsequent superficial phases to ensure sufficient mobilisation of deeper fluid.

[0082] Once the first mode is complete, the process proceeds to step 204, where the controller 104 switches to the second mode. The piezoelectric elements 103 are driven at 2.8-3.2 MHz, producing ultrasound with shallower penetration that interacts predominantly with the superficial lymphatic capillaries. This mode assists in draining fluid nearer the dermis and complements the prior mobilisation achieved in the first mode.

[0083] At step 205, the controller 104 may optionally alternate between the first and second modes in repeated cycles. This repeated alternation addresses both deep and superficial tissue layers within the same treatment session, progressively directingmobilised fluid into the corresponding lymphatic vessels for proximal transport. The timing of alternation and the relative durations of the two modes can be preprogrammed or adjusted remotely by a clinician using wireless control commands sent through the transceiver 105.

[0084] Step 206 illustrates how the controller 104 can further refine the therapy by varying activation timing between adjacent piezoelectric elements 103 to generate a propagating wavefront along the sleeve body 101. The wavefront is directed proximally to mimic lymphatic peristalsis, thereby reinforcing fluid transport toward regional lymph nodes. The propagation speed may be configured according to physiological contraction rates, for example one to three cycles per minute, to align with natural lymphatic pumping frequencies.

[0085] At step 207, the apparatus 100 continuously monitors sensor outputs during the session. The temperature sensor 108 ensures that the operational layer 102 remains below a preset safety threshold, while the bioimpedance sensor 109 provides data on tissue impedance, allowing the controller 104 to adapt drive parameters dynamically. For instance, if impedance measurements indicate reduced coupling, the controller 104 may increase drive voltage slightly within safe limits to maintain effective acoustic delivery.

[0086] Finally, at step 208, the treatment session is terminated once the programmed cycle length has elapsed, or earlier if the patient initiates termination via the remote control device. The controller 104 logs treatment data, including frequencies used, duty cycles, and overall duration, into its non-volatile memory. The data may then be transmitted via the wireless transceiver 105 to an external computing device for storage or clinical review. The sleeve body 101 can then be removed, and the inner breathable mesh layer 111 detached via hook-and-loop fastening 113 for cleaning if required.

[0087] In this manner, the method of Figure 2 illustrates a specific use case in which the therapeutic sleeve apparatus 100 delivers a dual-frequency regimen to a patient in the evening, mobilising both deep and superficial interstitial fluid, while employingclosed-loop control through sensors 108, 109, safety interlocks from sensor 110, and adaptive sequencing of the piezoelectric elements 103.

[0088] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.

Claims

Claims1. A therapeutic sleeve apparatus for reducing lymphedema, comprising: a sleeve configured to be worn on a limb extremity; an operational layer integrated with the sleeve, the operational layer comprising a plurality of piezoelectric elements operable to generate ultrasound waves in the range of 0.9 MHz to 3.2 MHz; and a controller configured to operate the piezoelectric elements in a dual-level regimen, wherein the controller drives the piezoelectric elements in a first mode at a frequency in the range of 0.9 MHz to 1.1 MHz to enhance drainage of lymphatic fluid associated with deeper lymphatic vessels, and in a second mode at a frequency in the range of 2.8 MHz to 3.2 MHz to enhance drainage of lymphatic fluid associated with superficial lymphatic vessels, and alternates or sequences between the first and second modes within a treatment cycle to promote lymphatic fluid movement toward proximal lymph nodes.

2. The therapeutic sleeve apparatus of claim 1 , wherein the treatment cycle is configured to commence with operation in the first mode to mobilise lymphatic fluid from deeper interstitial tissues, followed by operation in the second mode to promote additional drainage via superficial lymphatic vessels.

3. The therapeutic sleeve apparatus of claim 1 , wherein the treatment cycle is configured such that the duration of operation in the first mode exceeds the duration of operation in the second mode.

4. The therapeutic sleeve apparatus of claim 1 , wherein the treatment cycle is configured to alternate repeatedly between the first mode and the second mode so that lymphatic fluid present in both deeper interstitial tissues and superficial tissues is progressively mobilised and directed into corresponding lymphatic vessels for proximal drainage.

5. The therapeutic sleeve apparatus of claim 1 , wherein the operational layer is disposed between an inner breathable mesh layer and an outer breathable mesh layer, the mesh layers configured to dissipate heat from the operational layer whilst maintaining acoustic coupling with the skin of the user.

6. The therapeutic sleeve apparatus of claim 5, wherein at least one of the mesh layers comprises a mesh structure having a defined porosity configured to enhance airflow across the operational layer to promote convective heat dissipation.

7. The therapeutic sleeve apparatus of claim 5, wherein at least one of the mesh layers comprises thermally conductive fibres configured to conduct heat away from the operational layer.

8. The therapeutic sleeve apparatus of claim 5, wherein at least one of the mesh layers is removably attached to the sleeve by a hook-and-loop fastening system, thereby allowing cleaning or replacement of the mesh layer without removal of the operational layer.

