ELECTRONIC CIRCUIT TO BE WORN ON THE HUMAN BODY ON A CARRIER

Abstract

A circuit (2100, 2110, 2400) designed to be worn on the human body is presented on a carrier (1000). This carrier is configured to hold at least one functional element (2100, 2110) of the circuit in a predetermined position relative to—and preferably in contact with—a body part (K) of the human body. The circuit on the carrier is provided with a multistable spring mechanism (1200) that has at least two different locally stable states, and it is configured to hold the at least one functional element (2100, 2110) in the predetermined position relative to the body part (K) in a region surrounding a first locally stable state of the multistable spring mechanism, and to prevent it from being held in the predetermined position relative to the body part (K) in a region surrounding a second locally stable state of the multistable spring mechanism.

Description

INTRODUCTION AND STATE OF THE ART People with mobility impairments often need outside help in dealing with their own bodies and frequently have difficulties putting on clothes independently or properly fitting medical aids and objects that must be worn on the body for medical reasons. Movement restrictions can be caused, for example, by the fact that joint mobility is restricted or prevented after injuries and / or surgeries in order to promote and accelerate wound healing. Plaster casts were formerly the primary means of achieving this; more recently, orthoses and bandages have been used. More severe and permanent limitations in movement can be caused by limitations in motor skills, for example when people have lost several or - in extreme cases - all of their movement functions as a result of paralysis. Finally, limitations in movement can also be caused by joint pain, for example as a result of cartilage degeneration or inflammatory joint diseases. Assistance that individuals with mobility impairments, hereinafter also referred to as "patients with limited mobility," require in managing their own bodies is primarily provided through physical support from caregivers. In addition, various solutions have been developed over decades to support people with mobility impairments. These range from wheelchairs and grasping aids to exoskeletons and specialized rehabilitation programs. More recently, approaches have emerged to use body-worn sensors, some attached to textiles, to measure biosignals and convert them into models for movement intentions and / or controls for exoskeletons or universal controllers. In such approaches, functional elements, such as the aforementioned sensors, are often part of an electronic circuit worn on the human body, mounted on a carrier designed to keep the functional elements in contact with the body. Suitable carriers for wearable electronic circuits include, for example, elastically stretchable garments that fit snugly against the body, or elastically stretchable textiles, belts, or bandages that encircle a specific body part (e.g., thigh, forearm). However, with all such approaches, the question remains unanswered as to how patients with limited mobility are supposed to independently apply such wearable circuits to their own bodies.Even if some of the known carrier solutions for wearable electronic circuits are equipped with zippers, Velcro, or laces, the patient must still have the necessary motor skills to put them on independently. However, this is not the case in many instances of the aforementioned movement limitations. For example, if shortly after knee surgery the mobility of the knee joint is restricted to a few degrees by an orthosis set for severe movement restriction, the knee joint is practically straight, and the patient, without assistance, is usually unable to attach bandages, straps, or textiles to the lower leg as supports for functional elements, nor can they pull an elastic, stretchable textile, such as a compression stocking, over the foot of the straight or restricted leg in order to use the textile as a support for functional elements on the lower leg and / or thigh.For the same reason, it is also not possible for the patient to remove an orthosis or compression stocking worn on an extended or restricted leg in order to put on a carrier for functional elements designed for easier application and removal, such as for turning and closing from the side. Patients who, for example, have lost a significant portion of their hand motor skills, including the ability to grasp, as a result of paralysis, are particularly hindered by their movement restrictions from applying any of the aforementioned carriers (bandages, straps or textiles) for sensors to their own bodies. A similar situation affects patients with restricted movement due to painful conditions in the hand and finger joints, such as in cases of rheumatism or gout. In such cases, the ability to grasp or bend joints may be partially or even painfully preserved, but the necessary combination of strength and fine motor skills in the affected hands for handling bandages, straps, elastic textiles, or textiles with zippers, Velcro fasteners, or laces is often lacking, as is the knee joint mobility required to pull on stockings or tight-fitting legwear. One object of this invention is to provide an electronic circuit to be worn on the human body on a carrier which is designed to hold at least one functional element of the circuit in a certain position relative to a part of the human body, such as in touching contact with the human body, and which is further designed to facilitate independent putting on or dressing by a patient with limited mobility. This problem is solved by the subject matter of the independent claims. The dependent claims relate to advantageous embodiments. The invention is explained in more detail below with reference to exemplary embodiments and the figures. BRIEF DESCRIPTION OF THE FIGURES Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 to 18 serve to illustrate various aspects and embodiments of the present invention. Figures 1A to 1D show a first example of a multistable spring mechanism in various deformation states. Figures 2A to 2D show a second example of a multistable spring mechanism in various deformation states. Figures 3A to 3D show a third example of a multistable spring mechanism in various deformation states. Figures 4A to 4D show a first example of a multistable spring mechanism in various deformation states. Figures 5A to 5C are schematic energy diagrams illustrating different states of two different exemplary bistable leaf springs and their combined use.Figures 6A to 6G schematically show a first embodiment of the present invention. Figures 7A to 7C schematically show a second embodiment of the present invention. Figures 8A to 8D schematically show a third embodiment of the present invention. Figures 9A to 9C schematically show a fourth embodiment of the present invention. Figures 10A and 10B schematically show a fifth embodiment of the present invention. Figures 11A and 11B schematically show a sixth embodiment of the present invention. Figures 12A and 12B schematically show a seventh embodiment of the present invention. Figures 13A and 13B schematically show an eighth embodiment of the present invention. DESCRIPTION OF THE INVENTION The following description explains features, aspects, and embodiments of the invention with reference to the figures. Where the same reference numerals are used in different figures, repetitive explanations are omitted. Unless otherwise stated, the respective features and aspects of repeatedly used reference numerals are to be understood based on previously given explanations. Unless otherwise stated in the description, figures are to be understood as schematic drawings not to scale, and unless otherwise stated, details in the graphical representation serve to illustrate preferred aspects without being restrictive. The present invention relates to a circuit worn on the human body, mounted on a carrier designed to hold at least one functional element of the circuit in a specific position relative to—and preferably in contact with—a part of the human body. The specific position in which the at least one functional element is to be held relative to the body part can, for example, only be determined by placing the carrier against one of several possible body locations. Alternatively, the carrier can also be designed to be placed against a predetermined body location. In the following embodiments and illustrations, the body part relative to which the at least one functional element is to be held in a specific position is depicted as a section of a forearm or lower leg, but this is to be understood without limitation. Likewise, the body part relative to which the at least one functional element is to be held in a specific position can be another section of an upper extremity (upper arm, elbow, wrist, back of hand, fingers, etc.), a lower extremity (thigh, knee, ankle, etc.), or a section of any other body part (head, neck, rib cage, abdomen, shoulder, hip, etc.).It is also possible that the circuit to be worn on the human body comprises several functional elements on a carrier and that the carrier is designed to hold various of the several functional elements in specific positions relative to different parts of the human body, for example the thigh and lower leg of the same leg. The support is preferably flat and can be understood in the most general sense. In the embodiments and illustrations shown below, the support is mostly designed as a cohesive arrangement with interconnected or connectable components. Alternatively, the support can also be designed with several parts that are not interconnected or connectable, for example, such that different parts of the support can hold different functional elements in different, specific positions relative to different locations on the human body, such as on the left and right arms or legs simultaneously, or particularly at symmetrically corresponding locations on the same body. The carrier can contain textile and / or non-textile materials and components made of plastics, metals, or other materials, such as films, prints, struts, reinforcements, and other functional elements. Components of the carrier can be designed with openings and thus be gas- or liquid-permeable, for example, breathable, and / or gas- or liquid-tight. Various components of the carrier can be connected to one another in a variety of ways, for example, by a material bond such as welding, or detachably with mechanical fasteners, such as pockets, straps, belts, and connections like buttons, zippers, or hook-and-loop fasteners, or the like, in the case of textiles. According to the invention, at least one functional element, which the wearer holds in a specific position relative to—and preferably in contact with—a part of the human body when wearing the circuit, can preferably be a sensor or actuator, such as an electrode or a chemical sensor, for whose proper operation contact with the body is required. In such a case, the functional element is formed on a surface of the wearer that touches the body part when worn. For example, with electrodes in direct skin contact as ExG electrodes (EMG, ECG, EOG, etc.), voltages and currents can be measured as biosignals of the body. Furthermore, electrodes in direct skin contact can also function as active elements or actuators and, for example, apply electrical pulses, such as to stimulate muscles and / or nerves.Examples of functional elements that do not require physical contact for proper operation include temperature sensors or tactile actuators (vibrators) which, when the circuit is worn on the human body, must be held in a certain position relative to a body part, but not necessarily in physical contact with the body, if the temperature measurement or tactile signals are transmitted through thermally conductive or structure-borne sound-transmitting media. The circuit according to the invention can contain not only a single functional element, but several - similar and / or different - functional elements, for example an arrangement with several measuring and / or control electrodes that are kept in touching contact with the body when the circuit is worn on the human body. Parts of the circuit, such as at least one functional element that is to be held by the carrier in a specific position relative to—especially in contact with—a part of the human body, can consist of or comprise flexible and stretchable layers that fulfill various functions. Such layers can be produced by additive