Two-layer adhesion of electronics to a surface

Embodiments of the present invention are directed to a two-layer adhesive and methods of using the same to secure an electronic device to an organism. In a non-limiting embodiment of the invention, a surface of the organism is coated with a first adhesive layer (bottom layer). The first adhesive layer is cured and a surface of the cured first adhesive layer is coated with a second adhesive layer (top layer). An electronic device is positioned on the second adhesive layer prior to curing the second adhesive layer. The second adhesive layer is then cured, thereby embedding the electronic device within the second adhesive layer. The bottom layer and the top layer are selected such that the bottom layer releases upon exposure to a first solvent after a first duration and the top layer releases upon exposure to a second solvent after a second duration more than the first duration.

BACKGROUND

The present invention relates generally to wearable, flexible, healthcare and medical related electronics. More specifically, the present invention relates to a two-layer adhesive for securing flexible wearable sensor electronics to a surface of a live organism, including, but not limited to, the organism's fingernails, toenails, teeth, claw, hoof, and skin.

The development of technologies that enable the wireless collection and analysis of quantitative, clinically relevant information on a patient's physiological status is of growing interest. In particular, soft, biocompatible systems are widely regarded as important because they facilitate the mounting of wearable sensors on external (e.g., skin or nail) and internal (e.g., heart and brain) surfaces of the body. Wearable sensors allow for the collection and analysis of clinically relevant information directly on the patient, and ultraminiaturized, lightweight, and battery-free wearable devices have the potential to establish complementary options in biointegration, where longer duration (e.g., months) interfaces are possible on hard surfaces such as the fingernails and the teeth, with negligible risk for irritation or discomfort. Some example wearable sensors include strain gauges, temperature sensors, accelerometers, photoplethysmograms (PPGs), electrocardiograms (ECGs), electroencephalography (EEG) devices, respiration sensors, gyroscopes, and piezoelectric sensors.

Strain gauges, for example, are useful for measuring or monitoring stresses, forces, torques and a host of other stimuli including displacement, acceleration and position of the patient's body. The electrical conductance of a strain gauge (typically formed of a doped silicon or metal) varies with its geometry, such that a deformation of the strain gauge results in a change in its electrical resistance. The stress on a strain gauge can therefore be inferred from a measured resistance of the strain gauge using a known gauge factor, which is a ratio of relative change is resistance to the strain on the test piece. The resistance of the strain gauge can be measured using a Wheatstone bridge.

Regardless of the specific type of wearable sensor used in a given application, an adhesive is typically applied at the interface between the patient and the sensor to bond these wearable sensors to the patient's body. For example, cyanoacrylate-based adhesives can ensure the strong adhesion of a strain gauge to a fingernail or toenail. Cyanoacrylates are popular adhesives for wearable sensors because they offer a fast drying, semi-permanent bond that can be easily and conformally coated over a portion of the patient's body, such as a fingernail.

SUMMARY

Embodiments of the invention are directed to a method for using a two-layer adhesive to secure an electronic device to a patient (e.g., to a live nail) or an animal (e.g., claw, hoof). A non-limiting example of the method includes coating a surface of the nail with a first adhesive layer (bottom layer). The first adhesive layer is cured and a surface of the cured first adhesive layer is coated with a second adhesive layer (top layer). An electronic device is positioned on the second adhesive layer prior to curing the second adhesive layer. The second adhesive layer is then cured, thereby embedding the electronic device within the second adhesive layer. The bottom layer and the top layer are selected such that the bottom layer releases upon exposure to a first solvent after a first duration and the top layer releases upon exposure to a second solvent after a second duration more than the first duration.

Embodiments of the invention are directed to a method for removing an electronic device from a patient (e.g., from a live nail). A non-limiting example of the method includes forming an adhesive stack on a surface of the patient. The adhesive stack can include a bottom layer positioned between a top layer and the surface of the patient. The electronic device can be embedded in the top layer. The bottom layer and the top layer are selected such that the bottom layer releases upon exposure to a first solvent after a first duration and the top layer releases upon exposure to a second solvent after a second duration more than the first duration. The method can include exposing the adhesive stack to the first solvent for the first duration to release the adhesive stack from the surface of the patient. The method can include removing the adhesive stack from the patient.

Embodiments of the invention are directed to an adhesive stack for securing an electronic device to a live nail. A non-limiting example of the adhesive stack includes a top layer and a bottom layer positioned between the top layer and a surface of the live nail. The adhesive stack can further include an electronic device embedded in the top layer. The bottom layer and the top layer are selected such that the bottom layer releases upon exposure to a first solvent after a first duration and the top layer releases upon exposure to a second solvent after a second duration more than the first duration.

