Permanent fluidic magnets for liquid bioelectronics

Abstract

A permanent fluidic magnet device includes a carrier fluid, and a plurality of non-Brownian nanomagnets disposed within the carrier fluid in a three-dimensional (3D) oriented and ramified magnetic (ORM) network structure. The permanent fluidic magnet device can be utilized in a system for detecting biomechanical signals from a subject, for example, cardiac signals, acoustic signals, etc. The permanent fluidic magnet device can also be implemented in a liquid robot system where the permanent fluidic magnet device can be actuated by an external magnetic field.

Description

790482.00546PERMANENT FLUIDIC MAGNETS FOR LIQUID BIOELECTRONICSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on, claims priority to, and incorporates herein by reference in its entirety U.S. Serial No. 63 / 718,289 filed November 8, 2024 and entitled "‘Permanent Fluidic Magnets for Liquid Bioelectronics.”STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under award number R01 CA287326 awarded by the National Institutes of Health. The government has certain rights in the invention.BACKGROUND

[0003] Colloid suspensions of dispersed solid particles in fluids are commonly encountered in both natural materials and industrial products such as blood, cosmetics, and food. As a two-phase system in which one phase is dispersed in the other, the stability of colloidal suspensions is of vital importance and is determined by the competition between particle gravity and Brownian motion, which is a manifestation of the thermal fluctuation in a fluidic system. Gravity pulls particles downwards while Brownian motion tends to scatter them. Ferrofluid is a stable magnetic colloid due to the dominance of Brownian motion over gravity in small particles with a size of ~10 nm. When the particle size increases to the non- Brownian range, ferrofluid loses its stability because the settling effect of gravity overwhelms Brownian motion.

[0004] The Brownian motion in ferrofluids can lead to a quick magnetization relaxation and prohibits permanent magnetism, resulting in a statistically averaged net-zero magnetic orientation over time and volume. On one hand, this creates a dilemma that permanent magnetism and colloidal stability cannot be achieved simultaneously, leading to an unresolved scientific question, i.e., how to minimize Brownian motion to obtain microscopically stable physical orders such as permanent magnetism in a colloidal dispersion. On the other hand, the recent development of soft bioelectronic devices for disease prevention, diagnosis, and treatment presents pressing needs for the creation of an intimate interface between the electronic systems and the dynamically evolving biological tissues for precise physiological measurement. While ultrathin membrane-based soft bioelectronic devices can conform to biological tissue, mechanical mismatches between the solid materials and the biological tissue still existQB\99395764.1 1790482.00546

[0005] It would be desirable to provide a fluid-based material, methods, systems, and devices that overcome the challenges of prior bioelectronics techniques.SUMMARY

[0006] In accordance with an embodiment, a permanent fluidic magnet device includes a carrier fluid and a plurality of non-Brownian nanomagnets disposed within the carrier fluid in a three-dimensional (3D) oriented and ramified magnetic (ORM) network structure.

[0007] In accordance with another embodiment, a system for detecting biomechanical signals from a subject includes a permanent fluidic magnet sensor. The permanent fluidic magnet sensor includes a carrier fluid, and a plurality of non-Brownian nanomagnets disposed within the carrier fluid in a three-dimensional (3D) oriented and ramified magnetic (ORM) netw ork structure. The system can further include a receive coil electronically coupled to the permanent fluidic magnet sensor.

[0008] In accordance with another embodiment, a permanent fluidic magnet based liquid robot system includes at least one permanent fluidic magnet. The at least one permanent fluidic magnet includes a carrier fluid, and a plurality of non-Brownian nanomagnets disposed within the carrier fluid in a three-dimensional (3D) oriented and ramified magnetic (ORM) network structure. The at least one permanent fluidic magnet is configured to be actuated in response to an external magnetic field.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements.

[0010] FIG. 1A is a schematic diagram of a permanent fluidic magnet (PFM) in accordance with an embodiment;

[0011] FIG. IB is an example graph of a hysteresis loop corresponding to the PFM of FIG. 1A in accordance with an embodiment;

[0012] FIG. 2 is a schematic diagram of example components of a PFM in accordance w ith an embodiment;

[0013] FIG. 3 illustrates a method for fabricating a PFM in accordance with an embodiment;

[0014] FIG. 4 illustrates a PFM before magnetization and after magnetization in accordance with an embodiment;

[0015] FIG. 5 is a schematic block diagram of a system for detection of biomechanical signals from a subject using PFM-based liquid bioelectronics positioned externally to a subject in accordance with an embodiment.QB\99395764.1 2790482.00546

[0016] FIGs. 6A-6D illustrate example conformable receive coils in accordance with an embodiment;

[0017] FIGs. 7A and 7B illustrate an example PFM-based liquid cardiac sensor in accordance with an embodiment;

[0018] FIG. 8 illustrates an example PFM-based liquid acoustic sensor positioned on a subject in accordance with an embodiment;

[0019] FIG. 9 illustrates an example PFM-based liquid acoustic sensor positioned on the skin of a subject in accordance with an embodiment;

[0020] FIG. 10 shows a graph of a comparison of an electrical signal of a PFM-based liquid acoustic sensor with an emulsifier and a PFM-based liquid acoustic sensor without an emulsifier in accordance with an embodiment;

[0021] FIG. 11 is a schematic block diagram of a wearable voice recognition system using a PFM-based liquid acoustic sensor in accordance with an embodiment;

[0022] FIG. 12 is a schematic block diagram of a system for detection of biomechanical signals from a subject using injectable PFM-based liquid bioelectronics in accordance with an embodiment;

[0023] FIG. 13 is a schematic block diagram of a PFM-based liquid robot system in accordance with an embodiment; and

[0024] FIG. 14 is a block diagram of an example computer system in accordance with an embodiment.DETAILED DESCRIPTION

[0025] Permanent magnets that generate persistent magnetic fields generally exist in a solid form through the formation of aligned domains within the internal microcrystalline structure. This alignment can be achieved by the higher packing density of atoms or molecules in solid ferromagnetic materials, to enable exchange interaction and high emanant magnetization. Existing magnetic fluids, such as ferrofluids, form chain or column structures under an external magnetic field. Ferrofluids are paramagnetic and lose magnetization once the external magnetic field is removed. This is ascribed to the Brownian motion of magnetic nanoparticles with a size of 10 nm that induce magnetization relaxation. Namely, Brownian motion, which allows microscopically dispersed nanoparticles to be stable in a colloidal suspension, prohibits permanent magnetism in the ferrofluids. This is a long-existent dilemma in the field of materials science.

[0026] The present disclosure describes a permanent fluidic magnet (PFM) in which the Brownian motion is decoupled from the colloidal stability. The disclosed PFMQB\99395764.1 3790482.00546 advantageously has high permanent magnetization, flowability, and reconfigurability. In some embodiments, the stability of the PFM (e.g.. a magnetic colloidal material) can be maintained by using non-Brownian magnetic particles (or nanomagnets) to self-assemble a three-dimensional (3D) oriented and ramified magnetic (ORM) network structure in a carrier fluid to decouple the particle Brownian motion and colloidal stability . The disclosed PFM can have an overall macroscopic permanent magnetism through the alignment of magnetic moments inside the 3D ORM network structure. In some embodiments, the PFM can achieve, for example, a coercivity of 699.91 Oe, a remnant magnetization of 47.06 emu g’1, flowability (e.g., viscosity of 3000 centipoises), a long-term magnetization stability (e.g., being air-stable for more than three months), and reconfigurability. Accordingly, the disclosed PFM can realize the untapped combination of reconfigurability and ferromagnetism in a single material system.

[0027] In some embodiments, the PFM can be configured as an intimate liquid bioelectronics interface that can be directly applied to a surface of a subject, for example a patient or object, or injected into a region of interest in a subject. An injected PFM can be positioned in a target internal to the subject (e.g., in a blood vessel or other organ) or on the surface of a target internal to the subject (e.g., the heart or other organ). A PFM applied to the surface of the subject can be used as a sensor configured to detect biomechanical signals from the subject, for example, in some embodiments, a PFM can be used to detect cardiac signals or acoustic signals. An injectable PFM can also be used as a sensor and configured to detect biomechanical signals from the subject, for example, cardiac signals. In some embodiments, the PFM can be used to provide a controllable (or programmable) liquid robot device and system that can be injected into a region of interest of a subject and to perform, for example, drug delivery, therapeutics, etc. using an external magnetic field. Accordingly, the disclosed PFM can advantageously be used to provide various different types of liquid bioelectronics (both external and injectable) that can utilize the reconfigurable magnetism of the PFM for, for example, wireless monitoring (e.g., a cardiac sensor, an acoustic sensor), minimally invasive procedures (e.g., localized drug delivery, endovascular procedures), etc.

[0028] FIG. 1A is a schematic diagram of a permanent fluidic magnet (PFM) in accordance with an embodiment. The PFM 100 us a liquid material that can include a carrier fluid 102 and a plurality7of magnetic particles (or nanomagnets) 104 mixed with the carrier fluid 102. Accordingly , the PFM 100 mixture is a colloid. The PFM 100 can be achieved by decoupling Brownian motion and stability in magnetic colloidal suspensions, using non-Brownian magnetic particles 104 to construct a three-dimensional (3D) orientedQB\99395764.1 4790482.00546 and ramified magnetic (ORM) network structure within the carrier fluid 102. In FIG. 1A, the magnetic particles 104 are shown in an ORM network structure. The PFM 100 advantageously can have an overall macroscopic permanent magnetism through the alignment of magnetic moments inside the 3D ORM network structure. In some embodiments, a stable magnetic colloidal fluid (e.g., PFM 100) can be created using the non- Brownian magnetic particles to self-assemble in the 3D ORM network structure in the carrier fluid 102, which maintains its structural integrity and therefore oriented magnetic moments for permanent magnetism. FIG. IB is an example graph of a hysteresis loop corresponding to the PFM of FIG. 1A in accordance with an embodiment. The hysteresis loop 106 illustrates the relationship between an applied magnetic field or force (H) and an induced or resulting magnetization or magnetic flux density (B) in the PFM 100. For example, the resulting magnetization (M) can represent a remnant magnetization in the PFM 100 resulting from the application of an impulse magnetic field used in a formation(or fabrication) process for the PFM 100 (including the ORM network structure) as discussed further below with respect to FIG. 3. In some embodiments, the PFM 100 can demonstrate high remanent magnetization (e.g., 47.06 emu g'1), flowability (e.g., viscosity of 3000 centipoises), and ferromagnetism.