manufacturing processes, in particular by printed electronics, and can have layer thicknesses of up to 500 µm, preferably layer thicknesses in the range of 1 µm to 200 µm. If the circuit according to the invention comprises such layers on a substrate, these layers may preferably be arranged on one or more outer surfaces of the substrate, particularly if they are manufactured using printed electronics methods. However, the invention is not limited to circuit arrangements exclusively on outer surfaces of substrates; rather, at least parts of a circuit according to the invention may also be located inside the substrate. Furthermore, the circuit according to the invention can also include elements on the carrier that, in order to fulfill their function when the circuit is worn on the human body, do not need to have a specific position relative to the body, and in particular do not need to have any physical contact with the body. These can include, for example, circuit elements with functions for electronic control, data acquisition, and communication, which can be designed as semiconductor circuit components combined in one or more electronic modules. Such electronic modules can be composed as a combination of a removable electronic unit and a contact module that is electrically and mechanically fixed to the circuit for the electrically and mechanically detachable mounting of the removable electronic unit, or alternatively, as an integrated unit with a fixed electrical and mechanical connection to the rest of the circuit.Furthermore, it is possible to house circuit elements that should not or must not have direct contact with the body when the circuit is worn on the human body in one or more specially designed receptacles (e.g., electronic pouches) on the wearer. Electronic modules with removable electronic units are advantageous, for example, if wearers need to be easily changed, washed, and / or replaced during use, or to supply the systems with freshly charged energy storage devices. Furthermore, the circuit according to the invention can include a storage element permanently connected to the carrier, in which information that individually characterizes and preferably identifies the circuit is stored. Such a storage element can be connected to the rest of the circuit or designed separately, for example as an RFID module, in particular as an NFC module, and it can be read, for example, via a wireless connection, particularly when the circuit is put into operation, in order to check its intended use and to avoid, for example, mix-ups when inserting removable electronic units if a user has several circuits according to the invention on several carriers with identical contact modules in use.Such a storage element designed for wireless readout can be provided with a visible position marker on the carrier to facilitate its localization and wireless connection, and / or be arranged at or in the contacting module. According to a first aspect, the circuit on the carrier is equipped with a multistable spring mechanism that has at least two different locally stable states, in which the spring mechanism assumes differently shaped states. If the circuit is worn on the human body and the state of the multistable spring mechanism is in a region surrounding a first locally stable state, the carrier holds the at least one functional element in a specific position relative to—and preferably in contact with—a part of the human body. If, on the other hand, the multistable spring mechanism is in a state in a region surrounding a second locally stable state, the carrier does not hold the at least one functional element in the specific position relative to the part of the human body. According to a further aspect of the invention, the circuit on the carrier is provided with a multistable spring mechanism that has at least two different locally stable states, in which the spring mechanism assumes differently shaped states. If the circuit is worn on the human body and the multistable spring mechanism is in a state in the vicinity of a first locally stable state, the carrier presses the at least one functional element against the body part with a first pressure. If, on the other hand, the multistable spring mechanism is in a state in the vicinity of a second locally stable state, the carrier does not press the at least one functional element against the body part, or presses it with less pressure than the first. A multistable spring mechanism according to the present invention is an elastically deformable arrangement with at least two different locally stable states in which the spring mechanism can assume different geometric shapes without the influence of external forces, wherein a change between the different locally stable states is only possible due to the influence of an external force. Multistable spring mechanisms are known from various everyday applications, such as bistable switches with snap-action contacts, which are actuated by mechanical pressure. With sufficient pressure, they move from one switch position to another, and with insufficient pressure, they return to their starting position (see, for example, DE P 3831251 A1). Bistable spring mechanisms are also known, for example, for use in making shoes easier to put on (DE 10 2009 023 689 A1). Multistable spring mechanisms can, for example, be based on arrangements with pre-stressed spring elements, such as elastically compressed leaf springs that can be deformed in opposite bending directions and can assume two oppositely bent rest positions. Multistable spring mechanisms can also be based on shape memory effects, in which workpieces are impregnated with differently shaped internal stresses during manufacturing, usually through thermomechanical treatment cycles, and can assume correspondingly different locally stable states in use. For example, bistable metal sheets are known, with a rolled-up state as the first locally stable state and a stretched or less rolled-up state as the second locally stable state (Forsch. Ingenieurwes. 85 (2021), pp. 817-825). Multistable spring mechanisms can assume the form of bistable leaf springs and—preferably in their longitudinal direction—exhibit a first, most strongly curved, locally stable curvature state and a second, non-curved or only slightly curved (“stretched”) locally stable curvature state. Figures 1, 2, 3 to 4 show oblique views of exemplary bistable leaf springs in various states of curvature, each with an elongated, for example, rectangular, basic shape with a longer side along the y-direction and a shorter side along the x-direction. For clarity, the degrees of curvature are exaggerated to a lesser extent than shown. The ratio of the length of the longer side to the shorter side is preferably at least 2:1, more preferably at least 3:1, and particularly preferably at least 4:1. For leaf springs with non-rectangular, for example oval, basic shapes or quadrilaterals with rounded corners, corresponding ratios can be applied in the directions of the longest and shortest central axes. Figures 1A, 2A, 3A, and 4A show the exemplary leaf springs in their locally stable state, either stretched along their longer side or less curled, hereinafter also referred to as the "second locally stable state" or "stretched locally stable state"; Figures 1B, 2B, 3B, and 4B show the leaf springs in their curled locally stable state, hereinafter also referred to as the "first locally stable state" or "curled locally stable state". In their respective first locally stable states, the exemplary leaf springs are each curled around an axis in the x-direction, i.e., around an axis along their shorter side and transverse to their longer side, and are in their respective state of maximum curvature without any external force acting upon them. A complete roll-up is possible if the length of the longer side (Ly in Fig. 1A) is at least 2xPI times (PI = pi, i.e. 3.14159...) of the radius of curvature R (cf. diameter of curvature 2xR in Fig. 1B). In the examples shown, this is the case in each instance, without complete rolling being essential to the invention. In their respective second locally stable states, the four exemplary bistable leaf springs are either stretched or less curled in the y-direction (direction of greatest curvature in the respective first state). In the first example (Fig. 1), the bistable leaf spring in the second state is stretched in the y-direction (direction of greatest curvature in the respective first state) and curved in the x-direction about an axis in the y-direction, which causes the stretching in the y-direction to be curved in the second state, Fig. 1A. The two axes and directions of curvature are oriented at an obtuse angle to each other in the illustrated example – perpendicular in this specific example – without this being essential to the invention. This is similarly the case with the second example (Fig. 2). This leaf spring differs from the second example in the relative orientation of the curvatures in the "first locally stable state" and "second locally stable state." In the rolled-up locally stable state, the inner surface of the leaf spring forms (at least) a convex surface in the direction of curvature y for the bistable leaf spring in Fig. 1, whereas for the bistable leaf spring in Fig. 2 it forms (at least) a concave surface in the direction of curvature y. In the third example (Fig. 3), the bistable leaf spring in its second state contains an inner edge with an obtuse angle. This inner edge extends along the y-direction and causes the extension along this direction, Fig. 3A. Here, the inner surface of the leaf spring in its coiled, locally stable state comprises two convex surface sections that curve outwards in the y-direction of curvature. With multiple non-parallel inner edges, it is possible to easily realize several locally stable states, each extended but oriented differently, in a multistable spring mechanism. In the fourth example, the bistable leaf spring is also curved in the second state in the y-direction (direction of greatest curvature in the respective first state) about an axis in the x-direction, i.e. about an axis along its shorter side, but much less so with a much larger radius of curvature, Fig. 4A . If the multistable spring mechanism according to the invention is slightly elastically deformed relative to one of its locally stable states, it tends to return to this locally stable state and—in a simplified and approximate view—is subject to the spring law (Hooke's law), according to which a restoring force increases proportionally with the degree of the respective elastic deformation, and the energy stored by this deformation ("potential energy") increases proportionally with its square relative to the respective locally stable state. With a greater elastic deformation, however, the spring law no longer applies; rather, in a multistable spring mechanism, transitions between different locally stable states are possible. In general, various intermediate states and transition paths are possible, as illustrated by the exemplary comparisons of different intermediate states in the figures.1C vs. 1D, 2C vs. 2D, 3C vs. 3D and 4C vs. 4D are shown. In Fig. 1C, Fig. 2C, Fig. 3C and Fig. 4C, the four leaf springs are each curved less sharply along the y-direction (direction of greatest curvature in the respective first locally stable state) around the axis in the x-direction, i.e. around an axis parallel to their shorter side, than in the respective first locally stable state, but more sharply than in the respective second locally stable state, so that the stored potential energies in the respective intermediate states shown are higher than the potential energies in at least one of the two respective locally stable states. In Figures 1D, 2D, 3D, and 4D, the four exemplary leaf springs are shown curled along the y-direction (direction of greatest curvature) in a section closer to the viewer in the oblique view around the x-axis with a radius of curvature as in the respective first locally stable state, and stretched or less curled in a section further away from the viewer in the y-direction as in the respective second locally stable state. Here, too, the elastic potential energy stored in each leaf spring is higher than the elastic potential energy in at least one of the two locally stable states. Multistable spring mechanisms in general can take different transition paths and assume different forms when transitioning between locally stable states; Fig. 1, Fig. 2, Fig. 3 to Fig. 4 serve only to illustrate this. This will be