WO2021074664A1 - Method for manufacturing an ultra-thin epidermal sensor and sensor obtained. - Google Patents

Method for manufacturing an ultra-thin epidermal sensor and sensor obtained. Download PDF

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Publication number
WO2021074664A1
WO2021074664A1 PCT/IB2019/058726 IB2019058726W WO2021074664A1 WO 2021074664 A1 WO2021074664 A1 WO 2021074664A1 IB 2019058726 W IB2019058726 W IB 2019058726W WO 2021074664 A1 WO2021074664 A1 WO 2021074664A1
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WIPO (PCT)
Prior art keywords
sensor
electrode
thickness
acquisition portion
holes
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PCT/IB2019/058726
Other languages
French (fr)
Inventor
Andrea SPANU
Annalisa Bonfiglio
Stefano LAI
Piero COSSEDDU
Danilo Pani
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Universita' Degli Studi Di Cagliari
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Application filed by Universita' Degli Studi Di Cagliari filed Critical Universita' Degli Studi Di Cagliari
Priority to PCT/IB2019/058726 priority Critical patent/WO2021074664A1/en
Priority to EP19813642.6A priority patent/EP4044900A1/en
Publication of WO2021074664A1 publication Critical patent/WO2021074664A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1468—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using chemical or electrochemical methods, e.g. by polarographic means
    • A61B5/1477—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using chemical or electrochemical methods, e.g. by polarographic means non-invasive
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/25—Bioelectric electrodes therefor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/25—Bioelectric electrodes therefor
    • A61B5/279—Bioelectric electrodes therefor specially adapted for particular uses
    • A61B5/296—Bioelectric electrodes therefor specially adapted for particular uses for electromyography [EMG]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
    • A61B2562/0209—Special features of electrodes classified in A61B5/24, A61B5/25, A61B5/283, A61B5/291, A61B5/296, A61B5/053
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
    • A61B2562/028—Microscale sensors, e.g. electromechanical sensors [MEMS]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/12—Manufacturing methods specially adapted for producing sensors for in-vivo measurements
    • A61B2562/125—Manufacturing methods specially adapted for producing sensors for in-vivo measurements characterised by the manufacture of electrodes

Definitions

  • the invention is part of the so-called “epidermal electronics” or “tattoo electronics”. These are ultra-thin epidermal sensors connected to an acquisition electronics for the measurement of physiological electrical signals, in particular for the detection of EMG, ECG, EEG, EOG bio-potentials and other physical and chemical parameters such as for example pH and temperature.
  • These sensors are made in a sandwich configuration using a deposition techniques, in which an electrode is packed.
  • the sensor identifies an acquisition portion in which the acquisition portions of one or more electrodes and a connection portion are present, in which the buses of each isolated electrode, i.e. passivated with respect to the external environment, run up to define a sort of flat cable band suitable to be inserted in a ZIF connector or similar, associated with an electronic signal acquisition and processing card.
  • the senor is broken in the connection portion that allows the interconnection with the aforementioned ZIF connector or similar.
  • a further object of the present invention is to present a sensor that is more robust than known ones.
  • Another object of the present invention is to present a sensor which is simultaneously more robust than those known and less sensitive to sweating.
  • the basic idea of the present invention is to manufacture an ultra- thin epidermal sensor and to carry out a procedure of further selective removal of material after its manufacture. More precisely, through openings are made in the thickness of the sensor in order to promote sweat transpiration generated by the epidermis and/or a surface layer of material is removed from the acquisition portion of the sensor, by defining a thickening of the connecting portion of the sensor so as to make the sensor more resistant at the interface with the electronic card for acquisition and/or processing of physiological signals. More preferably, the removal of excess material is achieved by obtaining a moderate gradient between the two zones: acquisition portion and interconnection portion.
  • this allows to avoid the breakage of the interface portion between the sensor, intended to be attached to the epidermis, and the device for acquisition and/or processing of physiological signals.
  • Physiological signals are acquired in the form of electrical signals.
  • the sensor is of the passive type it is intended to directly acquire typical electrical signals for example of EMG, ECG, etc.