[0029] The 3D ORM network structure can enable the PFM from at least three aspects. First, the nanomagnets 104 inside the network structure can be approximated as nanomagnetic dipoles, and adopt a head-to-tail configuration to achieve equilibrium. When the nanomagnets (or magnetic particles) 104 are in a chain with a head-to-tail configuration, the system’s overall potential energy reaches a minimum. At this point, the attractive magnetic dipole-dipole interaction and steric repulsion are balanced, and the equilibrium distance between adjacent nanomagnets 104 can be approximated as De, which is equal to 27 / 6R, where R represents the radius of the nanomagnets. The translational perturbation that occurs to the nanomagnet, such as the nanomagnet deviation from the in-chain state with a horizontal distance th, will be prohibited by the restoring force to prevent the disassembly of the chain structure. As a result, the magnetic moments of the nanomagnets 104 are oriented along the chain direction microscopically, yielding magnetic ordering macroscopically for maintaining permanent magnetism. Secondly, the adoption of non-Brownian nanomagnets (or magnetic particles) 104 with strong coercivity can create a magnetic dipole force that is orders of magnitude higher than the gravity force upon the alignment of nanomagnets in the head-to-tail configuration and formation of the ORM network. This can efficiently mitigate the settling effect of single nanomagnets, with only the gravity of the whole network needing consideration. The 3D ORM network can withstand gravitational collapse throughQB\99395764.1 5790482.00546 compression stretch, and rotation of the network chains. Thirdly, the formed ORM network structure can convey stress, support its buoyant weight, and defy gravity for long-term stability from the network’s poroelasticity. In this way, the adversarial bonding between colloid stability and permanent magnetism can be broken, creating a PFM 100.

[0030] In some embodiments, the carrier fluid 102 can be a material such as, for example, vinyl-terminated silicone fluid or alginate (e.g., 2 wt% ). In some embodiments, the carrier fluid 102 can be a non-aqueous or an aqueous solution. The magnetic particles (or nanomagnets) 104 can be, for example, neodymium-iron-boron (NdFeB) magnetic particles (or nanomagnets), strontium / barium ferrite magnetic particles (or nanomagnets), iron magnetic particles (or nanomagnets), samarium-cobalt (SmCo) magnetic particles (or nanomagnets), iron oxide magnetic particles (or nanomagnets), or their mixture (e.g., two or more different types of magnetic particles). In some embodiments, the magnetic particles (or nanomagnets) can be nanoscale-to-microscale magnetic particles (or nanomagnets), for example, with a diameter of approximately 100 nm to 5 pm. In some embodiments, the carrier fluid 102 can be a higher viscosity fluids (> 2 Pa s) because a higher viscosity carrier fluid can prevent aggregation of the magnetic particles 102. In some embodiments, the PFM 100 can include a low particle concentrations of nanomagnets 104 such as, for example, 4 vol % concentration. In some embodiments, the weight percent of the magnetic particles 104 can vary from 4 vol% to 28 vol% with the carrier fluids 102. In some embodiments, the viscosity of the PFM 100 can increase with higher nanomagnet 104 concentrations.

[0031] FIG. 2 is a schematic diagram of example components of a PFM in accordance with an embodiment. The example PFM 200 is shown in FIG. 2 in the form of a droplet of fluid and consists of the components of a carrier fluid 202 and magnetic particles (or nanomagnets) 204. In this example, the carrier fluid 102 can be a vinyl-terminated silicone fluid. While vinyl -terminated silicone fluid is illustrated in FIG. 2, it should be understood that the carrier fluid can be other types of materials as discussed above The nanomagnets 204 can be, for example, neodymium-iron-boron (NdFeB) nanomagnets. NdFeB can be chosen because it can maintain its magnetization without Neel relaxation, preventing self-demagnetization and favoring the ferromagnetic ordering of magnetic particles in the 3D ORM network. While NeFeB is illustrated in FIG. 2, it should be understood that the nanomagnets 204 can be other ty pes of nanomagnets as discussed above. In some embodiments, to provide enhanced biocompatibility of the PFM 200, a coating 208 such as, for example silicon dioxide (SiO2. Silica) can be applied to the nanomagnets 204 as described further below with respect to FIG.QB\99395764.1 6790482.005463. For example, in some embodiments, a nanolayer of 5 nm can be coated on a outside surface of the nanomagnets 204.

[0032] Returning to FIG. 1 A, in some embodiments, the PFM 100 can maintain its remnant magnetization for periods of time (e.g., stable magnetic field performance over a period of months) even in the absence of an external magnetic field indicating the stability of the ferromagnetism of the PFM. As mentioned, the 3D ORM network structure of the nanomagnets 104 advantageously helps maintains both the ferromagnetism and stability simultaneously. For example, the magnetic particles 104 oriented in the ORM network exhibit macroscopically net magnetization alignment for ferromagnetism and the 3D ORM network binds the particles into chain structures to defy the particle gravity to ensure colloidal stability. In some embodiments, the ORM network structure can be the most energetically favorable configuration for the PFM 100.

[0033] The disclosed PFM 100 advantageously possesses a distinctive characteristic of reconfigurability while still retaining a degree of its permanent magnetism. This feature can arise from the flowability of the carrier fluid 102 and the permanent magnetic orientation of the 3D ORM network. In some embodiments, the PFM 100 can be moved or repositioned using an external magnetic field. For example, in a macroscopic view, a PFM 100 can exhibit various motions and rapid transformation when subjected to an external magnetic field including, for example, merging, separating, and changing shape (e.g., slenderizing forward, changing from a cylinder to a cone shape). At the microscopic view, the 3D ORM network can dynamically reconstruct along with an external magnetic field and reassemble on its own. Accordingly, as mentioned, the disclosed PFM can achieve an untapped combination of reconfigurability and ferromagnetism in a single material system.

[0034] Compared to previous magnetic colloids with chain or column structures, the PFM 100 material system is different in its material composition, formation mechanism, and magnetic properties. Thus, the PFM 100 offers several advantages including the absence of surfactants or the need for two immiscible fluids, faster formation speed, stronger permanent magnetism, and improved stability. The observed macroscopic phenomena of PFM via microscopic magnetic particle interaction could be generically applied to any dipolar and multipolar colloidal systems, as well as other anisotropic physical systems widely encountered in natural and industrial processes.

[0035] Understanding PFM as a self-assembly-induced phase separation phenomenon could provide insights into fundamental questions about phase separation in dipolar and multipolar fluids, and establish a mechanism-driven design framework for self-assembled percolatingQB\99395764.1 7790482.00546 networks with macroscopic physical orders. Furthermore, in the disclosed PFM 100 material system, an untapped combination of reconfigurability and ferromagnetism has been realized through the unique network structure self-disassemble / reassemble mechanism at the microscopic level.

[0036] FIG. 3 illustrates a method for fabricating (forming / formation process) a PFM in accordance with an embodiment. The process illustrated in FIG. 3 is described as being carried out by the system in FIGs. IA and 2, however, in some examples, the process of FIG. 3 may be implemented by another system. Although the blocks of the process of FIG. 3 are illustrated in a particular order, in some embodiments, one or more blocks may be executed in a different order than illustrated in FIG. 3, or may be bypassed.

[0037] At block 302, a plurality of magnetic particles (or nanomagnets) 104 are retrieved from storage, for example, a plastic jar. In some embodiments, the nanomagnets 104 are non- Brownian nanomagnets. In one example, the nanomagnets can be neodymium-iron-boron (NdFeB) nanomagnets and can have a diameter of approximately 100 nm. At block 304, a coating 208 can be applied to the outer surfaces of the nanomagnets (or magnetic particles) 104. In one example, the nanomagnets can be coated with a layer (e.g., a nanolayer or nanoshell layer) of silicon dioxide ( SiCh). In some embodiments, the coating can be applied through the hydrolysis and polycondensation of tetraethyl orthosilicate. The coating, e.g., SiCh, can be configured to, for example, enhance the biocompatibility of nanomagnets 104. In some embodiments, the coating layer on the nanomagnets can have a 5 nm layer thickness.

[0038] At block 306, the nanomagnets (or magnetic particles) 104 can be mixed with a carrier fluid 102 (e.g., forming a colloid). In some embodiments, the carrier fluid 102 can be, for example, alginate or a silicone fluid such as, for example, vinyl-terminated silicone fluid. In some embodiments, the earner fluid 102 can have a concentration of 2-5 wt.%. In some embodiments, the carrier fluid 102 can be non-aqueous or aqueous solutions. In some embodiments, the weight percent of the nanomagnets (e.g. NdFeB magnetic particles) can vary7from 4 vol% to 28 vol% with the carrier fluids. As mentioned, the carrier fluid 102 can be, for example, a higher viscosity fluids (> 2 Pa s) because a higher viscosity carrier fluid can prevent aggregation of the nanomagnets 104. Carrier fluids 102 with higher viscosity can help limit the diffusion length of the nanomagnets 104 during the magnetic-fi eld-guided selfassembly (discussed further below with respect to block 310), which promotes the formation of the 3D ORM network structure. In addition, a higher viscosity can increase the kinetic barrier of the nanomagnets 104 within the ORM network structure, hindering the motion ofQB\99395764.1 8790482.00546 the nanomagnets 104 in response to hydrodynamic interactions and thereby improving the stability of the PFM 100 system.