explained in more detail with reference to Fig. 5. Fig. 5A is a schematic and highly simplified energy diagram to illustrate different states of an exemplary bistable leaf spring, as shown in Fig. 2. The diagram schematically plots the elastic potential energy E stored in the bistable leaf spring due to internal stress as the ordinate, and the abscissa as a function of the "curvature" (deformation) of the bistable leaf spring along its longitudinal direction (i.e., direction y of its longer side in the rectangular basic shape). Due to the various possible transition paths between the locally stable states, only the locally stable states themselves are precisely defined with respect to the shape and elastic potential energy of the exemplary leaf spring as local minima of the curve. The curve's behavior between these local minima, however, depends on the transition path and the associated intermediate states of the spring, including the curvatures (deformations) along the transverse x-direction. Therefore, the curve's behavior between its local minima in Fig. 5A should be understood only as an illustrative schematic diagram. The lower part of the figure illustrates the coiled, first locally stable state Z1 and the extended, second locally stable state Z2 of the leaf spring. Similar to Figures 1, 2, 3 to 4, the leaf spring in its coiled "first" locally stable state Z1 is coiled around an axis in the x-direction, i.e., around an axis along its shorter side and perpendicular to its longer side, and is in its state of greatest curvature along its longitudinal direction. The extended state Z2 of the leaf spring (curvature = 0 along its longitudinal direction, in the diagram below, far left) is locally stable, meaning the energy curve has a local minimum here and increases—regardless of the exact shape of the curve—in a surrounding region U2. The coiled first locally stable state Z1 corresponds to the state the leaf spring assumes when coiled along its longitudinal direction without the influence of external forces (in the diagram below, in the right-hand region).Here too, the energy curve has a local minimum and rises – regardless of the exact shape of the curve – in a region U1 surrounding the locally stable state Z1, i.e., with greater and lesser curvature than in state Z1. Therefore, if the bistable spring is located in one of the regions U1 or U2, it tends towards the respective locally stable state Z1 or Z2, which is a state of lower energy. The upper part of the figure illustrates the transition of a leaf spring from the second locally stable state Z2 to the first locally stable state Z1 when triggered by (slight) deformation through pressure – for example, from a cylindrical body K – against the center of the inwardly curved side of the leaf spring in the first locally stable state Z1. Here, the outer diameter of the cylindrical body K is larger than the inner diameter of the leaf spring in its coiled "first" locally stable state Z1, and the axis of the cylindrical body K is parallel to a direction x around which the leaf spring coils in its first state.By applying pressure to the center of the leaf spring with body K, the spring is slightly deformed, increasing its internal tension and thus its elastic potential energy. With sufficient deformation due to sufficient pressure (sufficient external force), the leaf spring transitions from the second locally stable state Z2 and its surrounding region U2 to the surrounding region U1 of the first locally stable state Z1. The cylindrical body acts as a coiling limiter; that is, due to the larger outer diameter of the cylindrical body compared to the inner diameter of the leaf spring in the coiled "first" locally stable state Z1, its curvature is not reached. Instead, the leaf spring remains in a state Z1' with energy E1' in the surrounding region U1 of the first locally stable state Z1. In general, the energy curves of multistable spring mechanisms between different locally stable states are continuous, which allows a change between their surrounding areas with limited force expenditure, and such spring mechanisms can be designed in such a way that a user can switch between a rolled-up state Z1' and the stretched state Z2 without any special energy expenditure. Furthermore, multistable spring mechanisms, such as bistable leaf springs, allow energy curves to contain sub-regions with relatively constant slopes at inflection points between local minima (at the locally stable states) and local maxima (between the local minima). This results in correspondingly relatively constant (approximately locally constant) contact forces in these sub-regions. Thus, the energy curve in Fig. 5A has an inflection point between its local minimum E1 in the first locally stable state (Z1) and its local energy maximum EM between the two locally stable states, and around this point, a broad sub-region with relatively constant slopes. On the abscissa, this sub-region is located to the left of Z1, i.e.,The leaf spring is less curved there than in state Z1, and the relatively constant gradient in this sub-area allows for correspondingly relatively constant (approximately locally constant) contact forces if the rolling of the leaf spring is limited by rolling limits / cylinder bodies with different - or variable - curvatures / outer diameters in this sub-area. The energy curve shown in Fig. 5A has a local energy maximum between the two locally stable states Z1 and Z2. The energy E1 in the first, rolled-up locally stable state Z1 is significantly lower than the energy E2 in the second, stretched locally stable state Z1, and also lower than in any other state. The region U1 surrounding the first locally stable state Z1 encompasses a broad range of curvature. Within this region, adjustable states Z1' with a potential energy E1' significantly above the energy minimum E1 can be achieved by limiting the roll-up, for a wide range of cylinder radii corresponding to this broad range of curvature. Due to the higher potential energy E1', the leaf spring exerts pressure against the outer surface, i.e., the shell of the cylinder body K, for a wide range of cylinder radii within the region U1. In the example shown, the difference between the energy EM at the local energy maximum and the energy E2 in the second, stretched locally stable state Z2 is also significantly smaller than the difference between the energy EM at the local energy maximum and the energy E1 in the first, curled locally stable state Z1, and also smaller than the difference between the two energies E1 and E2 in the two locally stable states Z1 and Z2. The use of bistable leaf springs with a comparatively small difference between the energy EM at the local energy maximum and the second, stretched locally stable state Z2 is preferred if a transition from the stretched locally stable state Z2 to a coiled state is to require less energy or force than a transition in the opposite direction, i.e., from a lower-energy coiled state back to the stretched locally stable state Z2. Such leaf springs are also referred to below as "preferably coiled". In comparison, Fig. 5B shows a similar schematic and highly simplified energy diagram of another exemplary, "preferentially stretched" bistable leaf spring. To avoid repetition, only the differences from Fig. 5A are explained below. These differences consist, in particular, of the fact that the locally stable curvature states shown in the lower part of Fig. 5B differ from those of the exemplary bistable leaf spring considered in Fig. 5A with respect to their respective strain energies F1 and F2 (plotted along the ordinate), the curvature in the y-direction (schematically plotted along the abscissa) in the first locally stable state Z1, and the local energy maximum between the two states Z1 and Z2. In the example of Fig.5B The potential energy F2 in the second, extended locally stable state Z2 is lower than the potential energy F1 in the first, curled locally stable state Z1 and significantly lower than the potential energy F1' in the curled state in the vicinity V1 of the first locally stable state, which is brought about by the curling limitation imposed by the cylindrical body K. This potential energy F1', in turn, is comparatively slightly lower than the local energy maximum FM between the two locally stable states Z1 and Z2. This means that a transition from a curled state to the extended locally stable state Z2 requires less energy or force than a transition from the lower-energy extended locally stable state Z2 back to a curled state.In the examples shown, the surrounding area V2 of the stretched locally stable state Z2 of the "preferably stretched" bistable leaf spring is also larger than the surrounding area V2 of the stretched locally stable state Z2 of the "preferably rolled up" bistable leaf spring. In principle, both "preferably coiled" and "preferably extended" bistable leaf springs can be used according to the invention. Whether "preferably coiled" or "preferably extended" bistable leaf springs are used to a particular advantage depends on the circumstances of the individual case, including the type, shape, and size of the body part on which the device according to the invention is to be worn, the pressure and stability in the wearing state, the ease of putting on the device, the ease of taking off the device, and the type, shape, and size of the leaf spring. If, for example, the body part is an extremity (part of an arm or leg), bistable leaf springs with a first locally stable curvature state that is most strongly curved in the longitudinal direction and a second locally stable curvature state that is stretched (as in Figs. 1, 2, 3 to 4) can be used in such a way that, in the carrier's carrying state, i.e., when the circuit on the carrier is worn against the body, they fall within a respective region of their first locally stable curvature state. Since the curvature states of bistable leaf springs determine the shape of the carrier and spring forces are transmitted from the bistable leaf springs to the carrier, the carrier, when using such bistable leaf springs, can be designed to grip the body part in a bearing state with compression. If, during carrying, an extremity (part of an arm or leg) needs to be grasped as a body part, a bistable leaf spring that is (strongly) curved longitudinally in its initial locally stable state and, moreover, preferably rolled up, is advantageous for pressure and stability of the carrying position, as well as for ease of putting on the gearshift. Conversely, for ease of taking off the gearshift, the use of bistable leaf springs that are preferably straight is generally advantageous. According to the aspect of the invention explained above, the circuit and carrier are provided with a multistable spring mechanism – for example, a “preferably extended” or “preferably coiled” bistable leaf spring – which has at least two different locally stable states and is designed to hold the at least one functional element of the circuit in a carrying state in an area surrounding a first locally stable state (Z1) of the multistable spring mechanism in a position relative to the body part determined when the carrier is applied, and in a state in an area surrounding a second locally stable state (Z2) of the multistable spring mechanism not to hold it in the determined position relative to the body part (K). If the spring mechanism according to the invention comprises two or more bistable leaf springs, these can have the same or different properties. Furthermore, the support can be designed so that the two or more bistable leaf springs can change their respective locally stable curvature states independently of one another or in a mutually dependent manner. In the case of a mutually dependent change of state, the support establishes a mechanical connection between at least two bistable leaf springs, which is designed to transmit deformation forces between the at least two bistable leaf springs. It is preferred here to transfer all or part of the potential energy released during the change of state of one bistable leaf spring to another bistable leaf spring, thereby causing or facilitating its change of state. If the application and / or removal of a circuit equipped with two or more bistable leaf springs onto a support is to be possible with few and as simple a steps and / or movements as possible, it is particularly advantageous if the support forms a bistable overall system with two locally stable overall states, of which a first locally stable overall state corresponds to a carrying state