The diagrams depicted herein are illustrative. There can be many variations to the diagram or the operations described therein without departing from the spirit of the invention. For instance, the actions can be performed in a differing order or actions can be added, deleted or modified.

In the accompanying figures and following detailed description of the described embodiments of the invention, the various elements illustrated in the figures are provided with two or three-digit reference numbers. With minor exceptions, the leftmost digit(s) of each reference number correspond to the figure in which its element is first illustrated.

DETAILED DESCRIPTION

It is understood in advance that although example embodiments of the invention are described in connection with a particular wearable sensor (e.g., a strain gauge), embodiments of the invention are not limited to the particular sensor architectures described in this specification. Rather, embodiments of the present invention are easily capable of being implemented to bond a wide range of wearable sensors, such as an accelerometers, photoplethysmograms (PPGs), electrocardiograms (ECGs), electroencephalography (EEG) devices, gyroscopes, temperature sensors, respiration sensors, piezoelectric sensors, heart-monitoring devices, glucose-monitoring devices, and TENS (transcutaneous electrical nerve stimulation) electrode therapy devices, among others, to a body surface of an organism, including, for example, the organism's fingernails, toenails, teeth, claw, hoof, and skin.

Turning now to an overview of technologies that are more specifically relevant to aspects of the present invention, an adhesive such as a cyanoacrylate is commonly used to bond wearable sensors (electronic devices such as strain gauges) to a patient's body (often a fingernail). An ideal adhesive needs to satisfy several criteria. First, an adhesive should be stiff enough to allow viable signals to be read by a sensor/monitor. In other words, the young's modulus of the adhesive material needs to be large enough to allow deformations to not be dampened. An adhesive should be strong, allowing for the wearable sensor to remain on the patient for as long as needed. To ease application and patient distress, the adhesive should cure or dry in as short a time as possible. Similarly, the patient's body should not need to be put into an awkward position during application, due to patient's comfort as well as an inability to stay still long enough to allow the application of the sensor. Finally, once the wearable sensor is no longer needed, the adhesive should be easily removable, without causing harm to the patient's body or to the sensor itself (for reusability or further study).

Cyanoacrylates are ubiquitous as medical device adhesives, particularly with respect to wearable sensors placed on a patient's fingernail, in part because the cyanoacrylate family satisfies so many characteristics of an ideal adhesive. Cyanoacrylates are fast drying (typically around 30 seconds) adhesives that can be conformally coated onto a patient's body to provide a strong, semi-permanent bond. As a result, many methods used to attach a sensor to a fingernail rely upon products whose main ingredient is cyanoacrylate.

Cyanoacrylates make excellent adhesives, but they are very difficult to remove. Cyanoacrylates are typically removed using mechanical force—scratching off, scoring, scraping, etc. While effective at removing a cyanoacrylate-based adhesive, these methods are slow, will damage a patient's nail or skin, and can destroy the wearable sensor. This results in harm to the patient and prevents reuse of the sensor. To mitigate the damage to the patient and to the electronics and to speed up the removal process, the interface between the patient and the wearable sensor can be soaked in a solvent to release the adhesive. Acetone is typically used as exposure to acetone will soften a dried cyanoacrylate.

Adhesive removal even with a solvent soak, however, can take up to 30 minutes or even longer (depending on thickness of application) before the adhesive fully releases from the nail. Oftentimes, repeat soakings in the solvent are needed. This removal process is impractically long and burdensome. In addition, a surface such as a fingernail provides a very limited contact area between the solvent with the adhesive, further increasing removal time and inconvenience. Even worse, prolonged soaks in solvents such as acetone can weaken a nail—resulting in the same type of damage to the nail that a solvent soak is trying to prevent.

Turning now to an overview of aspects of the present invention, one or more embodiments of the invention address the above-described shortcomings of the prior art by providing a new two-layer adhesive for securing electronics to a patient's body (nails, skin, teeth, etc.). This two-layer adhesive includes a top adhesive layer and a bottom adhesive layer. The top adhesive layer is a fast drying, permanent bonding material that secures the sensor. As used herein, a “permanent” bonding material includes adhesive materials that require mechanical force (scratching off, scoring, scraping, etc.) or long solvent soaks (greater than about 5 minutes) to remove. This top layer can include strong adhesives such as cyanoacrylates. The bottom adhesive layer is a fast drying, temporary bonding material that is applied directly to the patient's body (e.g., nail) and binds the top adhesive layer to the patient. As used herein, a “temporary” bonding material includes adhesive materials that can be peeled or wiped off without requiring a long solvent soak time (e.g., materials that can be removed after a solvent soak of less than about 5 minutes, or materials that do not required any solvent soak). In other words, the material for the bottom adhesive layer is selected to be easily removable, ensuring that the two-layer adhesive can be removed from the patient without resorting to damaging mechanical processes or prolonged soak periods (e.g., soaks greater than 5 minutes).

