SE539992C2 - Method and arrangement for electrospinning of nanofibers - Google Patents

Abstract

A method and an arrangement for manufacturing of nanofibers involves a plurality of users (U1-U4) associated with a respective electrospinning unit (100), each electrospinning unit (100) being controllable by process parameters to produce fiber products (P).The users comprise providing users (U1, U2) and requesting users (U3, U4). Each providing user (U1, U2) runs the electrospinning unit (100) associated with the providing user using selected process parameters for producing a resulting fiber product, analyzes the resulting fiber product for obtaining associated product parameters and uploads parameters to a server (700), including at least one or more of said selected process parameters and one or more of said associated product parameters. Each requesting user (U3, U4) sends a parameter request to said server together with one or more desired product parameters. In response to the parameter request, the requesting user downloads one or more process parameters from the server (700), the downloaded process parameters being based on (i) said desired product parameters and (ii) said process parameters and said associated product parameters previously uploaded to the server by the providing users.

Description

METHOD AND ARRANGEIVIENT FOR ELECTROSPINNING OF NANOFIBERS TECHNICAL FIELD The present inventive concept relates to the field of nanofiber production,and more specifically the inventive concept relates to a method and an arrangement for electrospinning of nanofibers.

BACKGROUND AND SUMMARY OF THE INVENTION Today, electrospinning is the most common technique for creatingnanofibers. The thickness of fibers created by electrospinning is normally in theinterval 50 - 5000 nm. Depending on the actual size, fibers in this interval may bereferred to as nanofibers or microfibers. However, the literature in the technical fieldnormally refer to fibers in this interval as “nanofibers”, even if they are larger thanthe “nano interval” of 1-100 nm used in other technical fields. Throughout thepresent application, in the claims and in the description of the inventive concept andembodiments thereof, the term nanofiber should be considered to comprise bothnanofibers and microfibers within said interval, i.e. also fibers having a size abovethe more strict nano size of < 100 nm.

A basic electrospinning setup typically includes an electrospinning unitcomprising at least one emitter, a collector and a high-voltage source. The emitterand the collector may be of various designs. Fig. 1 schematically illustrates anexample of a prior-art electrospinning unit 10 including a needle-type emitter. Asolution 12, typically solution containing one or more polymers and a solvent, is heldin a syringe 14 and is fed by pump 16 to a needle tip 18 forming the emitter of theelectrospinning unit 10. A high-voltage 20 is applied to the emitter needle 18 forcreating a net charge in the solution. The solution at the emitter 18 will form a so-called Taylor cone pointing towards the grounded collector 22. lt may be noted thatin alternative setups, the emitter is grounded and the high-voltage is applied to thecollector or any other combination involving a potential difference between theemitter and the collector. At a certain voltage, a thin jet 24 is ejected from the emitter 18. On its way to the collector 22, the jet 24 accelerates and becomes thinner. lnitially, the jet 24 moves in a straight line but later it becomes unstable and deformsinto various loop shapes. The deformed jet reaches the collector 22 where it issolidified into a nanofiber network 26. The jet may also split into multiple jets in-flight(Splaw- Fig. 2 schematically illustrates an alternative prior-art electrospinning setup30 using a centrifugal emitter 32. This type of electrospinning is disclosed in e.g.SE 530 751. The emitter comprises a rotating disc-shaped element 32. The solution34 is fed to the rotating emitter 32 via a pump 36. The collector 38 forms a cylindershaped collector surface at a radial distance R from the emitter 32. Due to therotation of the disc 32, the solution is fed towards the periphery of the disc, and alarge number of radially extending jets 40 are formed. A high-voltage 42 is appliedbetween the rotating disc 32 and the grounded collector 38. Thereby, the solutionbecomes electrified and an electrical field is created between the emitter and thecollector driving the jets 40 towards the collector. The jets may be collected on asubstrate (not shown) moving along the collector surface. During the travel towardsthe collector 38, solvents of the solution will evaporate.

WO 2014/169239 discloses an alternative centrifugal electrospinning setupwhere the collector and a fiber receiving collector substrate moving along thecollector surface are instead disposed vertically over the rotating emitter. As inSE 530 751, the centrifugal process uses a combination of centrifugal forces andelectrostatic forces for generating the nanofibers.

Production of nanofibers is still rather confined to experimental productionset-ups (laboratory or R&D equipments). One major challenge is the fiber productionrate. Economical large-scale industrial-level nanofiber manufacturing techniqueswith satisfactory production rate and production consistency are still beingdeveloped. Accordingly, an enormous amount of research on nanofiber productiontechnology is presently being performed at many universities and research centers.

Although the basic electrospinning setup may seem simple at first sight,electrospinning as such is a complex and relative unpredictable process. Theprocess involves a large amount of variable process parameters as well as ambientparameters affecting the process. These parameters may be independent as well asdependent. Additionally, the production result is also heavily influenced by theselected solution and the parameters thereof (viscosity, concentration, etc.), whichin turn may be affected by ambient parameters. Accordingly, it may be very time- consuming and hard, if at all possible, to predict with a reasonable degree the resulting fiber netvvork morphology. The sheer amount of parameters often causeproblems and users or operators are required to have extensive experience andtraining in order to handle the electrospinning equipment properly and to get usefulresulting strings.