described above, in which the two or more leaf springs are in a region surrounding their respective first locally stable curvature state and encircle an affected body part, and of which a second locally stable overall state corresponds to a release of the encircled body part, in which the leaf springs are in their respective second locally stable, "stretched" curvature state.and if, in addition, a change of state of one of the leaf springs in the overall system between a first and second curvature state, without the influence of any further external force, causes a corresponding change of state in another of the two or more leaf springs. Through such a "domino effect," the change of state of just one of the bistable leaf springs can cause the entire system to change from a load-bearing state with leaf springs in the encompassing curvature state to a releasing state with leaf springs in the extended curvature state. If the spring mechanism according to the invention comprises, for example, two or more bistable leaf springs connected by a "domino effect" and preferably rolled up, this enables particularly easy application of the circuit as well as pressure and stability of the circuit when in use. However, removing such a circuit requires more force and energy. It is also possible, and in certain cases advantageous, if two or more bistable leaf springs of a spring mechanism according to the invention have different properties. For example, the spring mechanism according to the invention can comprise a combination of a "preferably coiled" bistable leaf spring and a "preferably extended" bistable leaf spring. In this case, one of the at least two leaf springs has a higher elastic potential energy in the second locally stable state than in the first locally stable state, and another of the at least two leaf springs has a lower elastic potential energy in the second locally stable state than in the first locally stable state. Such an exemplary combination of different leaf springs is explained in Fig. 5C. This schematic energy diagram shows a combination of the energy curves from Fig. 5A (dashed energy curve of a preferably coiled leaf spring 1202) and Fig.Figure 5B (the energy curve of a preferably extended leaf spring 1201, shown in dashed lines) illustrates this. To avoid repetition, reference is made to the explanations for Figures 5A and 5B. Both curves show two local minima: first local minima corresponding to the first, coiled, locally stable states in the right half of the image, and second local minima corresponding to the second, extended, locally stable states along the ordinate axis in the left half of the image. Local maxima are also shown between the respective first and second local minima. The local maximum of the preferably coiled leaf spring 1202 is located in the vicinity of the second, extended local state of the preferably extended leaf spring 1201, whereas the local maximum of the preferably extended leaf spring 1201 is located in the vicinity of the first, coiled local state of the preferably coiled leaf spring 1202.If the support is also designed so that the two or more bistable leaf springs can alternate between their respective locally stable curvature states in a mutually dependent manner, such a configuration allows a "domino" effect in both directions with comparatively low energy expenditure. For example, if the preferably coiled leaf spring 1202 is in a state at a local maximum with energy EM, then coiling it without any coiling limit into the first, coiled locally stable state releases a potential energy of (EM-E1), which is higher than the energy difference (FM-F2) required to bring the preferably extended leaf spring 1201 from its second, extended locally stable state with energy F2 into a state at a local maximum with energy FM and subsequently into its coiled state with energy F1.This “domino” effect to the rolled-up states is also possible with roll-up limits, where – as shown in the example – the rolling up leads to energy states E1' and F1' in the surrounding areas of the respective first locally stable states, and the potential energy of (EM-E1') released when the preferably rolled-up leaf spring is sufficient for a change of state of the preferably stretched leaf spring 1201 from its stretched locally stable state to the state at the local maximum.On the other hand, if, for example, the preferably stretched leaf spring 1201 is in a state at the local maximum with an energy FM, then during the transition to the second, stretched locally stable state, a potential energy of (FM-F2) is released, which is sufficient to bring the preferably rolled-up leaf spring 1202 from its rolling-limited state in the vicinity of its first locally stable state with the energy E1' to a state at the local maximum and subsequently to its stretched state with the energy E2. As explained in the example shown, it is possible to choose a combination of bistable leaf springs such that only comparatively small energy differences (EM-E2) and (F2-F1') between the local maximum and the respective higher-energy locally stable state or state of its surroundings are required to trigger a “domino” effect in both directions. For a carrier to undergo a state change in both directions that is facilitated – i.e., possible with comparatively little energy expenditure – it is not necessary that the aforementioned comparison relationships of the type of (EM-E1') > (FM-F2), (FM-F2) > (EM-E1') In a quantitative sense, the requirements are strictly met. This is because the lightening effect is based on the opposing effects of interconnected bistable leaf springs, one of which is of the preferably rolled and the other of the preferably extended type. According to the present invention, the effects and possibilities of multistable spring mechanisms are used. Bistable leaf springs with longitudinally rolled-up first locally stable states are particularly suitable, the surrounding regions of which are sufficiently wide to include at least those states that can be brought about by limiting the rolling-up by cylindrical bodies K with at least twice, preferably at least three times, the outer diameter compared to the inner diameter of the respective leaf spring in its respective rolled-up state. A key difference from classic elastic materials is that the latter are subject to a spring law in the broadest sense, meaning that elastic "restoring forces" increase with increasing degree of deformation relative to the rest state / energy minimum, and the maximum possible elastic deformations from the rest state / energy minimum are limited only by the elastic limits of the materials used. For circuits worn on the body, this means that textiles made of classic elastic materials, such as compression garments, which are subject to considerable pressure when put on and taken off, are difficult for users with limited mobility to handle, often requiring assistance. Furthermore, while compression garments such as compression stockings are available in various sizes, the pressure exerted within a given size varies depending on body measurements. Even when a garment is adjusted to individual body measurements (for example, through adjustable belts or Velcro fasteners), the pressure exerted by an elastic garment, which is subject to the principles of spring action, changes with variations in body measurements during movement or posture, such as changes in arm and leg circumference due to muscle contraction or chest circumference due to breathing.If the function of a functional element worn in contact with the body, for example a sensor for measuring a biosignal of muscle activity, depends on the pressure of the sensor on the muscle or, more generally, on the pressure of the functional element on the body, then the use of multistable spring mechanisms is advantageous, because, as explained above, these can be designed to maintain a largely unchanged pressure of the functional element on the body in the event of changing rolling limits due to changes in body dimensions during movements or changes in posture. If the multistable spring mechanism contains one or more bistable leaf springs with a longitudinally coiled, first locally stable state as exemplified in Figs. 1B to 4B and a longitudinally stretched, second locally stable state as exemplified in Figs. 1A to 4A, then – as exemplified in Figs. 5A and 5B, top left – a change of such a leaf spring from the second to the first locally stable state can be triggered by pressure against the center of the inwardly curved side of the leaf spring in the first locally stable state, if the leaf spring is sufficiently bent and deformed by this pressure and its internal tension and spring energy are thereby sufficiently increased.Such a deformation is possible, for example, if the support, in its extended, second locally stable state, lies with its side facing away from the body in the carrying state downwards and its contact surface upwards, and thus the leaf spring lies with its side facing away from the body in the carrying state downwards on a sufficiently compressible base (cushion or pillow) that yields to the pressure to the extent required for the deformation and the resulting change of state. Such deformation is also possible on a hard and flat contact surface if the support is provided with a specially designed bearing. This bearing can, for example, comprise a compressible layer between the leaf spring and the side of the support facing away from the body when in use. This layer is designed such that, when the support rests flat on a hard and flat contact surface with this side facing downwards, pressure applied from above to the center of the support allows for deformation of the support and curvature of the leaf spring to the extent necessary for its change of state. Alternatively, such a support can be shaped to create a gap between the support and the flat bearing surface, allowing for the necessary deformation of the support and the leaf spring to change from an extended to a coiled state. This prevents the support from lying flat on a flat bearing surface with the side facing away from the body during use. For example, such a support can include one or more projections in front of the main surface of said side of the support. These projections can accommodate circuit elements that, when the circuit is worn on the human body, can or should be positioned on the side of the support facing away from the body. In the following descriptions, the multistable spring mechanisms are designed as one or more bistable leaf springs with the properties and advantages explained above. However, the present invention is not limited to this, as other multistable spring mechanisms are also possible, as illustrated by the alternative examples mentioned above. Furthermore, the number of bistable leaf springs in the multistable spring mechanism is not limited by the embodiments shown below. Furthermore, in the following explanations, shape changes, in particular transitions between different locally stable states or their environments, can be triggered primarily by deformations of the spring mechanisms due to the influence of external forces. However, such transitions and shape changes can also be triggered by changes in other parameters such as temperature or the like. In all cases, an important function of the multistable spring mechanisms is to determine a shape state of the support in the area of ​​the body part to be encompassed and to make the support as a whole appear multistable in different shape states. For this purpose, the multistable spring mechanisms, such as leaf springs, can be connected to the support by a form-fit and / or material-fit connection, for example, by gluing, welding, or other methods of integral joining. In this case, the support directly participates in the deformations of the multistable spring mechanism and must therefore be sufficiently elastic and deformable in its shape and materials. Such integral designs of multistable spring mechanisms and supports offer advantages in terms of simpler assembly during the manufacture and use of the circuit. For example, if the spring mechanism exerts pressure in a direct line on the functional elements and the enclosed body part, the support can be made of a thin layer.In such a case, it is advantageous if the spring mechanism, such as the leaf spring, is provided with thin layers that can be produced by additive manufacturing processes, including parts of the circuit that can be produced by printed electronics processes, including the functional