Abstract:
A device for insertion into soft tissue including a micro electrode, a micro light source; a stiffening element having a material dissolvable or degradable in aqueous body fluid or a material swellable in such fluid to form a transparent gel; a coat of a flexible non-conducting polymer material on the stiffening element; a base disposed at the rear end of the device. The flexible coat has a distal opening allowing light emitted from the light source to leave the device upon said collapse or dissolution or swelling. Also disclosed is a therapeutic or diagnostic device formed in the tissue from the insertable device, uses thereof, and a method of disposing the insertable device in soft tissue.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a 35 U.S.C. §371 National Phase conversion of PCT/SE2014/000152, filed Dec. 18, 2014, which claims benefit of Swedish Application No. 1300786-9, filed Dec. 20, 2013, the disclosures of which are incorporated herein by reference. The PCT International Application was published in the English language. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a first device comprising a medical micro electrode and a micro light source for disposition in soft tissue, to a second device formed in tissue from the first device, to a method of producing the first device, and to the use of the devices. Furthermore the present invention relates to bundles and arrays comprising two or more first devices of the invention and to corresponding bundles and arrays of second devices disposed in soft tissue. 
       BACKGROUND OF THE INVENTION 
       [0003]    Devices for implantation into soft tissue comprising electrodes, light sources, and combinations thereof in tissue of the central nervous system (CNS), have a wide field of application. In principle, brain nuclei can be recorded from or stimulated by such devices and their functions monitored. Of particular interest are multichannel devices for brain nuclei stimulation. By multichannel devices, groups of nuclei or even individual nuclei can be addressed separately. This allows a user to select those nuclei whose stimulation produces a therapeutic effect. Selective stimulation should produce a result superior to non-selective stimulation. Stimulation of the brain or spinal cord can be of particular value in situations when brain nuclei are degenerated or injured. A multichannel design may provide for efficient measurement of the effects of systemic or local drug administration or gene transfer to neurons of the brain and spinal cord. Monitoring brain activity through implanted devices can be used to control drug delivery locally or systemically or to control electrical stimulation of brain nuclei. By infecting neurons with gene vectors that cause the neuron to express radiation sensitive, in particular visible light sensitive ion channels it is possible to stimulate or inhibit neurons by radiation, in particular visible light. This is referred to as an optogenetic technique. By combining electrode means, radiation or visible light emission means and radiation or visible light detection means it is possible to record neuron activity evoked by radiation, in particular visible light. 
         [0004]    An implanted device of this kind should affect the adjacent tissue as little as possible. Since the brain, the spinal cord, and peripheral nerves exhibit considerable movements caused by body movements, heart beats, and respiration, it is important that an implanted device is capable of following the movements of the tissue with as little as possible displacement relative to target tissue. 
         [0005]    US 2011-0046148 A1 discloses a hybrid optical-electrical neural interface. The interface can include an array comprising a plurality of micro optrodes combining optical stimulation and optional electric stimulation. 
         [0006]    US 2013-0253261 A1 discloses a method of sensing bioelectrical signals from a patient of a particular neurological condition using an implanted electrode combined with optical stimulation to cells transduced with a genetic agent of a viral vector to treat the condition. 
         [0007]    US 2013-0237906 A discloses a liquid chrystal polymer-based electro-optrode neural interface comprising an integrated electrode and optrode. 
       OBJECTS OF THE INVENTION 
       [0008]    A primary object of the invention is to provide device comprising a micro electrode and a micro light source for insertion into soft tissue, in particular one capable of subtly adapting to movements in surrounding tissue. 
         [0009]    Another object of the invention is to provide a device of the aforementioned kind capable of stimulating single nerve cells or groups of nerve cells upon insertion into soft tissue; 
         [0010]    A further object of the invention is to provide a device of the aforementioned kind capable of recording, upon insertion into soft tissue, optical and electrical signals originating from nerve cells; 
         [0011]    An additional object of the invention is to provide bundles and array of the device; 
         [0012]    Still another object of the invention is to provide a method for producing the insertable device of the invention; 
         [0013]    Further objects of the invention will become apparent from the following summary of the invention, the description of preferred embodiments thereof illustrated in a drawing, and from the appended claims. 
       SUMMARY OF THE INVENTION 
       [0014]    In this application “water insoluble” signifies insoluble in aqueous body fluid, that is, interstitial or extracellular fluid but also serum. “Flexible” signifies a degree of flexibility that allows displacement of a portion of the device by movement of tissue adjacent to that portion. Displacement of a portion of the device does not necessarily comprise displacement of the entire device. “Electrically insulating” signifies electrically insulating at voltages/currents used in treating of human nervous tissue. “Oblong” signifies a structure of a length greater by a factor of five or more, in particular of ten or more, than its diameter. “Swellable” means capable of forming a transparent gel on contact with aqueous body fluid accompanied by expansion of volume, such as by a factor of 1.1 or 1.2. “Porous” signifies permeable for aqueous body fluid and biomolecules dissolved therein. 
         [0015]    According to the present invention is disclosed a medical device for insertion into soft tissue having a front or distal end and a rear or proximal end, comprising: 
         [0016]    a micro electrode; 
         [0017]    a micro light source capable of emitting light in a distal direction; 
         [0018]    a stiffening element comprising one of:
       a) a material dissolvable or degradable in aqueous body fluid in an amount sufficient to make the stiffening element collapse in contact with aqueous body fluid;   b) a material swellable in aqueous body fluid to form a transparent gel;       
 
         [0021]    a coat of a flexible non-conducting polymer material on the stiffening element preventing or at least delaying contact between the electrode and soft tissue upon collapse or swelling of the stiffening element, the coat having a distal opening allowing light emitted from the light source to leave the device upon said collapse or swelling; 
         [0022]    a base disposed at the proximal end of the device. 
         [0023]    It is preferred for the base to be of an electrically non-conducting material or to consist to 80% or 90% or more of such a material. It is preferred for the base to be of about circular form, such as the form of a flat cylinder. The base is preferably rigid. 
         [0024]    It is preferred for the electrode, the light source and/or the coat of flexible material to be firmly attached to the base and to extend from the distal face of the base in a distal direction. It is preferred for the electrode and the light source to extend from the distal face for a smaller distance than the flexible coat. 
         [0025]    Any miniature light source can be used but the use of an LED or a micro laser is preferred. In the present the invention “light source” comprises an optical fiber which receives, at its one end, light from a source which may or may not be comprised by the device and which fiber emits the received light at its other, distal end. The light emitted from the light source is preferably visible light, in particular monochrome light, such as red light, but may also be infrared light. 
         [0026]    The micro electrode of the invention comprises or consists of a metal or a metal alloy or an electrically conducting polymer or carbon. Preferred metals include aluminum, silver, gold, iridium, platinum, and their alloys. The micro electrode can have the form of a straight or curved rod or a layer on an optical fiber or on the face of the polymer coat facing the stiffening element. The micro electrode is preferably electrically insulated except for a portion extending from its distal end in a proximal direction. Electrode insulation is provided by a layer of lacquer or polymer on the electrode. 
         [0027]    It is preferred for the device for insertion into soft tissue to be of about rotationally symmetric form, in particular of about cylindrical form, in respect of a central longitudinal axis. The flexible, non-conducting polymer coat and the stiffening element are also preferred to be of about rotationally symmetric form, in particular of cylindrical form. It is preferred for the distal end of the electrode and/or of the optical fiber to be withdrawn from the distal opening in a proximal direction. It is also preferred for the electrode to be electrically insulated except for at its distal tip or end, or a portion extending from its distal tip or end in a proximal direction. 
         [0028]    According to a first preferred aspect of the invention the electrode is electrically shielded by an electrically conducting layer kept at earth potential or animal ground potential integrated into the flexible polymer coat or attached to one face of the flexible polymer coat and covered by an electrically insulating layer. 
         [0029]    According to a second preferred aspect of the invention the stiffening element comprises or consists of a carbohydrate and/or proteinaceous material and/or a mixture thereof. It is also possible to use other biocompatible gel forming polymers such as polyethylene glycol (PEG) and polypropylene glycol (PPG). 
         [0030]    Upon insertion into soft tissue and dissolution, degradation or swelling of its stiffening element the device for insertion into soft tissue is extendable in a longitudinal (proximal-distal) direction, in particular by a portion of its polymer coat being extendable. To be extendable the flexible polymer coat need not be of a resiliently flexible material. The polymer coat, which is preferably non-resilient or only faintly resilient, is made extendable by providing it or at least a portion of it in a bellows shaped configuration. Thus, according to a third preferred aspect of the invention the flexible polymer coat of the device for insertion into soft tissue is bellows-shaped and the stiffening element does reflect this shape. 
