Affordable and customizable electrospinning set-up based on 3D printed components

The widespread use of electrospinning, a technique widely used for fabricating micro/nanofibrous materials, has been limited by the high acquisition costs of commercial equipment. This study introduces an accessible alternative by leveraging 3D-printing technology, providing detailed insights into the design and functionality of each component. Specifically, a cost-effective syringe pump, a rotating collector that allows fiber orientation control, and a user-friendly control unit are described. The affordability and customizability of the proposed setup are emphasized, demonstrating its versatility in accelerating material research. Experimental results on polyvinyl difluoride (PVDF) showcase successful electrospinning, validating the efficacy of the 3D-printed electrospinning device. This innovative solution aims to increase the method’s availability and broader utilization in research and development applications.

The electrospinning setup typically consists of three main components: syringe pump, 4 collector, and highvoltage power source [16].The syringe pump is responsible for the controlled delivery of the polymer solution or melt through a fine needle.The high-voltage (HV)(ranging from 1kV [17] to tens of kV [18]) power source applies an electric field between the needle and a grounded or oppositely charged collector, inducing the formation of a Taylor cone [19] and ultrafine fibers from the droplet.The collector, often a rotating drum or stationary plate, collects the electrospun fibers.Despite the efficacy of electrospinning in producing nanofibrous materials with diverse applications as mentioned above, the high cost of the syringe pump, collector, and highvoltage power source poses a challenge for widespread adoption.An integrated electrospinning solution costs multiple thousands or even tens of thousands of dollars and a custom-built solution with all the parts purchased individually costs approximately $1000-2000 with significantly reduced ease of use.These expenses can limit the accessibility of electrospinning for smaller research labs.Therefore, a 3D-printed solution was designed with the aim of making electrospinning more accessible and thus accelerating the research in this area.

Subject & methods
The advantages of 3D printing have been exploited to significantly reduce the device price.The presented models are publicly available [20] and can be locally printed on demand without shipping costs.For increased simplicity and availability the Arduino UNO board was used as a logical unit with publicly available code [20].
Figure 1 shows a 3D model of the designed setup with the 3D-printed parts colored in green.All 3D-printed parts were printed from a PLA 1.75 mm filament on a Prusa i3 Mk3 3D printer (Prusa Research a.s.) with a layer thickness of 0.2 mm and the models are available on the author's GitHub [20].The design of all three main components, the syringe pump, the collector, and the control unit are discussed in the following sections.

Syringe pump
A typical commercially available programmable syringe pump costs approximately $1000.Therefore, cheaper alternatives were designed [21,22].The syringe pump design introduced in this study is fine-tuned to the requirements of electrospinning, particularly concerning flow rate.Except for the 3D-printed parts, thread rods and nuts are required, but can be obtained from any hardware store.The rotary motion was provided by a 28BYJ-48 stepper motor controlled by a control unit described in section 2.3.The pump was designed for 5 ml syringes but the model could be easily modified for different syringe volumes.
The flow rate of ejected solution was determined by the time between steps of the stepper motor Δ. Knowing the syringe radius r = 6.035 mm [23], the screw thread pitch p = 0.5 mm and number of steps per rotation N = 4096 a simple formula for the flow rate Q can be derived For flow rate Q in mlh −1 and dwell time Δ in milliseconds we get The smallest possible dwell time Δ = 1 ms determines the maximal flow rate to be Q ≈50.3 mlh −1 .The minimal flow rate was on the other hand not so obvious since the dwell time Δ can be theoretically infinite.The practical limitation is the continuity of the flow.Thus dwell times Δ above 1000 ms are not recommended.
The accuracy of commercial syringe pumps is ±1% [24].The accuracy of the 3D-printed syringe pump was characterized similarly to [22].All flow rate measurements were performed with deionized water weighted on the KERN ABJ analytical scale in 30-min intervals.For pre-calibration measurements the dwell time Δ = 50 ms and the expected flow rate based on Formula 2 Q B 1.0057 mlh −1 .Table 1 shows pre-calibration pumped volumes, flow rates, their respective deviations δ from the expected flow rate, and calibration radii calculated by simply expressing it from the Formula 1 as follows The mean absolute deviation δ of the pumped volume from the expected flow rate was 1.44% without calibration (relying on the dimensions provided by suppliers).The determined mean calibration radius was r B 6.0779 mm.Using this value, post-calibration flow rates were measured with dwell time Δ = 51 ms and expected flow rate Q B 1.0000 mlh −1 .The measured volumes, flow rates, and their respective absolute deviations δ from the expected flow rate are shown in table 2. The mean absolute deviation from the expected flow rate decreased to 0.15%.The standard deviation of the measured flow rates was 0.14%.

Collector
Fibers with random orientation are deposited on a static collector-15 cm×15 cm plate customized for conductive substrate mounting.The dominant orientation of fibers was achieved with a rotating collector when the velocity of fibers toward the collector is negligible compared to the circumferential velocity of the collector.
The rotary motion was provided by a brushless DC electric motor SURPASS HOBBY C2826 powered by a 12 V power supply with FlyColor ESC regulator.The rotor rpm was controlled by a servo tester (potentiometer setting).The electric motor rotates at 1000 rpm per volt.Since the motor is operated at 12 V the maximum rpm of this setup is 12000 rpm.For a cylindric collector with a diameter of 5 cm, the circumferential velocity is approximately 31 m•s −1 .
In the case of a rotating collector the delivery of HV is not so trivial.The conductive substrate mounted on the rotating cylinder has to be conductively connected to the HV supply while well isolated from the DC motor.In this design, the isolation was ensured by the PLA parts.The conductive connection was ensured through steel ball bearings and a copper wire leading to the cylinder surface through its body.

