Neural implant based on a cellulose thin film and corresponding fabrication process
A novel ultra-thin neural implant ( 1 ) is provided that is based on a cellulose thin film ( 4 ) featuring an array ( 2 ) of electrodes ( 3 ). Due to the use of cellulose as the base material, the implant ( 1 ) can be safely handled during a micro-surgery, despite its high softness and conformability. Such an implant ( 1 ) may be useful in numerous applications ranging from electrical stimulation in neural prostheses, electro-stimulated regeneration of neural tissue to accurate recording of nerve signals. The robustness of the implant ( 1 ) results from a woven fabric ( 5 ) that is integrated in the cellulose carrier thin film ( 4 ). Several approaches for enhancing the tissue compatibility of the implant ( 1 ) are also provided.
1 . A conformal neural implant ( 1 ) comprising:
an array ( 2 ) of electrodes ( 3 ) for forming a neural interface with living neural tissue,
a carrier thin film ( 4 ) made from cellulose that carries the array ( 2 ), and
a woven fabric ( 5 ) that reinforces the carrier thin film ( 4 ).
2 . The conformal neural implant ( 1 ) according to claim 1 , wherein the woven fabric ( 5 ) comprises silk threads.
3 . The conformal neural implant ( 1 ) according to claim 1 , wherein the woven fabric ( 5 ) comprises threads ( 6 ) with a diameter that is at least one of larger than 1 μm or smaller than 200 μm.
4 . The conformal neural implant ( 1 ) according to claim 1 , wherein the carrier thin film ( 4 ) comprises cellulose fibers.
5 . The conformal neural implant ( 1 ) according to claim 1 , wherein the electrodes ( 3 ) are formed from a conductive thin film ( 7 ),
or
the electrodes ( 3 ) are formed by conductive fibers ( 8 ) or conductive threads ( 8 ).
6 . The conformal neural implant ( 1 ) according to claim 1 , wherein the carrier thin film ( 4 ) forms a surface micro-structure ( 9 ), with a minimum peak-to-valley depth/roughness of at least 500 nm,
and
the electrodes ( 3 ) are deposited on the surface micro-structure ( 9 ).
7 . The conformal neural implant ( 1 ) according to claim 6 , wherein the surface micro-structure ( 9 ) at least one of has an aspect ratio of at least 1:1, or
the surface micro-structure comprises micro-corrugation that have lateral dimensions that are larger than 500 nm but smaller than 50 μm.
8 . The conformal neural implant ( 1 ) according to claim 1 , wherein the carrier thin film ( 4 ) is perforated by micro-sized perforations ( 11 ), and
a conductive thin film ( 7 ) forming the electrodes ( 3 ) covers sidewalls ( 12 ) of the micro-perforations ( 11 ) such that conductive vias ( 13 ) are formed.
9 . The conformal neural implant ( 1 ) according to claim 1 , wherein the electrodes ( 3 ) are covered by a 3D-matrix ( 14 ) of intertwined nano- to micro-scaled fibers ( 15 ), and
the fibers ( 15 ) at least one of:
are made from cellulose, and/or
are deposited by an electro-spinning process, or
have a diameter below 20 μm and a length of at least 100 μm.
10 . The conformal neural implant ( 1 ) according to claim 9 , wherein a bioactive substance ( 16 ) is embedded in the 3D-matrix ( 14 ) of fibers ( 15 ), and
the bioactive substance ( 16 ) is releasable from the 3D-matrix ( 14 ) after implantation of the implant ( 1 ).
11 . The conformal neural implant ( 1 ) according to claim 9 , wherein at least one of
a) the 3D-matrix ( 14 ) is covered by a layer of methylcellulose,
b) the carrier thin film ( 4 ) comprises polydimethylsiloxane (PDMS) that is functionalized with thiol-groups and/or thiol-functionalized cellulose,
c) the woven fabric ( 5 ) is made from two layers of threads ( 6 ), the layers being interwoven with each other in a regular pattern, or
the woven fabric ( 5 ) comprises at least one layer of warp threads ( 17 ) aligned along a first direction ( 17 ) that is interwoven with a respective corresponding layer of weft threads ( 19 ) running along a second direction ( 20 ).
12 . The conformal neural implant of claim 11 , wherein the woven fabric ( 5 ) comprises two layers of warp threads ( 17 ), having said first directions ( 17 ) that enclose an angle of at least 10°.
13 . A process for fabricating a conformal neural implant ( 1 ), comprising the steps of:
forming a carrier thin film ( 4 ) from a liquid composition of cellulose, and
at least one of attaching a woven fabric ( 5 ) is to or embedding the woven fabric into the carrier thin film ( 4 ).
14 . The process for fabricating the conformal neural implant ( 1 ) according to claim 13 ,
wherein polymer fibers are embedded into the carrier thin film ( 4 ) and oriented in a preferential direction by heating up the film ( 4 ) and applying a mechanical strain to the film ( 4 ).
15 . The process for fabricating the conformal neural implant ( 1 ) according to claim 13 ,
wherein the implant ( 1 ) is thermoformed into a non-planar 3D-shape, by heating up the film ( 4 ) and deep-drawing the film ( 4 ) onto a model that forms the non-planar 3D-shape.
16 . The process for fabricating the conformal neural implant ( 1 ), according to claim 13 , further comprising:
forming a surface micro-structure ( 9 ) on a front side ( 21 ) of the carrier thin film ( 4 ), and at least one of
a) patterning an array ( 2 ) of electrodes ( 3 ) on the micro-structure ( 9 ),
b) prior to deposition of the array ( 2 ) of electrodes ( 3 ), forming micro-perforations ( 11 ) in the carrier thin film ( 4 ),
or
c) depositing a 3D-matrix ( 14 ) of micro- to nano-scaled fibers ( 15 ) on the array ( 2 ) of electrodes ( 3 ).
17 . The process for fabricating the conformal neural implant of claim 15 , wherein the model is fabricated based on 3D-data obtained by a 3D-scan of a living tissue.