[0039] At block 308, once the nanomagnets 104 are mixed with the carrier fluid 102 (e.g., to firm a magnetic colloid), a dispersion process can be performed on the mixture of the nanomagnets 104 and the carrier fluid 102. In some embodiments, the dispersion process can be a sonication (e.g., ultrasonication) dispersion performed using, for example, an ultrasonic homogenizer. For example, the nanomagnets 104 can be subjected to a sonication dispersion using an ultrasonic homogenizer operating at a power of 550 W for three hours. Ultrasonication can prevent particle aggregation and evenly (or uniformly) disperse the nanomagnets 104 in a state of equilibrium. Accordingly, the dispersion process (e.g., ultrasonication) can be used to uniformly disperse the nonmagnets 104 in the carrier fluid 102 in a state of equilibrium.

[0040] At block 310, the mixture (e.g., colloid) of nanomagnets 104 and the carrier fluid 102 can then be magnetized to form the PFM (i.e., the nanomagnets 104 in the carrier fluid 102 can be magnetized), and in particular, to arrange the nanomagnets 104 and form a 3D ORM network structure of the nanomagnets 104 within the carrier fluid 102. In some embodiments, the formed 3D ORM network can uniformly span over the entire colloid. In some embodiments, the mixture can be magnetized by applying impulse magnetic fields (or a pulse magnetization field) using, for example, an impulse magnetizer. In one example, the impulse magnetic fields can range from 0.05 to 2.65 T. FIG. 4 illustrates an example of an arrangement 410 of nanomagnets 404 in a carrier fluid 402 before magnetization with the impulse magnetic fields and the arrangement 412 of the nanomagnets 404 in the carrier fluid 402 after magnetization with the impulse magnetic fields. In response to the impulse magnetic field, the microstructures of the colloids (e.g., the mixture of the carrier fluid 402 and nanomagnets 402) can undergo a transformation from an evenly dispersed state 410 to a 3D ORM network 412 as the magnetic field is increased. An increase in the impulse magnetic fields and magnetic concentration can increase the likelihood of forming the 3D ORM network without sedimentation.

[0041] Returning to block 310 of FIG. 3, with an increasing impulse magnetic field, a parabolic increase of the macroscopic magnetic ordering in the nanomagnet 104 and carrier fluid 102 mixture can be observed. The onset of the significant increase of the macroscopic magnetic ordering can correspond to a critical magnetic field Bc, which is a formation criteria of the 3D ORM network in the carrier fluid 102. Accordingly, the critical magnetic field Bccan be defined as a magnetic field of the impulse magnetic field required for the formation ofQB\99395764.1 9790482.00546 the 3D ORM network and the PFM. In some embodiments, the critical magnetic field Be can vary based on the concentration of nanomagnets 104 in the carrier fluid 102. In one example, the critical magnetic field Bccan decrease with increasing volume concentration of nanomagnets 104.

[0042] In a PFM system, there are two main contributions to the total free energy: the dipolar interaction energy EdiPand the entropic contribution of the hard-sphere fluids Es. The scale of dipolar interaction energy Edip in the PFM system can be given by:where m is the magnetic moment of each nanomagnet, d is the diameter of the nanomagnet, / r0is the vacuum permeability, and N is the number of nanomagnets in the system. The scale of entropic energy Es in the PFM system can be described by a lattice gas model as below:Es- M x [<pln<p + 1 — <p)ln l — p)]kBT (2) where p is the volume concentration of the freely movable nanomagnets, M is the total available sites in the PFM, kBis the Boltzmann constant, and T is the temperature. The increase of the magnetostatic energy drives the PFM formation process, competing with the decrease of the entropic energy. When the PFM forms, the dipolar interaction energy EdiPdominates over the entropic energy Es. Balancing the dipolar interaction and the entropic energy gives the critical magnetic moment of the nanomagnets:Eliminating all the constants, replacing N / M with p. and linking the applied magnetic flux density with m through the B oc m gives the following relationship for critical magnetic field Bc:

[0043] In one example, under a magnetization of 0. 1 T, no evident orientation was observed in an example mixture of a carrier fluid 102 and nanomagnets 104. However, in this example, upon increasing the magnetization to 0.2 T, clusters began to form in the cross-section areas. With further external magnetization of 0.5 T, a greater degree of orientation became apparent. Notably, under a magnetization of 1.5 T, the clusters grew and interconnected in branch-like patterns, forming a well-defined 3D ORM network structure. With further external magnetization of 0.5 T, a greater degree of orientation became apparent. Notably, under a magnetization of 1.5 T, the clusters grew and interconnected in branch-like patterns, forming a well-defined 3D ORM network structure.QB\99395764.1 10790482.00546

[0044] As mentioned, the stable 3D ORM structure of the PFM is achieved through magnetic interactions among the nanomagnets 104. The material stability is achieved by the rigidity of the 3D network structure. This structure retains its magnetization even after the external magnetic field is removed. At block 312, the PFM can be stored, for example, by placing or maintaining the material within a glass container.

[0045] The disclosed PFM can differ from conventional ferromagnetic liquid droplets (FMLD) in a number of different aspects. First, the materials usage and materials science in the disclosed PFM systems are different from those of the FMLD systems. For example, the disclosed PFM systems use nanoscale-to-microscale hard permanent magnetic particles (e.g. , NdFeB, - 100 nm to 5 pm) or their mixture with soft permanent magnetic particles (e.g., iron particles. 100 nm to 5 pm) to construct the PFM, whereas FMLD adopts iron oxide (FesOi. -20 nm). The permanent magnetic particles (e.g., NdFeB nanomagnets) of the PFM retain their permanent magnetism in the nanoscale. However, the iron oxide becomes superparamagnetic, rendering ferrofluid a paramagnetic material. In some FMLD, the iron oxide nanoparticles are coated with a layer of surfactant (oleic acid, - 4 nm) whereas the nanomagnets in the PFM can be coated with, for example, a silica nanolayer. In terms of carrier fluids, as mentioned PFM can use various carrier fluids including non-aqueous and aqueous solutions, as long as the viscosity requirement is met. In contrast, FMLD has used water-based ferrofluids. A prerequisite for the formation of FMLD is the usage of amine- modified polyhedral oligomeric silsesquioxane(POSS- NH2) in toluene solution, which can assemble and become anchored onto the iron oxidenanoparticles at the oil-water interface to induce interface jamming.

[0046] Second, the formation mechanism of the disclosed PFM is distinct from that of FMLD. FMLD relies on the interfacial assembly and jamming of paramagnetic iron oxide at the interface between an aqueous phase containing functionalized nanoparticles (NPs) and a toluene solution with functionalized ligands. This interfacial jamming restricts the translation and rotational degree of the freedom of the NPs and enhances the magnetic dipole interactions between adjacent NPs by increasing the packing density. This jamming phenomenon can be considered as a liquid-to-glass transition, which generates a two- dimensional layer of NPs on the curved surface and produces a remanent magnetization of the droplet. On the contrary, the disclosed PFM is created through the construction of a three- dimensional (3D) ORM network structure inside the carrier fluid. The particle Brownian motion and colloidal s tabi 1 ity in condensed matter are decoupled to create the PFM systemsQB\99395764.1 11790482.00546 with high permanent magnetization, flowability, and reconfigurability'. The 3D ORM network structure can span the entire 3D volume of a PFM droplet, not just the surface, and generates a remnant magnetization along a certain direction while maintaining the gravitational stability of the droplet through the poroelasticity of the 3D ORM network structure. The formation of the 3D ORM network can be considered as a directional strong flocculation based on magnetic dipole interaction. Instead of utilizing dense packing to restrict the random movement of the surface NPs as in FMLD, strong interparticle magnetic interactions can be employed to restrict the movement of nanomagnets in the PFM. To ensure the formation of a loose network structure rather than a dense aggregate (as seen in pure deionized water), an appropriate viscosity of the carrier fluid can be selected to tune the kinetics, such as the diffusion length of the nanomagnets during the self-assembly process. In this way, in some embodiments the disclosed PFM can be considered a special type of volumetric jamming, rather than the surface jamming observed in the FMLD. This property can endow an elastic modulus that resists droplet deformation and indefinitely locks in the shape of the droplet.

[0047] Third, the properties of the disclosed PFM significantly differ from those of FMLD, due to the distinct formation mechanisms. One notable difference lies in the formation timescale. The formation of FMLD occurs within a time range of minutes, varying from a few to several hundred minutes, which is limited by the interfacial magnetic NP-surfactants assembly process. On the contrary, the disclosed PFM can be formulated within seconds upon an external impulsed magnetic field as described above. The disclosed PFM also can display enhanced magnetic properties compared to FMLD. The remanence of the disclosed PFM, for example, can reach up to 47.06 emug’1, approximately four times of magnitude higher than that of the FMLD. Similarly, the coercivity of the disclosed PFM can reach, for example, 699.91 Oe. 7.7 times higher than the value obtained in FMLD. These results indicate that the disclosed PFM possesses stronger permanent magnetism than the FMLD, which can be attributed to the higher utilization efficiency of the magnetic nanoparticles. In the disclosed PFM, the entire ensemble of dispersed nanomagnets contributes to the magnetism, as opposed to FMLD. where only a densely packed surface layer participates. Moreover, the disclosed PFM demonstrates better stability under an external magnetic field compared to the FMLD. Studies have shown that an external magnetic field of less than 20 mT can be utilized to manipulate the physical orientation of FMLD. However, exceeding this threshold may cause the magnetization of individual magnetic NP-surfactants to switch, potentially resulting in instability and disassembly of the FMLD. The disclosed PFM can be capable of being manipulated by higher external magnetic fields, for example, up to 69 mT.QB\99395764.1 12790482.00546

[0048] Fourth, the applications of the disclosed PFMs significantly differ from those of FMLD systems. Since PFM shows better stability and flexibility than FMLD, it can be suitable for a wide range of applications. In one example, as discussed further below, the disclosed PFM can be used as a liquid biosensor that utilizes reconfigurable magnetism to wirelessly quantify cardiovascular functions in a self-powered manner. In other examples, PFM can be employed in liquid-based robotics, high-precision magnetic sensors, and tissue engineering applications within the human body. In contrast, FMLD has limitations in performing complex tasks as it relies solely on the interface between two distinct liquid media. Thus, the application of FMLD is limited to operating exclusively within liquid interfaces.