  • the electrical signals can be either both EMG, ECG signals, etc., and signals of chemical nature (for example the chemical composition of sweat, pH skin, etc.).
  • the material deposited in the deposition procedures is in excess of that is strictly necessary and is followed by a further selective removal procedure, aimed at making openings passing through the thickness of the sensor and/or aimed at determining a thinning of the acquisition portion with a corresponding thickening of the connecting portion of the sensor.
  • the sensor obtained by the present method can advantageously be used for the detection of EMG, ECG, EEG, EOG bio-potentials and other physical and chemical parameters such as for example pH and temperature, by solving the problem of dermis transpiration. It also allows the simultaneous dosing of a fluid substance through the same sensor, in order to stimulate a bioelectric response or to restore the hydration of the dermis.
  • the present invention also finds application in the field of robotics and in particular in the field of tactile sensors.
  • the claims describe preferred embodiments of the invention, forming an integral part of the present description.
  • Figure 1 shows a part of a method of manufacturing an epidermal sensor according to the present invention
  • Figure 2 shows a portion of the method which replaces or integrates the last step of the method of Figure 1 ;
  • Figure 3 shows an assembly and a relative exploded view of an example of a sensor obtained according to a variant of the method of the present invention
  • Figure 4 shows an assembly and a relative exploded view of another example of a sensor obtained according to another variant of the method of the present invention.
  • the proposed technique is compatible with known manufacturing processes per se, such as standard photolithography, ink-jet printing, silk- screen printing, micro-contact printing, roll-to-roll and allows to obtain ultra-thin sensors with high transpiration properties as well as of biocompatibility and conformability, i.e. an optimal adherence to any substrate, skin, mucosa, etc..
  • the sensor Sens according to the present invention includes a flat and ultra-thin casing of Parylene C in which a flat electrode L3 is embedded, of which only one acquisition portion is uncovered on one of the two opposite faces of the sensor. Therefore, the sensor defines an acquisition portion SA in which the acquisition portion of the electrode is present and reachable from the outside and a connecting portion PB which incorporates and isolates the buses of at least one electrode from the outside.
  • the connection portion on one side prevents the buses from contacting the epidermis or mucosa by collecting unwanted signals. On the other hand it allows the sensor to be connected to a socket of the signal acquisition and/or processing device.
  • the senor defines an ultra-thin and flexible flat plate.
  • the manufacturing method object of the present invention comprises the following steps in succession.
  • Step 1 Deposition of a water-soluble polymeric sacrificial first LI layer, such as preferably PVA (polyvinyl alcohol) on a support plastic substrate L0, called carrier, such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), KaptonTM (polyamide film developed from DuPont®), etc.
  • Step 2. Vapor phase chemical deposition, known with Anglo-
  • a second ultra- thin L2 layer preferably of Parylene C or Torlon ® (polyamide-imide) on said first layer, preferably with a thickness of between 300 and 500 nm.
  • Step 3 Arrangement of at least one measuring electrode L3, preferably in silver or silver-chloride, preferably by photolithographic technique, known per se, on said second layer.
  • the measuring electrode that defines a third layer of the sensor has a predetermined shape. It may include matrices of electrodes, microelectrodes, both passive and active, as they can include organic transistors for the detection of chemical and physical parameters etc.
  • the electrode can be either metallic or carbon-based, and it is important that it is conductive.
  • Step 4 Deposition of a fourth layer L4 of Parylene C with a thickness between 500 nm and 4,5 pm, in the same manner as in step 2, so that the electrode is packed between the second and fourth layers, both made of Parylene C.
  • Parylene C is mentioned as being considered to be particularly suitable, but it is not the only material that can be used for these purposes.
  • the upper limit of 4,5 pm is chosen as a function of the flexibility and adhesion capacity conferred by Parylene C on the dermis. Therefore, if materials are identified that offer better adhesion, this limit may be exceeded.
  • step SP4 it is clearly seen in step SP4 that the thickness of the fourth layer L4 of Parylene C is greater than the thickness of the second layer L2 of Parylene C.
  • the second and fourth layers of Parylene C are in direct contact with each other in the perimeter areas with respect to the electrode L3.