9. The therapeutic sleeve apparatus of claim 1 , wherein the controller is configured to vary activation timing between adjacent piezoelectric elements to set a wavefront propagation velocity along the limb, the wavefront being directed proximally to mimic lymphatic peristalsis.

10. The therapeutic sleeve apparatus of claim 9, further comprising a wireless transceiver configured to receive electronic control instructions from a remote control device, wherein the control instructions define the activation timing between adjacent piezoelectric elements.

11. The therapeutic sleeve apparatus of claim 9, wherein the controller is further operable to adjust the direction of the wavefront propagation.

12. The therapeutic sleeve apparatus of claim 1 , wherein the piezoelectric elements are arranged in a matrix distributed across the operational layer to provide substantially uniform coverage of the sleeve.

13. The therapeutic sleeve apparatus of claim 1 , wherein the sleeve is elasticised to conform to the shape of the limb extremity, the operational layer comprising flexible conductive traces and resilient encapsulation around the piezoelectric elements to allow stretching of the sleeve without electrical or mechanical failure of the piezoelectric elements.

14. The therapeutic sleeve apparatus of claim 1 , wherein the controller is configured to adjust the treatment cycle in response to a time-of-day setting, such that operation parameters are adapted for morning or evening use to address diurnal variation in oedema.

15. The therapeutic sleeve apparatus of claim 1 , wherein the controller is configured to adjust treatment intensity according to patient demographic data including age or comorbid conditions stored in the control software.

16. The therapeutic sleeve apparatus of claim 1 , further comprising at least one temperature sensor disposed adjacent the operational layer, the temperature sensor configured to monitor heat generated by the piezoelectric elements.

17. The therapeutic sleeve apparatus of claim 16, wherein the controller is configured to reduce or suspend power to the piezoelectric elements when the temperature sensor detects a threshold temperature.

18. The therapeutic sleeve apparatus of claim 1 , further comprising at least one bioimpedance sensor configured to measure tissue impedance of the limb during operation.

19. The therapeutic sleeve apparatus of claim 18, wherein the controller is configured to adjust the drive frequency of the piezoelectric elements in response to measured impedance values.

20. The therapeutic sleeve apparatus of claim 1 , wherein the controller is configured to drive the piezoelectric elements in a pulsed mode comprising ultrasound bursts separated by intervals of non-operation.

21. The therapeutic sleeve apparatus of claim 20, wherein the duty cycle of the pulsed mode is adjustable between 10% and 90%.

22. The therapeutic sleeve apparatus of claim 1 , wherein the operational layer is segmented into a plurality of independently addressable zones each comprising a subset of the piezoelectric elements.

23. The therapeutic sleeve apparatus of claim 22, wherein the controller is configured to sequentially activate the independently addressable zones from a distal region of the limb toward a proximal region.

24. The therapeutic sleeve apparatus of claim 1 , further comprising an inductive charging coil electrically connected to the controller and the piezoelectric elements for wireless recharging of the apparatus.

25. The therapeutic sleeve apparatus of claim 1 , wherein the controller is configured to record treatment session data including frequency settings, duration, and number of cycles.

26. The therapeutic sleeve apparatus of claim 25, wherein the wireless transceiver is further configured to transmit the recorded treatment session data to an external computing device.

27. The therapeutic sleeve apparatus of claim 1 , further comprising a contact sensor disposed on an inner surface of the sleeve, the contact sensor configured to detect when the sleeve is properly fitted to the limb.

28. The therapeutic sleeve apparatus of claim 27, wherein the controller is configured to enable operation of the piezoelectric elements only upon confirmation of proper contact detected by the contact sensor.

29. The therapeutic sleeve apparatus of claim 1 , wherein the controller is programmed to enforce a maximum continuous treatment time of less than 60 minutes.

30. A method of reducing lymphedema, comprising fitting a therapeutic sleeve apparatus of claim 1 around a limb extremity and driving the piezoelectric elements at a frequency in the range of 0.9 MHz to 1.1 MHz to act upon deeper interstitial tissues.

31. The method of claim 30, further comprising subsequently driving the piezoelectric elements at a frequency in the range of 2.8 MHz to 3.2 MHz to act upon superficial tissue regions.

32. The method of claim 30, wherein the driving of the piezoelectric elements alternates between the frequencies in repeated cycles, each cycle comprising a first mode in the 0.9-1.1 MHz range and a second mode in the 2.8-3.2 MHz range.

33. The method of claim 30, further comprising varying activation timing between adjacent piezoelectric elements to generate a proximally directed wavefront propagation along the limb.

34. The method of claim 33, further comprising transmitting activation timing parameters wirelessly from a remote control device to the therapeutic sleeve apparatus.

35. The method of claim 30, further comprising recording treatment parameters including frequency settings, cycle duration, and number of cycles, and transmitting the recorded parameters wirelessly to an external computing device.

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