[0049] The disclosed PFM is fundamentally different from FMLD in terms of materials, formation mechanism, associated magnetic properties, and applications. Compared to the FMLD, the disclosed PFM offers several advantages including the absence of surfactants or the need for two immiscible fluids, faster formation speed, stronger permanent magnetism, and improved stability .

[0050] As mentioned, the disclosed PFM can be used for various different applications including for liquid bioelectronics. Advantageously, the disclosed PFM possesses the ability to maintain its permanent magnetism during shape reconfiguration, and its magnetic field can penetrate human tissues. In some embodiments, the PFM 100 can be used as a sensor for detecting biomechanical signals (e.g., cardiac signals, acoustic signals). In some embodiments, the PFM can be used for liquid based robotics, for example, for localized drug delivery or therapeutics / In some embodiments, the PFM can be used for tissue engineering applications where it could be used to initiate cell differentiation for neural cell regeneration and align collagen fibers. For example, by incorporating PFM into microfluidic devices, it may become possible to grow and regenerate blood vessels, cartilage, and nerve tissue.

[0051] FIG. 5 is a schematic block diagram of a system for detection of biomechanical signals from a subject using PFM-based liquid bioelectronics positioned externally to a subject in accordance with an embodiment. The system 500 can include a PFM 502, a receive coil 508, a controller 510, data storage 512, and a display 514. The PFM 502 can be the PFM described above with respect to FIGs. 1A-4. As discussed, the PFM 502 can include a carrier fluid and a plurality of non-Brownian nanomagnets within the carrier fluid in a 3D ORM network structure. The PFM 502 can be applied to an external surface 506 of a subject 504, for example, to the skin of a patient. A receive coil 508 can be positioned in proximity to the PFM 502. In some embodiments, the receive coil 508 is a confirmable coil that can be placed on the external surface 506 of the subject 504, for example, on the skin of the patient. ForQB\99395764.1 13790482.00546 example, in some embodiments, the receive coil may be incorporated into a material or patch that may be placed on and removably adhere to the surface 506 of the subject 504. In some embodiments, the receive coil 508 can be positioned near or next to the PFM 502. In some embodiments, the receive coil 508 may be positioned such that it surrounds the PFM 502. For example, if the receive coil 508 is incorporated into a patch, the patch may have an opening that can receive the PFM 502 (e.g., a droplet of the PFM) and allow the PFM to be positioned on the surface 506 of the subject 504. The receive coil 508 can be in communication with the controller 510 using, for example, a wired or wireless connection. FIGs. 6A-6D illustrate example conformable receive coils in accordance with an embodiment. In some embodiments, the conformable receive coil can be in the form of a patch that can be applied to the external surface of the subject. For example, FIG, 6A illustrates a conformable coil 602 that has a round shape and includes a receive coil 610 and FIG. 6B illustrates a conformable coil 604 that has aa rectangular shape and includes a receive coil 610. In some embodiments, the conformable coils 602, 604 can include an antenna 612 that can be used to communicate electrical signals wirelessly to. for example, a controller (e.g.. controller 510 shown in FIG. 5). As mentioned, in some embodiments, a conformable coil can be configured to be positioned around a PFM on a surface of a subject. FIG. 6C illustrates a conformable coil 602 that has a round shape and includes a receive coil 610, an antenna 612, and an opening 614 configured to receive a PFM 616 so that the PFM can be in contact with the surface of the subject. FIG. 6B illustrates a conformable coil 604 that has aa rectangular shape and includes a receive coil 610, an antenna 612, and an opening 614 configured to receive a PFM 616 so that the PFM can be in contact with the surface of the subject. While round and rectangular shapes are illustrated in FIGs. 6A -6D, it should be understood that a conformable coil can have other shapes configured to be received on the external surface 506 of the subject 504.

[0052] Returning to FIG. 5, when the PFM 502 is exposed to pressure generated by biomechanical signals (e.g., associated with an organ such as the heart, liver, lung, etc.) from the subject, the PFM 502 can undergo a deformation that generates magnetic field fluctuations of the PFM ’s 502 permanent magnetic field. The receive coil 508 can detect the magnetic field fluctuations (e.g., via electromagnetic induction) and generate electrical signals that can be provided to the controller 510. As mentioned, the electrical signals generated by the receive coil 508 can be communicated to the controller 510 via a wired or wireless connection. The controller 510 can be configured to process the electrical signals received from the receive coil 508. For example, the controller 510 can store the electrical signals in data storage 512 or display the electrical signals on a display 514. In someQB\99395764.1 14790482.00546 embodiments, the controller 510 can convert the received electrical signals into a selected measurement format depending on the type of biomechanical signals from the subject that are being detected and monitored. In some embodiments, the biomechanical signals can be quantified. After a measurement is complete, the PFM 502 can be easily removed from the surface 506 of the subject 504).

[0053] In some embodiment, the controller 510 may be any general -purpose computing system or device, such as a personal computer, workstation, cellular phone, smartphone, laptop, tablet, or the like. As such, the controller 510 may include any suitable hardware and components designed or capable of carrying out a variety of processing and control tasks, including steps for receiving and processing electrical signals from the receive coil 508. For example, the controller 520 may include a programmable processor or combination of programmable processors, such as central processing units (CPUs), graphics processing units (GPUs), and the like. In some implementations, the controller 510 may be configured to execute instructions stored in a non-transitory computer readable-media. In this regard, the controller 510 may be any device or system designed to integrate a variety of software, hardware, capabilities and functionalities. Alternatively, and by way of particular configurations and programming, the controller 510 may be a special -purpose system or device. For instance, such special-purpose system or device may include one or more dedicated processing units or modules that may be configured (e.g., hardwired, or preprogrammed) to carry out steps, in accordance with aspects of the present disclosure. In some embodiments, controller 510 can be a computer system such as computer system 1400 described below with respect to FIG. 14.

[0054] In some embodiments, the PFM 510 can be used as a liquid cardiac sensor for cardiac monitoring. Cardiovascular diseases (CVDs) have been the leading cause of premature death, causing tens of millions of deaths each year. Despite its high prevalence, the detection of CVDs has posed significant challenges: frequently, symptoms remain unnoticed or misdiagnosed as significantly less severe conditions, thereby greatly increasing the risk of a cardiac episode. To prevent the onset of the life-threatening effects of CVDs, early monitoring of cardiovascular health through the examination of biomarkers is the first line of defense. Traditionally, heart rate and blood pressure are measured through equipment such as cardiac ultrasound, electrocardiograms, sphygmomanometers, and invasive arterial monitoring, however, these methods are not convenient as they produce only point-in-time measurements and require complicated setups.QB\99395764.1 15790482.00546

[0055] Unlike traditional in-office monitoring, ambulatory monitoring allows continuous assessment of cardiac activity over an extended period. Uninterrupted monitoring provides a more comprehensive picture of a patient’s cardiac health status, capturing any irregularities of abnormalities that may occur intermittently or during daily activities. Thus, recent wearable bioelectronics such as resistive, piezoelectric, magnetoelastic, triboelectric, capacitive mechanism-based sensors, and photoplethysmography (PPG) have shown great potential in non-invasive and continuous detection of human physiological signals such as blood pressure and heart rate. However, many of these sensors rely on solid materials for sensing, which tend to be rigid and fail to conform well with the surface of various tissues like skin. This issue is usually circumvented by either applying an external pressure to tightly adhere sensors to the skin surface or by introducing structural and mechanical alterations to match the skin’s surface geometry. However, these approaches can result in signal disruptions due to interfacial issues between the solid devices and the dynamic skin surface. Therefore, there is a significant demand for monitoring techniques that offer continuous, accurate, stable, and accessible cardiac evaluation.

[0056] In some embodiments, the PFM 502 can advantageously be used as an ultrasensitive liquid cardiac sensor for wearable pulse wave monitoring. For example, the biomechanical signals detected by the PFM 502 can be pulse waves. Human pulse waves result from the rhythmic expansion and contraction of arteries through the passage of blood and can be readily detected at various points throughout the body. Biomarkers obtained from human pulse waves provide crucial insight into hemodynamic parameters such as cardiovascular pulse waves and stroke volume. The PFM 502 is capable of adapting to dynamic biological tissues, and facilitating ambulatory cardiac monitoring unhindered by motion artifacts or interference from other biological activities. Advantageously, the PFM 502 can be applied to the surface 506 of the subject 504, e.g., the skin of the subject 504, and can form a seamless interface to the wrinkles and creases on the skin surface. When applied to, for example, the wrist of the subject 504, for pulse wave measurement with a conformal soft coil 508, the PFM 502 liquid bioelectronics can yield a stable electrical output even during biomechanical movement, enabling highly sensitive and precise monitoring of cardiovascular systems with mitigated motion artifacts. This superior performance of PFM-based soft bioelectronics can be attributed to the unique integration of flow ability and magnetic functionality inherent to the PFM 502 material. PFM is flowable, allowing it to fill the hierarchical creases and wrinkles, and conform to the complex geometry of skin surfaces. In addition, despite undergoing shape changes during the interface fillingQB\99395764.1 16790482.00546 process, the magnetization of PFM remains intact, enabling the sensing functionality. PFM 502 can readapt to the newly generated wrinkles and grooves and, therefore, accommodate the skin’s dynamic surfaces during biomechanical movement benefiting from its reconfigurability.

