Patent Application
20200406584
This invention pertains generally to the field of flexible conductive and electronic devices, to substrates for use in making flexible conductive and electronic devices, to their use as force sensors and to methods of manufacture.
There is considerable development in the field of flexible electronic devices. There remain some significant difficulties, particularly as regards the development of flexible conductive devices that are required to be conformable, such as sensors for soft robotic applications.
Devices having a conductive layer or patterned conductive layer on a polymer substrate suitable for a flexible application tend to suffer from cracking on flexing of the device or thermal expansion and contraction. This results in short lifetimes and/or inconsistent function.
There is a need for improvements in flexible and conformable conductive devices, for example for use as force senors.
It is an object of this invention to provide a substrate for use in the manufacture of a flexible conductive device which is durable and effective.
It is an object of this invention to provide a flexible conductive device which has a long lifetime and does not become irreparably damaged during normal use.
In accordance with a first aspect of the invention, there is provided a flexible conductive or electronic device comprising a polymer base, a poly-para-xylylene layer which is bonded to the polymer base by a first adhesive layer and a conductive layer which is bonded to the poly-para-xylylene layer by a second adhesive layer.
In a second aspect of the invention, there is provided a substrate for use in the manufacture of a flexible conductive or electronic device, the substrate comprising a polymer base and a poly-para-xylylene layer which is bonded to the polymer base by a first adhesive layer.
The conductive device of the invention provides a flexible and even conformable substrate and a conductive, typically patterned, layer for a functional use such as a force sensor that is robust, survives flexing and thermal expansion and may be incorporated into other substrates for use.
FIG. 1 is a
The invention provides for an improved flexible conductive or electronic device and to a substrate for making such a device. The substrate according to one aspect comprises a polymer base and a poly-para-xylylene layer which is bonded to the polymer base by a first adhesive layer. Preferably a second adhesive layer is disposed on the poly-para-xylylene layer on the side opposing the side bonded to the polymer base. The flexible conductive device according to another aspect comprises the substrate above having a conductive layer (e.g. a patterned conductive layer) disposed thereon and bonded thereto by a second adhesive layer.
Preferably, the device and substrate are conformable.
The polymer base may be of any suitable base and may comprise one or more of PDMS, PI, polybutyrate, PMMA, acrylate, polyethylene, HDPE, LDPE, PET, TPU, polyurethane, PVC, PEI, PEN, PP, polystyrene, aliphatic or semi-aromatic polyamide, PTFE, PVDF or a blend thereof.
The polymer base preferably comprises and more preferably is a polymer having a Young's modulus of up to 1.5 MPa, more preferably up to 1.2 MPa, still more preferably up to 1 MPa and preferably at least 500 kPa, such as in the range 700 kPa to 1 MPa, e.g. 700 to 800 kPa.
Preferably, the polymer base comprises or is PDMS and/or PI (polyimide), more preferably PDMS (polydimethyl siloxane).
The polymer base may be of any suitable thickness but is preferably thin enough to achieve the desired flexibility or conformity. Preferably, the polymer base has a thickness of up to 1 mm, more preferably from 50 to 500 μm, still more preferably from 60 to 250 μm, such as from 75 to 175 μm.
The first adhesive layer and second adhesive layer can each be any suitable adhesive, preferably a molecular bonding adhesive. This may be a click chemistry bonding material. Preferably the first and/or second adhesive layer comprises a mercaptan, more preferably comprises a mercaptosilane and still more preferably comprises or is (3-mercaptopropyl)trimethoxysilane.
The first adhesive layer and/or the second adhesive layer preferably has a thickness of up to 10 nm and is preferably a monolayer, which may be self-assembling in the case of (3-mercaptopropyl)trimethoxysilane.
Preferably, the poly-para-xylylene layer is a parylene layer, more preferably a parylene-C layer.
The poly-para-xylylene layer preferably has a thickness in the range 10 nm to 10 μm. It may comprise a single layer of poly-para-xylylene or a plurality of two or more layers of poly-para-xylylene bonded together, e.g. 3 layers of from 20 to 100 nm bonded by an adhesive such as the mercaptan adhesive referred to above. Preferably, the poly-para-xylylene layer has a thickness in the range 50 nm to 500 nm.
In the conductive device of the invention, the conductive layer may comprise a graphene, a graphite, a metal oxide, a metal alloy or a metal, which is preferably patterned as required (e.g. by screen printing, photolithography or shadow masking application techiniques).
The conductive layer preferably comprises a metal selected from one or more of zinc, aluminium, copper, gold, silver, platinum, chromium, tungsten or titanium. More preferably, the conductive layer comprises gold.
The conductive layer has a thickness of from 20 nm to 250 nm, preferably 50 nm to 100 nm.
The substrate and device as described herein may be manufactured by any suitable method known in the art.
The invention has been described with reference to a preferred embodiment. However, it will be appreciated that variations and modifications can be effected by a person of ordinary skill in the art without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1719697.3 | Nov 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2018/053417 | 11/27/2018 | WO | 00 |