         [0031]    According to a fourth preferred aspect of the invention the device for insertion into soft tissue comprises a microprocessor control unit. The microprocessor can control one or more of electrode voltage; electrode potential including its variation over time; emission of light over time. The microprocessor unit may be capable of detecting voltage phenomena emanating from tissue structures, in particular neurons. In addition, the microprocessor unit can control a radiation sensor, in particular one for visible and/or near infrared light. The radiation sensor is preferably mounted at the base. It can detect light reflected from tissue structures, such as neurons, and/or fluorescent light emitted from such structures. 
         [0032]    According to a fifth preferred aspect of the invention the stiffening element comprises two or more cylindrical sections of different composition disposed adjacent to each other in a longitudinal (distal-proximal) direction. At least one section thereof can comprise a pharmacologically active agent, in particular an agent affecting neurons or glia cells, such as dopamine, dopamine agonist, dopamine antagonist, serotonin, serotonin antagonist. In another preferred embodiment the pharmacologically active agent is one having anti-inflammatory properties. In still another preferred embodiment the pharmacologically active agent is selected from neurotropic factor, in particular BDNF and NGF. The pharmacologically active agent also comprises genes. 
         [0033]    According to a sixth preferred aspect of the invention the stiffening element comprises two sections of different composition disposed adjacent to each other in a radial direction. It is preferred for at least one section thereof to comprise a pharmacologically active agent, in particular an agent affecting neurons, such as dopamine, dopamine agonist, dopamine antagonist, serotonin, serotonin antagonist, neurotropic factors such as BDNF, NGF, and genes. 
         [0034]    According to a seventh preferred aspect of the invention the device for insertion into soft tissue comprises a reservoir filled with a solution of a pharmacologically active agent, in particular an aqueous solution. The reservoir is disposed in a proximal section of the device, in particular at or near its proximal end. Dissolution or degradation of the stiffening element puts the reservoir in communication with soft tissue into which the device has been inserted. The communication is provided by the body fluid filled column delimited by the flexible polymer coat through which the solution of pharmacologically agent can be forced by applying pressure to the reservoir or through which the pharmacologically agent can diffuse so as to leave the column at its open distal end. 
         [0035]    According to an eight preferred aspect the device for insertion into soft tissue comprises, at its rear end, a means for wireless communication with an external control unit and/or a non-wireless means for electrical and/or optical communication with such unit, such as one or more electrically insulated electrical conductors and/or one or more optical fibers. 
         [0036]    According to another preferred embodiment, the device of the invention comprises a radiation sensor, in particular one sensitive to visible and/or near infrared light. It is preferred for the sensor to be mounted in the base. 
         [0037]    According to still another preferred aspect of the invention the distal opening is selected from axial distal opening and radial distal opening. In a first variety of the proto device of the invention and a corresponding device of the invention a distal opening is covered by a sheet of translucent polymer material, which is preferably as flexible or is more flexible than the polymer coat. Illumination of soft tissue adjacent to an radial distal opening can occur directly by a beam of light emitted from the radiation source or indirectly by such beam being reflected one more times from an inner wall face of the device before leaving the inner void M through the radial opening. To enhance the intensity of the portion of the beam escaping through a radial distal opening section(s) of the inner face of the wall can be made more reflective by, for instance, using an appropriate polymer material of high reflectivity and/or by applying a high reflectivity polymer coat on an inner face of the wall. A high reflectivity polymer coat can comprise microscopic inorganic or organic particles of high reflectivity, such as TiO 2  or platinum micro particles in the micrometer range. 
         [0038]    The device for therapeutic and/or diagnostic use of the invention is capable of being used for one or more of: a) emission of light into surrounding soft tissue; b) detection of light emitted from surrounding soft tissue; c) electrical stimulation of surrounding tissue structures; d) detection of electrical signals emitted from surrounding soft tissue. 
         [0039]    The device for therapeutic and/or diagnostic use of the invention disposed in soft tissue has a front (distal) end and a rear (proximal) end, and comprises:
       a micro electrode;   a micro light source capable of emitting light in a distal direction;   an about cylindrical coat of a flexible non-conducting polymer material comprising a distal opening allowing light emitted from the light source to leave the device, the coat delimiting an about cylindrical space filled with aqueous body fluid and/or a transparent gel;   a base disposed at the proximal end of the device.       
 
         [0044]    Upon insertion into soft tissue the device of the invention for insertion into soft tissue is transformed into a device for therapeutic and/or diagnostic use by dissolution, degradation or swelling of its stiffening element. Except for substitution of the stiffening element by aqueous body fluid and/or a transparent gel, which renders the device flexible and capable of adapting to movements of adjacent tissue, and the optional cap of body fluid soluble material disposed on the distal face of the device for insertion into soft tissue, the device for therapeutic and/or diagnostic use of the invention shares most or all features of the former, its design and structure thus being identified. 
         [0045]    According to the invention is also disclosed the use of the device for therapeutic and/or diagnostic use for providing optical and/or electrical stimulation to structures of soft tissue such as neurons, for recording electrical signals emanating from such structures, for lesioning such structures, for combined drug delivery, for recording of nerve cell signals and for nerve cell stimulation. 
         [0046]    According to the invention is furthermore disclosed a method of disposing the device for therapeutic and/or diagnostic use of the invention in relation to a selected structure in the tissue, comprising:
       inserting a device of the invention for insertion into soft tissue with its distal end foremost to make it take up a first position;   maintaining the device in the first position until the stiffening element has been dissolved, degraded or swelled to form a transparent gel;   making the light source emit light in the direction of the selected tissue structure;   monitoring the position of the selected tissue structure by detecting light reflected from the structure;   displacing the device in respect of the selected tissue structure to make it assume a second position.       
 
         [0052]    The invention will now be explained in greater detail by reference to a number of preferred embodiments illustrated in a rough drawing, which is only intended to show the principles of the invention. The drawings are not to scale. Radial dimensions are greatly exaggerated. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0053]    All figures illustrate embodiments of the invention. In some of them the combination of light source and electrode of the invention is only shown schematically to illustrate its disposition in the prestage device, the proto device or the device of the invention. It should be understood that each of the embodiments of combination of electrode and light source illustrated in  FIGS. 1 h -1 s   ′ and  FIGS. 15, 16  is comprised by all embodiments of the prestage device, the proto device and the device of the invention. 