The above mentioned problem relating to the vast amount of parameters andthe difficulty to predict the outcome of electrospinning experiments also has thenegative effect that users or operators may tend to avoid making too many changesto the setup and settings and alternative experiments once a working setup andparameter setting have been obtained. All this have a negative impact on thedevelopment of techniques for large scale production of nanofiber products. ln order to better clarify the underlying problem of the present inventiveconcept, the various parameters or variables will now be further discussed. Theparameters that will control or affect the outcome of an electrospinning may beclassified or divided into the following groups: solution parameters, processparameters and ambient parameters. Fig. 3 illustrates a chart of the typicalparameters included in these three groups. The arrow 50 in Fig. 3 indicates that thesolution parameters may be dependent on the ambient parameters.

Already the initial choice of which solution to use in an electrospinningprocess involves selecting numerous parameters including viscosity, conductivity,surface tension, polymer molecular weight and dielectric constant, which all willaffect the outcome of the electrospinning process in various ways often hard topredict. Normally, each parameter has to be chosen in a proper range for theprocess to yield useful results. ln the present context, the name or brand of achosen solution may also be considered as being a solution parameter.

The second group of parameters affecting the spinning process includes theactual process parameters (user settings). Process parameters involve thoseparameters which are associated with the design, arrangement and setting of thedifferent components of the electrospinning unit. Process parameters include(depending on the actual setup) at least the solution feed rate (pump speed) to theemitter, spinning time, voltage or the electrical field strength between the emitter andthe collector, the distance between the emitter and the collector, the emitter design(needle, disc, number of emitters, etc), the collector design (stationary, moving,substrate, etc), the spatial relative arrangement of the emitter and the collector,needle tip design, rotational speed of centrifugal type collectors and collector substrate feed rate. As an example, changing the setup from a needle-type emitter to a centrifugal disc type emitter would involve changing several of the processparameters at the same time, making such a simple structural change an actualchallenge for the user in terms of predictability.

The third group of parameters affecting the spinning process includes theambient parameters. The ambient parameters involve those parameters which areassociated with the environment at which the different parts of the electrospinningapparatus are located, including the emitter location, the jet in-flight area betweenthe emitter and the collector, and the collector location. These ambient parametersinclude at least air temperature, relative humidity and air velocity. For instance, anincreased temperature may yield fibers with a decreased fiber diameter, which maybe attributed to a decrease in solution viscosity due to the temperature increase.This example demonstrates how a variation among ambient parameters may affectsolution parameters, which in its turn may affect the resulting outcome of thespinning process in an often highly unpredictable way.

The arrows 50, 52, 54 and 56 in Fig. 3 illustrate the direct or indirectdependency between the high number of parameters mentioned above and theresulting fiber product.

Also the resulting fibers and fiber network may be characterized by a pluralityof parameters, termed product parameters, which include at least the fiber diameter,the fiber diameter distribution, the fiber pore size and the fiber pore distribution, thenetwork porosity, the fiber network thickness and the fiber network basis weight(g/m2). These parameters may be established by various analysis techniques, suchas by SEM.

Throughout the present application, in the claims and in the description of theinventive concept and embodiments thereof, the terms solution parameters, processparameters, ambient parameters and product parameters are to be understood asincluding at least but not limited to the above mentioned individual parameters andvariables. The diagram in Fig. 3 illustrates the plurality and the resulting complexityof parameters involved in electrospinning.

Electrospinning is still very much on laboratory scale stage due to the aboveproblems. Accordingly, there is a need to facilitate the electrospinning process forcreating nanofibers and nanofiber networks, and especially a need to facilitateexperiments and R&D work relating to nanofiber production techniques for obtainingmore predictable results. The present invention aims at solving or at least reducing the above mentioned problems.

According to a first aspect of the inventive concept, there is provided a method for manufacturing of nanofibers involving a plurality of users associated with a respective electrospinning unit, each electrospinning unit being controllable by process parameters to produce fiber products characterized by product parameters, wherein said plurality of users comprise providing users and requesting USGFS, said method comprising: at each providing user: running the electrospinning unit associated with the providing userusing selected process parameters for producing a resulting fiberproduct, analyzing the resulting fiber product for obtaining associatedproduct parameters; uploading parameters to a server, including at least one or more ofsaid selected process parameters and one or more of said associated product parameters; and at each requesting user: sending a parameter request to said server together with one ormore desired product parameters, in response to said parameter request, downloading on ore moreprocess parameters from the server, the downloaded processparameters being based on (i) said desired product parameters and(ii) said process parameters and said associated productparameters previously uploaded to the server by the providingusers, and running the electrospinning unit associated with the requesting user using said downloaded process parameters.

According to a second aspect of the inventive concept there is provided an arrangement for manufacturing of nanofibers, comprising: a plurality of electrospinning units, each unit being associated with a respective one of a plurality of users and each electrospinning unit being controllable by process parameters to produce fiber products characterized by product parameters, and a server hosting a database, wherein each electrospinning unit has an associated computer meansproviding a user interface for the associated user, wherein said plurality of users comprise providing users and requestingusers, wherein at each providing user, said computer means being arranged torun the associated electrospinning unit using selected process parameters enteredat said user interface for producing a resu|ting fiber product and to uploadparameters to a server, including at least one or more of said selected processparameters and one or more product parameters of said resu|ting fiber product, wherein said server being arranged to store the parameters uploaded bythe providing users in said database, wherein at each requesting user, said computer means being arranged tosend a parameter request to said server together with one or more desired productparameters entered at said user interface by the requesting user, wherein the server, in response to said parameter request received fromthe requesting user, being arranged to provide one or more suggested processparameters based on (i) said desired product parameters and (ii) processparameters and associated product parameters previously uploaded to the server bythe providing users and stored in said database, and wherein at each requesting user, said computer means being arranged todownload said suggested process parameters from the server and to run theelectrospinning unit associated with the requesting user using said downloadedsuggested process parameters.