[0057] FIGs. 7A and 7B illustrate an example PFM-based liquid cardiac sensor in accordance with an embodiment. In FIGs. 7 A and 7B. a PFM 702 (e.g.. a droplet of PFM) can be applied to the skin 706 of a subject, for example, on the wrist for pulse wave measurement. The skin’s surface 706 is characterized by a complex topography with various contours, curves, and irregularities, such as wrinkles, grooves, and creases, which are present at rest and become more pronounced during biomechanical movement. Conventional solid materials fail to adequately adapt their geometry to match these skin contours, which could result in noticeable air gaps, leading to noise, low-accuracy measurement, and even electrical spikes. A liquid PFM 702 is reconfigurable and can easily adapt to the skin 706 contours automatically without the need of external pressure. This reconfigurability allows the PFM 702 to conform well to the wrinkled skin surface 706 for accurate measurement.

[0058] In FIG. 7A, a conformable receive coil 704 can be positioned around the PFM 702. The PFM 702 can detect biomechanical movement (e.g., pulse waves) from, for example, a blood vessel 708 beneath the skin 706 surface. The biomechanical signals (e.g., pulse waves) can cause magnetic field (or flux) variation in the PFM 702 magnetic field (e.g., when pressure from the pulse waves causes a deformation of the PFM 702). To obtain electrical signals from the PFM, the receive coil 704 can detect the magnetic field variations from the PFM 702 and generate electrical signals. The receive coils can then provide the electrical signals to a controller (e.g., controller 510 shown in FIG. 5). The controller 50 can, for example, record the electrical signals, perform further processing on the electrical signals, and detect the presence of abnormalities in the electrical signals (e.g., a pulse wave signal). After measurement, in some embodiments, the PFM 702 can be easily removed from the skin 706 of the subject, for example, the PFM 702 can be wiped from the skin 706 of the subject and / or rinsed with water.

[0059] The liquid cardiac sensor 702 can provide stable signals. In some embodiments, the measurements provided by the PFM 702 can be combined with electrocardiogram (ECG) measurements from the subject to provide a comprehensive evaluation of the cardiovascular health status of the subject. In some embodiments, the PFM 702 can accurately capture the pulse wave at the same frequency as an ECG. The ECG can recordQB\99395764.1 17790482.00546 the electrical signals of the heart beating, while the PFM liquid sensor 702 can record the pulse wave containing information of changes in blood flow caused by the heart pumping.

[0060] Returning to FIG. 5, in some embodiments, the PFM 510 can be used as a liquid acoustic sensor. Acoustic waves are an essential component of natural systems, allowing for efficient communication and exchange of information such as the role of voice and language in our society. The rapid advancement of artificial intelligence (Al) is renovating our lifestyles in meaningful and fundamental ways, and the cornerstone of such transformation is the robust and accurate communication between humans and machines. The current humanmachine interaction relies primarily on human gestures, which are challenged by the limited vocabulary and low communication efficiency. However, the ultimate goal of Al is to be comparable with the natural intelligence (e.g., consciousness and emotionality) displayed by humans, which lies beyond the current capabilities of gesture-enabled human-machine interaction. Voices could convey emotional information during communication, using voices to interact with machines could be a compelling approach to realizing a ubiquitous and natural mode of communication between humans and machines. Attaching an acoustic sensor directly to the throat allows for immediate capturing of vocal cord vibrations. However, conventional wearable acoustic sensors for voice recognition are ty pically composed of solid materials such as piezoelectric ceramic, polymer thin film, metal, graphene, etc. These sensors operate based on the materials deformation or vibrations induced by sound pressure. The wide-range adoption of these sensors is largely shadowed by poor skin conformability', limited sensitivity', narrow pressure detection range, and instability' against motion artifacts.

[0061] Motion artifacts can cause fluctuations or distortions in the signals measured by wearable sensors. This leads to inaccurate data, potentially affecting the reliability of measurements for physical signals and missing detecting important events due to signal interference. Moreover, mitigating motion artifacts often requires complex signal processing algorithms, which can increase computational demands and power consumption, potentially impacting battery’ life and overall device performance. The high acoustic impedance and nonconformal contact between the solid sensor materials and the curved skin surface render unavoidable mechanical mismatches, causing limited SNR and low-frequency motion artifacts.

[0062] In some embodiments, the PFM 502 can advantageously be used as an ultrasensitive liquid acoustic sensor for wearable acoustic measurements and. for example, voice recognition. Advantageously, the PFM 802 (e.g., PFM 502 shown in FIG. 5) can be a dilatantQB\99395764.1 18790482.00546 fluid that exhibits an increased viscosity in response to increasing shear rate which allows it to respond to high-frequency signals such as acoustic voice. The PFM 502 can advantageously mitigate the motion artifacts better than solid acoustic sensors, and it holds distinct advantages in offering high quality signals. The PFM 502 can possess a mechanical stiffness of 100-1000 Pa that is approximately three orders of magnitude lower than conventional solid acoustic sensors. The PFM 502 can also eliminate the non-conformal acoustic coupling, demonstrating an acoustic impedance that is ~11 times lower (1.61 Mrayls vs 40 Mrayls) than conventional solid acoustic sensors. This property can ensure the high- fidelity transmission of voice signals while reducing information loss. In addition, the PFM 502 can provide in-sensor noise filtering capability since the PFM holds tunable rheological properties that can selectively dampen mechanical noise below 30 Hz to ensure high-quality signals due to the high rate of viscous deformation. The developed liquid acoustic sensors hold several advantages over conventional solid acoustic sensors, including, for example, the discrimination of subtle pressures of 0.9 Pa, high signal-to-noise ratio (SNR) (69.1 dB vs 18.4 dB), improved frequency detection resolution of 0.001 Hz, and a large frequency response range of 30 Hz- 10 kHz.

[0063] The PFM 502 implemented as a liquid acoustic sensor can attach to an external surface 506 of the subject 504, for example, the skin on the throat of the subject. FIG. 8 illustrates an example liquid acoustic sensor positioned on a subject in accordance with an embodiment. In FIG. 8, a PFM 802 (e.g., PFM 502 in FIG. 5) is shown positioned on the throat of a subject 810. In addition, a conformal receive coil 804 is also applied to the throat of the subject 810. As discussed above, in some embodiments, the receive coil 510 can be placed in proximity to the PFM 802, for example, next to the PFM 802 as shown in FIG. 8 or the receive coil 810 can be positioned around the PFM 802 (e.g., as discussed above with respect to FIGs. 6C and 6D). In other embodiments, a liquid acoustic sensor can be formed by injecting the PFM 802 into a conductive coil structure (e.g., a helix coil) which can be provided with a thin membrane on one side of the surface ff the sensor and the other side of the sensor can be attached to the skin of the subject in a conformal manner. In such embodiments, the conformal receive coil 804 can be placed on the skin of the subject in proximity to the sensor. When exposed to acoustic pressure 806, the PFM 802 undergoes deformation in response to the subtle throat vibrations, which can convert the sound pressure 806 into magnetic field fluctuations through the PFM's displacement relative to the throat. Subsequently, the receive coil 804 can detect the magnetic field variations and generate electrical signals through magnetic induction according to Faraday’s law. Accordingly, theQB\99395764.1 19790482.00546PFM-based liquid acoustic sensor can efficiently convert subtle sound pressure into high fidelity electrical signals for self-powered acoustic sensing. As mentioned, in some embodiments, the receive coil 804 (e.g., receive coil 508 shown in FIG. 5) can communication or transmit the electrical signals over a wired (not shown) or wireless 808 connection.

[0064] The high sensitivity of the PFM 802 can be at least partially ascribed to its better skin conformability, namely, the PFM 802 used as a liquid acoustic sensor can provide conformable contact with the curves skin of the subject 810. FIG. 9 illustrates an example PFM-based liquid acoustic sensor positioned on the skin of a subject in accordance with an embodiment. In FIG. 9, a PFM 902 that include a carrier fluid 904 and a plurality of nanomagnets 906 is positioned on a surface 910 of the skin 908 of a subject. As illustrated in FIG. 9, the conformability of the PFM 902 prevents air gaps from forming between the PFM 902 and the skin surface 910. An acoustic wave 912 can pass through the skin and apply pressure to the PFM 902 through a transmitted acoustic wave 914. The PFM 902 can lower the acoustic impedance mismatches between the human body (e.g., the surface 910 of the kin 908) and the PFM 902, minimize the reflections, and promote the transmission 914 of the acoustic waves.

[0065] Returning to FIG. 5, as mentioned, another feature of the PFM 502 is its adjustable and adaptable rheological properties which can enable self-filtering and mitigate or dampen noise (e.g.. mechanical noise below 30 Hz). In some embodiments, the feature of adjustable rheological properties can, for example, enable the modification and optimization of the PFM’s frequency detection range to naturally occurring human voice w aves. The PFM-based liquid acoustic sensor can, for example, allow for the effective extraction of clean sound pressure signals through the mitigation of low-frequency motion artifacts. In some embodiments, the deformability of the ORM in the PFM 502, manifested as the variation of macroscopic magnetic flux density, is frequency -dependent and can be tuned by the shearthinning or shear-thickening additives. This feature can be utilized to design liquid acoustic sensors capable of filtering out specific frequencies or ranges

[0066] In some embodiments, the tunable rheological properties of the PFM 502 can be enabled by modifying the PFM 502 with an emulsifier, for example, diethylene glycol (DEG). The emulsifier can create a shear thickening property' which can tend to form temporary' clusters, which in turn can increase the flowing resistance and raise the viscosity' of the PFM 502 fluid. With an increase in the added emulsifier (e.g., DEG), the PFM 502 can exhibit a more pronounced viscoelastic behavior with an increase in shear stress.QB\99395764.1 20790482.00546Accordingly, in some embodiments, the rheological behavior of the PFM 502 can be controlled and modified by adjusting the magnetization along with the concentration of emulsifiers. A PFM 502 with DEG can provide improved responsiveness to high-rate frequency signals, making it effective in mitigating low-frequency motion artifacts for acoustic sensing. For example, noises emanating from human bodily activities typically fall within a low-frequency range (-0.5-10 Hz), such as respiration, heartbeats, and gait. The tunable rheology of the PFM 502 can allow for efficient transduction of the acoustic energy into applicable signals at higher frequencies (>30 Hz) which can enable accurate capture and conversion of the acoustic waves into high-fidelity electrical signals for sensing, effectively filtering the low-frequency noise signals in a self-administration manner.