           [0054]      FIGS. 1 a  through 1 g    illustrate, in a more general manner, distal terminal portions of a prestage, a proto device and a device of the invention. In particular, it is shown in: 
           [0055]      FIG. 1 a    a prestage of the device of the invention, in a longitudinal axial section corresponding to axial section B-B in  FIG. 1   e;    
           [0056]      FIG. 1 b    a distal terminal portion of the prestage of  FIG. 1 a   , in the same view; 
           [0057]      FIG. 1 c    a distal terminal portion of a proto device of the invention manufactured from the prestage of  FIGS. 1 a , 1 b   , in the same view as in  FIG. 1   a;    
           [0058]      FIG. 1 d    a distal terminal portion of the proto device of  FIG. 1 c    upon insertion into soft tissue and partial dissolution of its stiffening element, in the same view as in  FIG. 1   a;    
           [0059]      FIGS. 1 e , 1 f   , a distal terminal portion of a first embodiment of the device of the invention ( FIG. 1 e   ) and a major portion of the device ( FIG. 1 f   ) formed from the proto device of  FIGS. 1 c , 1 d    by contact with aqueous body fluid, in the same view as in  FIG. 1   a;    
           [0060]      FIG. 1 g    a radial section A-A ( FIG. 1 b   ) of the proto device of  FIG. 1   c;    
           [0061]      FIG. 1 h    a distal terminal portion of the prestage of a second embodiment of the proto device of the invention, in a longitudinal axial section B*-B*; 
           [0062]      FIG. 1 i    the prestage of  FIG. 1 h   , in a radial section A*-A*; 
           [0063]      FIG. 1 l   ′ a distal terminal portion of a first embodiment of the proto device of the invention, manufactured from the prestage of  FIGS. 1 h , 1 i   , in an axial section corresponding to section B*-B* in  FIG. 1   i;    
           [0064]      FIG. 1 m   ′ the proto device of  FIG. 1 l   ′, in radial section A*-A*; 
           [0065]      FIG. 1 l , 1 m    a distal terminal portion of a first embodiment of the device of the invention, formed from the proto device of  FIGS. 1 l   ′,  1   m ′ by contact with aqueous body fluid, and in the same view; 
           [0066]      FIG. 1 l   * a variation of the proto device of  FIGS. 1 l   ′,  1   m ′, and in the same view as in  FIG. 1   l′;    
           [0067]      FIG. 1 j    a distal terminal portion of a prestage of a second embodiment of the proto device of the invention, in an axial section B*-B* ( FIG. 1 i   ); 
           [0068]      FIG. 1 k    the prestage of  FIG. 1 j   , in a radial section A*-A*; 
           [0069]      FIG. 1 n   ′ a distal terminal portion of a second embodiment of the proto device of the invention, manufactured from the prestage of  FIGS. 1 j , 1 k    in a radial plane A″-A″ to remove its rounded tip section, in a longitudinal axial section B*-B* ( FIG. 1 i   ); 
           [0070]      FIG. 1 o   ′ the proto device of  FIG. 1 n   , in a radial section A**-A**; 
           [0071]      FIG. 1 n    a distal terminal portion of a second embodiment of the device of the invention formed from the proto device of  FIGS. 1 n   ′,  1   o ′ upon insertion into soft tissue, in an axial section; 
           [0072]      FIG. 1 o    the device of  FIG. 1 n   ′, in a radial section A**-A**; 
           [0073]      FIG. 1 n   * a variation of the proto device of  FIGS. 4 n   ′,  4   o ′, in a the same view as in  FIG. 1   n;    
           [0074]      FIG. 1 p   ′ a distal terminal portion of a third embodiment of the proto device of the invention, in an axial section B**-B** ( FIG. 1 i   ); 
           [0075]      FIG. 1 q   ′ the proto device of  FIG. 1 p   ′, in a radial section A*-A*; 
           [0076]      FIG. 1 p    a distal terminal portion of a third embodiment of the device of the invention, formed from the proto device of  FIGS. 1 p   ′,  1   q ′ upon contact with aqueous body fluid, in an axial section corresponding to that of  FIG. 1 i   ); 
           [0077]      FIG. 1 q    the embodiment of  FIG. 1 p   , in a radial section A*-A*; 
           [0078]      FIG. 1 r   ′ a distal terminal portion of a fourth embodiment of the proto device of the invention, in an axial section; 
           [0079]      FIG. 1 s   ′ the proto device of  FIG. 1 r   ′, in a radial section A**-A**; 
           [0080]      FIG. 1 r    a distal terminal portion of a fourth embodiment of the device of the invention, formed from the proto device of  FIG. 1 r   ′ upon contact with aqueous body fluid, in an axial section; 
           [0081]      FIG. 1 s    the device of  FIG. 1 r   , in a radial section A**-A**; 
           [0082]      FIG. 2  a fifth embodiment of the proto device of the invention, in an axial section; 
           [0083]      FIG. 3  a sixth embodiment of the proto device of the invention, in an axial section; 
           [0084]      FIG. 4  a distal terminal portion of an seventh embodiment of the proto device of the invention, in an axial section; 
           [0085]      FIG. 5  a distal terminal portion of an eight embodiment of the proto device of the invention, in an axial section; 
           [0086]      FIG. 6  a distal terminal portion of a ninth embodiment of the proto device of the invention, in an axial section; 
           [0087]      FIG. 7  a distal terminal portion of a tenth embodiment of the proto device of the invention comprising a drug delivery compartment, in an axial section; 
           [0088]      FIG. 8  a tenth embodiment of the device of the invention corresponding to the proto device of  FIG. 7 , in an axial section; 
           [0089]      FIGS. 9 a -9 c    a bundle of four proto devices of the invention, in a longitudinal section R-R ( 9   a ) and two radial sections O-O and P-P ( 9   b ,  9   c ); 
           [0090]      FIGS. 10, 11  an array comprising six bundles, each bundle comprising two proto devices of the invention, in a longitudinal section ( FIG. 10 ) and a corresponding bundle in a perspective view ( FIG. 11 ); 
           [0091]      FIG. 12  an array comprising nine bundles, each bundle comprising five proto devices of the invention, in an angular side view; 
           [0092]      FIG. 13  a distal portion of an eleventh embodiment of the proto device of the invention, in an axial section; 
           [0093]      FIG. 14 a    an eleventh embodiment of a proto device of the invention, in an axial section; 
           [0094]      FIG. 14 b    a twelfth embodiment of the device of the invention corresponding to the proto device of  FIG. 14 a   , in the same view; 
           [0095]      FIG. 15  a thirteenth embodiment of the proto device of the invention, in an axial section; 
           [0096]      FIG. 16  a fourteenth embodiment of the proto device of the invention, in an axial section comprising, in addition to the features of the thirteenth embodiment radiation sensing means; 
           [0097]      FIG. 17  a fifteenth embodiment of the proto device of the invention in an axial section A-A ( FIG. 29 ), comprising an axial distal opening and three lateral distal openings; 
           [0098]      FIG. 18  a device of the invention formed from the proto device of  FIG. 17  upon implantation into soft tissue, in an axial section A-A ( FIG. 30 ); 
           [0099]      FIG. 19  a sixteenth embodiment of the proto device of the invention in an axial section corresponding to that of the embodiment of  FIG. 17 , comprising three lateral distal openings; 
           [0100]      FIG. 20  a device of the invention formed from the proto device of  FIG. 19  upon implantation into soft tissue, in an axial section corresponding to that of the embodiment of  FIG. 18 ; 
           [0101]      FIG. 21  a seventeenth embodiment of the proto device of the invention in an axial section corresponding to that of the embodiment of  FIG. 17 , comprising an optical sensor; 
           [0102]      FIG. 22  a device of the invention formed from the proto device of  FIG. 21  upon implantation into soft tissue, in an axial section corresponding to that of the embodiment of  FIG. 18 ; 
           [0103]      FIG. 23  an eighteenth embodiment of the proto device of the invention in an axial section corresponding to that of the embodiment of  FIG. 17 , comprising a light reflecting inner wall section and a body fluid permeable wall section; 
           [0104]      FIG. 24  a device of the invention formed from the proto device of  FIG. 23  upon implantation into soft tissue, in an axial section corresponding to that of the embodiment of  FIG. 18 ; 
           [0105]      FIG. 25  a nineteenth embodiment of the proto device of the invention in a radial section corresponding to that of the embodiment of  FIG. 17  except for having its lateral distal openings covered by a translucent flexible polymer coat; 
           [0106]      FIG. 26  a device of the invention formed from the proto device of  FIG. 25  upon implantation into soft tissue, in a corresponding radial section; 
           [0107]      FIG. 27  a twentieth embodiment of the proto device of the invention in a radial section corresponding to that of the embodiment of  FIG. 17  except for having its lateral distal openings covered by flexible sheets of translucent polymer material; 
           [0108]      FIG. 28  a device of the invention formed from the proto device of  FIG. 27  upon implantation into soft tissue, in a corresponding radial section; 
           [0109]      FIG. 29  the proto device of  FIG. 17 , in a radial section B-B; 
           [0110]      FIG. 30  the device of  FIG. 18 , in a corresponding radial section; 
           [0111]      FIG. 31  a bellows-type axial section of a flexible wall of a device of the invention consisting of the layer combination flexible coat/flexible electrode layer/flexible insulation layer. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Example 1 
     General Disposition of a Combination of Micro Electrode and Optical Fiber in a Prestage Device, a Proto Device and a Device of the Invention 
       [0112]      FIGS. 1 a , 1 b    show axial sections of a terminal portion and a major portion including the terminal portion of a prestage device  1 ″ of the composition. The multi-S-formed portion extending from the terminal portion is extendable in a distal/proximal direction. The terminal portion comprises a blunt distal tip  9 . A combination  2  of optical fiber and electrode is schematically rendered. The combination  2  is centered in the distal and main portions. The terminal portion is rotationally symmetric, cf central axis B-B in  FIG. 1 f   . The combination of electrode and optical fiber  2  is enclosed by a stiffening element or layer  3 , which is also rotational symmetric at least in the straight distal terminal portion. The stiffening element  3  is of a material dissolvable in aqueous body fluid including water or degradable by the fluid or water, and is preferably of a biocompatible carbohydrate and/or proteinacious material such as glucose and albumin. Alternatively, the stiffening element  3  is of a biocompatible material gelling by contact with aqueous body fluid, such as gelatin or hyaluronic acid or a mixture of gelatin or hyaluronic acid with carbohydrate and/or proteinacious material. In a gelled state the gelling material is translucent. A thin layer  4  of a flexible, electrically insulating material such as parylene C is disposed on the stiffening element so as to enclose it completely. 