The plurality of users would typically be geographically distributed, such as indifferent cities and/or countries, and typically be located remotely from the server.The number of users involved may be very high, for instance many thousands ormillions. The term “user”' should be interpreted in a wide sense and shouldespecially include also a team or only the actual spinning apparatus or unitcomprising computer means managing the uploading and downloading ofparameters, running the process as well as forwarding requests to the server. Someusers may act as both providing users and requesting users.

The inventive method may be wholly or partly controlled by an interactivecomputer interface or computer program running on for example in a built-incomputer in the electrospinning apparatus or on an external computer. This interface allows full control of the electrospinning process, by allowing the user to shift any of the parameters affecting the process in real time. The computer mayalso automatically read changes of add-on units and modules as described below.The user interface may preferably be accessible from outside the machine sincecontrolling these parameters from outside reduces human interference and thusreduces risk of injury and contamination.

The server may be a single server or a distributed server. The server maytypically implement a “cloud service”, i.e. be a “cloud server” accessible over theinternet via its IP address. The server may include and/or host a database. The term“server” should be construed as involving and/or managing any technical meanswhich may be used for providing the required “services” to the users, includingreceiving uploaded data/parameters, handling and/or managing storage of uploadeddata/parameters, handling user requests, performing or managing any requiredcalculations or estimates of parameters to be downloaded, and managingdownloading of parameters to requesting users. ln some embodiments, the serverservice/database may be accessible via an API (application programming interface)at a computer/tablet/phone.

The interpretation and meaning of the expressions “process parameters",“solution parameters” and “ambient parameters” have been discussed above.However, it should be understood that some parameters may be entered manuallyby a user at a user interface, such as the process parameter spinning time, whereasother parameters may be provided automatically, for example a built-in computermay automatically receive process parameters relating to the design or type ofemitter selected (see below regarding modular setup). This applies also to theproduct parameters, which may be transferred automatically from fiber productanalysis means to built in computer means.

According to the invention, a requesting user will, in response to andfollowing the parameter request, download suggested process parameters from theserver. The downloaded process parameters will be based at least on parameterspreviously uploaded to the server by the providing users. This will advantageouslyallow a given set of downloaded process parameters, i.e. a specific downloadoperation to a specific requesting user, to be based on parameters uploaded fromtwo or more providing users. Especially, the server may be arranged tocalculate/estimate/suggest parameters to the requesting user by interpolation or other techniques using data from more than one providing user.

The inventive concept makes it is possible to create an extensive parameterdatabase hosted by the server, which database may be distributed by databasemanagement in order to allow users to reproduce each other's experiments andachieve predictable results, limiting the time that has to be spent on characterizingeach users own nanofiber networks.

Saving the data, including production results, from numerous users(providing users) and making this data accessible for multiple users (requestingusers) allows for a fast buildup of empirical data to include in the database.

The inventive concept will advantageously make it possible for users torequest a suggestion for parameters to use for a given spinning outcome (i.e. fiberswith a diameter of 500 nm and a porosity of 85%), reducing the technical know-howrequired to design the process and making it more available to new users.

The inventive concept will advantageously also make it possible to basepredictions regarding the outcome of spinning with different parameters. The systemallows users to base predictions of the outcome of their experiments on a largeamount of data from other users' experiments, making planning easier. ln preferred embodiments, each electrospinning unit is provided with orattached to an interactive computer interface. The interface may be running oncomputer means built in into the electrospinning setup or, alternatively, on anexternal computer. This interface will allow full control of the electrospinningprocess, by allowing the user to shift any of the parameters affecting the process inreal time. ln some embodiments of the invention, it would also be possible for theprogram to automatically set parameters based on the user's desired fibermorphologies (such as diameter and/or porosity) given a the use of a specificpolymer solution. The computer means or user interface may in this context alsohandle all communication with the server automatically (uploading parameters andrequests and downloading parameter suggestions) and for running the processbased on downloaded parameters.

With enough empirical data it will also be possible to derive an equationprecisely describing the spinning process, which would allow the user interface atthe user locations to compensate for any fluctuations in parameters (for exampleto maintain desired fiber lowering the voltage if the humidity increases), morphologies throughout longer spinning sessions.

The inventive concept enables streamlining of the fiber production processfrom start to finish (design of experiments to produced fiber network), and reducesthe costs of production, as less time and money has to be spent characterizing eachfiber network (something that is usually done using an SEM, which is bothexpensive to buy and run) to verify the quality of the produced fibers. Thus, therequesting users downloading process parameters from the server may dispensewith at least some post-spinning product analysis work.