  • the electrode covers only a portion of the surface of the second layer allowing a subsequent mutual adhesion between the second and the fourth layer to be determined.
  • the deposition technique allows that in direct contact portions between the second and fourth layer, a single and isotropic layer is defined, in which it is not possible to recognize an interface between the second and fourth layer.
  • the fourth layer of Parylene C is intended to come into contact with the epidermis and must therefore expose the electrode towards the outside, so that the latter can carry out the aforementioned physiological acquisitions.
  • Step 5 Removal of the portion of the fourth layer covering the acquisition portion of the electrode, for example by means of the photolithography technique based on plasma etching.
  • the ultra-thin sensor obtained is similar to that of the known art.
  • further removal of material is performed, - in order to obtain a diversification between the thickness of the acquisition portion and the connecting portion, and/or - in order to drill through holes at least in the thickness of the acquisition portion of the sensor.
  • Step 5bis Removal of material to obtain a greater thickness in the connection portion of the sensor with respect to the active portion of the same sensor and to uncover the acquisition portion of the electrode, and/or
  • the removal of material to diversify the thicknesses can be carried out before or after the removal of material for uncovering the acquisition portion of the electrode.
  • the through holes are made as the last procedure.
  • the holes are preferably distributed evenly over the surface of the sensor so as to optimize the transpiration of the epidermis or in an appropriate way in cases where the openings are made to allow the administration of a fluid stimulation substance.
  • the holes are distributed not only peripherally with respect to the electrode, but also through the electrode, therefore the following step is performed.
  • Step 7 Making of holes in the electrode by means of a photolithographic technique and subsequent continuation of the holes with the same masking made for removing the electrode portions, in the second layer L2 of Parylene C, thus creating openings passing through the second and third layer.
  • step 6 the typical secondary steps of the photolithographic technique are shown in which a layer of photoresist is deposited, which is selectively removed in order to define the uncovered portions of the underlying material subject to subsequent removal, the removal of the underlying material and finally of the photoresist being made by means of a suitable diluent.
  • the through holes can also be made by mechanically drilling the sensor.
  • a roller with sharp bumps can be pressed and slid on the sensor so as to perforate the sensor itself. In other words, it is a punching procedure.
  • a laser emitter can be used to pierce the sensor.
  • the through openings described above may have a more or less regular geometry depending on the drilling technique used. It is believed that the geometry of the through openings is not essential, although it is preferable to make holes, i.e. approximately circular- shaped openings.
  • the first sacrificial layer can be removed after the aforementioned steps, for example by immersion in a diluent, for example water, capable of dissolving the material of which the sacrificial layer is made or by mechanical removal, peeling (peel-off).
  • a diluent for example water
  • the thinning of the fourth layer for obtaining a more or less gradual thickening of the portion of the sensor which contains the buses intended to be connected to the socket of the signal acquisition and/or processing device, it is envisaged to carry it out using the technique of plasma etching by performing a step 5 c after step 5 a or 5b or it can be performed simultaneously.
  • the sensor Sens of the present invention has been tested in electromyographic applications by making matrices of passive and tactile electrodes and to realize temperature and pressure sensors based on organic field effect devices.
  • Figure 3 shows a variant in which they are present simultaneously: - Thinning of the acquisition portion SA of the sensor with respect to a connection portion SB in which the electrode connection buses are collected.
  • Figure 4 shows a variant in which they are present simultaneously:

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Abstract

Method for manufacturing an ultra-thin epidermal sensor (Sens) of the type in which an electrode (L3) is embedded in a flat casing (L2, L4) of polymeric material that can be deposited by vapor or liquid phase deposition, having a micrometric or sub-micrometric thickness, and wherein the sensor comprises an acquisition portion (SA) in which the electrode is accessible from the outside by a face of the casing and a connection portion (SB) which incorporates and isolates at least one electrical bus (PE) connecting the electrode (L3), the method comprising a step of removal of material on one of the faces of the sensor, to obtain a diversification (Step 5bis) between a thickness of the acquisition portion and a thickness of the connecting portion, and/or to drill through holes (Step 6) at least with the thickness of the acquisition portion of the sensor.