         [0113]      FIG. 1 c    illustrates the distal terminal portion of a proto device  1 ′ of the invention obtained by radially cutting the prestage device  1 ″ in plane A-A. Reference numbers  2 ,  3 ,  4  identify the same features as in  FIGS. 1 a , 1 b   . By cutting the prestage device  1 ″ a circular, flat terminal face  6  illustrated by  FIG. 1 g    is produced. 
         [0114]      FIG. 1 d    shows a state of the proto device  1 ′ upon insertion into soft tissue for a short period of time. By contact with aqueous body fluid a terminal portion of the stiffening element  3  has been dissolved or degraded or transformed to a translucent gel, the transformed portion being identified by  8 . 
         [0115]    In  FIGS. 1 e  and 1 f    the entire layer of stiffening element  3  has been transformed. Reference numbers  2 - 4  and  8  retain their meaning explained above. 
       Example 2 
     Prestage Device, Proto Device and Device of the Invention Comprising a First Combination of Micro Electrode and Optical Fiber 
       [0116]      FIGS. 1 h  and 1 i    illustrate axial B*-B* and radial A*-A* sections of the distal terminal portion of a prestage device  40 ″ comprising a first combination of micro electrode  22  and optical fiber  21 . The fiber  21  and the electrode  22  are disposed in parallel and attached to each other by permanent adhesive bridges  25 . The combination of optical fiber  21  and electrode  22  is enclosed by a layer or element  23  of a stiffening material. The optical fiber  21  has polished flat distal face  31  disposed at about the same radial level as the distal end of the electrode  22 . 
         [0117]    By cutting the prestage device  40 ″ radially in a plane A′-A′ distally of the face  31  the proto device  40 ′ illustrated in  FIGS. 1 l   ′,  1   m ′ is formed, in which the reference numbers of  FIGS. 1 h , 1 i    retain their meaning. 
         [0118]    Upon insertion of the proto device  40 ′ with its distal end foremost into soft tissue, the stiffening element  23  is dissolved or degraded by contact with aqueous body fluid  8  and substituted by it or is transformed into a translucent gel  28 ,  FIGS. 1 l , 1 m   . Cutting the prestage device  40 ″ distally of the end face  31  of the optical fiber  21  and the distal end or tip of the electrode  22  the fiber  21  and the electrode  22  are disposed withdrawn from the distal face  26  of the stiffening element  23  and of the distal circular rim  26  ( FIG. 1 l   ) of the flexible polymer coat  24 , respectively, thereby preventing or at least delaying contact of the electrode  22  and the optical fiber  21  of the device of the invention with surrounding tissue. 
         [0119]    In  FIG. 1 l   * a variety  40 ′* of the proto device  40 ′ is shown, of which the distal face  26  is covered by a cap  27  of a water soluble material such as glucose or a mixture of glucose with lactose or gelatin. The function of the cap  27  is to facilitate insertion of the proto device into soft tissue and to delay contact of the electrode  22  with surrounding tissue. 
       Example 3 
     Prestage Device, Proto Device and Device of the Invention Comprising a Second Combination of Micro Electrode and Optical Fiber 
       [0120]      FIGS. 1 j  and 1 k    illustrate axial B**-B** and radial A′-A″, A**-A** sections of the distal terminal portion of a prestage device  50 ″ comprising a second combination of micro electrode  22  and optical fiber  21  enclosed by a layer or element  23  of stiffening material. The electrode  22  has polished flat distal face  31  and is enclosed by an electrically conducting layer  22  forming an electrode. The distal end of the electrode layer  22  and the distal face  31  of the optical fiber  21  are disposed at the same radial level. 
         [0121]    By cutting the prestage device  50 ″ radially in a plane A**-A** distally of the face  31  of the proto device  40 ′ illustrated in  FIGS. 1 l   ′,  1   m ′ is formed, in which the reference numbers of  FIGS. 1 h , 1 i    retain their meaning. 
         [0122]    Upon insertion of the proto device  50 ′ with its distal end foremost into soft tissue, the stiffening element  23  is dissolved or degraded by contact with aqueous body fluid  8  and substituted by it or is transformed into a translucent gel  28 ,  FIGS. 1 l , 1 m   . Cutting the prestage device distally of the end face  31  of the optical fiber and of the electrode tip disposes the end face  31  withdrawn from the distal face  26  of the stiffening element  23  and of the distal circular rim  26  ( FIG. 1 l   ) of the flexible polymer coat  24 , thereby preventing or at least delaying contact of the electrode  22  and the optical fiber  21  with surrounding tissue. 
         [0123]    In  FIG. 1 n   ′* a variety  50 ′* of the proto device  50 ′ is shown, the distal face  26  of which is covered by a cap  27  of a water soluble material such as glucose. The function of the cap  27  is to facilitate insertion into soft tissue. 
       Example 4 
     Prestage Device, Proto Device and Device of the Invention Comprising a Third Combination of Micro Electrode and Optical Fiber 
       [0124]      FIGS. 1 p   ′,  1   q ′ illustrate axial B*-B* and radial A*-A* sections of the distal terminal portion of a proto device  60 ′ of the invention, comprising a third combination of micro electrode  22  and optical fiber  21 . The fiber  21  and the electrode  22  are disposed in parallel and attached to each other by permanent adhesive bridges  25 . The combination of optical fiber  21  and electrode  22  is enclosed by a layer or element  23  of a stiffening material, which is in turn enclosed by a coat  24  of flexible polymer material such as Parylene C. The optical fiber  21  has polished flat distal face  31  disposed at about the same radial level as the distal end of the electrode  22 . Except for a distal end portion the electrode  22  is electrically insulated by a lacquer coat  29 . The proto device  60 ′ has been produced from a corresponding prestage device (not shown) in a manner described in Examples 2 and 3. 
         [0125]    Upon insertion of the proto device  60 ′ with its distal end foremost into soft tissue, the stiffening element  23  is dissolved or degraded by contact with aqueous body fluid  8  and substituted by it or is transformed into a translucent gel  28 , to form a third embodiment  60  of the device of the invention,  FIGS. 1 p   ,  1   q.    
       Example 5 
     Prestage Device, Proto Device and Device of the Invention Comprising a Fourth Combination of Micro Electrode and Optical Fiber 
       [0126]      FIGS. 1 r   ′,  1   s ′ illustrate axial and radial A**-A** sections of the distal terminal portion of a proto device  70 ′ of the invention, comprising a fourth combination of micro electrode  22  and optical fiber  21 . The combination of micro electrode  22  and optical fiber  21  is enclosed by a layer or element  23  of stiffening material. The optical fiber  21  has a polished flat distal face  31 . It is enclosed by an electrically conducting layer  22  forming the electrode. Except for a portion  33  extending proximally from its distal end the electrode layer  22  is covered by an insulating lacquer  32 . The lacquer  32  is disposed between the electrode layer  22  and the stiffening element  23 . The distal end of the electrode layer  22  and the distal face  24  of the optical fiber  21  are disposed at the same radial level. 
         [0127]    Upon insertion of the proto device  70 ′ with its distal end foremost into soft tissue, the stiffening element  23  is dissolved or degraded by contact with aqueous body fluid  8  and substituted by it or is transformed into a translucent gel  28 . Thereby a corresponding device  70  of the invention is formed,  FIGS. 1 r   ,  1   s.    
       Example 6 
     Fifth Embodiment of the Proto Device of the Invention 
       [0128]    The proto device  201 ′ of  FIG. 2  is about rotationally symmetric in respect of a central longitudinal axis D-D. The proto device  201 ′ comprises, in addition to a combination of optical fiber and electrode  202 , a stiffening element  203  of a water dissolvable or degradable material and a coat  204  of a flexible, water insoluble polymer material on the stiffening element  203 . The proto device  201 ′ is provided with a rounded cap  207  on its front end. The purpose of the cap  207  is to minimize tissue damage caused by inserting the proto device  201 ′ into soft tissue. The material of the cap  207  is one that is readily dissolvable in body fluid, that is, within a couple of minutes, but which is different from water soluble material of the stiffening element  203 . The electrode and the optical fiber are electrically and optically, respectively, connected with a control unit  230  disposed at the proximal end of the proto device  201 ′. The control unit is of the same kind as that of the following example. 