Additionally, the inventive concept makes the electrospinning process userfriendly, as not all users have the necessary theoretical physics knowledge requiredto comfortably fine-tune the process, while maintaining the option to customizespinning parameters for more experienced users. The inventive concept effectivelyallows the electrospinning production technique to be spread to even more newusers, both in the industry and academia, as the demands on the knowledge of theuser is lowered, which is a limiting factor in the use of the technique today. ln preferred embodiments of the invention, the parameters uploaded by theproviding users and/or downloaded by the requesting users are stored locally at therespective user. This may preferably be done automatically by the computersoftware. Thereby, saved parameter settings can be re-used during later spinningsessions. At the providing users, the parameters may typically be locally stored andthereafter uploaded to the server.

According to the inventive concept, a plurality of users and associatedelectrospinning apparatuses interact with a server hosting a database. Data storageand data analysis may take place at all locations. ln one embodiment, the storage and analysis may be divided as follows: At the server hostinq the database: o Storage of data at a web-hotel/web-server. o Access distributed to users/customers. network dimensions, based on a process algorithm derived from the data o Calculations of suggested parameters for pre-set fiber collected from user spinning sessions (uploads from providing users) o Providing data back to the user/machine that requests it.

Bv each users individual setup:o Data is saved and stored locally after each run by default, with the option to add "results". The interface after each completed run, or at the command of the user, access the web server |.P using a pre-determinedport, and uploads the saved parameters to the database. ø lf a user decides to run the spinning apparatus using suggestedparameters for pre-determined fiber dimensions a request will be sent tothe server hosting the database, where parameters will be retrievedand/or calculated and returned to the requesting user interface.

With respect to the option of “adding results” mentioned above, the resultmay for instance be fiber diameter, porosity, fiber network thickness or fiberdiameter variation. The result may also involve that some additional information hasoccurred during the spinning process, such as artifacts and disturbances, forexample an uneven fiber layer thickness, clods or impurities. The term "result" mayalso involve “non-results”, such as an voltage insufficient to create a fiberjet/Taylorcone, or a to short emitter collector distance so that the solvent has not evaporatedwhen the jet hits the collector. The "result" may also involve electro spraying whichoccurs when the voltage is too high resulting in small polymer spheres being“sprayed” on the collector. An insufficient emitter collector distance may also resultin solid fibers being formed between the emitter and the collector Whereby additionalfibers are “caught” and formed in-between the emitter and the collector. For someresults, such as the fiber diameter, an analysis has to be performed, for instance inan SEM, but in general the user will be able, by the naked eye only, to evaluate theresult by observing the process running and by observing the fiber surface. The userwill normally easily see if the process is Working, i.e. if fibers are formed or not, if thesolution is just flowing out of the emitter or if the solution forms clods on its way tothe collector.

The requesting user (or rather the associated computer means) mayoptionally send a second and optionally further requests for obtaining even bettersuggested parameters and thereby a final fiber product better matching the desiredresult. Thus, a requesting user may send a first request to the server as statedabove and then perform a first run using first parameters downloaded from theserver to produce a first fiber product associated with first product parameters. Aftersaid first run and analyzing the first fiber product, the requesting user (or rather theassociated computer means) may then, automatically or not, send a secondparameter request to the server together with at least some of said first productparameters. The second request may also contain the data from the first request, including the desired product parameters. Based on the received first product 11 parameters, the server may then provide a second or updated set of suggestedprocess parameters to be downloaded by the requesting user for performing asecond run. Obviously, when sending the second request, the requesting user mayoptionally also simultaneously act as a providing user, i.e. provide the resultachieved using the first parameters downloaded together with other local settings sothat the server receives a set of parameters according to what has been described above for a providing user.

Modular electrospinning unit ln some embodiments of the inventive concept, the electrospinning unit itselfis modular in the sense that one or more of the individual components of the unit areeasily detachable and exchangeable by the user, especially the emitter(s) and/or thecollector, giving the user the ability to choose from a variety of both emitters andcollectors. Such a modular setup would allow production of multiple types of fibersand even combination of different fiber types and polymers.

The present inventive concept will be especially useful when used incombination with such modular electrospinning units. Changing the emitter and/orcollector design (including types of emitter/collector and numbers of emitters) will nolonger be a complicated and unpredictable task. Users running their setups withdifferent modules will upload the corresponding process parameters and resultingproduct parameters to the server. Requesting users will thereby be able to easilyswitch modules, sending a request to the server for parameter settings for theselected module, typically in combination with desired fiber product parameters. lnsome embodiments, a user may also order a desired “module kit” including aphysical emitter or collector module together with the associated processparameters to be downloaded by the user from the server. ln such a modular spinning unit, the emitter(s) may be designed as emittermodules in the sense that the user may easily exchange one or more emittermodules of a first design with one or more emitter modules of a second design. Asan example, a needle-type emitter module may be exchange to a rotating disc typeemitter. As another example, a setup may easily be changed from a first designincluding a plurality of rotating emitters to a second design including a mix of needleemitters and disc emitters.

The emitters can consist of one or several needles, arranged in any formation such an array (regular or irregular) or a in a circle. The emitters can 12 consist of one or several plate like organs (such as a circular, star-shaped, saw-toothed, convex/concave, cone shaped dishes or cones) , rotating around its/theirown axis. There are also other emitter types, for instance a tensioned wire which isinserted into a polymer bath and along which Taylor cones are formedsubsequently. lt is also known to use a flat head from which the polymer is ejectedby the use of pressurized air. Another example is a rotating ring of needles. Stillanother example is the use of a sphere which is inserted into or covered by apolymer solution.