Description

METHOD FOR MANUFACTURING AN ULTRA-THIN EPIDERMAL SENSOR AND SENSOR OBTAINED.
DESCRIPTION
Scope of the invention
The invention is part of the so-called "epidermal electronics" or "tattoo electronics". These are ultra-thin epidermal sensors connected to an acquisition electronics for the measurement of physiological electrical signals, in particular for the detection of EMG, ECG, EEG, EOG bio-potentials and other physical and chemical parameters such as for example pH and temperature.
State of the art
Several approaches to the realization of electronic devices on ultra-thin substrates intended to be applied to the epidermis and mucous membranes in general without the use of glues and adhesives in general are known in the literature, for a wide range of applications, both biomedical and robotic, some of them requiring the use of Parylene C as the material making up the ultra-thin substrate. Some publications related to the known technology are listed as follows:
- Kim, Dae-Hyeong, et al. "Epidermal electronics." Science 333.6044 (2011): 838-843. - Jeong, Jae Woong, et al. "Materials and optimized designs for human- machine interfaces via epidermal electronics." Advanced Materials 25.47 (2013): 6839-6846.
- Peng, Hui-Ling, et al. "Parylene -based flexible dry electrode for biopotential recording." Sensors and Actuators B: Chemical 231
(2016): 1-11.
- Kabiri Ameri, Shideh, et al. "Graphene electronic tattoo sensors."
ACS nano 11.8 (2017): 7634-7641.
These sensors are made in a sandwich configuration using a deposition techniques, in which an electrode is packed.
The sensor identifies an acquisition portion in which the acquisition portions of one or more electrodes and a connection portion are present, in which the buses of each isolated electrode, i.e. passivated with respect to the external environment, run up to define a sort of flat cable band suitable to be inserted in a ZIF connector or similar, associated with an electronic signal acquisition and processing card.
This technology suffers from some problems. Sometimes the sensors detach from the epidermis due to sweat.
In other cases, the sensor is broken in the connection portion that allows the interconnection with the aforementioned ZIF connector or similar.
If not specifically excluded in the following detailed description, what is described in this chapter is to be considered as an integral part of the detailed description. Summary of the invention
The object of the present invention is to indicate a method of manufacturing an ultra-thin epidermal sensor capable of solving or mitigating the problems mentioned above. Another object of the present invention is to present a sensor less subject to possible detachment during use due to sweating.
A further object of the present invention is to present a sensor that is more robust than known ones.
Another object of the present invention is to present a sensor which is simultaneously more robust than those known and less sensitive to sweating.
The basic idea of the present invention is to manufacture an ultra- thin epidermal sensor and to carry out a procedure of further selective removal of material after its manufacture. More precisely, through openings are made in the thickness of the sensor in order to promote sweat transpiration generated by the epidermis and/or a surface layer of material is removed from the acquisition portion of the sensor, by defining a thickening of the connecting portion of the sensor so as to make the sensor more resistant at the interface with the electronic card for acquisition and/or processing of physiological signals. More preferably, the removal of excess material is achieved by obtaining a moderate gradient between the two zones: acquisition portion and interconnection portion. Advantageously, this allows to avoid the breakage of the interface portion between the sensor, intended to be attached to the epidermis, and the device for acquisition and/or processing of physiological signals.
Physiological signals are acquired in the form of electrical signals. In other words, if the sensor is of the passive type it is intended to directly acquire typical electrical signals for example of EMG, ECG, etc.
When the sensor is active, for example as it comprises organic transistors, the electrical signals can be either both EMG, ECG signals, etc., and signals of chemical nature (for example the chemical composition of sweat, pH skin, etc.).
Unlike the known methods of manufacturing ultra-thin sensors, the material deposited in the deposition procedures is in excess of that is strictly necessary and is followed by a further selective removal procedure, aimed at making openings passing through the thickness of the sensor and/or aimed at determining a thinning of the acquisition portion with a corresponding thickening of the connecting portion of the sensor.