       Example 7 
     Sixth Embodiment of the Embodiment of the Proto Device of the Invention 
       [0129]    The proto device  301 ′ of  FIG. 3  is about rotationally symmetric in respect of a central longitudinal axis E-E. The proto device  301 ′ comprises, in addition to a combination of optical fiber and electrode  302 , a stiffening element  303  and a coat  304  of a flexible, water insoluble polymer material on the stiffening element  303 . The proto device  301 ′ is provided with a rounded cap  307  on its front end. The purpose of the cap  307  is to minimize tissue damage caused by inserting the proto device  301 ′ into soft tissue. The material of the cap  307  is identical with the material of the stiffening element  303 . The electrode and the optical fiber are electrically and optically, respectively, connected with a control unit  330  disposed at the proximal end of the proto device  301 ′. The control unit  330  can be of various kinds and for various purposes, such as for controlling the current and voltage of power fed to the electrode and/or for recording and/or transmitting electric signals received from the electrode and/or for emitting radiation into the optical fiber or receiving radiation emanating from the tissue through the optical fiber and detecting it. 
       Example 8 
     Seventh Embodiment of the Proto Device of the Invention 
       [0130]    Of the seventh embodiment  401 ′ of the proto device of the invention illustrated in  FIG. 4  is only shown a distal terminal portion. The proto device  401 ′ is rotationally symmetric about a central longitudinal axis J-J and comprises an optical fiber  421 , an electrically conducting coat  422  forming an electrode on the fiber  421 , a stiffening layer or element  423  on the electrode  422  and a second coat  424  of flexible, water insoluble polymer material on the stiffening element  423 . A distal terminal section of the electrode layer  422  has the form of a brush  422 * of tiny metallic fibers extending in a radial direction from the layer  422  so as to provide for a large electrode tip surface. Except for the brush section  422 * the electrode  422  is insulated by a lacquer (not shown). The optical fiber has a distal terminal flat face  431  disposed in the same radial plane as the distal rim of the flexible polymer coat  424 . 
       Example 9 
     Eight Embodiment of the Proto Device of the Invention 
       [0131]    Of the eight embodiment  501 ′ of the proto device of the invention illustrated in  FIG. 5  is only shown a distal terminal portion. The proto device  501 ′ is rotationally symmetric about a central longitudinal axis K-K and comprises an optical fiber  521 , an electrically conducting coat  522  forming an electrode on the fiber  521 , a stiffening layer or element  523  on the electrode  522  and a coat  524  of flexible, water insoluble polymer material on the stiffening element  523 . An electrically conducting layer  533  is provided on the flexible polymer coat  524  and is covered by a coat  524 ′ of same material as the flexible polymer coat  524 , so as to be fully enclosed by the insulating coats  524 ,  524 ′. The conducting layer  533  is kept on earth potential for shielding the electrode  522 . The optical fiber  521  has a distal terminal flat face  531  disposed in the same radial plane as the distal rim of the flexible polymer coat  524 . 
       Example 10 
     Ninth Embodiment of the Proto Device of the Invention 
       [0132]    The proto device  601 ′ of cylindrical form (central axis M-M) of the invention of  FIG. 6  is similar to that of  FIG. 1 c    except for the water soluble stiffening element consisting of two sections, a frontal (distal) section  603  and a proximal section  603 ′ extending rearwards from the distal end of the frontal section  603 . Elements  602 ,  604 ,  606  correspond functionally to elements  2 ,  4  and  6  of the embodiment of  FIG. 1 c   . By providing two or more water soluble stiffening element sections joining each other in radial plane(s) it is possible to vary its dissolution profile more than what is possible with a one-section stiffening element. 
       Example 11 
     Tenth Embodiment of the Proto Device of the Invention 
       [0133]    The tenth embodiment of the proto device of the invention  701 ′ of  FIG. 7  (axial section N-N) comprises a front portion functionally corresponding to that of the embodiment of  FIG. 1 c   , elements  702 ,  703 ,  704 , corresponding to elements  2 ,  3 , and  4 , respectively. The water soluble material of the stiffening element  703  does not extend along the entire proto device  701 ′ but only over a portion thereof extending rearwards from its distal end. At the rear end of the stiffening element  703  a bulged container  715  of polymer material through which the combination of optical fiber and electrode  702  extends centrally is joined. The rear end of the container  715  of a polymer material such as parylene or silicone rubber is joined to a stiff polymer tube  717  through which the combination of optical fiber and electrode  702  further extends. The stiff tube  717  is so dimensioned that a tubular void  718  is formed between it and the container  715 . The container  715  is filled with a porous, water insoluble material  716 , for instance silica. A pharmacologically active agent, such as dopamine, is adsorbed on the porous material  716 . By dissolution of the water soluble stiffening agent  703  by aqueous body fluid entering through the distal terminal opening  719  the void between the combination of optical fiber and electrode  702  and the flexible coat  704  of water insoluble polymer material becomes filled with body fluid. By this process the proto device of  FIG. 7  is transformed to the device  701  of  FIG. 8 ). By provision of a controlled forward flow F of saline in the void  718  of tube  717  dopamine adsorbed on the porous material  716  is dissolved and diffuses into the void  708  and, from there, through the distal terminal opening  719  into adjoining tissue to exert its effect on biological structures, such as neurons, the electrical activity of which can be monitored by the electrode and which can be irradiated by radiation conducted by the optical fiber of the combination of optical fiber and electrode  702 . 
       Example 12 
     Bundle of Proto Devices of the Invention 
       [0134]    In the bundle  800 ′ of four proto devices  801   a ′ through  801   d ′ of  FIG. 9 a    (section R-R),  9   b  (section O-O) and  9   c  (section P-P) the proto devices are disposed in parallel and mounted in through bores of a cylindrical base  820 . Each of the proto devices  801   a ′,  801   b ′,  801   c ′,  801   d ′ comprises a central combination of optical fiber and electrode  802   a ,  802   b ,  802   c ,  802   d , a water soluble stiffening element or layer  803   a ,  803   b ,  803   c ,  803   d  on each of the combinations of optical fiber and electrode  802   a ,  802   b ,  802   c ,  802   d  and a flexible water-insoluble polymer coat  804   a ,  804   b ,  804   c ,  804   d  on the corresponding stiffening element  803   a ,  803   b ,  803   c ,  803   d . The proto devices  801   a ′,  801   b ′,  801   c ′,  801   d ′ are arranged symmetrically in respect of a central bundle axis Q-Q. Proximal sections  810   a ,  810   c  of the optical fibers and electrical conductors of the bundle are connected with a control unit (not shown). 
         [0135]    Each of the various proto devices of the invention described in the preceding embodiments can be bundled to form a bundle of proto devices of the invention. A bundle of proto devices of the invention can comprise two or more different proto devices of the invention. By insertion of a bundle of proto devices of the invention into soft tissue a corresponding bundle of devices of the invention is formed by dissolution or degradation of the water soluble or degradable stiffening elements. 
         [0136]    To facilitate insertion into soft tissue, the bundle of proto devices of the invention can be incorporated into a shell of a water soluble material (not shown). The shell has a sharp of blunt front end and is preferably rotationally symmetric about the bundle axis Q-Q and extends to the base  820 . 
       Example 13 
     First Embodiment of an Array of Bundles of Proto Devices of the Invention 
       [0137]    The array  950  of the invention shown in  FIG. 10  (section V-V) comprises six bundles  901 ′ a ,  902 ′ a ,  903 ′ a ,  904 ′ a ,  905 ′ a ,  906 ′ a  of proto devices of the invention. Each bundle comprises a pair of proto devices. Each of the bundles  900   a ′,  900   b ′,  900   c ′,  900   d ′,  900   e ′,  900   f ′ is mounted at its rear end in a bundling holder ( FIG. 11 ). Only the holder  911   a  for bundle  900   a ′ is specifically identified in  FIG. 11 . The bundling holders  911  are mounted by gluing on an oblong, about rectangular flat base  910  with a pointed front end  909 . The base  910  is preferably of a biocompatible polymer material like polypropylene, polyacrylate or polycarbonate. The holders  911   a  are mounted symmetrically in respect of the long base axis U-U so that three of the bundles  900   a ′,  900   b ′,  900   c ′ of proto devices are mounted at the left hand long edge  970  of the base  910  and the other three  900   d ′,  900   e ′,  900   f ′ at the right hand long edge  971  in a manner so as to have front end portions of the bundles  900   a ′,  900   b ′,  900   c ′,  900   d ′,  900   e ′,  900   f ′ of proto devices extend over the respective edge in oblique forward directions. Near the rear end of the base  910  electrical and, optionally, optical conductors connecting the electrodes and optical fibers of the left hand  900   a ′,  900   b ′,  900   c ′, and right hand  900   d ′,  900   e ′,  900   f ′ bundles are combined in flexible polymer tubes  907 ,  908 . To facilitate insertion into soft tissue the array of proto bundles can be incorporated in a shell of a water soluble material (not shown). 
