Monitoring, control, forecasting, and stimulating functions

Non-invasive wearable devices that operate in real-time enable uninterrupted monitoring of the people being cared for and thus provide appropriate health information to determine their overall condition of health and, moreover, a primary picture of health assessment [17–22]. Additionally, connectable or detachable intelligent detecting tools that besides serve as instantaneous condition supervising means provide personally useful warnings related to physical disorders. These warnings relate to heart rate, pressure of blood circulation, rate of respiration, etc. This personalized healthcare monitoring delivers relevant medical data [23–25]. Moreover, modern advances in biocompatibility and biodegradability of materials [26–37] have facilitated advancements in the field of integrated fixed inactive tools enabling identification and prediction by means of miniature sensors, thus intensely improving the value and the effectiveness of individual health care [38–42]. Other embedded devices, stationary but active, are intended to stimulate or activate a part of the body, such as cardiac pacemakers, neurostimulators, or pumps [43–47].

Post-treatment and connected personalized home clinics

In addition to the mentioned roles of monitoring, forecasting, stimulation, etc. of the mentioned devices, these also make it possible to supervise the post-treatment condition of patients [48, 49]. Moreover, following health management recommendations, the paradigm of personalized healthcare through a connected integrated strategy is booming. Thus, replacing face-to-face care with connected assistance using the three mentioned categories of body-onboard tools in individualized care [50–54].

Wireless power and communication routines

Wireless, power supply, and information communication routines are necessary for the intelligent operation of body-onboard tools [55]. This important feature of an onboard device reflects some vulnerabilities. Besides the conventional security of transmitting personal data via wireless communication networks [56], the physical nature of wireless could experience EMF exposures. Thus, in addition to the harmful effects of external exposure to EMFs on the body-onboard tool itself, this can disrupt its wireless transmission procedures.

EMC onboard devices control

A significant attribute of the position of such a tool (recipient) versus radiation (supply) is if it were able to function as usual in a radiation environment, this defines its performing aptitude. Nevertheless, once this receiving tool undergoes field radiation, its key performance signs might be disrupted by a reduction in the signal-to-noise ratio, signal carryover, etc., and therefore, its operation might be reduced. Subject to the domain of use, a receiving tool has certain practical requests and its EMC control assessment relates to subsequent criteria [58, 59]. Such criteria are principally established on static methods. So, the EMC check examination achieved on the tool is built on a universally mounted waveform whereas the control is executed based on the results of the test. This convolution of reflecting a complex EMF radiation environment dynamic behavior is challenged by the device function. Several researches have been achieved to enhance the verification methods of EMC evaluation [60–66].

The experimental control techniques designated overhead are rather complicated and frequently need specialized and costly protected locations. In such circumstances, an alternate answer can be verified by numerical computations through an EMC study to confirm the reliability of different concerned devices [67–70]. Indeed, the legitimacy of an approach guarding a tool against field radiation might be ensured by an EMC examination verifying the invariance of device fields due to radiation.

EMFs governing equations

The general EMF four equations, in their differential form, based on Maxwell’s microscopic local equations [71] are given by:

∇ × E = − ∂_t B (Maxwell – Faraday), ∇ × H = σ E + ∂_t D (Maxwell – Ampère), ∇ · D = ρ_e (Maxwell – Gauss), and ∇ · B = 0 (Maxwell – Thomson).

For harmonic fields’ case, the EMF equations can be given by:

(1) ∇ × H = J

(2) J = J_e + σ E + j ω D

(3) E = −∇ V – j ω A

(4) B = ∇ × A

In the above EMF equations, H and E are the vectors of the magnetic and electric fields in A/m and V/m, B and D are the vectors of the magnetic and electric inductions in T and C/m², A and V are the magnetic vector and electric scalar potentials in W/m and volt. J and J_e are the vectors of the total and source current densities in A/m², σ is the electric conductivity in S/m, ρ_e is the volume density of electric charges in C/m³, and ω = 2πf, where f is the frequency in Hz of the exciting EMF. The vector ∇ is a partial derivative operator, with three likely inferences gradient (product with a scalar field), divergence and curl (dot and cross products respectively, with a vector field). The sign ∂_t corresponds to the operator of partial time derivative. The magnetic and electric behavior laws respectively between B/H and D/E correspond to the permeability μ and the permittivity ε in H/m and F/m.