The sensor obtained by the present method can advantageously be used for the detection of EMG, ECG, EEG, EOG bio-potentials and other physical and chemical parameters such as for example pH and temperature, by solving the problem of dermis transpiration. It also allows the simultaneous dosing of a fluid substance through the same sensor, in order to stimulate a bioelectric response or to restore the hydration of the dermis.
The present invention also finds application in the field of robotics and in particular in the field of tactile sensors. The claims describe preferred embodiments of the invention, forming an integral part of the present description.
Brief description of the Figures
Further aims and advantages of the present invention will become clear from the following detailed description of an embodiment of the same (and its variants) and from the annexed drawings given purely as an explanatory and non-limiting example, in which:
Figure 1 shows a part of a method of manufacturing an epidermal sensor according to the present invention;
Figure 2 shows a portion of the method which replaces or integrates the last step of the method of Figure 1 ;
Figure 3 shows an assembly and a relative exploded view of an example of a sensor obtained according to a variant of the method of the present invention and
Figure 4 shows an assembly and a relative exploded view of another example of a sensor obtained according to another variant of the method of the present invention.
The same numbers and the same reference letters in the Figures identify the same elements or components. Within the present description the term "second" component does not imply the presence of a "first" component. These terms are in fact used as labels in order to improve clarity and should not be understood in a limiting way. Elements and features illustrated in the various preferred embodiments, including the drawings, can be combined with one another without however departing from the scope of protection of the present application as described below.
Detailed description of examples of embodiment The present invention is based on the technique of manufacturing electronic devices on ultra-thin, i.e. sub-micrometric, polymeric substrates.
The proposed technique is compatible with known manufacturing processes per se, such as standard photolithography, ink-jet printing, silk- screen printing, micro-contact printing, roll-to-roll and allows to obtain ultra-thin sensors with high transpiration properties as well as of biocompatibility and conformability, i.e. an optimal adherence to any substrate, skin, mucosa, etc..
The sensor Sens according to the present invention includes a flat and ultra-thin casing of Parylene C in which a flat electrode L3 is embedded, of which only one acquisition portion is uncovered on one of the two opposite faces of the sensor. Therefore, the sensor defines an acquisition portion SA in which the acquisition portion of the electrode is present and reachable from the outside and a connecting portion PB which incorporates and isolates the buses of at least one electrode from the outside. The connection portion on one side prevents the buses from contacting the epidermis or mucosa by collecting unwanted signals. On the other hand it allows the sensor to be connected to a socket of the signal acquisition and/or processing device.
In other words, the sensor defines an ultra-thin and flexible flat plate.
Subsequently, according to the present invention, previously deposited material is removed in order to reduce the thickness of the acquisition portion SA of the sensor and/or to drill through holes in the thickness of the acquisition portion. For this purpose steps SP5 and SP7 respectively of Figures 1 and 2 must be considered.
The manufacturing method object of the present invention comprises the following steps in succession. Step 1. Deposition of a water-soluble polymeric sacrificial first LI layer, such as preferably PVA (polyvinyl alcohol) on a support plastic substrate L0, called carrier, such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), Kapton™ (polyamide film developed from DuPont®), etc.. Step 2. Vapor phase chemical deposition, known with Anglo-
Saxon terminology as "chemical vapor deposition" of a second ultra- thin L2 layer, preferably of Parylene C or Torlon® (polyamide-imide) on said first layer, preferably with a thickness of between 300 and 500 nm. Step 3. Arrangement of at least one measuring electrode L3, preferably in silver or silver-chloride, preferably by photolithographic technique, known per se, on said second layer. The measuring electrode that defines a third layer of the sensor has a predetermined shape. It may include matrices of electrodes, microelectrodes, both passive and active, as they can include organic transistors for the detection of chemical and physical parameters etc. The electrode can be either metallic or carbon-based, and it is important that it is conductive.
Step 4. Deposition of a fourth layer L4 of Parylene C with a thickness between 500 nm and 4,5 pm, in the same manner as in step 2, so that the electrode is packed between the second and fourth layers, both made of Parylene C. It must be noted that Parylene C is mentioned as being considered to be particularly suitable, but it is not the only material that can be used for these purposes. It must be noted that the upper limit of 4,5 pm is chosen as a function of the flexibility and adhesion capacity conferred by Parylene C on the dermis. Therefore, if materials are identified that offer better adhesion, this limit may be exceeded.