elements to be kept in contact with the body and associated conductor tracks, as well as optionally other printable circuit elements such as RFID elements. In general, however, the type and design of the mounting of the multistable spring mechanism in the carrier are not subject to any restrictions. In some applications, for example, the fact that it is worn on the human body with direct body contact may result in different material requirements for the carrier. For example, the carrier according to the invention can comprise a flat material, such as a textile, which is deformable and optionally stretchable, preferably having an elongation of at least 10% and, in special cases, particularly preferably at least 30%. In embodiments without a material-bonded connection between the carrier and the multistable spring mechanism, the carrier accommodates the spring mechanism in such a way that the spring mechanism determines a shape state of the flat, for example, textile, carrier material.In such a case, it may be advantageous if the multistable spring mechanism is guided in a movable manner relative to the support, in particular if surfaces of the spring mechanism that deform when switching between different locally stable states are guided in a sliding manner relative to surfaces of the support. Regardless of the textile or other nature of the support, a guided relative mobility between parts of the spring mechanism and the support makes it possible to influence or determine the shape of the support without the shape changes of the spring mechanism and the support being coupled with exactly synchronous elastic deformations, which allows greater freedom in the choice of shape and materials of the support on the one hand and of the multistable spring mechanism on the other. For example, if the multistable spring mechanism is a bistable leaf spring with a locally stable state in both an extended and a coiled position, and this spring is slidably guided within a pocket by the support structure, then the support structure can change its shape when the bistable leaf spring coils or extends without the lengths of the pocket on the inside and outside of the coiled leaf spring having to change in the same way as the deformation-related changes in the side lengths of the leaf spring. Therefore, the leaf spring and the support structure can have different elastic material properties without being subject to strict mutual limitations. Enclosures or pockets for multistable spring mechanisms can be open, closed, or closable, for example, with a zipper or snap fastener.Furthermore, sections of a multi-stable spring mechanism can be fixed in an open pocket relative to the wearer and / or held in position and / or guided relative to the wearer using appropriately arranged tabs. In general terms, the support has a position-limiting device that restricts the position of the multistable spring mechanism relative to the support in at least one direction transverse to the direction of the strongest curvature (transverse to the direction of the strongest change in expansion during the change of state) of the multistable spring mechanism, such as a support with a pocket for receiving a bistable leaf spring that can restrict its position transverse to the direction of its strongest curvature. Furthermore, a circuit according to the invention can include sensors that detect the state of the support as a load-bearing or non-load-bearing state and / or the shape state of the multistable spring mechanism (for example, the curvature state of a bistable leaf spring), preferably in particular detecting whether the multistable spring mechanism is in a state in a region surrounding the first locally stable state. Depending on the detection result of these sensors, a control device can be triggered to perform a control action and / or an output device can be triggered to output a signal. Finally, the circuit, support, and multistable spring mechanism—for example, bistable leaf spring(s)—can be designed and arranged such that the at least one functional element is located in a supporting state of the circuit between the body part and the spring mechanism—a leaf spring—and is pressed against the body part by the latter. Alternatively, a pressure mechanism (1600) can be provided to increase the contact area of ​​the spring mechanism, for example, by widening a bistable leaf spring transversely to the direction of its greatest curvature in the first locally stable curvature state, which has a stiffening effect at least in the curved state, or by a sufficiently stiffening connection between two bistable leaf springs arranged side by side. Alternatively or additionally, the carrier can comprise a deformable chamber containing a fluid material and be configured such that, in a carrying state, i.e., an ambient region (U1) of a first locally stable state (Z1) of the multistable spring mechanism, at least one functional element is located on a contact surface of the carrier between the body part and the chamber containing the fluid material and is pressed against the body part by the chamber containing the fluid material. The fluid material can be a gas, a liquid, or a gel. Furthermore, the chamber can permanently enclose the fluid or be equipped with a valve. The chamber can comprise one or more, preferably interconnected, cavities for receiving the fluid. Pressing at least one functional element against the enclosed body part on a contact surface of the carrier by means of a chamber containing fluid material has the advantage of a uniform pressure distribution across the contact surface onto the enclosed body part. Such pressure equalization is advantageous, for example, when the multistable spring mechanism comprises different leaf springs, for example, both of the preferably open and the preferably coiled type. To build up pressure in the deformable chamber during use, one section of the chamber containing the fluid material can be positioned between the body and the multistable spring mechanism, experiencing a pressure applied perpendicular to the chamber wall. Alternatively, another section of the chamber containing the fluid material can be positioned laterally next to the multistable spring mechanism, experiencing tensile forces tangential to the chamber wall and directly towards the body. These forces are then redirected as pressure against the body via the contact surface. The chamber can also be equipped with a valve and be inflatable; in this case, the pressure of at least one functional element against the body part being enclosed can only be achieved by inflating the chamber. When using multi-stable spring mechanisms, the stability and / or pressure of the garment can be increased by combining them with additional fastening mechanisms such as hook-and-loop fasteners. Additional fastening mechanisms are particularly suitable in combination with preferably elongated bistable leaf springs for easier removal, or with weaker leaf springs to facilitate a domino effect. Furthermore, multistable spring mechanisms can be combined with additional locking mechanisms in such a way that, when the device is applied, a desired wearing state is initially only approximately achieved and maintained by changing the state of the multistable spring mechanism. This facilitates subsequent manual adjustment of the wearer's precise position relative to the body and subsequent fixation by actuating additional locking mechanisms. Holding the wearer approximately in a desired wearing state can, for example, enable or facilitate one-handed operation of such additional locking mechanisms, which allow for various adjustable locking positions and are normally operated with both hands. First example: Fig. 6 schematically shows a first embodiment of the circuit according to the invention. In this embodiment, the shape of the carrier corresponds to a sheath around a leaf spring, with a length appropriately chosen to grasp a body part, in this case the forearm, and a width appropriately chosen to support circuit elements on the sides facing the body and away from it. Fig. 6A is a schematic oblique view showing a functional element 2100, in this case eight contact electrodes 2110, which, when the circuit is worn, are to be held in tactile and electrically conductive contact with a forearm, on a contact surface 1100-F of a carrier 1000. The functional element 2100 and the contact surface 1100-F lie flat, open in the z-direction, in an xy-plane. The carrier has a rectangular base shape with a longer side along the y-direction and a shorter side along the x-direction. Fig. 6B is a view from the same perspective, in which a bistable leaf spring 1200 is shown schematically as a dashed line. Matching the basic shape of the support 1000, the bistable leaf spring 1200 has a rectangular shape with a longer side of length Ly along the y-direction and a shorter side along the x-direction. It is in a stretched, locally stable state, similar in this respect to the exemplary leaf springs shown in Figs. 1A, 2A, and 3A in their respective second locally stable (stretched) state. For the sake of simplicity, bistable leaf springs are shown here, as well as subsequently, without any curvature deviating from the direction of incurvature in the first, most curved, locally stable state. The carrier 1000 is designed as a casing or pocket 1400 to receive the bistable leaf spring 1200 and comprises a flat material that is deformable and has an elongation of at least 20%. Because of this deformability and elongation, as well as its size and shape suitable for the leaf spring, the carrier receives the bistable leaf spring in such a way that the spring determines the shape of the carrier. The figure shows the bistable leaf spring 1200 in its locally stable "extended" state, in which it is not curved in its longitudinal direction y and gives the support 1000 an overall flat and elongated shape in the y-direction. In the oblique view of the figure, the pocket 1400 is open to the rear (in the y-direction) to allow the leaf spring 1200 to be inserted and removed in its extended state, and the leaf spring 1200 is slidably guided within the receiver 1400. Fig. 6C is a schematic oblique view from the opposite direction and shows the side of the present embodiment opposite the contact surface 1100-F of the carrier. On this side – which faces away from the body when worn – are circuit elements that should not or must not have any physical contact with the body when the circuit is worn on the human body, for example an RFID module 2130, in which information that characterizes the circuit and / or individually identifies it can be stored and retrieved wirelessly, and an electronic module 2400 with semiconductor circuit components, which projects in front of the main surface of the carrier 1000 in the direction -z.The electronics module 2400 of the exemplary embodiment incorporates semiconductor circuit components with functions for the electronic control of the functional elements 2100, power supply, data acquisition, and communication with another electronic device (not shown), such as a smartphone. Furthermore, the electronics module of the exemplary embodiment includes a user interface with the buttons "+", "on / off", and "-" to provide the user with a means of simple operation directly on the circuit while wearing it. Fig. 6D shows in a side view the first embodiment in the extended, second locally stable state with the contact surface 1100-F and the functional element 2100 with eight contact electrodes 2110 facing upwards and the electronic module 2400 facing downwards on a flat support surface T, for example a table top. The electronic module forms a projection in front of the main surface of the carrier opposite contact surface 1100-F and serves as a support, preventing it from resting flat on the support surface T. In the y-direction, the electronic module 2400 is arranged off-center on the carrier 1000 and rests on the support T together with the opposite end 1000-Y of the carrier 1000. Except for the aforementioned contact points, the side opposite contact surface 1100-F has no contact with the flat support, so that there is a gap between the carrier 1000 and the support surface T. In this gap, the carrier 1000, with the leaf spring contained therein, can deflect downwards in the area between the contact points on the support T and the opposite end 1000-Y when pressure is applied from above to the contact surface 1100-F, in the movement required to change state into a rolled-up state. Fig. 6E shows the circuit according to