Advantageously, the bottom adhesive layer prevents the top adhesive layer from making direct contact with the patient's body. This allows for the use of conventionally strong adhesives (e.g., cyanoacrylates) without needing to worry about the difficult removal requirements of those adhesives. In other words, this two-layer adhesive inserts an easily removable temporary adhesion material between a strong, permanent bonding material and the patient's body. Once removed from the patient's body, the top adhesive layer and the sensor layer can be soaked in a solvent for separation and eventual reuse of the sensor layer (without patient aggravation).

Turning now to a more detailed description of aspects of the present invention,FIG. 1depicts an electronic device102attached to a body surface (as shown, a fingernail104) in accordance with one or more embodiments of the present invention. In some embodiments of the invention, multiple instances of the electronic device102are attached to the same or various body surfaces (e.g., to the same fingernail or to a combination of fingernails, toenails, teeth, skin, etc.), optionally at different orientations/locations. However, embodiments are contemplated herein where a single electronic device102is employed at a single location of a person's body.

In some embodiments of the invention, the electronic device102is a wearable sensor. For example, the electronic device102can be a strain gauge. In some embodiments of the invention, the electronic device102is an accelerometer, photoplethysmogram (PPG), electrocardiogram (ECG), electroencephalography (EEG), temperature sensor, respiration sensor, gyroscope, piezoelectric sensor, heart-monitoring device, glucose-monitoring device, TENS (transcutaneous electrical nerve stimulation) electrode therapy device, or any other type of wearable device. In some embodiments of the invention, the body surface is the fingernail104. In some embodiments of the invention, the body surface is one or more of a patient's fingernails, toenails, teeth, or skin. Although the body surface depicted inFIG. 1is a fingernail104, the two-layer adhesion processes and resulting structures described in connection with the fingernail104apply equally to various body surfaces, including, for example, toenails, teeth, and skin.

As further shown inFIG. 1, the footprint of the electronic device102can be configured to fit on the respective body surface (e.g., 15 mm×15 mm or less for a human fingernail104). For instance, in the present example, each sensor (electronic device102) is smaller than the respective fingernail104to which it is attached, thereby enabling multiple sensors to be attached to the same fingernail104. In some embodiments of the invention, the footprint (a×b) of the electronic device102is less than or equal to 15 mm×15 mm, although other sizes are within the contemplated scope of the invention. In other words, the configuration shown inFIG. 1is merely an example, and the number, orientation, and size of the sensors can be adjusted (e.g., the footprints can be scaled up or down, etc.) depending on the particular application.

A magnified view106of the electronic device102is provided. In some embodiments of the invention, the electronic device102is a strain gauge sensor having multiple stacked layers. In some embodiments of the invention, the strain gauge sensor version of the electronic device102can include a metal sensor wire108placed over a flexible substrate110. As will be described in detail below, embodiments of the invention are contemplated herein where the flexible substrate110includes a two-layer adhesive112.

As further shown inFIG. 1, the metal sensor wire108can be configured to have a serpentine layout to increase the available length of the metal sensor wire108, and hence the resistance. While a serpentine layout of the metal sensor wire108is shown, other configurations are possible. With the constraints on the overall footprint of the electronic device102(see above), the length of the sensor wire108can only be made so long. In some embodiments of the invention, to further increase the overall resistance, and thereby decrease the total current and power consumption of the sensor, multiple sensor layers are stacked (not shown). Interconnects can be used to electrically couple the stacked layers.

FIG. 2depicts a cross-sectional view of the electronic device102and the two-layer adhesive112shown inFIG. 1. As discussed previously herein, the electronic device102is built on a flexible substrate110. The flexible substrate110can include the two-layer adhesive112.

In some embodiments of the invention, the two-layer adhesive112can include a top adhesive layer114and a bottom adhesive layer116. The top adhesive layer114can include a fast drying, permanent bonding material that secures the metal sensor wire108. For example, the top adhesive layer114can include strong adhesives such as cyanoacrylates.