Such emitter modules will be associated with a number of correspondingprocess parameters, such as emitter type, number of emitters and emitter-collectordistance.

The use of more than one emitter means that the user has the option to spinseveral different polymer solutions simultaneously, or increase the deposition rate ofa single one by spinning it through more emitters.

As mentioned above, also the collectors may be designed as collectormodules in the sense that the user may easily replace a collector module of a firstdesign, e.g. comprising a flat collector surface with a collector module with adifferent design, e.g. comprising a rotating drum or a collector substrate runningthrough the entire setup.

The collector can be static or rotating. A static collector can be either flat orhave a structured surface (such as a grid, a regular/irregular meshwork or bars withvaried spacing). The collector could also consist of a rotating cylinder (either acontinual surface or composed of wires stretched along the axis of rotation). ln some designs, the electrospinning setup also enables substrate coveringby moving a substrate (for example a polymer film) through the electrospinning unit,close to the collector, thus depositing the fibers on the substrate rather than theactual collector. lt is also possible to arrange a stationary object to be covered withfibers in front of the collector. lt will be appreciated that the inventive method is especially advantageous incombination with a modular spinning unit having a large variety of changeableemitters/collectors, and combinations thereof. The invention allows for greatcustomization and tailoring of spun fiber networks for various applications despite the variations of multiple process parameters. 13 Modular add-on units Today, the electrospinning process is normally performed in a closedcompartment (due to high voltage and toxic/flammable solvents involved in theprocess). After the spinning process is complete, the fibers must be moved forfurther processing (heat drying, coating, cutting, analysis etc.). These processes areusually performed at a different location. Nanofibers are very fragile, and eachtransport risks both damaging and contaminating the fibers. ln a preferred embodiment of the invention, the apparatus is thereforemodular with add-on units with different purposes, automatically executing thesesteps without removing the fibers from the closed compartment. Embodiments ofsuch add-on units will be described in the following. Each add-on unit may perform aspecific task that to some extent affects the finished electrospun nanofiber materialproduced from the electrospinning process. Examples of add-on units include (butare not limited to):- Pre-/post- treatment of the substrate the fibers are to be deposited on (for example sterilization with UV-light, chemicals or heat.- Coating of the substrate and/or the fibers (for example laminin or collagencoating).- Cutting of the fibers into desired shapes (for example mechanical cutting orlaser cutting).

- Analysis and documentation of the produced fiber network (fiber diameter, alignment, network porosity, uniformity etc.) BRIEF DESCRIPTION OF THE DRAWINGS The inventive concept and advantages thereof, as well as some non-limitingembodiments and examples thereof, will now be further described with reference tothe drawings, in which: Fig. 1 schematically illustrates a prior-art needle-type electrospinning setup.

Fig. 2 schematically illustrates a prior-art centrifugal-type electrospinningsetup.

Fig. 3 is a parameter chart.

Fig. 4 is a schematic illustration of an embodiment of an electrospinning apparatus for use in the present invention. 14 Fig. 5A to 5C are schematic illustrations of modular add-on units of anelectrospinning apparatus.

Fig. 6A to 6D are schematic illustrations of an electrospinning frame unit.

Fig. 7 to 10 are schematic illustrations of an embodiment of a modularelectrospinning unit for use in the present invention.

Fig. 11 is a schematic diagram illustrating the inventive method.

Fig. 12 is a schematic diagram illustrating part of the inventive method inmore detail.

Fig. 13 is a flowchart illustrating an embodiment of the invention at aproviding user.

Fig. 14 is a flowchart illustrating an embodiment of the invention at a requesting user.

DESCRIPTION OF E|\/|BOD||\/IENTS Fig. 4 schematically i||ustrates an example of an electrospinning setup orapparatus 400 which may be used in connection with the present invention. Fig. 4shows the a main spinning unit 100 of the apparatus 400, comprising an airtightframe 402 having a substrate in|et 404 and a substrate out|et 406 for a collectorsubstrate 104. Inside the frame 402, the unit 100 comprises an electrospinningemitter 102 of centrifugal type arranged on a height-adjustable table 109, and acollector 103, wherein the substrate 104 passes between the emitter and thecollector closer to the latter. During the production process, the substrate 104 ismoving from the in|et 404 to the out|et 406 via a number of substrate redirectors 408in order to receive the upwardly directed solution jets from the emitter 102. Theapparatus frame 402 is further provided with ventilation means 410 for removingsolvents from the interior.

As will be discussed further below, the apparatus 400 may also include post-spinning product analysis means for analyzing the product produced by the mainunit 10 for obtaining one or more associated product parameters, and/or post-spinning fiber treatment means for treatment of the product produced by the mainunit 100.

Fig. 5A schematically i||ustrates a modular arrangement which may be usedin some embodiments of the present invention. ln this arrangement, the overall electrospinning apparatus 400 is modular in the sense that one or more add-on units can be easily attached externally to the main spinning unit 100 to Customize itaccording to the needs of the user. This modularity may be present during themanufacturing of the apparatus 400, but especially also at the user site so that theuser may add and remove add-on units as desired. Changing/adding/removing add-on units may affect the above-mentioned process parameters. Thus, a providinguser using one or more add-on units for a spinning run will upload parameters to theserver including process parameters also reflecting the specific add-on units usedfor the run.