         [0138]    After insertion into soft tissue, the array  950  of bundles  900   a ′,  900   b ′,  900   c ′,  900   d ′,  900   e ′,  900   f ′ of proto devices of the invention is transformed to a corresponding array of bundle of devices of the invention (not shown) by dissolution, degradation or swelling of their stiffening elements. 
       Example 14 
     Second Embodiment of an Array of Bundles of Proto Devices of the Invention 
       [0139]    The array  1001  of  FIG. 12  comprises a thin circular flat support of polyurethane  1002  from one (top) face of which nine bundles of proto devices of the invention  1003 ,  1004 ,  1005 ,  1006 ,  1007 , etc. of the invention extend perpendicularly so as to be disposed in parallel in respect of each other. Each bundle comprises five proto devices of the invention. The proto devices of the bundles  1003 ,  1004 ,  1005 ,  1006 ,  1007 , etc. penetrate the support  1002  and extend for a short distance from its other (bottom) face. They are bundled in a flexible tube  1008  and optically and electrically connected with a control unit  1009 . The control unit  1009  allows a person to activate optical fibers and electrodes of selected bundle(s) and even selected optical fibers and electrodes of one bundle, as well as to receive optical and electrical signals emitted from soft tissue for transmission to the control unit. The control unit  1009  also allows a person transmit radiation of different kind through selected optical fibers of the bundles. Various energizing and radiation patterns can thus be realized as well as electrical signal and radiation patterns emanating from soft tissue received and detected. 
       Example 15 
     Eleventh Embodiment of the Proto Device of the Invention 
       [0140]    In  FIG. 13  is shown an axial section F′-F′ of a distal terminal portion of a tenth embodiment  1201 ′ of the proto device of the invention. Reference number  1202  identifies a combination of optical fiber and electrode, which is withdrawn in a proximal direction by a distance h from the distal face  1206  a bellows-shaped stiffening element  1203  of corresponding geometry on which a correspondingly shaped flexible polymer coat  1204  is disposed. On dissolution of the water soluble stiffening element  1203  by tissue fluid contacting the stiffening element  1203  at its flat distal face  1206  a corresponding device of the invention is formed. The coat  1204  of device of the invention thus formed is extendible in a proximal/distal direction, thereby is designed to adapt to movements of different portion of the tissue into which the device is inserted, and to be anchored in the tissue. 
       Example 16 
     Twelfth Embodiment of the Proto Device of the Invention 
       [0141]    The rotationally symmetric (central axis F-F) twelfth embodiment of the proto device  1301 ′ of the invention illustrated in  FIG. 14 a    comprises an LED  1309  as a light source and a cylindrical layer  1302  of gold or platinum on the inner face of a cylindrical flexible polymer coat  1302 . A cap  1307  of a water soluble material is attached to the distal face of the coat  1304 , the proximal end of which is attached to a circular base  1330 . The coat  1304 /gold layer  1308 , the cap  1307  and the base  1330  define a cylindrical space occupied by a stiffening element  1303  of a water soluble mixture of glucose and albumin or gelatin selected from natural gelatin and gelatin cross linked by heat or chemically. The LED  1309  and the electrode layer  1302  are electrically connected with a control unit (not shown) via a multiple lead  1331 . 
         [0142]    Upon insertion of the proto device  1301 ′ into soft tissue ST the stiffening element is contacted by aqueous soft tissue fluid STF at its distal face and dissolved. A device of the invention  1301  is thereby formed,  FIG. 14 b   . Over time the solution of glucose and albumin in the void formerly occupied by the stiffening element  1303  is substituted by pure soft tissue fluid STF or, if the stiffening element is swellable like gelatin the void becomes filled with a translucent gel. By energizing the LED a neuron  1320  disposed distally of the device  1301  is irradiated. By detecting light fluorescent light emitted from the neuron  1320  is position relative to the device  1301  can be determined, allowing the device to be displaced in a desired direction in respect of the neuron to dispose it optimally for optical and/or electric interaction with the neuron  1320 . 
       Example 17 
     Thirteenth Embodiment of the Proto Device of the Invention 
       [0143]    The twelfth embodiment  1401 ′ of the proto device of the invention shown in  FIG. 15  corresponds to the eleventh embodiment  1301 ′ of  FIG. 14 a    except for the electrode being insulated except at its distal terminal portion and by a shielding metallic layer  1405  being disposed on the outer face of the flexible polymer coat  1404 . On its outer face the shielding layer  1405  is covered by a coat  1406  of same material as the coat  1404  so as to be fully insulated. The layer  1404  shielding the electrode  1402  is kept on earth potential to protect the electrode  1402  from being disturbed by external electrical fields. The electrode  1402  is insulated by a lacquer  1408  at its inner face except for a small portion at  1410  extending from its distal end. To avoid or at least delay contact with soft tissue the electrode  1402  is withdrawn in a proximal direction by a distance h from the distal faces  1411  of the stiffening element  1403  and the flexible polymer coat  1404 . The electrode layer  1402  and the shielding layer  1405  as well as the flexible polymer layers  1404 ,  1406  are attached to the base  1430  and electrically connected with the multiple lead  1431  via the base  1430 . The elements identified by reference numbers  1407  and  1409  correspond to elements  1307  and  1309 , respectively, of the embodiment of  FIG. 14   a.    
       Example 18 
     Coating an Metallic or Polymer Element with Water Soluble Material 
       [0144]    From the combination of optical fiber and electrical conductor or light source grease and oil are removed by dipping the combination into diethyl ether for 10 seconds, removing it and drying. A sugar coating of about 30 μm thickness is applied to the combination in the following manner. Sucrose (100 g) is dissolved in 50 ml water. The solution is boiled for about 5 min until it appears clear. The solution is allowed to cool to 80° C. The combination held at its rear end by a pair of stainless steel pincers is dipped fully into the solution. It is removed from the solution by withdrawing it vertically with a speed of 6 mm/s. The sucrose coated combination is dried overnight so as to form a dry sucrose coat on the body of about 40 μm thickness. The thickness of the coat can be selected by varying the speed of withdrawal and or by multiple dipping. Lowering the speed renders a thinner coat. 
       Example 19 
     Manufacture of a Prestage of Device the Invention by Coating the Dry Sucrose Element of Example 14 with Parylene C 
       [0145]    A coat of Parylene C of about 4 μm thickness is applied by a state-of-the-art vacuum coating process (http://www.scscookson.com/parylene/properties.cfm) in which di-paraxylylene is vaporized and then pyrolized to paraxylylene, which is adduced under high vacuum to a deposition chamber kept at about room temperature and there deposited on the sucrose coated element of Example 17. The twice coated device thus obtained corresponds to a prestage device of the invention. 
       Example 20 
     Manufacture of a Proto Device of the Invention from the Prestage Device of Example 19 
       [0146]    The prestage device of Example 18 is dipped with its front end foremost into molten high melting paraffin (m.p. of about 40° C.) in a short 3 mm diameter polypropylene cylinder. After cooling to room temperature, the paraffin block containing the prestage device is put on a polypropylene support and cut radially with a razor blade so as to sever its tip. After removing most of the paraffin by melting the block and withdrawing the proto device thus formed the latter is rinsed several times with pentane and dried. The recorded impedance of the insulated electrode body prior to cutting is &gt;10 megohm, measured with the electrode body immersed into saline. The recorded impedance after cutting the tip and immersion of the proto device into saline for 2-3 h is &lt;50 kohm. Alternatively, the prestage device of Example 15 is fixed under a microscope and portions of the Parylene C coat near the front end are removed by scraping the coat with a micro file made by coating a thin steel wire (0.1 mm diameter) with titanium oxide powder (grain of about 10 μm) by means of cyanoacrylate pre-polymer dissolved in diethyl ether, into which the wire is dipped immediately prior to the application of the powder. 
         [0147]    Dimensions of the proto device can vary within a broad range: diameters of up to 100 μm or more are useful. A preferred diameter is from 5-30 μm. The length of the proto device can be adapted to its desired location after insertion. 