the invention in such a flat arrangement for the first embodiment, whereby the support / tabletop is not shown in this oblique view. To place the circuit against a right forearm, the forearm rests on the contact surface 1100-F in the area between the electronic module 2400 (recognizable by the dashed outline 2400-U of its underside) and the opposite end 1000-Y of the carrier 1000 and exerts a pressure corresponding to the weight on it (typically between 2 kg and 5 kg for adults, depending on posture and build; in individual cases and for children, it may be less, for example, between 1 kg and 2 kg), so that the carrier with the leaf spring 1200 contained therein is bent downwards in its longitudinal direction y.The support and leaf spring are designed such that the pressure exerted by the weight of the resting forearm is sufficient to cause the leaf spring to change from the area U2 of the second locally stable state Z2 to the area U1 of the first locally stable state Z1, i.e., from a stretched to a coiled state. This change corresponds to the change of the leaf spring from the area U2 of the second locally stable state Z2 to the area U1 of the first locally stable state Z1 shown in the upper part of Fig. 5A, triggered in Fig. 6E by the pressure exerted by the forearm K instead of by a cylinder as in Fig. 5A. The support and leaf spring are designed such that the length Ly of the leaf spring, as well as the inner diameter of the support with the leaf spring in the rolled-up, "first" locally stable state Z1, is smaller than the outer diameter of the forearm K (typically between 20 cm and 30 cm in adults, and in some cases and in children even smaller, for example between 12 cm and 20 cm) in its contact area with the support 1000. Then the forearm—similar to the cylindrical body K in Fig. 4—acts as a roll-up limiter parallel to a direction x around which the roll-up of the support with the leaf spring occurs in its first state. Due to the roll-up limiting effect of the forearm, the curvature of the rolled-up "first" locally stable state Z1 is not reached; rather, the state of the leaf spring in the surrounding region U1 of the first locally stable state Z1 remains in a state Z1' with energy E1'. Fig. 6F shows the circuit in a corresponding rolled-up state worn on the body, in which the carrier 1000 embraces the right forearm K in such a way that the surface 1100-F of the carrier exposed in the z-direction in Fig. 6A with the functional elements 2100 of the circuit is held in touching contact with the forearm K and pressed against the forearm with pressure. Fig. 6G shows a cross-section through the carrier 1000 in a carrying state with its inwardly directed surface 1100-F and the functional element 2100 of the circuit in direct contact (in z-direction) with the forearm K (shown dotted) in a carrying state. Generally, and regardless of the present embodiment, the support 1000, in its supporting state, encompasses the body part K with the leaf springs to more than half of its outer circumference. Preferably, the lengths Ly of the leaf springs in their longitudinal direction are more than 60%, more preferably more than 75%, and most preferably more than 90%, of the outer circumference of the body part K at the respective point encompassed. This is the case in the example shown. In the example shown, the support 1000, when in the carrying position, encircles body part K to less than its full outer circumference; that is, the encircling of the body part is "partial." This should not be understood as a general limitation; the length of the support along the leaf springs can just as easily correspond to or exceed the outer circumference of the encircled body part, provided that the two sides of the support meeting during the encircling of the body part do not obstruct each other. The off-center positions of the electronic module 2400 and the functional elements 2100, which are to be held in contact with the body when worn, do not restrict the functioning of the invention. Rather, the relative position of the electronic module and the functional elements on the carrier is determined by their respective preferred positions when the circuit is worn on the human body as intended. In the first embodiment, the electronic module and the contact electrodes are worn on different sides of the forearm: the contact electrodes, as is functional, on the muscles of the inner forearm, and the electronic module, for comfort, on its upper outer side. This results in a mutual distance between the electronic module and the functional elements on the carrier. Second example: Fig. 7 schematically shows a second embodiment of the circuit according to the invention. It corresponds to the first embodiment in numerous features, and the differing features are explained below. In contrast to the first embodiment, the carrier is not designed as a casing or pocket for receiving a bistable leaf spring, but rather the carrier is made of plastic material with a smooth and liquid-repellent outer surface, and the bistable leaf spring and the carrier are bonded together and thus formed as a single piece. As can be seen from Figs. 7A and 7B, this arrangement allows for a particularly small size of carrier 1000 with circuits 2100 and 2400. As can also be seen from Fig. 7C, the electronic module 2400 is designed here as an integrated unit permanently connected to the carrier and provided with a cable connection for connection to a stationary medical device. In this embodiment, other advantages of the circuit according to the invention are emphasized: Together with the carrier made of plastic material with a smooth and liquid-repellent outer surface, the embodiment enables easy cleaning and disinfection of the contact surface 1100-K and thus allows its use in medical facilities with multiple patients. If the functional elements 2100 contain electrodes and / or sensors, these can be brought into "dry" contact with the respective patients and thus replace gelled and / or adhesive electrodes and / or sensors. Third example: Fig. 8 schematically illustrates a third embodiment of the present invention. Fig. 8A schematically shows an oblique view of a circuit with a functional element 2100 on a contact surface 1100-F of a carrier 1000, which is to be kept in direct contact with the body when the circuit is worn. The functional element 2100 and the surface 1100-F lie flat, open in the z-direction, in an xy-plane. The carrier has a rectangular base shape and, on two sides opposite each other in the x-direction, receptacles 1401 and 1402 in the form of pockets for receiving two bistable leaf springs 1201 and 1202 (shown with dashed lines), which form the multistable spring mechanism. Similar to the examples shown in Figs. 1, 2, 3 to 4, the leaf springs 1201 and 1202 also have a rectangular base shape with a longer side along the y-direction and a shorter side along the x-direction.The pockets are open on one short side – in the drawing, looking backwards in the y direction – to allow the leaf springs to be inserted and removed, as shown for pocket 1402 and leaf spring 1202. In the exemplary embodiment, the leaf springs 1201 and 1202 are received in the pockets 1401 and 1402 of the support 1000 in such a way that they are guided to slide freely in their longitudinal direction (y direction) relative to the support and are guided with restricted movement in other directions.If, when the leaf springs are rolled up, their lengths change in the longitudinal direction, for example, such that they increase on the outside compared to the length in the extended state and decrease on the inside compared to the length in the extended state, the sliding movement of the leaf springs in the pockets allows the support to change its shape when the leaf springs are rolled up, without the lengths of the pockets on the inside and outside of the rolled-up leaf springs having to change in the same way as the lengths of the leaf springs. The support 1000 according to the exemplary embodiment comprises a flat textile material which is deformable and in this case has an elongation of 2%. The support accommodates the multistable spring mechanism (the two bistable leaf springs) in such a way that a shape of the spring mechanism determines a shape of the flat textile material. In Fig. 8A, the bistable leaf springs 1201 and 1202 are in a locally stable state in which they are not curved in their longitudinal direction y and give the support 1000 an overall planar and flat shape. Similar to the examples shown in Figs. 1, 2, 3 to 4, the bistable leaf springs 1201 and 1202 have a locally stable state stretched along their longer sides, whereby the support also has a flat, stretched shape, as well as a rolled-up locally stable state in which they are rolled up around an axis along their shorter side x and transversely to their longer side y, whereby the support also assumes a rolled-up shape, in such a way that the surface 1100-F of the support open in the z-direction with the functional element 2100 of the circuit comes into contact with the internally open inner side of the support when rolling up. Fig. 8B shows a schematic side view of the embodiment. In the upper section, the functional element 2100 is shown on the contact surface 1100-F of the carrier 1000. Furthermore, the carrier has a compressible layer 1300 on its side opposite the contact surface 1100-F – in this case designed as a foam pad – which is designed such that, when the carrier with the foam pad facing downwards rests flat on a hard and flat support surface, pressure applied to the carrier from above in the central area of ​​each of the leaf springs allows for a deformation of the carrier and a curvature of the leaf spring sufficient to change the state of the leaf spring from the extended to the coiled state. Figure 8C schematically illustrates how such pressure can be exerted by placing a body part K of a human body, in this case a right forearm, onto a longitudinally (y-direction) central area of ​​the carrier and thus onto corresponding central areas of the leaf springs 1201 and 1202. The axis of the forearm runs in the x-direction and thus transversely to the longitudinal direction of the leaf springs. This pressure in the central area of ​​each of the leaf springs causes the carrier 1000 to change into a rolled-up state worn on the body, as shown in Figure 80. In this worn state, the carrier 1000 encircles the right forearm K in such a way that the surface 1100-F of the carrier, which lies in the xy-plane and is open in the z-direction in Figure 8A, is held in contact with the functional element 2100 of the circuit, lying flat against the forearm K. The position of the functional element 2100 of the circuit relative to the forearm when the user is wearing the device can be determined when putting on the device, particularly when placing the arm on the device in a stretched, locally stable position. If, for example, the functional element is to be positioned on the outside of the forearm when worn, as schematically shown in Fig. 5C, the forearm can be placed on the functional element with this side facing downwards (and simultaneously with the elbow and back of the hand facing downwards; see Fig. 5B). The position of the functional element 2100 between the elbow and wrist when worn can also be selected by placing the forearm in the desired position between the elbow and wrist. The example shown makes it generally clear that the dimensions of the carrier and the locally bistable leaf springs, the latter especially in their longitudinal direction, as well as their radius in the rolled-up state, must be selected to match the dimensions, especially circumference, of the body part with which the functional element 2100 of the circuit is to be held in touching contact and / or mutual pressure. The radii of the leaf springs in the coiled state, without the influence of external forces, are selected to be smaller than the radii of the body part K to be enclosed and are preferably between 50% and 95%, and particularly preferably between 60% and 90%, of the smallest radii of the body part K at the respective enclosed points. This is not to be understood as a limitation; rather, the leaf springs in the coiled state, without the influence of external forces, can also have larger radii than the enclosed body and press one or more intermediate bodies surrounding the enclosed body part against the enclosed body part from the outside. In the carrying state shown in Fig. 8D, the leaf springs 1201 and 1202 are in a state Z1' within a surrounding area U1 of