The bottom adhesive layer116can include a fast drying, temporary bonding material that is applied directly to the patient's body (e.g., fingernail104). The bottom adhesive layer116binds the top adhesive layer114to the fingernail104. As discussed previously herein, the material for the bottom adhesive layer116is selected to be easily removable, ensuring that the two-layer adhesive112can be removed from the patient without resorting to damaging mechanical processes or prolonged soak periods (e.g., soaks greater than 5 minutes). In some embodiments of the invention, the bottom adhesive layer116is selected from one of three classes of composite materials, described sequentially below.

In some embodiments of the invention, the bottom adhesive layer116includes a film former, plasticizer, and solubilizing agent (also referred to as a stabilizer). The film former, plasticizer, and solubilizing agent collectively define a first class of adhesive materials. In some embodiments of the invention, the film former can include polyurethane-35 or acrylic or vinyl pyrrolidone (VP) crosspolymer resins. In some embodiments of the invention, the plasticizer can include glycerine. In some embodiments of the invention, the solubilizing agent can include laureth-21. Forming the bottom adhesive layer116from a film former, plasticizer, and solubilizing agent in this manner results in the bottom adhesive layer116having an air dry time of about 30 to 300 seconds. Advantageously, a removal time of only about 3 to 120 seconds can be achieved using only a water soak. The bottom adhesive layer116can be removed after the water soak by peeling or rubbing.

In some embodiments of the invention, the bottom adhesive layer116includes a film former, chain transfer agent, and photoinitiator. The film former, chain transfer agent, and photoinitiator collectively define a second class of adhesive materials. In some embodiments of the invention, the film former can include acrylates copolymer. In some embodiments of the invention, the chain transfer agent can include pentaerythrityl tetra mercaptopropionate. In some embodiments of the invention, the photoinitiator can include trimethyl benzoyl diphenyl phosphine oxide. In some embodiments of the invention, the bottom adhesive layer116includes a film former, chain transfer agent, photoinitiator, plasticizer, and photosensitizer. The plasticizer can include, for example, dimethicone. The photosensitizer can include, for example, isopropyl thioxanthone. Forming the bottom adhesive layer116from a film former, chain transfer agent, and photoinitiator in this manner results in the bottom adhesive layer116having a UV-based dry time of about 60 seconds. Advantageously, a removal time of only about 3 to 120 seconds can be achieved using only a water soak. The bottom adhesive layer116can be removed after the water soak by peeling or rubbing.

In some embodiments of the invention, the bottom adhesive layer116includes a film former, solvent, and plasticizer. The film former, solvent, and plasticizer collectively define a third class of adhesive materials. In some embodiments of the invention, the film former can include nitrocellulose, tosylamide-based resins, or formaldehyde-based resins (e.g., tosylamide formaldehyde resin). In some embodiments of the invention, the solvent can include ethyl acetate, butyl acetate, propyl acetate, isopropyl alcohol, or diacetone alcohol. In some embodiments of the invention, the plasticizer can include trimethyl pentanyl diisobutyrate, triphenyl phosphate, ethyl tosylamide, or camphor. In some embodiments of the invention, the bottom adhesive layer116includes a film former, solvent, plasticizer, and diluent. The diluent can include, for example, dimethicone. Forming the bottom adhesive layer116from a film former, solvent, and plasticizer in this manner results in the bottom adhesive layer116having an air dry time of about 60 to 300 seconds. Advantageously, a removal time of only about 10 to 120 seconds can be achieved using an acetone soak. The bottom adhesive layer116can be removed after the acetone soak by soaking or wiping.

An exemplary system300employing the electronic device102attached to a patient via the two-layer adhesive112is depicted schematically inFIG. 3. In some embodiments of the invention, system300can include a strain gauge sensor and Wheatstone bridge circuit302, an amplifier304, an analog to digital converter module306that includes an analog to digital converter306a(i.e., ADC), a radio frequency (RF) controller306band a micro-controller306c, a network antenna308, and a portable device310. As further shown inFIG. 3, the electronic device102serves as a resistor in the Wheatstone bridge circuit302. In some embodiments of the invention, the Wheatstone bridge circuit302receives power from power supply312. It is notable that the values (i.e., power supply voltage, resistances, etc.) shown inFIG. 3are merely given as examples and not intended to in any way limit the embodiments to these particular values.