[0067] The addition of an emulsifier to the PFM 502 can also enable the mitigation of low- frequency motions artifacts for acoustic sensing. FIG. 10 shows a graph of s comparison of an electrical signal 1008 of a PFM-based liquid acoustic sensor with an emulsifier (e.g., DEG) and an electrical signal 1006 of a PFM-based liquid acoustic sensor without an emulsifier. The graph 1000 illustrates the frequency 1002 vs the output electrical sign 1004. The electrical signal 1008 of the PFM-based liquid acoustic sensor with the emulsifier exhibits a lower amplitude compared to the electrical signal 1006 of the PFM-based liquid acoustic sensor without the emulsifier. This indicates the effective mitigation of motion artifacts by the presence of an emulsifier in the PFM-based liquid acoustic sensor. With the presence of motion artifacts caused by movement of, for example, the neck, the PFM-based liquid acoustic sensor with an emulsifier can exhibit stable performance even in the presence of such interferences.

[0068] As mentioned, in some embodiments, the PFM-based liquid acoustic sensor can be used in a voice recognition system, for example, a wearable voice recognition system that can be configured to control a controllable device using voice signals. FIG. 1 1 is a schematic block diagram of a wearable voice recognition system using a PFM-based liquid acoustic sensor in accordance with an embodiment. The system 1100 can include a liquid acoustic sensor 1102, a controller 1104 and a controllable device 1106. The liquid acoustic sensor 11032 can include a PFM 1108 (e.g., PFM 502 shown in FIG. 5), a conformable receive coil 1 110 (e.g., receive coil 508 shown in FIG. 5), and one or more amplifiers 1112. As described above, with respect to FIG. 5-10, the PFM 1108 and receive coil 1110 can be positioned on a surface (e.g., the skin on the throat) of the subject (e.g., subject 504 shown in FIG. 5 and subject 810 shown in FIG. 8). The PFM 1108 can detect acoustic signals generate by the subject which can produce magnetic field fluctuations in the magnetic field of the PFM 11 10.QB\99395764.1 21790482.00546The receive coil 1110 can detect the magnetic field fluctuations and generate electrical signals. The electrical signals can be analog signal and the amplifier(s) 1112 can be configured to improve the quality of the analog electrical signals generated by the receive coil 1110.

[0069] The electrical signals can then be communicated (e.g., by a wired or wireless connection) to the controller 1104. The controller 1104 can include an analog to digital converter (ADC) 1114, a trained machine learning model 1116. and one or more command signals 1118. The ADC 1114 can be configured to collect the electrical signals receive from the liquid acoustic sensor 1102 and convert the analog electrical sound signals to digital sound signals. The digital sound signal scan then be provided to the trained machine learning model 1116. The machine learning model 1116 can be trained to recognize the sound signals acquired from the liquid acoustic sensor 1 102 and generate one or more command signals 1118. In some embodiments, the trained machine learning model can be trained for signal feature extraction and automatic recognition of voice signals. The machine learning model 1116 can be, for example, a convolutional neural network and can be trained with training data using known methods and techniques. In some embodiments, the training data can include a plurality of voice commands that are repeated for a redetermined number of iteration to create a set of training samples. In one example, the voice commands can include: “go”, “stop”, “left”, “right”, and “back”.

[0070] The generated command signa(s) 1118 can then be provided to the controllable device 1 106. The controllable device 1 106 can be, for example, an electronic device, or a mobile device such as, for example, a device configured to transport a subject. In some embodiments, the controllable device 1108 can be a motorized wheelchair. The controllable device 1106 can include one or more digital to analog converters (DACs) 1120 and one or more controlled features 1122. In some embodiments, a separate DAC can be provided for each controllable feature 1122. For example, for a motorized wheelchair, a DAC 1120 can be coupled to a front / back movement joystick input of the motorized wheelchair and one DAC 1120 can be coupled to a stop movement joystick input of the motorized wheelchair. A DAC 1120 can convert a command signal 1118 to an analog command signal and the analog command signals can be used to control corresponding actions of the controlled device 1106. In an example where the controllable device is a motorized wheelchair, the voice recognition system 1100 can allow a user to move around independently and reduce social exclusion and marginalization. The wearable voice recognition system 1100 can facilitate timely control ofQB\99395764.1 22790482.00546 the wheelchair's movement through voice commands, making it particularly beneficial for individuals with physical disabilities.

[0071] In some embodiments, the controller 1 104 may be any general -purpose computing system or device, such as a personal computer, workstation, cellular phone, smartphone, laptop, tablet, or the like. As such, the controller 1104 may include any suitable hardware and components designed or capable of carrying out a variety of processing and control tasks, including steps for receiving and processing electrical signals from the receive coil 1110, and generating command signals 1118 for a controllable device 1106. For example, the controller 1104 may include a programmable processor or combination of programmable processors, such as central processing units (CPUs), graphics processing units (GPUs), and the like. In some implementations, the controller 1104 may be configured to execute instructions stored in a non-transitory computer readable-media. In this regard, the controller 1104 may be any device or system designed to integrate a variety of software, hardware, capabilities and functionalities. Alternatively, and by way of particular configurations and programming, the controller 1104 may be a special-purpose system or device. For instance, such specialpurpose system or device may include one or more dedicated processing units or modules that may be configured (e g., hardwired, or pre-programmed) to cany7out steps, in accordance with aspects of the present disclosure. In some embodiments, controller 1104 can be a computer system such as computer system 1400 described below with respect to FIG. 14.

[0072] FIG. 12 is a schematic block diagram of a system for detection of biomechanical signals from a subject using injectable PFM-based liquid bioelectronics in accordance with an embodiment. The different geometries that can be achieved with the reconfigurability of the PFM 1202 can enable localized mechanical measurements within the internal environment of a subject's body and enable the formation of a conformable biological interface for monitoring the biomechanical motions of, for example, inner organs (e.g., the heart, liver, lung, etc.). The system 1200 can include a PFM 1202, a receive coil 1208, a controller 1210, data storage 1212, and a display 1214. The PFM 1202 can be the PFM described above with respect to FIGs. 1 A-4. As discussed, the PFM 1202 can include a carrier fluid and a plurality of non-Brownian nanomagnets within the carrier fluid in a 3D ORM network structure. The PFM 1202 can be injected into a region of interest of a subject 1204, for example, proximate to a target 1216. In some embodiments, the target 1216 can be anatomy of the subject such as an organ, tissue, or blood vessel. Accordingly, the PFM 1202 can be used for physiological measurements. In some embodiments, the PFM 1202 can be positioned on a surface 1218 of the target 1216. Advantageously, the liquid PFM 1202 can be applied to targets 1216 withQB\99395764.1 23790482.00546 different moduli and irregular geometries. In some embodiments, a shape and magnetization distribution for the PFM 1202 can be determined based on the target 1216 (e.g., the specific organ, tissue, etc.) and the target surface 1218 (e.g., a contact angle of the target surface 1216). In some embodiments, the shape of the injected volume of the PFM 1202 can be controlled to control the shape of the PFM 1202.

[0073] In some embodiments, to inject the PFM 1202 into the region of interest proximate to the target, an incision can be made in the subject 1204 and a light-equipped endoscope can be inserted and used to locate the target 1216. The PFM 1202 (e.g., a droplet of PFM 1202) can then be injected onto or proximate to the target 1216 using a needle or syringe, for example a minimally invasive needle or syringe. In one example, for cardiac monitoring, the PFM 1202 can be injected onto the cardiac pericardium surfaces. Advantageously, the reconfigurability and ferromagnetism properties of the PFM 1202 can enable the PFM 1202 to maintain its functional magnetism during the injection process. In some embodiments, the size of the needle or syringe, e.g., the diameter, can be based on, for example, the concentration of the PFM 1202.

[0074] A receive coil 1208, e.g.. a confirmable receive coil, can be placed on an external surface 1206 of the subject 1204, for example, on the skin of the subject. For example, in some embodiments, the receive coil 1208 may be incorporated into a material or patch that may be placed on and removably adhere to the surface 1206 of the subject 1204, for example, as discussed above with respect to FIGs. 6A and 6B. In some embodiments, the receive coil 1208 can be positioned in an area over the location of the injected PFM 1202 in the subject. For example, the receive coil 1208 can be positioned on the surface 1206 of the subject 1204 so that it is a predetermined distance or within a predetermined range of distances from the injected PFM 1202. The receive coil 1208 can be in communication with the controller 1210 using, for example, a wired or wireless connection.

[0075] When the PFM 1202 is exposed to pressure generated by biomechanical signals from the subject 1204, the PFM 1202 can undergo a deformation that generates magnetic field fluctuations of the PFM ‘s 1202 permanent magnetic field. The receive coil 1208 can detect the magnetic field fluctuations (e.g., via electromagnetic induction) and generate electrical signals that can be provided to the controller 1210. As mentioned, the electrical signals generated by the receive coil 1208 can be communicated to the controller 1210 via a wired or wireless connection. The controller 1210 can be configured to process the electrical signals received from the receive coil 1208. For example, the controller 1210 can store the electrical signals in data storage 1212 or display the electrical signals on a display 1214. In some embodiments, the controller 1210 can convert the receive electrical signals into a selectedQB\99395764.1 24790482.00546 measurement format depending on the type of biomechanical signals from the subject that are being detected and monitored. In an example, the electrical signals received from the receive coil 1208 can be used to monitor and interpret the local biomechanics (e.g., motion) of the target 1216. After a measurement is complete, the PFM 1202 can be removed from the subject 1204. For example, after acquiring electrical signals, the PFM 1202 can be retrieved from the target 1216 in the subject 1204 using a needle.