their respective rolled-up, locally stable state Z1, with the outer shape of the forearm K limiting the rolling of the leaf springs, so that—as explained in connection with Fig. 4—they exert pressure against the outer surface of the forearm and cause the functional element 2100 to also be pressed against the forearm K with a certain degree of pressure. This pressure remains largely unchanged during muscle movements or changes in posture. Comparing the states shown in Fig. 8A and Fig. 8D, in the wearing state according to Fig. 8D the functional element 2100 of the circuit is held in touching contact with the body part and pressed against the body part (K) with a certain pressure, whereas this is not the case in the state of the circuit shown in Fig. 8A. Both leaf springs are of the "preferentially coiled" type, meaning that the energies in their respective coiled, locally stable state are minimal and lower than in any other state of the respective leaf spring. This results in the advantages of easier installation and good stability and pressure when the circuit is in use, as explained in Fig. 5A. Fourth example: Figures 9A to 9C schematically show a fourth embodiment of the present invention. It agrees with the previous embodiments in several features, and the differing features are explained below. Fig. 9A is a schematic oblique view of the contact surface 1100-F of the carrier 1000 with elements of the circuit, including four contact electrodes 2111, 2112, 2113, and 2114 as the functional element of the circuit, which is to be held in tactile and electrically conductive contact with a forearm when wearing the circuit, as well as circumferentially electrically insulated conductor tracks 2120, which are electrically conductive in their interior, for the connection between the contact electrodes and an electronic module 2400, the underside 2400-U of which is shown in a schematic through-view with dashed lines and is designed for functions as have been explained by way of example in connection with Fig. 6C. The carrier has three pockets 1401, 1402, and 1403 for the sliding support of three leaf springs 1201, 1202, and 1203 (shown in dashed lines in the view diagram). On its side opposite the functional element, it has three foam pads 1301, 1302, and 1303 as a compressible layer. These pads are designed such that, when the carrier rests on them and on a hard, flat support surface, pressure applied to the carrier at the center of one of the leaf springs causes a deformation of the carrier and a curvature of the leaf spring sufficient to change the state of the leaf spring from its extended to its coiled state. The electronic module 2400 projects outside the section plane shown in Fig. 9B, in front of the outer side of the carrier in its supported state, and can thus facilitate the change of state of the adjacent leaf springs. Fig. 9B is a schematic sectional view in the yz plane in the area of ​​the contact electrodes 2111 and 2112. In this area, the section plane includes a cut through the central pocket 1402 and the central leaf spring 1202. The contact electrodes 2111 and 2112 are located on the contact surface 1100-F and, when the device is in use, are held in direct contact with the enclosed body part K (forearm) by the central leaf spring 1202. As can be seen in Fig. 9A, this is also the case for the contact electrodes 2113 and 2114. The wearing state of the circuit is shown in Fig. 9C. In this embodiment, the dimensions of the carrier are selected to match the body part K (forearm) to be grasped. On the elbow side, its shape is determined by the shape of the leaf spring 1201, which is located in a region surrounding its first, rolled-up, locally stable state. On the wrist side, the shape of the carrier is determined by the shape of the leaf spring 1203, which is located in a region surrounding its first, rolled-up, locally stable state. The two outer leaf springs ensure that the carrier rests against the grasped body part at its corresponding edges when worn. If their mutual spacing (in the x-direction in Fig. 9A) is selected to match the distance between the elbow and wrist, it accordingly determines the position of the entire carrier and thus also the position of the contact electrodes between the elbow and wrist. In general, when using multiple leaf springs to grip a body part, it is advantageous if their lengths are adapted to the circumference of the gripped body part at the respective point of gripping. The circumference of a forearm is usually larger near the elbow than near the wrist; therefore, it is advantageous if the outer leaf spring on the elbow side is longer than the outer leaf spring on the wrist side. This results in a trapezoidal basic shape for the wearer with two different side lengths L1 and L2 on its two sides opposite each other in the x-direction, as shown in Fig. 9A. Corresponding to the different lengths of the outer leaf springs, the support has a trapezoidal basic shape with two different side lengths L1 and L2 on its two sides opposite each other in the x-direction. Such a trapezoidal shape also generally serves to prevent the circuit from being accidentally applied upside down. This is particularly important when the functional element, which must be held in a specific position relative to the body, is located at different distances from the two outer leaf springs. In the illustrated embodiment, the group of four contact electrodes is located closer to the elbow side than to the wrist side of the wearer. Due to its low elasticity (2%, as in the previous embodiment), the support of the embodiment establishes a sufficiently tensile-strength mechanical connection between the outer leaf spring 1201 near the elbow and the middle leaf spring 1202, so that these can only change their locally stable curvature states mutually dependent on each other and, without the influence of external forces, are either both in the extended state or in a rolled-up state. In this embodiment, the middle leaf spring 1202 is of the "preferably rolled-up" type and, when worn, holds the contact electrodes in stable contact with the body by applying pressure. The outer leaf spring 1201, located near the elbow, is of the "preferably extended" type and facilitates putting the circuit down. The outer leaf spring 1203, located near the wrist, has a comparatively lower spring force than the other two leaf springs and its shape follows their changes in state. Fifth example: Figures 10A and 10B schematically show a fifth embodiment of the present invention. This embodiment also agrees with the previous embodiments in several features, and the differing features are explained below. Fig. 10A is a schematic oblique view of the contact surface 1100-F of the carrier 1000 with twelve contact electrodes 2110 as a functional element, which are to be held in pressure and with touching and electrically conductive contact with a forearm when carrying the circuit. The carrier has three pockets 1401, 1402, and 1403 for receiving three bistable leaf springs 1201, 1202, and 1203 (shown as dashed lines in the view diagram), and on its side opposite the contact surface, three compressible bearing layers 1301, 1302, and 1303 with properties and functions described above at the positions of the three bistable leaf springs. The three bistable leaf springs are preferably of the rolled type. The twelve contact electrodes 2110 extend over an area wider than the contact surface of each individual leaf spring, and they extend – in a direction transverse to the longitudinal direction of the leaf springs – over an area between two adjacent leaf springs 1202 and 1201. The present embodiment has a deformable, liquid-filled chamber 1620 between the pockets 1401, 1402, 1403 containing the leaf springs 1201, 1202, 1203 and the contact surface 1100-F, serving as a pressure mechanism to increase the contact area of ​​the leaf springs. Fig. 10B shows the embodiment in a wearing state on a forearm K. The carrier encircles the forearm K with the three leaf springs 1201, 1202, 1203, each in a coiled state, in the vicinity of their first locally stable state. In this external view, the leaf springs are located below their respective support layers 1301, 1302, 1303 in their respective pockets 1401, 1402, 1403 and exert external pressure on the liquid-filled chamber 1620. The twelve contact electrodes 2110 on the contact surface 1100-F are located between the body part and the liquid-filled chamber in the wearing state and are pressed against the body part by the pressure of the leaf springs, which is uniformly distributed by the liquid in the chamber. An electronic module 2400 is located on the side of the carrier opposite the contact surface 1100-F and facing outwards in the carrying state, specifically close to its side edge above an outer leaf spring 1201 to ensure short conductor connections. As shown in Fig. 10A, the conductor tracks 2120 for connecting the contact electrodes 2110 on the contact surface 1100-F of the carrier to the electronic module 2400 on the opposite side of the carrier run over said side edge to get from the contact surface to the opposite side of the carrier, thereby bypassing the liquid-filled chamber and the pocket 1401. Sixth example: Figures 11A and 11B schematically show a sixth embodiment of the present invention, which can be understood as a variant of the fifth embodiment. The differing features are explained below. Fig. 11A is a schematic oblique view of the contact surface 1100-F of the carrier 1000 with twelve contact electrodes 2110 as a functional element, which are held in pressure and in contact with a forearm when the circuit is worn. In contrast to the fifth embodiment, the carrier has only two pockets 1401 and 1402 for receiving only two (shown in dashed lines in the view) bistable leaf springs 1201 and 1202 of the preferably rolled type, and also a deformable inflatable chamber 1630 as a pressure mechanism in an area only between these leaf springs. Fig. 11B shows the sixth embodiment in a carrying state on a forearm K with the inflatable chamber 1630 in an inflated state. The carrier encompasses the forearm K with the two leaf springs 1201, 1202 in their respective rolled-up state in a region surrounding their first locally stable state. Since the chamber is located only between the leaf springs, the leaf springs do not exert any vertical pressure against the chamber; instead, its side wall is drawn tangentially towards the body by the leaf springs. A valve 1631 on the outside of the chamber, when the wearer is in the wearing position, allows the chamber to be inflated and an internal pressure to be set. This allows a portion of the spring forces of the leaf springs to be redirected as a uniformly distributed pressure against the body, and the twelve contact electrodes 2110, which are located between the body part and the chamber when the wearer is in the wearing position, can be pressed against the body part by the inflated chamber. An electronic module 2400 is located on the side of the carrier opposite the contact surface 1100-F and facing outwards in the operating state. For the sake of short connection paths, the conductor tracks 2120 for connecting the contact electrodes 2110 to the electronic module 2400 switch in an area between the inflatable chamber 1630 and one of the leaf springs 1201 from the side of the contact surface 1100-F to the opposite side of the carrier, in order to bypass both the inflatable, liquid-filled chamber and the pocket 1401 of the leaf spring 1201. Seventh example: Fig. 12A and Fig. 12B schematically show a seventh embodiment of the present invention, like the fourth and fifth embodiments with three bistable leaf springs. Similar to the fifth embodiment, the functional element of the circuit, which is held in the wearing position under pressure and in contact with a forearm K, comprises twelve contact electrodes extending transversely to the longitudinal direction of the leaf springs over a large area, in this case almost to the two outer leaf springs 1203 and 1201. As in the fifth embodiment, the carrier therefore includes a pressure mechanism for increasing the contact area of ​​the leaf springs.However, in the present embodiment, this is not designed as a deformable, liquid-filled chamber, but rather as an elastic structure of struts that stiffens the support material (in this example, textile). These struts extend over the spaces between adjacent leaf springs and can absorb the pressure forces generated by the rolled-up leaf springs against the forearm being supported, partially