As a non-limiting example, Fig. 5A illustrates one pre-spinning add-on unit200 and one post-spinning add-on unit 300. As illustrated schematically, the units100, 200, 300 are designed to allow the collector substrate 104 to move through thewhole apparatus 400 from a source roll 411 at the apparatus inlet to a collecting roll412 at the apparatus outlet. The rolls 411, 412 may be implemented as separateelement to be connected to/detached from the add-on units as needed. ln some embodiments, each one of the main unit 100 and the add-on units200, 300 is built with a framing that easily can be attached to and detached from theother units. Figs. 6A to 6D illustrates an example of such a frame 500 of thespinning unit 100 As shown, the frame 500 includes the emitter 102 mounted on atable 109 and the collector 103. The frames may be implemented as essentially air-tight units for better control of the process.

An example of a post-spinning add-on unit 300 would be a first separateadd-on unit 300A in line with the primary spinning unit 100 (the unit housing theelectrospinning process) for sterilizing the produced fiber network using ethanolsoaking in combination with UV-radiation. This first add-on unit could be followed bya second add-on unit for shaping the fiber substrate into the desired end-shape (byfor example mechanical cutting, laser cutting, stretching it onto a given detail etc.). ln one embodiment shown in Fig. 5B, a post-spinning unit 300A may bearranged for treating the fiber network deposited on the moving collector substrate104. ln the unit 300A, the substrate 104 with the fiber product thereon is passedover an ethanol spraying unit 301, including a ethanol pump and an ethanol emittingnozzle for treatment of the fiber product. Other coatings would be possible. AUV radiation source 302 mounted on a support 304 is arranged to next irradiate thefiber network on the substrate 104 with UV radiation. Next, the fiber network on thesubstrate 104 is subjected to IR radiation from a IR source 306 before leaving the apparatus 400 at the substrate outlet. The final result is wound on a substrate roll 16 412. The IR radiation may be used to evaporate solvent residuals in the fibers, i.e. todry the fibers. The IR radiation may also be used to fuse or connect the fibers toeach other. The UV radiation is primarily for sterilization purposes but may also beused to crosslink polymers for increasing stability. ln one embodiment shown in Fig. 5C, a post-spinning unit 300B may bearranged to run an analysis on the resulting fiber network, in order to determineFig. 5B schematically illustrates an example of such a post-spinning analyzing unit 300 product parameters such as thickness, porosity, uniformity etc.which receives the substrate with fibers from the main unit 100 or from a previouspost-spinning unit and which comprises analyzing means in the form of amicroscope 310 and a laser or light source 312 in combination with a detector 314.The microscope 310 may be used to determine fiber diameter, pore size and similarparameters. The images may be saved to database. The laser/light source 312 maymeasure reflected intensity. The detector 314 may be used to measure transmittedlight in order to determine porosity, density or thickness.

Add-on units 200 may also be placed ahead of the main unit 100 as well, forexample with the purpose of chemically treating or priming the surface of thesubstrate 104 prior to it being covered by nanofibers. ln preferred embodiments, as indicated in Fig. 5A, all units, i.e. both the mainspinning units 100 and any add-on units 200, 300 are made with similar framesessentially as shown in Fig. 6 for establishing a modular system in which the fibersupport is running through all frames. lt will be appreciated that the use of add-on units as described above incombination with the inventive concept gives a great flexibility when it comes toprocess design. lt allows for customization of the setup to fit the applications theuser has in mind. The modularity concept with add-on units also advantageouslyreduces the risk of contaminating the fiber networks, since the design will limit thedegree of fiber transport outside the process. Experiments using differentcombinations of add-on units may easily be performed by users by using theuploaded parameters from other users having run identical or similar setups.

The electrospinning unit 100 may itself be modular in the sense thatindividual components of the unit, especially the emitter and/or the collector, may beeasily exchangeable. This gives the user the ability to choose from a variety ofemitters and collectors. Thereby, the user may use one spinning unit for producing multiple types fibers and fiber networks, and even combinations of different fiber 17 types and polymers. As for the modular add-on units, the emitter and/or collectormodules will be associated with respective process parameters.

As non-limiting examples, Fig. 7, 8 and 10 disclose three different setupswith different emitter and collector setups, using one and the same basic unit 100.The modular unit 100 may be used in connection with add-on units as describedabove.

Fig. 7 discloses a first setup in which a single disc-shaped centrifugal emittermodule 102a is mounted on a table 109 of the unit 100. The table 109 is providedwith fittings for other/additional modules. The rotating emitter module 102a is drivenby an electrical motor 110 via a belt drive mechanism 112. The solution is fed fromthe solution pump 106 to the emitter 102a via conduit means 108. ln this first setup,the fiber jets are collected on a stationary plate-shaped collector module 103adetachably mounted in the ceiling of the frame 500. Reference numeral 120illustrates the high-voltage unit of the spinning unit 100. Reference numeral 600relates to a computerized user interface or computer program comprising a display612 and allowing the user to set different process parameters and to read differentsettings. All parameters affecting the spinning process may be set at the userinterface 600. Also, chosen parameters may be saved locally and, as will bedescribed in the following, uploaded to a server. The computer means may beimplemented as an integral part of the unit 100 or as an external computer.