[0076] In some embodiment, the controller 1210 may be any general-purpose computing system or device, such as a personal computer, workstation, cellular phone, smartphone, laptop, tablet, or the like. As such, the controller 1210 may include any suitable hardware and components designed or capable of carrying out a variety of processing and control tasks, including steps for receiving and processing electrical signals from the receive coil 1208. For example, the controller 1210 may include a programmable processor or combination of programmable processors, such as central processing units (CPUs), graphics processing units (GPUs), and the like. In some implementations, the controller 1210 may be configured to execute instructions stored in a non-transitory computer readable-media. In this regard, the controller 1210 may be any device or system designed to integrate a variety of software, hardware, capabilities and functionalities. Alternatively, and by way of particular configurations and programming, the controller 1210 may be a special-purpose system or device. For instance, such special-purpose system or device may include one or more dedicated processing units or modules that may be configured (e.g., hardwired, or preprogrammed) to carry out steps, in accordance with aspects of the present disclosure. In some embodiments, controller 1210 can be a computer system such as computer system 1400 described below with respect to FIG. 14.

[0077] As mentioned, in some embodiments, the PFM 1202 can be used as an injectable and retrievable liquid sensor for detection and quantification of biomechanical signals or motions of organs such as, for example, the heart, liver, lung, etc. As discussed above with respect to FIG. 5-10, the PFM 1202 can be modified to include an emulsifier to mitigate motion artifacts. Accordingly, the biomechanical activities of organs such as, for example, the heart, lung, and liver can be precisely monitored by the injectable PFM-based liquid sensor without the influence of artifacts caused by, for example, body movements.

[0078] In some embodiments, the injectable PFM 1202 can be used for arrhythmia monitoring. Ventricular fibrillation, an erratic and disorganized firing of impulses from ventricles, is the most common life-threatening arrhythmia and is often asymptomatic. Current implantable bioelectronics directly attached to the surface of a heart can accuratelyQB\99395764.1 25790482.00546 monitor arrhythmias but face central challenges due to poor interface to the anatomical heart surface and the need for thoracotomy implantation surgery. Therefore, the PFM-based liquid bioelectronics can be advantageous to monitor the arrhythmias during, for example, arrhythmia treatment, coronary artery bypass graft surgery, and coronary stent implantation to significantly reduce the patient’s unexpected death during surgery7and improve the surgical success rate.

[0079] Compared to implantable solid-state devices, PFM-based liquid bioelectronics (e.g., a sensor) possess several advantages. First, the PFM 1202 can enable minimally invasive and safe operation, since the PFM 1202 is injectable and retrievable through, for example, a small needle or syringe due to its reconfigurable and transformable properties. In contrast, traumatic open-heart implantation surgery is required for traditional implantable devices. Second, the electrical signals generated by PFM 1202 from the inner body of a subject 1204 can be in a self-powered working manner, which can be wirelessly collected by a conformal coil 1208. This configuration eliminates the need for the implantation of rigid and bulky electronic components for signal processing, transmission, and power supply inside the human body. Therefore, PFM-based liquid bioelectronics (e.g., a sensor) have several unique capabilities: (1) it overcomes the challenge of intimate interfaces in solid bioelectronics through an unconventional liquid-biological interface; (2) it could be minimally invasive; (3) it can be injectable and recyclable through aneedle or syringe with good adaptability to different biological tissues; (4) it can wirelessly transmit the magnetic field variation in a self- powered working fashion; and (5) it has a higher SNR (57 dB) than solid electronics (21 dB) to monitor subtle biomechanical activities. These advancements can enable PFM-based liquid bioelectronics to obtain more accurate and richer physiological information than conventional solid counterparts.

[0080] In some embodiments, PFM (e.g., the PFM 100 described above with respect to FIGs. above with respect to FIGs. 1 A-4 can be utilized in conjunction with an external magnetic field to enable anew degree of liquid-based robotics, wireless liquid drug delivery, and other magnetic field-assisted applications inside a subject’s body. Soft robotics has unlocked new possibilities in adaptability, and bioinspired functionality, but a fundamental limitation remains: the lack of tunable mechanical stiffness for task-specific performance. The disclosed PFM can be used to create a new class of stiffness-programmable liquid robots, capable of dynamically modulating their rigidity on demand while maintaining a fluidic architecture. By integrating PFM. a stimuli-responsive material with phase-change elements, and magnetic actuation and control, these PFM-based robots’ can transition seamlessly between soft,QB\99395764.1 26790482.00546 flowable states and rigid, load-bearing configurations. This enables the PFM-based liquid robots to adapt to a wide range of functions, including, for example, flowing through narrow channels, reshaping themselves to conform to surfaces, and stiffening to grasp, lift, or manipulate drugs. The disclosed PFM-based liquid robots can provide untethered locomotion, reconfigurable shape morphing, and adaptive grasping across diverse environments, including constrained and submerged spaces. The disclosed PFM-based programmable stiffness robots can enable multimodal functionality and enhanced versatility for applications in biomedical devices, and soft-bodied robotics.

[0081] FIG. 13 is a schematic block diagram of a PFM-based liquid robot system in accordance with an embodiment. The system 1300 can include a PFM-based liquid robot 1302, a controller 1310, a display 1314, a magnetic field generator 1320 and an imaging system 1324. The PFM-based liquid robot 1302 can be a PFM such as, for example, the PFM described above with respect to FIGs. 1A-4. As discussed, the PFM 1302 can include a carrier fluid and a plurality of non-Brownian nanomagnets within the carrier fluid in a 3D ORM network structure. While FIG. 13 illustrate one PFM (or liquid robot) 1302 in a subject, it should be understood that in some embodiments, a plurality of PFMs 1302 can be injected into a region of interest of the subject 1304. One or more PFM 1302 can be injected into the region of interest of a subject 1304, for example, proximate to a target. In some embodiments, the target can be anatomy of the subject such as an organ, tissue, or blood vessel. In some embodiments, the PFM 1302 can be positioned on a surface of the target. Advantageously, the liquid PFM 1302 can be applied to targets 1316 with different moduli and irregular geometries.

[0082] In some embodiments, to inject the PFM 1302 into the region of interest of the subject 1304, an incision can be made in the subject 1304 and a light-equipped endoscope can be inserted and used to locate the region of interest. The PFM 1302 (e.g., a droplet of PFM 1302) can then be injected into the region of interest using a needle or syringe, for example a minimally invasive needle or syringe. Advantageously, the reconfigurability7and ferromagnetism properties of the PFM 1302 can enable the PFM 1202 to maintain its functional magnetism during the injection process. In some embodiments, the size of the needle or syringe, e g., the diameter, can be based on, for example, the concentration of the PFM 1302.

[0083] The magnetic field generator 1320 can be configured to apply a magnetic field 1322 to the PFM 1302 to actuate and control the PFM 1302 to perform certain functions or tasks. The magnetic field generator 1320 can be couped to the controller 1310. In some embodiments, the controller 1310 can provide control signals or instructions to the magneticQB\99395764.1 27790482.00546 field generator 1320 to control the parameters of the applied magnetic field 1322 based on the desired actions for the PFM 1302. In some embodiments, an increased nanomagnet concentration in the PFM 1302 can enhance the PFMs response to the external magnetic field 1322. An imaging system 1324 can be used to monitor and track the motion and actions of the PFM 1302 or a plurality of PFMs 1302. The imaging system 1324 can be, for example, a fluoroscopy system that can acquire images of the subject 1304 and the PFM 1302 in real time. In some embodiments, the imaging system 1324 can be coupled to a display 1314 to display the acquired images of the PFM 1302.

[0084] As mentioned, magnetic fields 1322 with different parameters, for example, field strength and direction, can be applied to actuate and control the PFM 1302. The external magnetic field 1322 can generate attractive and repulsive forces on the PFM(s) 1302 (e.g., the liquid robots). In one example, when subjected to a rotating magnetic field 1322, the nanomagnets within the PFM 1302 align and the PFM 1302 (i.e., the liquid robot) rotates. In some embodiments, the PFM 132 can deform and orient according to the field lines of the applied magnetic field 1322. Both elastic and viscous responses of the PFM 1302 can be tuned in real time by adjusting the external magnetic field 1322, thus enabling adaptive stiffness behavior. In some embodiments, an internal stiffness of the PFM 1302 can be tuned by adjusting an alignment angle 0 between the nanomagnets (i.e., the magnetic particles). In some embodiments, the applied magnetic field 1302 can be configured to cause the PFM 1302 to split into multiple PFMs.

[0085] The PFM(s) 1302 (or liquid robots) can advantageously be controlled and actuated using the external magnetic field 1322 to perform various tasks including, for example, torque generation, object manipulation, and controlled locomotion. In one example, a rotating magnetic field can be applied to the PFM 1302 to generate torque on the PFM 1302. The PFM 1302 experiences periodic torque under a rotating magnetic field 1322 as a result of the cyclic magnetic field which can result in rotation by the PFM 1302. In some embodiments, sustained direction motion of the PFM(s) 1302 or directional steering of the PFM(s) 1392 can be achieved by controlling and repeating the application of the rotating magnetic field.