redirecting them to the spaces they cover. In the illustrated embodiment, the structure of struts comprises ribs 1610 that run parallel to one another in a direction transverse to the longitudinal direction of the leaf springs. Alternatively or additionally, the ribs can run in other directions, including multiple directions, and, for example, form a truss or mesh structure. In the example shown, the rib structure extends over all the spaces between adjacent leaf springs. Alternatively, it may suffice to cover only those spaces with a stiffening rib structure where parts of the functional element that is held in contact with the body under pressure are located. The rib structure is appropriately connected to the carrier material – in this example, textile – for instance, by a fabric-bonded connection, integrated as part of the textile structure, or sewn on or attached. Similar to the fourth embodiment, an electronic module 2400 is arranged on the outer side of the carrier opposite the contact electrodes in the load-bearing state, specifically in the intermediate area between the elbow-side and the middle leaf spring. In this area, the contact electrodes on one side of the carrier can be connected through the carrier to the electronic module on the other side of the carrier. The leaf springs are mechanically connected to each other via the rib structure. This connection, which is both elastic and stiffens the support, ensures that a change in the state of one leaf spring causes a change in the state of the other springs ("domino effect"). In this embodiment, the support has a compressible support 1300 (support pad) only in the area of ​​the wrist-side leaf spring to facilitate the change from an open state (Fig. 12A) to a supported state (Fig. 12B). If necessary, such a change in the state of the other two leaf springs is also facilitated by the electronic module 2400. Eighth example: Fig. 13A and Fig. 13B schematically show an eighth embodiment of the present invention. In contrast to the previous embodiments, here a lower leg is to be grasped, in which, when the circuit is worn, eight contact electrodes 2110 in the area of ​​the calf are to be held in contact with the body with pressure and are arranged on an outside of the lower leg via conductor tracks 2120 with an electronic module 2400 (underside 2400-U shown in a schematic view with dashed lines in Fig. 13A) ( Fig. 13B). The carrier contains a textile layer 1800 with two pockets 1841 and 1842 for the sliding guided reception of two bistable leaf springs 1201 and 1202 at the upper and lower edge of the carrier with lengths L1 and L2 adapted to the lower leg. In the intermediate area between the two leaf springs, the support is provided with an elastic rib structure 1610 of the type described in the previous embodiment, whereby the leaf springs are mechanically connected to one another, so that a change of state in one leaf spring causes a change of state in the other springs (“domino effect”). The upper leaf spring 1201 is preferably of the open type, the lower leaf spring 1202 preferably of the rolled type, and the two leaf springs are designed for a “domino effect” in both directions. To increase the stability of the carrying position, the upper pocket 1841 is equipped with a hook-and-loop fastener 1900, visible in Fig. 13A at the end furthest from the viewer on the top and at the end closer to the viewer on the underside. A fastener in this position is also relatively easy to reach manually for users with limited knee mobility. Opening and removing the carrier requires only the manual release mechanism and a relatively small manual change of position of the upper leaf spring. The lower pocket 1842 is equipped with a compressible support 1302 on its outer surface. To approximate the carrier's wearing position, the lower leg is placed on the middle section of the lower leaf spring, applying pressure. Final adjustment and securing of the carrier in the wearing position are then done manually using the hook-and-loop fastener. Overall, even with limited knee movement, both putting on and taking off the lower leg shifter is made easier. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature DE P 3831251 A1

[0028] DE 10 2009 023 689 A1

[0028] Cited non-patent literature Forsch. Ingenieurwes. 85 (2021), pp. 817-825

[0030]

Claims

Circuit to be worn on the human body with at least one functional element (2100, 2110) on a carrier (1000) which is designed to hold the at least one functional element (2100, 2110) of the circuit in a predetermined position relative to - and preferably in contact with - a body part (K) of the human body, characterized in that the circuit and carrier are connected by a multistable spring mechanism (1200;4000) are provided with at least two different locally stable states (Z1, Z2) and are designed to hold the at least one functional element (2100, 2110) of the circuit in a carrying state (Z1') in an area (U1) of a first locally stable state (Z1) of the multistable spring mechanism in the predetermined position relative to the body part (K) and in a state (Z2') in an area (U2) of a second locally stable state (Z2) of the multistable spring mechanism not in the predetermined position relative to the body part (K). Circuit on carrier according to claim 1, wherein the circuit and carrier with the multistable spring mechanism (1200) are designed to press the at least one functional element (2100, 2110) of the circuit with a first pressure against the body part (K) in the wearing state (Z1') and not to press against the body part (K) in the surrounding area (U2) of the second locally stable state (Z2) of the multistable spring mechanism or with a lesser pressure than the first pressure. Circuit on carrier according to claim 1 or two, wherein the spring mechanism in its first locally stable state (Z1) contains a lower potential energy (E1) than when it is in another state. Circuit on a carrier according to one of the preceding claims, wherein the multistable spring mechanism (1200) comprises a bistable leaf spring (1200, 1201, 1202, 1203) with two different locally stable curvature states (Z1, Z2) and the bistable leaf spring (1200, 1201, 1202, 1203) in its first locally stable curvature state (Z1) has a smaller radius of curvature in the direction (y) of its greatest curvature than the smallest radius of curvature in its second locally stable curvature state (Z2), and wherein the carrier is designed to at least partially grip the body part (K) with pressure when the circuit is worn on the human body, when the bistable leaf spring is in a wearing state (Z1') in an area (U1) surrounding its first locally stable curvature state (Z1), and not to grasp the body part (K) that is at least partially enclosed in the carrying state, or to grasp it with less pressure,when the state (Z2') of the bistable leaf spring is located in a region (U2) surrounding its second locally stable state of curvature (Z2). Circuit on a support according to one of claims 1 to 4, wherein the multistable spring mechanism comprises two or more bistable leaf springs (1200, 1201, 1202, 1203), each of which has different locally stable curvature states and in its first locally stable curvature state has a smaller radius of curvature in the direction of its strongest curvature (y) - which is preferably also the direction of its longest extent in an uncurved state - than the smallest radius of curvature in its second locally stable curvature state;and wherein the carrier is designed to at least partially grip the body part (K) with pressure when the circuit is worn on the human body, when the bistable leaf springs are each in a carrying state (Z1') in an area (U1) of their respective first locally stable curvature state (Z1), and not to grip the body part (K) at least partially gripped in the carrying state, or to grip it with less pressure, when the states (Z2') of the bistable leaf springs are each in an area (U2) of their respective second locally stable curvature state (Z2). Circuit on a carrier according to claim 4 or 5, wherein the one or more bistable leaf springs in their respective second locally stable curvature state are not curved in the direction (y) of their strongest curvature in their first locally stable curvature state - which is preferably also the direction of their respective longest extension in an uncurved state - or have a radius of curvature that is larger than the smallest radius of curvature in the respective first locally stable curvature state. Circuit on a support according to claim 5 or 6, wherein the support is configured to form a bistable overall system with two locally stable overall states, wherein in a first locally stable overall state the two or more leaf springs are in their respective first locally stable state and in a second locally stable overall state are in their respective second locally stable state, and wherein a change of state of one of the leaf springs between a first and second individual state without the action of a further external force causes a corresponding change of state of another of the two or more leaf springs. Circuit on a support according to the preceding claim, wherein one of the at least two leaf springs has a higher elastic potential energy in the second locally stable state than in the first locally stable state and another of the at least two leaf springs has a lower elastic potential energy in the second locally stable state than in the first locally stable state. Circuit on support according to the preceding claim, wherein the one or more bistable leaf springs in their respective second locally stable curvature state (Z2) change from their second locally stable curvature state to their first locally stable curvature state by pressing against their inside, i.e. the side which is concavely curved in their respective first locally stable curvature state. Circuit on carrier according to one of claims 4 to 9, further comprising a pressure mechanism (1600) for increasing the pressure area of ​​the spring mechanism beyond the width of the one bistable leaf spring or the widths of the several bistable leaf springs in a direction transverse to the respective direction (y) of their strongest curvature in their first respective locally stable curvature state. Circuit on a carrier according to one of the preceding claims with the features of claims 4 or 5, wherein the carrier comprises a position limitation device which limits the position of the or a bistable leaf spring relative to the carrier in at least one direction transverse to the direction of the strongest curvature (y) of the or a bistable leaf spring. Circuit on a carrier according to one of the preceding claims, wherein the carrier comprises a flat, preferably textile material (1800) which receives and encloses the multistable spring mechanism in such a way that the latter determines a shape of the flat, preferably textile material. Circuit on a carrier according to one of the preceding claims, wherein surfaces of the multistable spring mechanism, which deform when switching between different locally stable states, are guided to be slidably movable relative to surfaces of the carrier. Circuit on a carrier according to one of the preceding claims, wherein the carrier comprises a deformable chamber containing a fluid material and designed to press the at least one functional element (2100, 2110) of the circuit against the body part (K) in a carrying state in an environment (U1) of a first locally stable state (Z1) of the multistable spring mechanism. Circuit on a carrier according to one of the preceding claims, further comprising a sensor system configured to detect the curvature state of the bistable leaf spring and preferably to detect whether the bistable leaf spring is in a state in an area surrounding its first locally stable curvature state; as well as a control device for performing a control operation depending on a detection result of the sensor system and / or an output device for outputting a signal depending on a detection result of the sensor system. Circuit on a carrier according to one of the preceding claims, wherein the at least one functional element (2100) is configured as a sensor and / or as an actuator, for example as an electrode (2110) serving as a sensor or actuator, or as a field of such sensors and / or actuators. Circuit on a carrier according to one of the preceding claims, wherein the at least one functional element 2100 is formed as one or more thin layers on a surface of the carrier.

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