Amplifier304serves to amplify the (voltage) signal output from the Wheatstone bridge circuit302. Analog to digital converter306a(i.e., ADC) in module306converts that amplified signal into a digital signal. Module306can also include a micro-controller306c(e.g., a processor—CPU) that prepares (e.g., conditions, buffers, etc.) the signal for the radio frequency (RF) controller306bthat then transfers the digitized signals to a receiver.

Network antenna308transmits the digital signals from analog to digital converter306. These digital signals are transmitted, for example, via near-field communication (NFC), WiFi, Bluetooth® technology, etc. to one or more user devices, such as a smartphone314(or other smart devices such as a smartwatch, smart glasses, etc.) and/or computer316.

Turning now toFIG. 4, a block diagram is shown of an apparatus400for implementing one or more of the techniques presented herein. By way of example only, apparatus400can be configured to serve as the micro-controller306cand/or as one or more of the user devices (e.g., smartphone314, computer316, etc.) of system300(FIG. 3).

In some embodiments of the invention, apparatus400includes a computer system410and removable media450. Computer system410includes a processor device420, a network interface425, a memory430, a media interface435and an optional display440. Network interface425allows computer system410to connect to a network, while media interface435allows computer system410to interact with media, such as a hard drive or removable media450.

The processor device420can be configured to implement the methods, steps, and functions described herein. The memory430can be distributed or local and the processor device420could be distributed or singular. The memory430could be implemented as an electrical, magnetic or optical memory, or any combination of these or other types of storage devices. Moreover, the term “memory” should be construed broadly enough to encompass any information able to be read from, or written to, an address in the addressable space accessed by processor device420. With this definition, information on a network, accessible through network interface425, is still within memory430because the processor device420can retrieve the information from the network. It should be noted that each distributed processor that makes up processor device420generally contains its own addressable memory space. It should also be noted that some or all of computer system410can be incorporated into an application-specific or general-use integrated circuit.

In some embodiments of the invention, the optional display440can include any type of display suitable for interacting with a human user of apparatus400. Generally, display440is a computer monitor, LCD or LED screen, or other similar display.

FIG. 5depicts a flow diagram500illustrating a method for securing an electronic device to a live nail using a two-layer adhesive according to one or more embodiments of the invention. As shown at block502, a surface of the nail is coated with a first adhesive layer. In some embodiments of the invention, the first adhesive layer is selected from a first class of materials, a second class of materials, and a third class of materials.

In some embodiments of the invention, the first adhesive layer includes a film former, a plasticizer, and a solubilizing agent (collectively the first class of materials). In some embodiments of the invention, the film former includes one of polyurethane-35, acrylic crosspolymer resin, and vinyl pyrrolidone (VP) crosspolymer resin. In some embodiments of the invention, the plasticizer includes glycerine and wherein the solubilizing agent includes laureth-21.

In some embodiments of the invention, the first adhesive layer includes a film former, a chain transfer agent, and a photoinitiator (collectively the second class of materials). In some embodiments of the invention, the film former includes an acrylates copolymer, the chain transfer agent includes pentaerythrityl tetra mercaptopropionate, and the photoinitiator includes trimethyl benzoyl diphenyl phosphine oxide.

In some embodiments of the invention, the first adhesive layer includes a film former, a solvent, and a plasticizer (collectively the third class of materials). In some embodiments of the invention, the film former includes at least one of nitrocellulose, a tosylamide-based resin, or a formaldehyde-based resin. In some embodiments of the invention, the solvent includes one or more of ethyl acetate, butyl acetate, propyl acetate, isopropyl alcohol, and diacetone alcohol. In some embodiments of the invention, the plasticizer includes one or more of trimethyl pentanyl diisobutyrate, triphenyl phosphate, ethyl tosylamide, and camphor.

At block504, the first adhesive layer is cured. In some embodiments of the invention, curing the first adhesive layer includes an air cure of about 30 to 300 seconds (e.g., for the first class of materials). In some embodiments of the invention, curing the first adhesive layer includes exposing the first adhesive layer to UV light for about 60 (e.g., for the second class of materials). In some embodiments of the invention, curing the first adhesive layer includes an air cure of about 60 to 300 seconds (e.g., for the third class of materials).

At block506, a surface of the cured first adhesive layer is coated with a second adhesive layer. In some embodiments of the invention, the second adhesive layer includes cyanoacrylate.

At block508, an electronic device is positioned on the uncured second adhesive layer (i.e., prior to curing the second adhesive layer). At block510, the second adhesive layer is cured. In some embodiments of the invention, curing the second adhesive layer embeds the electronic device within the second adhesive layer or to the surface of the second adhesive layer. In some embodiments of the invention, the second adhesive layer is cured using an air cure of about 30 seconds, although other cure durations are within the contemplated scope of the invention depending on the particular material selected for the second adhesive layer.

