Patent Application
20170144373
This invention relates to three-dimensional printing of filaments containing conductive materials. More specifically, this invention relates to application of a magnetic field to the filament during printing to increase or decrease the resistance and utility of the material.
Many processes have been developed for biological and chemical detection that use traditional cleanroom facilities and lots of capital equipment to produce materials that can be functionalized for specific detection domains. For example, many new biological detectors use a mesh of polymer that has been electro-spun with carbon nano-tubes and activated by applying an antibody to these carbon locations. These types of detectors require very sophisticated laboratories for production and are hard to create in bulk.
The present invention is directed to methods and systems for three-dimensional printing of conductive materials. In one embodiment of the present invention, a method of three-dimensional printing of conductive materials is disclosed. The method includes extruding a molten filament containing a conductive material from a print head of a three-dimensional printer, and applying a magnetic field to the print head.
The magnetic field may be a magnet or an electromagnet.
In one embodiment, the filament is a polymer. The polymer may be, but is not limited to, acrylonitrile butadiene styrene (ABS), Nylon, polyethylene terephthalate (PET), or polylactic acid (PLA).
The conductive material may comprise at least one of the following: graphene, carbon black, multi-walled or single wall carbon nanotubes, a carbon nanotube composite, carbon fibers, a metal, metal nanoparticles, or combinations thereof.
In one embodiment, the print head comprises an extruder including a nozzle with a tip. The magnetic field may be applied at a tip of the extruder, nozzle, or nozzle tip of the print head.
The method may further include functionalizing the filament after the extruding and applying steps. In one embodiment, the filament is functionalized with an antibody.
In another embodiment of the present invention, a method of three-dimensional printing of conductive materials is disclosed. The method includes applying a magnetic field to a print head of a three-dimensional printer as an extruded molten filament containing a conductive material is being extruded through the print head.
In another embodiment of the present invention, a system for three-dimensional printing of a conductive material is disclosed. The system includes a filament containing a conductive material; a three-dimensional printer including a print head; and a magnetic field applied to the print head as the filament containing the conductive material is being extruded through the print head in a molten state.
In another embodiment of the present invention, a composition suitable for three-dimensional printing is disclosed. The composition includes a filament containing a conductive material, when exposed to a magnetic field and extruded through a print head of a three-dimensional printer, has a resistivity below 500 KOhms/cm.
In another embodiment of the present invention, an apparatus for three-dimensional printing is disclosed. The apparatus includes a three-dimensional printer including a print head, and a magnet or electromagnet coupled to the printer or the print head.
The following description includes the preferred best mode of embodiments of the present invention. It will be clear from this description of the invention that the invention is not limited to these illustrated embodiments but that the invention also includes a variety of modifications and embodiments thereto. Therefore the present description should be seen as illustrative and not limiting. While the invention is susceptible of various modifications and alternative constructions, it should be understood, that there is no intention to limit the invention to the specific form disclosed, but, on the contrary, the invention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined in the claims.
Disclosed are methods and systems for three-dimensional printing of conductive materials. In one embodiment, the method of three-dimensional printing of conductive materials includes extruding a molten filament containing a conductive material from a print head of a three-dimensional printer, and applying a magnetic field to the print head. The magnetic field may be, but is not limited to, a magnet or electromagnet.
The filament may be, but is not limited to a polymer. The polymer can be ABS, Nylon, PET, or PLA.
The conductive material is, but not limited to, at least one of the following: graphene, carbon black, multi-walled or single wall carbon nanotubes, a carbon nanotube composite, carbon fibers, a metal, metal nanoparticles, or combinations thereof.
In one embodiment, the print head comprises an extruder including a nozzle with a tip. The magnetic field may be applied to the tip of the extruder, nozzle or nozzle tip of the print head.
In another embodiment, a magnetic field is applied to the tip of a three-dimensional printer that is laying down fibers with paramagnetic fillers. The applied magnetic field causes the paramagnetic filler to be drawn to the surface of the fiber. Different field strengths, field alignments, and combinations of flux lines through magnetic or electromagnetic means can be used to further control and influence the structure of the material. After the magnetic field is applied, the printed filament may be labeled with antibodies.
An increase in the conductivity of the material has been shown, as well as a surface roughness associated with more carbon locations on the outside of the material.
Scanning electron microscopy (SEM) was used to visualize the physical changes to the original filament and the filament exposed to a magnetic field, as shown in
An important characteristic of a conductive filament that is used to detect a chemical or biological agent is that the measurable output (resistance) only changes in the presence of the target. Two untreated conductive filament and two filament exposed to the magnetic field were cut in half and the eight resultant segments were measured for their resistivity. Each filament was measured three times for n=12 measurements at time zero or prior to treatment, as detailed in Table 1 below. For filaments that were not in a buffer, the resistance of the untreated sample was 36 KOhms, the magnetic treated was 64 KOhms. The fold change in resistance was 1.7. For filaments placed in a 2 mL microfuge tube with 0.5 mL Phosphate buffered saline with 0.02% Tween 20 (PBST) solution the untreated filament had a resistance of 70 compared to the treated with 149 for a fold change of 2.1. To determine the effect of Bacillus anthracis Sterne spores, approximately 82 spores were added to treated or untreated filaments. The samples were mixed by inversion for approximately 90 minutes. Results are preliminary, but show promise and need to be repeated due to high standard deviation. Filament exposed to this particular magnetic field had an increase in resistance between 2.0 and 5.2 compared to the untreated filament. Additional experiments may need to be completed to determine if this variation is due to spore interaction with the filament.
B. anthracis spores T = 0
B. anthracis spores T = 0
B. anthracis spores T = 90
B. anthracis spores T = 90
The present invention takes advantage of the paramagnetic properties of conductive materials, such as carbon additives, in commercial 3D printer filaments to control and direct the location and alignment of the carbon in the filament carrier by introducing a magnetic field around the liquid state of the material. Inducing this field while the filament, such as a polymer carrier, is in a liquid state allows for the mass transport of the conductive material, and as the polymer cools the carbon structures are fixed in the aligned state. Further, by controlling the mass transit of conductive sites in three-dimensional printed materials and increasing their local density on the outside of the extruded filament, commercially available and inexpensive materials can be used to create a biological or chemical detector by functionalizing the conductive sites with antibodies specific to the targeted biomarker or chemical. This will greatly reduce the cost, development time, and complexity of these types of detector systems.
Additionally, methods of the present invention can change the electrical properties of the material being used, as a localization of the conductive sites increases conductance of the material. This can be used to develop electrical systems on the printer, including printing of coils, motors, and electrical traces. By controlling the temporal state of the magnetic field, the material can be quickly changed from a conductor to an insulator, allowing for a single print material to be used to create complex designs.
The present invention allows for inexpensive and commercially available three-dimensional printers to produce sophisticated and functional materials quickly. The processes require very little capital equipment and can be done on, for example, a desk, in the back of a vehicle, or out in the field. The methods open up a wide variety of application possibilities in, for example, the electric and magnetic (E&M) space, through printing a polymer based material at a relatively low print temperature.
While a number of embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims, therefore, are intended to cover all such changes and modifications as they fall within the true spirit and scope of the invention.
This invention was made with Government support under Contract DE-AC05-76RL01830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.