The excitation in (1–4) is current density J_e = σ E_e = j ω D_e = j ω ε E_e. The choice of the form of the source term depends on the nature of the exposure and the exposed material nature.

Equation solution and EMC

In general, depending on the geometric complexity and inhomogeneity of the materials, the solution of (1–4) must be local in the device using 3D discretized methods as finite elements [72–79] in the appropriate element of the material. The discretized 3D elements are volume sections delimited by surface elements, each bordered by edge elements, each terminated by two nodes. Fields could be expressed at the level of nodes, edges, faces, or volume depending on the nature of the field such as field continuity constraints, etc.

An EMC analysis aims to monitor, through the solution of EMF equations, disturbances due to an external source of EMF exposure on a recipient tool, revealing its measure of EMF reaction. In the present work, we need to verify the onboard devices’ inattention to EMF exposures. Such control may be accomplished by matching the distributions of fields in the device with and free of interfering sources. The field constancy in shielded onboard devices will be checked without and with exposure. Actually, for a certain source field E_e linked to J_e, solving (1–4) will provide the induced values of the EMF, E_i, B_i, and J_i in each element of the discretized domain. The resulting distributions of EMFs allow the control of EMC. The solution domain in this case corresponds to the structure of the device. The verified EMC control due to an EMF exposure involves the constancy confirmation of the field values in the domain. Such an EMC check could be accomplished on the single being checked instrument to ensure its own running. Still, such devices generally operate neighboring to living tissues and can act together. Such a coupling can modify the comportments of the device along with the tissues [80].

Smart shielding

As stated previously, to decrease the influences of radiation of EMF on onboard medical tools, we can manage each shielding of the recipient and radiation supply or modify each of the constructions employing tools for design and optimization. These approaches can be supported and confirmed by control through EMC analysis. Protecting equipment by shields in general employs constituents displaying behaviors of absorbing or reflecting the radiated fields to inhibit its traversing between the two borders of the shield. Electromagnetic interference (EMI), coverings, sheets and shields, which support holding EMF radiation, are necessary for the customary action of medical tools and the protection of living tissues. Magnetic and electric fields composing an EMF wave are directed in the space perpendicularly. Thus, EMI shielding methods are categorized into EMI electric, magnetic, or their coupling shields. It should be noted that high-frequency EMF waves, such as RF waves, mainly distinguish radiation, showing interrelated electric and magnetic fields. So, if one of the two fields is shielded, the other will also be hidden. Due to this occurrence, shields are taken simply as electric conductives. However, shields with a simple conductive material could exhibit, under EMF exposure, induced currents, which would involve EMF dissipated losses causing heating. The closeness of the shielded device to tissues could cause temperature rise and adverse effects on body tissues [80]. In such conditions, the conductive nature of the shield should be adapted to account for this body tissue adverse effect. In general, the function of target nature and shielding technologies use materials of different types. These include clothing fabrics, adhesives rubbers, and coatings. Such diverse constituents are associated with the needed elasticity, the fixative ability, the easiness of processing, and consistency. The investigation domain of protective shields is very dedicated because of the development of everyday EMF exposures [81–92]. Concerning the adjustment of the shield conductive character indicated above, the use of multifunctional accorded substances for shielding low-reflectivity could present improved defense. The matter adapting can decrease the tough EMF reflection triggered by the matter’s high conductivity. Furthermore, a particular fabricating procedure allows diminishing of the substance coefficient of reflected power, along with lessened heat dissipation and enhanced isolation and kind ecologically defending substances [93–95]. In ending, solitary a tool built of EMF-indifferent constituents or smart shielded, can be safe.