Fig. 8 discloses a second setup of the unit 100 in which two additional disc-shaped centrifugal emitter modules 102b and 102c have been added, also driven bythe electrical motor 110 via a modified belt drive mechanism 112”. The solution isfed from the solution pump 106 to all three emitters 102a-c via the conduit system108. ln alternative embodiments, the unit 100 may comprise multiple pumps forfeeding different solutions to different emitters, including emitters of different type. lnthis second setup, the fiber jets are collected on a moving substrate 104 movingover a collector plate module 103b mounted at the ceiling of the frame 500. Feedmeans 411, 412 for the substrate 104 have also been attached to the frame 500.

Fig. 9A and 9B disclose an example of a disc-shaped emitter module 102 inwhich the upper part is fitted on a threaded base in order to adjust the heightindicated by a double arrow 107, for adjusting the emitter-collector distance.

Fig. 10 discloses a third setup of the unit 100 in which the rotating emittermodules have been removed and replaced by a needle-array type emitter module 102d, receiving the solution from the pump 106 via the conduit system 108. ln this 18 third setup, the fiberjets are collected on a rotating collector module 103d mountedvia a support 103' at the ceiling of the frame 500.

Fig. 11 illustrates how manufacturing of nanofibers may be performed inaccordance of an embodiment of the invention. A plurality of users U1, U2, U3 andU4 are associated with a respective electrospinning unit 100. Each electrospinningunit 100 is controllable by process parameters as mentioned above, and eachprocess is performed using a solution having certain solution parameters and underambient conditions in the unit defined by ambient parameters. ln a real embodiment of the present invention, the number of users wouldtypically be essential higher in order to build an efficient and useful parameterdatabase. For sake of simplicity, Fig. 11 discloses four users only of which U1 andU2 are termed providing users and U3 and U4 are termed requesting users.Obviously, each providing user may also act as a requesting user and vice versa.

At each user there is thus provided a respective spinning unit 100, and also auser interface/computer means 600 and local storage means 602. As mentionedabove, the user interface/computer means may be part of the unit 100 orimplemented as external computer means. ln Fig. 11, at each providing user U1, U2, the following actions areperformed: - The user runs the associated electrospinning unit 100 user usinguser-selected process parameters entered at the user interface forproducing a resulting fiber product.

- The resulting fiber product is analyzed, e.g. automatically by ananalyzing add-on unit, for obtaining associated product parameters.

- The process parameters used, the ambient parameters measured,the solution parameters used and the product parametersassociated with the resulting fiber product are locally stored at 602and uploaded to a server 700, as indicated at 710, and stored in adatabase 702 hosted by the server 700. ln Fig. 11, at each requesting user U3 and U4, the following actions areperformed: - The user sends a parameter request to the server at 712 togetherwith one or more desired product parameters. - ln response to said parameter request 712, the requesting user downloads at 714 suggested process parameters from the server, 19 the downloaded process parameters being based on (i) said desiredproduct parameters in the request and (ii) said process parametersand said associated product parameters previously up|oaded to theserver by the providing users.

- The user will then run the electrospinning unit using saiddownloaded process parameters, which may be done automaticallyby the computer means.

Fig. 12 schematically illustrates in greater detail the parts of the methoddescribed performed at a providing user U1, U2. The user decides to run a spinningprocess using a solution S which is fed to a spinning unit 100. The user entersdesired process parameters at a user interface, and computer means 600 willcontrol the unit 100 accordingly. The resulting fiber product P is received from theunit 100 and then analyzed in a suitable manner, optionally in an modular add-onunit 300a. The thus obtained product parameters are stored together with otherparameters at a local storage 602. All relevant parameters from the run are then (bydefault) automatically up|oaded to the server 700.

The double arrow in Fig. 12 between the computer means 600 and thespinning unit 100 indicates that the computer means 600 on the one hand sendsprocess parameters to the unit for controlling the process and, on the other hand,also may receive process parameters from the spinning unit 100, for example if anemitter module is changed to another emitter module.

Fig. 13 illustrates a more detailed example of how a providing user U1, U2could interact with the interface: The user decides to run a custom electrospinning session usingpolycaprolactone (PCL) solved in acetone. The solution is prepared and loaded intoa compartment connected to the pump in the electrospinning unit, the compartmentis shut, the housing is sealed and the user starts the computer interface.

After booting up and logging in, the user sets his input parameters (forexample: Field strength: 30 kV, Pump speed: 20 mL / h, Working distance: 20 cm,Emitter rotational speed: 1500 RPM, Spinning time: 30 min etc.) as well as solutionparameters (for example: Fiber material: PCL, Solvent: Acetone 99.5%, SolutionConcentration: 15% and comments: PCL with a molecular weight of 80 000 kDa wassolved in 99.5% acetone at room temperature for 2 h under constant stirring), and initiates the spinning process.

While the process is run, ambient parameter data (for example temperature,humidity, pressure) is collected by sensors in the unit and stored along with thespinning parameters.

Assuming the spinning process is completed (i.e. the spinning is run for itsfull duration) the interface, in addition to storing the data locally, wirelessly connectsto a web server l.P hosting a parameter database and uploads the parameters,where the parameters are now stored as well. lf the user has an add-on unit capable of analysis of the produced fibers,data concerning the fiber netvvork is uploaded by default as well (for example fiberdiameter, alignment, porosity, uniformity), if not, the user has the option to runcharacterization using other equipment and then come back to upload results at alater time.