With reference to Figure 1 , it is clearly seen in step SP4 that the thickness of the fourth layer L4 of Parylene C is greater than the thickness of the second layer L2 of Parylene C.
It is evident that the second and fourth layers of Parylene C are in direct contact with each other in the perimeter areas with respect to the electrode L3. In other words, the electrode covers only a portion of the surface of the second layer allowing a subsequent mutual adhesion between the second and the fourth layer to be determined. Among other things, the deposition technique allows that in direct contact portions between the second and fourth layer, a single and isotropic layer is defined, in which it is not possible to recognize an interface between the second and fourth layer.
The fourth layer of Parylene C is intended to come into contact with the epidermis and must therefore expose the electrode towards the outside, so that the latter can carry out the aforementioned physiological acquisitions.
In order to uncover an acquisition portion of the electrode intended to contact the epidermis or mucosa, the following step is performed:
Step 5. Removal of the portion of the fourth layer covering the acquisition portion of the electrode, for example by means of the photolithography technique based on plasma etching.
Regarding the acquisition portion SA, the ultra-thin sensor obtained is similar to that of the known art.
According to the present invention, further removal of material is performed, - in order to obtain a diversification between the thickness of the acquisition portion and the connecting portion, and/or - in order to drill through holes at least in the thickness of the acquisition portion of the sensor.
Therefore following step is executed - Step 5bis. Removal of material to obtain a greater thickness in the connection portion of the sensor with respect to the active portion of the same sensor and to uncover the acquisition portion of the electrode, and/or
- Step 6. Removal of material to make through holes passing through the second and fourth layers, both of Parylene C, in the areas in which they are in mutual direct contact, i.e. peripherally with respect to the electrode.
Preferably, the removal of material to diversify the thicknesses can be carried out before or after the removal of material for uncovering the acquisition portion of the electrode.
Preferably, the through holes are made as the last procedure.
The holes are preferably distributed evenly over the surface of the sensor so as to optimize the transpiration of the epidermis or in an appropriate way in cases where the openings are made to allow the administration of a fluid stimulation substance.
Subsequently, according to another preferred variant of the invention, the holes are distributed not only peripherally with respect to the electrode, but also through the electrode, therefore the following step is performed.
- Step 7: Making of holes in the electrode by means of a photolithographic technique and subsequent continuation of the holes with the same masking made for removing the electrode portions, in the second layer L2 of Parylene C, thus creating openings passing through the second and third layer.
In step 6 the typical secondary steps of the photolithographic technique are shown in which a layer of photoresist is deposited, which is selectively removed in order to define the uncovered portions of the underlying material subject to subsequent removal, the removal of the underlying material and finally of the photoresist being made by means of a suitable diluent.
The through holes can also be made by mechanically drilling the sensor. For example, a roller with sharp bumps can be pressed and slid on the sensor so as to perforate the sensor itself. In other words, it is a punching procedure. Alternatively, a laser emitter can be used to pierce the sensor.
It is worth noting that the through openings described above may have a more or less regular geometry depending on the drilling technique used. It is believed that the geometry of the through openings is not essential, although it is preferable to make holes, i.e. approximately circular- shaped openings.
The first sacrificial layer can be removed after the aforementioned steps, for example by immersion in a diluent, for example water, capable of dissolving the material of which the sacrificial layer is made or by mechanical removal, peeling (peel-off).
As regards the thinning of the fourth layer for obtaining a more or less gradual thickening of the portion of the sensor which contains the buses intended to be connected to the socket of the signal acquisition and/or processing device, it is envisaged to carry it out using the technique of plasma etching by performing a step 5 c after step 5 a or 5b or it can be performed simultaneously. The sensor Sens of the present invention has been tested in electromyographic applications by making matrices of passive and tactile electrodes and to realize temperature and pressure sensors based on organic field effect devices.