[0086] As mentioned, in some embodiments, the PFM(s) 1302 can be actuated and controlled using external magnetic fields 1322 to interact with (e.g., manipulate) target object or object(s). In one example, multiple PFM(s) 1302 (e.g., two PFMs) can be actuated so as to manipulate a drug pay load in the region of interest. The PFMs (or liquid robots) can be guided via magnetic actuation to converge around a target particle at a first position, entrapping it securely, and then relocating it to a new second position. This exampleQB\99395764.1 28790482.00546 illustrates how the magnetic fields (e.g., the magnetic field gradients) can be programmed to execute coordinated tasks, enabling precise object manipulation in microscale environments. Such control is crucial for applications like targeted drug delivery, micro-assembly, or in vivo biomedical interventions. In some embodiments, PFMs (or liquid robot) could be used to mix drugs under magnetic field.

[0087] In some embodiments, external magnetic fields 1322 can be used to actuate and control the PFM(s) 1302 (e.g., liquid robots) to execute distinct motion patterns including translational locomotion and axial rotation. In one example, the PFM 1302 the applied magnetic field(s) 1322 can be configured to actuate the PFM 1302 to move in a linear path, for example, the applied magnetic field 1322 can induce a unidirectional propulsion force. As mentioned, rotating motion of the PFM 1302 can be induced using a rotating magnetic field 1322. Rotation of the PFM 1302 can be using in applications such as, for example, macromixing, localized drilling, or stirring in biochemical systems.

[0088] In some embodiments, the PFM-based liquid robots can be used for minimally - invasive surgical procedures, for example, for occulting and releasing a blood vessels on demand through external magnetic field control. In some embodiments, a PFM 1302 (or liquid robot) can be injected in a subject and placed inside a blood vessel. Upon activation of an external magnetic field 1322, the PFM 1302 can undergo a stiffness transformation where the PFM 1302 expands and solidifies to mechanically occlude the vessel. When the magnetic field is applied, the nanomagnets in the carrier fluid of the PFM 1302 align and interlink, increasing crosslink density and mechanical stiffness. This magnetically induced order transforms the robot from a soft, deformable state to a rigid, load-bearing configuration. When the external magnetic field 1322 is removed (or turned off), the PFM can return to a soft, flow-permeable state. Demagnetization relaxes the nanomagnets alignment, restoring the PFM's 1322 soft state. This reversible mechanism forms the basis of dynamic stiffness control, offering adaptability for diverse biomedical applications. For example, the stiffness control cand be used to control a PFM 1302 injected inside the blood vessels to control the blood velocity.

[0089] In some embodiment, the controller 1310 may be any general-purpose computing system or device, such as a personal computer, workstation, cellular phone, smartphone, laptop, tablet, or the like. As such, the controller 1310 may include any suitable hardware and components designed or capable of carrying out a variety of processing and control tasks, including steps for controlling the magnetic field generator 1320 and the PFM-based liquid robot 1302. For example, the controller 1310 may include a programmable processor orQB\99395764.1 29790482.00546 combination of programmable processors, such as central processing units (CPUs), graphics processing units (GPUs), and the like. In some implementations, the controller 1310 may be configured to execute instructions stored in a non-transitory computer readable-media. In this regard, the controller 1310 may be any device or system designed to integrate a variety of software, hardware, capabilities and functionalities. Alternatively, and by way of particular configurations and programming, the controller 1310 may be a special-purpose system or device. For instance, such special-purpose system or device may include one or more dedicated processing units or modules that may be configured (e.g., hardwired, or preprogrammed) to carry out steps, in accordance with aspects of the present disclosure. In some embodiments, controller 1310 can be a computer system such as computer system 1400 described below with respect to FIG. 14.

[0090] In addition to medical uses, in some embodiments, the disclosed PFM-based liquid robots can be \used for applications in microassembly, soft micromanipulation, and adaptive material systems. The programmable mobility of the disclosed PFM-based liquid robots can allow them to operate in confined or dynamically changing environments where rigid systems would fail. For example, in lab-on-a-chip platforms PFM-based liquid robots liquid robots could be used to transport reagents, mix samples, or reconfigure flow paths with high spatial and temporal resolution.

[0091] FIG. 14 is a block diagram of an example computer system in accordance with an embodiment. Computer system 1400 may be used to implement the systems and methods described herein. In some embodiments, the computer system 1400 may be a workstation, a notebook computer, a tablet device, a mobile device, a multimedia device, a network server, a mainframe, one or more controllers, one or more microcontrollers, or any other general- purpose or application-specific computing device. The computer system 1400 may operate autonomously or semi-autonomously, or may read executable software instructions from the memory or storage device 1416 or a computer-readable medium (e.g., a hard drive, a CD- ROM, flash memory), or may receive instructions via the input device 1420 from a user, or any other source logically connected to a computer or device, such as another networked computer or server. Thus, in some embodiments, the computer system 1400 can also include any suitable device for reading computer-readable storage media.

[0092] Data, such as data acquired with an imaging system (e.g., a CT imaging system) may be provided to the computer system 1400 from a data storage device 1416, and these data are received in a processing unit 1402. In some embodiment, the processing unit 1402 includes one or more processors. For example, the processing unit 1402 may include one or more of aQB\99395764.1 30790482.00546 digital signal processor (DSP) 1404, a microprocessor unit (MPU) 1406, and a graphics processing unit (GPU) 1408. The processing unit 1402 also includes a data acquisition unit 1410 that is configured to electronically receive data to be processed. The DSP 1404, MPU 1406, GPU 1408, and data acquisition unit 1410 are all coupled to a communication bus 1412. The communication bus 1412 may be, for example, a group of wires, or a hardware used for switching data between the peripherals or between any component in the processing unit 1402.

[0093] The processing unit 1402 may also include a communication port 1414 in electronic communication with other devices, which may include a storage device 1416, a display 1418, and one or more input devices 1420. Examples of an input device 1420 include, but are not limited to, a keyboard, a mouse, and a touch screen through which a user can provide an input. The storage device 1416 may be configured to store data, which may include data such as, for example, electrical signals, biomechanical signals, magnetic field parameters, etc., whether these data are provided to, or processed by, the processing unit 1402. The display 1418 may be used to display images and other information, such as CT images, patient health data, and so on.

[0094] The processing unit 1402 can also be in electronic communication with a network 1422 to transmit and receive data and other information. The communication port 1414 can also be coupled to the processing unit 1402 through a switched central resource, for example the communication bus 1412. The processing unit can also include temporary storage 1424 and a display controller 1426. The temporary storage 1424 is configured to store temporary information. For example, the temporary storage 1424 can be a random access memory.

[0095] Computer-executable instructions for performing processes according to the abovedescribed methods may be stored on a form of computer readable media. Computer readable media includes volatile and nonvolatile, removable, and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer readable media includes, but is not limited to, random access memory (RAM), read-only memoiy (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technology, compact disk ROM (CD-ROM), digital volatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired instructions and which may be accessed by a system (e.g., a computer), including by internet or other computer network form of access.QB\99395764.1 31790482.00546

[0096] The present disclosure has been described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention.QB\99395764.1 32

Claims

1. 790482.00546CLAIMS:1 . A permanent fluidic magnet comprising: a carrier fluid; and a plurality' of non-Brownian nanomagnets disposed within the carrier fluid in a three- dimensional (3D) oriented and ramified magnetic (ORM) network structure.

2. The permanent fluidic magnet according to claim 1, wherein the plurality of non- Brownian nanomagnets are neodymium-iron-boron (NdFeB) nanomagnets.

3. The permanent fluidic magnet according to claim 1. wherein the diameter of the plurality of non-Brownian nanomagnets is 100 nm.

4. The permanent fluidic magnet, according to claim 1, wherein the carrier fluid has a viscosity greater than 2 Pa - s.

5. The permanent fluidic magnet according to claim 1, wherein the permanent fluidic magnet is configured as a liquid cardiac sensor.

6. The permanent fluid magnet according to claim 1. wherein the permanent fluidic magnet is configured as a liquid acoustic sensor.

7. The permanent fluidic magnet according to claim 1, wherein the permanent fluidic magnet is configured as a liquid robot.

8. A system for detecting biomechanical signals from a subject, the system comprising: a permanent fluidic magnet sensor comprising: a carrier fluid; and a plurality of non-Brownian nanomagnets disposed within the earner fluid in a three-dimensional (3D) oriented and ramified magnetic (ORM) network structure; and a receive coil electronically coupled to the permanent fluidic magnet sensor.QB\99395764.1 33790482.005469. The system according to claim 8, wherein the permanent fluidic magnet sensor is configured to generate magnetic field fluctuations in response to the biomechanical signals from the subject.

10. The system according to claim 9, wherein the receive coil is configured to detect the magnetic field fluctuations generated by the permanent fluidic magnet sensor and to generate electrical signals based on the detected magnetic field fluctuations.

11. The system according to claim 10, further comprising a controller in signal communication with the receive coil and configured to receive the generated electrical signals and to quantify the biomechanical signals based on the received electrical signals.

12. The system according to claim 8, wherein the biomechanical signals are cardiac pulse waves.

13. The system according to claim 8, wherein the biomechanical signals are acoustic signals.

14. The system according to claim 1, wherein the permanent fluidic magnet sensor and the receive coil are configured to be positioned on a surface of the subject.

15. The system according to claim 1 , wherein the permanent fluidic magnet sensor is configured to be positioned in an internal region of interest of the subject and the receive coil is configured to be positioned on a surface of the subject.

16. A permanent fluidic magnet based liquid robot system, the system comprising: at least one permanent fluidic magnet comprising: a carrier fluid; and a plurality of non-Brownian nanomagnets disposed within the carrier fluid in a three-dimensional (3D) oriented and ramified magnetic (ORM) network structure; and wherein the at least one permanent fluidic magnet is configured to be actuated in response to an external magnetic field.

17. The system according to claim 16, wherein the permanent fluidic magnet sensor is configured to be positioned in an internal region of interest of a subject.QB\99395764.1 34

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