       Example 21 
     Fourteenth Embodiment of the Proto Device of the Invention 
       [0148]    The fourteenth embodiment  1501 ′ of the proto device of the invention shown in  FIG. 16  differs from the thirteenth embodiment  1401 ′ by comprising, in addition to a light source  1509  mounted in basis  1530 , a light sensor  1532 , in particular one for fluorescent light, also mounted in basis  1530 . The radiation sensor  1532  is electrically connected by a flexible, electrically conducting wire  1533  with a recording unit (not shown) comprising a microprocessor, a memory and a data output means such as a printer. The other features  15 XX of the proto device  1501 ′ correspond to respective features  14 XX of the proto device  1401 ′ of the thirteenth embodiment. 
       Example 22 
     Fifteenth Embodiment of the Proto Device of the Invention and of a Corresponding Device of the Invention Formed from the Proto Device Upon Implantation into Soft Tissue 
       [0149]    The fifteenth embodiment  1601 ′ of the proto device of the invention shown in  FIGS. 17, 29  comprises a stiffening element  1603 , which is degradable or soluble in aqueous body fluid. The stiffening element  1603  is mounted on a rigid cylindrical base  1613  of polymer material such as highly cross-linked polyurethane. An LED light source  1609  is mounted on the distal face of the base  1613  and is energized by means of an insulated flexible conductor  1614  connected to a power source. The stiffening element  1603  is of substantially cylindrical form a rotationally symmetric in respect of its longitudinal axis F-F. The stiffening element  1613  and the base  1603  have about the same diameter. The stiffening element  1603  is covered by consecutive layers of electrically insulating flexible polymer  1608 , an electrically conducting flexible electrode layer  1604 , and a flexible coat layer  1602 . The flexible electrode layer  1604  has been attached to the insulating polymer layer  1608  and, to a narrow zone distal zone of the stiffening element  1603  not covered by the insolating polymer layer  1608  by a suitable method such as metal ion sputtering. Metals of high conductivity like gold and copper, are preferred for this purpose. The polymer layers  1608  and  1602  have been attached by dipping the proto device under formation in solutions of the respective polymer in an organic solvent of low polarity in which the stiffening element  1603  material is not soluble. The distal face  1611  of the stiffening element is then covered with a rounded cap  1610  of a material, which is readily soluble in aqueous body fluid. The cap  1610  is provided to facilitate insertion of the device into soft tissue. To avoid or at least make contact upon implantation of the electrode with surrounding soft tissue more difficult the electrode layer  1604  is slightly withdrawn from the distal rim of the flexible polymer coat as indicated by “h” in  FIG. 17 . A distal terminal portion of the electrode layer  1604  is not covered by the insulating inner flexible polymer layer  1608  to provide for electrical contact with body fluid. In addition to the distal axial opening  1615  are provided three distal radial openings  1605 ,  1606 ,  1607  of circular form with their centers disposed in the same radial plane B-B. The radial openings are arranged to allow light to emanate in a radial direction to affect or visualize neighboring soft tissue structures. To enhance radial escape of light the inner face of the electrically insulating polymer layer  1608  can be provided with a reflective coat, such as a thin coat of silver or platinum, or by using a polymer with good visible light reflectance properties for layer  1608 . The wide beam of visible light emitted by the light source  1609  is directed in a distal direction; a portion of it hits the inner face of the insulting polymer layer or of a reflective coat on that layer. From there it is reflected, in part in the direction of a distal lateral opening  1605 ,  1606 ,  1607  through which it escapes. Non-insulated annular portions of the electrode layer  1604  are disposed in the lateral openings, only one  1604 * of them being indicated in  FIGS. 17 and 18 . These two kinds of blank electrode faces can be used in combination. Alternatively, if only one of them is desired to be used, the other can be made inactive by applying a layer of electrically insulating material on it (not shown in the Figures). 
         [0150]    Upon implantation into soft tissue the proto device  1601 ′ is transformed into a device  1601  of the invention shown in  FIGS. 18, 30  by dissolution or degradation of its stiffening element. “M” designates the inner space of the device  1601  filled with body fluid upon complete dissolution of the stiffening element  1603 . 
         [0151]      FIG. 31  illustrates a section  1601 * of a physically modified wall of the device  1601  of the invention. The modification consists in providing the wall with the form of a meander or bellows form. The wall section  1601 * comprises a flexible polymer coat  1604 *, an electrode layer  1602 *, and an inner insulating polymer layer  1608 *. By such modification a device of the invention comprising or consisting of non-resilient wall materials can be made extendible in an axial direction. 
       Example 23 
     Sixteenth Embodiment of the Proto Device of the Invention and of a Corresponding Device of the Invention Formed from the Proto Device Upon Implantation into Soft Tissue 
       [0152]    The proto device  1701 ′ of the invention illustrated in  FIG. 19  is shown in an axial view corresponding to the proto device of  FIG. 17 , from which it differs by substitution of cap  1610  by a portion of its flexible polymer coat  1704 . Upon implantation into soft tissue the stiffening element  1703  is dissolved or degraded and substituted by aqueous body fluid. Thereby a corresponding device  1701  of the invention illustrated in  FIG. 20  is formed. Reference numbers  17 XX in  FIGS. 19 and 20  not specifically addressed refer to elements of corresponding kind  16 XX illustrated in  FIGS. 17 and 18 . 
       Example 24 
     Seventeenth Embodiment of the Proto Device of the Invention and of a Corresponding Device of the Invention Formed from the Proto Device Upon Implantation into Soft Tissue 
       [0153]    The proto device  1801 ′ of the invention illustrated in  FIG. 21  is shown in an axial view corresponding to the proto device of  FIG. 17 , from which it differs by provision of an optical sensor  1815  mounted on the distal face of the base  1813 . The sensor  1815  is sensitive to visible light. It is particularly suited for monitoring fluorescent radiation of a certain wavelength, and is so selected from a number of commercially available light sensors. It is electrically coupled with a recording unit (not shown) by insulated flexible lead  1816 . The recording unit can transform electrical signals from the sensor to numerical data and store these data in a memory. The recording unit is also capable of coordinating tissue irradiation by light source  1809 , recording of sensor  1815  data, and electrode  1802  control. Reference numbers  18 XX in  FIG. 21  not specifically addressed refer to elements of corresponding kind  16 XX illustrated in  FIGS. 17 and 18 . Upon implantation into soft tissue the proto device  1801 ′ is transformed into a device  1801  of the invention by dissolution or degradation of its stiffening element  1803 , as shown in  FIG. 22 . 
       Example 25 
     Eighteenth Embodiment of the Proto Device of the Invention and of a Corresponding Device of the Invention Formed from the Proto Device Upon Implantation into Soft Tissue 
       [0154]    The proto device  1901 ′ of the invention illustrated in  FIG. 23  is shown in an axial view corresponding to the proto device of  FIG. 17 , from which it differs by a reflective inner wall portion  1919  and a distal wall portion  1918  provided with micro openings. The micro openings are provided by laser technique; their function is to provide access of body fluid to the stiffening element  1903  to allow or facilitate its dissolution and the transport of its constituents out of the interior M of the device. The diameter of the micro openings are in the order of a 50 μm or less, more preferred from 5 μm to 30 μm. Reference numbers  19 XX in  FIG. 23  not specifically addressed refer to elements of corresponding kind  16 XX illustrated in  FIGS. 17 and 18 . Upon implantation into soft tissue the proto device  1901 ′ is transformed into a device  1901  of the invention by dissolution or degradation of its stiffening element  1903 , as shown in  FIG. 24 . 
       Example 26 
     First Variety of the Proto Device of the Invention Illustrated in FIG.  17  and of a Corresponding Device of the Invention Illustrated in FIG.  18  Formed from the Proto Device Upon Implantation into Soft Tissue 
       [0155]    The proto device  2001 ′ of the invention illustrated in  FIG. 25  is shown in a sectional radial view only, which correspond to the radial view of  FIG. 29  of the proto device of  FIG. 17  (section B-B). The section B-B dissects the centers of the circular windows  2005 ,  2006 ,  2007 , which are covered by portions of the flexible polymer coat  2004 . The coat  2004  is of a translucent polymer material. 
         [0156]    Upon implantation into soft tissue the proto device  2001 ′ is transformed into a device  2001  of the invention by dissolution or degradation of its stiffening element  2003 , as shown in  FIG. 26 . The void filled with body fluid is designated M. Reference numbers  20 XX in  FIG. 24  not specifically addressed refer to elements of corresponding kind  16 XX illustrated in  FIG. 17 . 
       Example 27 
     Second Variety of the Proto Device of the Invention Illustrated in FIG.  17  and of a Corresponding Device of the Invention Illustrated in FIG.  18  Formed from the Proto Device Upon Implantation into Soft Tissue 
       [0157]    The proto device  2101 ′ of the invention illustrated in  FIG. 27  is shown in a sectional radial view only, which correspond to the radial view of  FIG. 29  of the proto device of  FIG. 17  (section B-B). The section B-B dissects the centers of the circular windows  2105 ,  2106 ,  2107 , which are covered sheets of a translucent flexible polymer material  2115 ,  2116 ,  2117 . 