Fig. 14 illustrates a more detailed example of how requesting user U3, U4could interact with the interface: The user decides that he/she would like a suggestion for appropriatespinning parameters to use to electrospin PCL nanofibers with a diameter of forexample 600 nm and a network porosity of 90%.

These desired product parameters are input into the interface. Theelectrospinning unit and/or the computer means will then connect to the serverhosting the parameter database making the request for suggested parameters.

At the server, a program running an algorithm describing the spinningprocess (derived from all the uploaded data from providing users) takes the inputparameters from the requesting user into consideration and suggests appropriateparameters to use to achieve the given fiber morphology.

The data is sent back to the requesting user and the associatedelectrospinning unit where it is input as suggested parameters for the spinning. lf the user is satisfied with the suggestion he can then initiate the spinningprocess.

Optionally, and parameters will be stored and uploaded as in the exampleabove for a providing user.

Obviously, if the downloaded parameters are locally stored once downloadedfrom the database hosted by the server, the computer program can be arranged toautomatically set process parameters in the future without further downloading if theuser has the same requests regarding desired fiber morphologies and specific polymer solution.

Claims (10)

21 CLA||\/IS

1. A method for manufacturing of nanofibers involving a plurality of users(U1-U4) associated with a (100), electrospinning unit (100) being controllable by process parameters to produce fiber respective electrospinning unit eachproducts (P) characterized by product parameters, wherein said plurality of users comprise providing users (U1, U2) andrequesting users (U3, U4), said method comprising: at each providing user (U1, U2): - running the electrospinning unit (100) associated with the providinguser using selected process parameters for producing a resultingfiber product, - analyzing the resulting fiber product for obtaining associatedproduct parameters; - uploading (710) parameters to a server (700), including at least oneor more of said selected process parameters and one or more ofsaid associated product parameters; and at each requesting user (U3, U4): - sending a parameter request (712) to said server (700) togetherwith one or more desired product parameters, - in response to said parameter request, downloading (714) one ormore process parameters from the server (700), the downloadedprocess parameters being based on (i) said desired productparameters and (ii) said process parameters and said associatedproduct parameters previously uploaded to the server by theproviding users, and - running the electrospinning unit (100) associated with the requesting user using said downloaded process parameters.

2. A method as claimed in any of the preceding claims, wherein saidrunning the electrospinning unit at the requesting user constitutes a first runningproducing a first fiber product, and wherein said method further comprises, at the requesting user: 22 - analyzing the first fiber product for obtaining associated first productparameters; and- sending a second parameter request to the server together with at least some of said first product parameters.

3. A method as c|aimed in any of the preceding claims, wherein theparameters uploaded by the providing users (U1, U2) are stored in a database (702) hosted by said server (700).

4. A method as c|aimed in any of the preceding claims, wherein parametersuploaded by the providing users (U1, U2) to the server (700) and/or parametersdownloaded by the requesting users (U3, U4) are stored locally (602) at the providing users and at the requesting users, respectively.

5. A method as c|aimed in any of the preceding claims, wherein theparameters uploaded by each providing user (U1, U2) further include solutionparameters associated with a solution (S) used by the providing user when running the associated electrospinning unit (100).

6. A method as c|aimed in any of the preceding claims, wherein theparameters uploaded by each providing user (U1, U2) further include ambientparameters measured at the providing user when running the associated electrospinning unit (100).

7. A method as c|aimed in any of the preceding claims, wherein for saidproviding user:- said parameter request further includes one or more solutionparameters associated with an intended solution,- said downloaded process parameters being based also on saidsolution parameters included in the request, and- said running the electrospinning unit associated with the requesting user is performed using said intended solution. 23

8. A method as claimed in any of the preceding claims, wherein the processparameters include parameters relating to the design of different emitter modules (102a-d) of said electrospinning unit.

9. A method as claimed in any of the preceding claims, wherein the processparameters include parameters relating to the design of different collector modules(103a, 103b, 103d) of said electrospinning unit.

10. An arrangement for manufacturing of nanofibers, comprising: a plurality of electrospinning units (100), each one being associated with arespective one of a plurality of users (U1-U4) and each electrospinning unit (100)being controllable by process parameters to produce fiber products (P)characterized by product parameters, and a server (700) hosting a database (702), wherein each electrospinning unit (100) has an associated computermeans providing a user interface for the associated user, wherein said plurality of users comprise providing users (U1, U2) andrequesting users (U3, U4), wherein at each providing user (U1, U2), said computer means beingarranged to run the associated electrospinning unit (100) using selected processparameters entered at said user interface for producing a resulting fiber product andto upload (710) parameters to a server (700), including at least one or more of saidselected process parameters and one or more product parameters of said resultingfiber product, wherein said server (700) being arranged to store the parameters uploadedby the providing users in said database (702), wherein at each requesting user (U3, U4), said computer means beingarranged to send a parameter request (712) to said server (700) together with oneor more desired product parameters entered at said user interface by the requestingusen wherein the server (700), in response to said parameter request receivedfrom the requesting user, being arranged to provide one or more suggested process parameters based on (i) said desired product parameters and (ii) process 24 parameters and associated product parameters previously uploaded to the server(600) by the providing users and stored in said database (602), and wherein at each requesting user, said computer means being arranged todownload said suggested process parameters from the server (600) and to run theelectrospinning unit (100) associated with the requesting user using said downloaded suggested process parameters.