FIG. 6depicts a flow diagram600illustrating a method for removing an electronic device from a patient (e.g., a patient's live nail) using a two-layer adhesive according to one or more embodiments of the invention. As shown at block602, an adhesive stack is formed on a surface of the patient.

In some embodiments of the invention, the adhesive stack releases upon exposure to a first solvent after a first duration and an electric device releases upon exposure to a second solvent after a second duration more than the first duration. For example, the bottom layer can be removed using water as a first solvent, and the cyanoacrylate top layer can be removed using acetone as the second solvent. In other words, the whole adhesive stack including the organism surface, bottom layer, top layer, and the electronic device will be exposed to the first solvent (e.g., water) for a set duration (e.g., 3 minutes). Exposure to the first solvent minimizes the amount of bottom layer material leftover and releases the remaining stack from the organism surface, exposing a discrete stack of top layer (e.g., cyanoacrylate) and the electronic device. The second solvent exposure releases the electronic device from the top layer. As discussed previously, in some embodiments of the invention, the second solvent exposure is done after separation from the organism and can include an arbitrarily longer duration than the first solvent exposure (e.g., 5 minutes, 10 minutes, 30 minutes, hours, etc.).

In some embodiments of the invention, the adhesive stack releases upon exposure to a first solvent (e.g., acetone) after a first duration and the electric device releases upon exposure to the first solvent (e.g., acetone) after a second duration more than the first duration. In other words, complete separation can be achieved using two soaks in the same solvent. For example, a relatively short soak in acetone can be used to remove the adhesive stack and electronic device from the surface of the organism, and a second, relatively longer soak in acetone can be used to remove the top layer from the electronic device.

In some embodiments of the invention, the electronic device is released from the adhesive stack prior to removal of the adhesive stack from the organism. In other words, in some embodiments of the invention, the adhesive stack is exposed to the second solvent prior to the first solvent.

In some embodiments of the invention, the top layer includes cyanoacrylate. In some embodiments of the invention, the bottom layer includes one or more of polyurethane-35, acrylic crosspolymer resin, vinyl pyrrolidone (VP) crosspolymer resin, an acrylates copolymer, nitrocellulose, a tosylamide-based resin, or a formaldehyde-based resin.

At block604, the adhesive stack is exposed to the second solvent for the second duration to release the adhesive stack from the surface of the patient. At block606, the adhesive stack is removed from the patient.

At block608, after removing the adhesive stack, the adhesive stack is exposed to the second solvent for the second duration to separate the electronic device from the top layer. In some embodiments of the invention, the first solvent and the second solvent are the same. In some embodiments of the invention, the first solvent includes water and the second solvent includes acetone.

As can be seen from the foregoing detailed descriptions, technical effects and benefits of embodiments of the invention provide a new two-layer adhesive and methods of using the same to secure an electronic device to an organism (e.g., to a live nail of a patient). This new two-layer adhesive can be easily and quickly removed due to the inclusion of a temporary bottom layer, directly addressing the shortcomings of conventional adhesives (e.g., cyanoacrylate-based adhesives). Advantageously, the top layer of the two-layer adhesive can include conventionally strong, long lasting adhesives such as cyanoacrylates (for binding the electronic device), while the bottom layer can include an easily removable resin, such as one or more of polyurethane-35, acrylic crosspolymer resin, vinyl pyrrolidone (VP) crosspolymer resin, an acrylates copolymer, nitrocellulose, a tosylamide-based resin, or a formaldehyde-based resin.

Various embodiments of the present invention are described herein with reference to the related drawings. Alternative embodiments can be devised without departing from the scope of this invention. Although various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings, persons skilled in the art will recognize that many of the positional relationships described herein are orientation-independent when the described functionality is maintained even though the orientation is changed. These connections and/or positional relationships, unless specified otherwise, can be direct or indirect, and the present invention is not intended to be limiting in this respect. Similarly, the term “coupled” and variations thereof describes having a communications path between two elements and does not imply a direct connection between the elements with no intervening elements/connections between them. All of these variations are considered a part of the specification. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship. As an example of an indirect positional relationship, references in the present description to forming layer “A” over layer “B” include situations in which one or more intermediate layers (e.g., layer “C”) is between layer “A” and layer “B” as long as the relevant characteristics and functionalities of layer “A” and layer “B” are not substantially changed by the intermediate layer(s).