         [0158]    Upon implantation into soft tissue the proto device  2101 ′ is transformed into a device  2101  of the invention by dissolution or degradation of its stiffening element  2103 , as shown in  FIG. 28 . The void filled with body fluid is designated M. Reference numbers  21 XX in  FIGS. 27, 28  not specifically addressed refer to elements of corresponding kind  16 XX illustrated in  FIG. 17 . 
       Materials 
     Electrode. 
       [0159]    The electrode is preferably of a noble metal or an alloy of noble metals or comprising noble metals such as gold, silver, platinum, iridium, but other biologically acceptable metals such as stainless steel and tantalum can also be used as well as gold plated copper. Aluminum is a preferred metal for coating an optical glass fiber. Instead of a metal or metal alloy the electrical conductor may consist of or comprise an electrically conducting polymer such as PEDOT. Electrically conducting states of carbon may also be used. Portions of the electrical conductor that are not electrically insulated from tissue fluid upon removal of the first coat may be advantageously provided with surface enlarging elements or structures such as a roughened surface, forests of conducting nanowires, for instance carbon nanowires, or be porous. Surface enlarging structures of this kind will reduce the impedance of the electrical conductor. The electrical connection of the conductor with a control unit can be provided by a metal wire or similar coupled between the rear end of the electrical conductor and the control unit or by the conductor itself, a rear section thereof functioning as an electrical coupling means. In such case the rear section has to be electrically insulated. 
       Stiffening Element Coat. 
       [0160]    The combination of electrode and light source of the invention is embedded in/coated with one or more biocompatible first coat materials, which may be water dissolvable, swellable and/or degradable. If embedded in two or more of such materials they differ in their dissolution rate. Preferred first coat materials are water soluble carbohydrates and proteins as well as mixtures thereof. However, it is also possible to use water insoluble polymer materials swellable in water and/or degradable in body fluid. A suitable stiffening element coat material of which the dissolution time can be controlled is obtained by repeatedly boiling and cooling an aqueous solution of a sugar or a mixture of sugars selected from sucrose, lactose, mannose, maltose and an organic acid selected from citric acid, malic acid, phosphoric acid, tartaric acid. By selecting particular combinations of sugar(s) and organic acid(s) it is possible to obtain materials with different dissolution times. Gelatin may also be used as a first coat material. It is well known that different types of gelatin or gelatin based materials have different dissolution rates. If the first coat of water soluble or swellable material comprises two or more sections disposed along oblong combination of optical fiber/light source and electrode. The selection of a proper combination of gelatins provides a distal first coat section of shorter dissolution time and a proximal first coat section of longer dissolution time. The use of a sugar-based first coat material for the distal first coat section and of a gelatin-based first coat material for the proximal first coat section or vice versa is also possible, as well as the use of gelatin for a distal first coat section and of gum arabic for a first coat proximal section. The selection of further useful combinations of first coat materials, such as various types of natural gums, is within the easy reach of a person skilled in the art. Optionally, first coat materials with substantially longer dissolution times, such as modified collagen, cellulose derivatives, modified starch or other biocompatible materials, such as poly-glycolic acid can also be used. 
         [0161]    Optionally a polymer insulating coat of the prestage device, the proto device, the bundle of proto devices and the array or proto devices and bundles of the invention or a further coat of water dissolvable material on the first coat can be covered, completely or in part, by a biocompatible gliding agent to reduce friction during insertion into tissue. Useful gliding agents include glycerol monopalmitate, glycerol dipalmitate, glycerol monostearate, glycerol distearate, palmityl alcohol, stearyl alcohol. A thin coat of gliding agent can be applied by, for instance, spraying with a solution of the agent in ethanol or ethyl acetate. 
       Flexible Polymer Coat. 
       [0162]    In principle, polymer materials of all kinds suitable for electrical insulation can be used. However, the tiny structure of the prestage device of the invention to be produced by polymer coating restricts the number of application methods and useful polymers. While deposition of monomer from the gas phase is preferred, such as for providing a parylene coat, dipping of a prestage device coated with water soluble/swellable/degradable stiffening element material into a polymer or prepolymer solution, withdrawing it from the solution, and evaporating the solvent, optionally allowing a prepolymer to settle, is also useful. The dipping method should take recourse to a polymer solvent that does not interact with the water soluble/swellable/degradable material, in particular a non-polar solvent such as an alkane or alkene or cycloalkane or a non-polar aromatic solvent or a mixture thereof, in particular pentane or hexane but also diethyl ether or dichloromethane. Suitable polymers comprise biocompatible types of polyurethane, polyurethane urea and polyimide. Other useful polymers include silicones of various kind. Further useful polymers include polyethylene terephthalate (PET). The flexible polymer coat of the invention moves with surrounding tissue and does not restrict tissue movement. The thickness of the flexible coat is from a few μm and up to 20 μm or 50 μm or more. 
       Bundles of Proto Electrodes. 
       [0163]    Proto devices of the invention can be bundled in different ways, such as by incorporation of their rear end portions in a base of polymer or other material or by joining their rear end portions with glue. The bundling can be temporary, such as for keepings the devices in a fixed relationship prior to and during insertion into soft tissue, or permanent. A bundle of proto devices comprises a bundling means disposed in a proximal direction from the distal end of the two or more devices comprised by the bundle and aligned in parallel or about in parallel. The bundling means is preferably permanent, that is, is not dissolved or degraded by body fluid but may also be temporary, that is, be dissolved or degraded upon disposition of the bundle in soft tissue. A preferred permanent bundling means is an adhesive, in particular a cold setting polymer adhesive, such as a polyurethane or polyacrylate adhesive. The polymer adhesive is one not dissolvable or degradable by body fluid, except for over very long periods of more than a year or five years the adhesive is applied to the aligned proto devices at proximal portions thereof. 
         [0164]    A water dissolvable or degradable adhesive of corresponding properties allows the proto devices to dissociate quickly or slowly upon insertion. A swellable but not water soluble adhesive allows the proto devices inserted into soft tissue and the devices of the invention formed from them to be displaced in a restricted manner while an insoluble and non-swellable adhesive will restrain their movement to bending and, if designed extendable, to changes in length. 
         [0165]    Individual proto devices of a bundle may differ in length. For instance, a central proto device of a bundle may be longer than peripheral devices thereof to provide a central bundle point. 
         [0166]    Upon insertion into soft tissue, the proto devices of a bundle are transformed to devices of the invention and the bundle of proto devices is thereby transformed to a bundle of devices of the invention. 
         [0167]    In this application an array of proto devices or bundles of proto devices forms a proto device pattern comprising numerous proto devices and/or bundles of proto devices bundles of the invention disposed on and attached to at least one face of an electrically non conducting support. Thin supports of a suitable polymer like polypropylene, polyacrylate, polycarbonate and parylene C comprising substantially only two faces are preferred. The supports can be flat but may also be curved. The proto devices and/or bundles of proto devices can be mounted on one or both surfaces of the support. The proto devices and the bundles of proto devices attached to the support can protrude from the support at an angle, in particular an angle of from about 15° to about 75° and even up to about 90°, the angle being one included by the device or bundle of devices and its projection onto the mounting face of the support and/or at an angle of from about 15° to about 75° included by the proto device or proto device bundle long axis and a central long axis of the support. The support may contain pores or be semi-permeable to body fluids, that is, permeable to at least water and inorganic salts. 
         [0168]    Upon insertion into soft tissue and contact with aqueous body fluid in the tissue, the proto device, the bundle of proto devices and the array of proto devices or bundles of proto devices are transformed to a corresponding device, a bundle of devices and an array of devices of the invention. 
         [0169]    The support of an array of the invention can also be of a material that is soluble or degradable in soft tissue. Useful materials comprise those identified above as useful water soluble/swellable/degradable first coat materials. 
         [0170]    If desired an array support can be equipped with a control unit, such as one comprising or consisting of an electronic chip in electric contact with the electrical conductor(s) of individual devices. The control unit can comprise or be in electrical contact with a unit for electric tissue stimulation and/or signal amplifier(s) for recording electrical nerve signals. The array support can also be equipped with a radiation control unit, which comprises radiation emitting means such as one or more LEDs optically coupled with optical fibers of the array. Furthermore the array support can also be equipped with light sensor(s).