Figure 3 shows a variant in which they are present simultaneously: - Thinning of the acquisition portion SA of the sensor with respect to a connection portion SB in which the electrode connection buses are collected.
- Making of holes passing through the thickness of the acquisition portion SA of the sensor peripherally with respect to the electrode L3.
Figure 4 shows a variant in which they are present simultaneously:
- thinning of the acquisition portion SA of the sensor with respect to a connection portion SB in which the electrode connection buses are collected, - making of trough holes through the thickness of the acquisition portion SA of the entire acquisition portion SA including the L3 electrode. For each of Figures 3 and 4, the thicknesses of the individual layers L2-L4 respectively of the acquisition portion SA and of connection SB are shown to the right and to the left.
Possible embodiments of the non-limiting example described are possible, without however departing from the scope of protection of the present invention, including all the equivalent embodiments for a person skilled in the art, to the content of the claims.
From the description given above the person skilled in the art is able to realize the object of the invention without introducing further construction details.

Claims

1. Method for manufacturing an ultra-thin epidermal sensor (Sens) of the type in which an electrode (L3) is embedded in a flat casing (L2, L4) of polymeric material that can be deposited by vapor or liquid phase deposition, having a micrometric or sub-micrometric thickness, and wherein the sensor comprises an acquisition portion (SA) in which the electrode is accessible from the outside by a face of the casing and a connection portion (SB) which incorporates and isolates at least one electrical bus (PE) connecting the electrode (L3), the method comprising a step of removal of material on one of the faces of the sensor
- to obtain a diversification (Step 5bis) between a thickness of the acquisition portion and a thickness of the connecting portion, and/or
- to make through holes (Step 6) at least through the thickness of the acquisition portion of the sensor.
2. Method according to claim 1, wherein said removal (Step 6) of material for making said through holes is carried out by a photolithography procedure based on plasma etching which allows to obtain through holes at least in the acquisition portion (SA) of the sensor, peripherally with respect to the electrode (L3).
3. Method according to claim 2, further comprising a photolithographic procedure (Step 7) for making through holes in the electrode (L3) and subsequently in an underlying layer (L2) of polymeric material that can be deposited by vapor or liquid phase deposition.
4. Method according to claim 1, wherein said step of removal of material on one of the faces of the sensor to make through holes is made by punching or by laser removal.
5. Ultra- thin epidermal sensor (Sens) of the type in which an electrode (L3) is embedded in a flat casing (L2, L4) of polymeric material that can be deposited by vapor or liquid phase deposition, having a micrometric or sub-micrometric thickness, and in which the sensor comprises an acquisition portion (SA) in which the electrode is accessible from the outside by a face of the casing and a connection portion (SB) which incorporates and isolates at least one electrical bus (PE) connecting the electrode (L3), the sensor being characterized in that it comprises through holes at least through the thickness of the acquisition portion of the sensor.
6. Sensor according to claim 5, wherein said through holes are evenly and peripherally distributed around the electrode or evenly across the electrode.
7. Sensor according to any one of claims 5 or 6, wherein said acquisition portion has a thickness lower than said connecting portion.
8. Ultra-thin epidermal sensor (Sens) of the type in which an electrode (L3) is embedded in a flat casing (L2, L4) of polymeric material that can be deposited by vapor or liquid phase deposition, having a micrometric or sub-micrometric thickness, and wherein the sensor comprises an acquisition portion (SA) in which the electrode is accessible from the outside by a face of the casing and a connection portion (SB) which incorporates and isolates at least one electrical bus (PE) connecting the electrode (L3), the sensor being characterized in that said acquisition portion has a thickness lower than said connecting portion.
9. Sensor according to any one of claims 7 or 8, wherein a change in thickness between said acquisition portion and said connecting portion is gradual.
10. Sensor according to any one of claims 8 and 9, wherein the casing is made of Parylene C and the acquisition portion has a thickness comprised between 500 nm and 900 nm and in which the connecting portion has a thickness comprised between 1400 nm and 4500 nm.
PCT/IB2019/058726 2019-10-14 2019-10-14 Method for manufacturing an ultra-thin epidermal sensor and sensor obtained. WO2021074664A1 (en)

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