Control unit
The control unit serves two main purposes.First, it controls the motion of the syringe pump and second, it monitors the rotating collector rpm.The whole unit was enclosed in a 3D-printed case and consists of the following main parts: • Arduino UNO • LCD shield for Arduino UNO-display module

• Stepper motor 28BYJ-48 driver
• IR reflective sensor QRD1114 and small parts such as a 12V fan, button, 3-pin connector, resistors, and wires.Figure 2 shows a circuit schema with the Arduino UNO as the main board with a stepper motor and driver connected to digital pins.The IR sensor for collector rpm measurement is also included in the schema.The button connected to digital pin 2 is for the interrupt signal pausing the pump.LCD shield is not included in the schema since it is attached to the top of the Arduino UNO board.The fan is powered directly from the 12 V power supply powering the whole Control unit and therefore is not included in the schema.
Using the six buttons present on the LCD shield users can simply control the motion of the pump, change the flow rate, and monitor the volume pumped or the collector speed.The source code is available at the author's GitHub [20].

HV power source
The most reliable option is to use a commercial HV power source.Both safety and the desired value of HV are guaranteed.But it is the most expensive solution.Prices for these devices start approximately $2000 for integrated solutions or approximately $500 for modules that require additional operating electronics.On the other hand, the cheapest solution is a boost step-up power module working on the Tesla coil principle.These HV generators can be purchased for as little as $2 and the produced HV can reach hundreds of kilovolts.Thanks to a low inner capacity these devices are nonlethal.However, the major disadvantage is the lack of the ability to set a specific value of voltage.Furthermore, the value constantly changes based on the current between electrodes and generator power.Therefore, achieving a stable jet of material is complicated.The last option covered in this work is a custom-built HV power source based on a flyback transformer like the one used in CRT monitors.Numerous instructional resources describing the construction of such a high-voltage power source are available online.HV sources based on flyback transformers are more stable than when using the boost stepup power module.However, there is a big downside to this solution, due to the presence of big capacitors in the design an incautious manipulation can be lethal.It is therefore strongly recommended that this device is only used by experienced professionals and with built-in discharge protection.

Results & discussion
The finished 3D-printed setup consisting of the rotating collector, syringe pump, and control unit mounted on Thorlabs XT95 construction rail [25] placed in a fume hood is shown in figure 3.One of the main advantages this setup provides is its high modularity and customizability.For example, one can easily switch between collectors or rotating collector drums with different diameters.Furthermore, small features like needle-collector distance ruler can be added with ease.The functionality of the 3D-printed electrospinning device was demonstrated on polyvinyl difluoride (PVDF).Dimethylformamide (DMF) and Acetone in a ratio of 7:3 were used to dissolve PVDF in order to create 10% w/V solution as described in [26].This solution was then successfully electrospun at 10 kV with a needlecollector distance of 10 cm.Yielded fibers are shown in SEM images in figure 4 acquired using Axia ChemiSEM Scanning Electron Microscope (Thermo Fisher Scientific Inc.).
The average fiber diameter of (419 ± 35) nm and the diameters' distribution shown in figure 5 were determined using ImageJ software [27] and DiameterJ plugin [28].
The SEM image of fibers with the dominant orientation shown in figure 4 was analyzed using Python and OpenCV library.The following steps were performed in order to measure the relative angular distribution: blurring (Gaussian filter), edge detection (Sobel filter), line detection (Hough transform), and finally statistical analysis of detected lines.The SEM image with detected lines (643) highlighted in blue is shown in figure 6.
The final relative angular distribution of detected lines is shown as a polar histogram in figure 7. The mean of the relative angular distribution is meaningless since it is only dependent on the image orientation.The standard    deviation on the other hand can be considered a measure of the degree of orientation (how well the fibers are aligned) and for this sample is 17.8°(calculated based on 643 lines detected).
In order to achieve stable and reproducible results the whole electrospinning setup must be placed in a dedicated chamber (cabinet) to ensure safety and to eliminate unfavorable conditions such as dust and temperature differences that may arise from the environment.Potential enhancements to the configuration include incorporating extra needles for a multijet system and integrating additional syringes for multipolymer layer manufacturing.

Conclusion
In this work, an affordable solution for electrospinning is introduced.This design's most significant benefit lies in its remarkably low cost, roughly ten times cheaper than commercially available alternatives, and its straightforward customizability.Thus making it a perfect tool for accelerating material research in the field of electrospinning.The design, manufacturing process, and parameters of each part are discussed and the functionality of the setup was successfully demonstrated on PVDF fibers.

Figure 1 .
Figure 1.3D model of a syringe pump, rotating collector, and control unit.

Figure 2 .
Figure 2. Circuit schema of the control unit.

Figure 4 .
Figure 4. SEM image of fibers with dominant orientation.

Figure 5 .
Figure 5. Diameter analysis of fibers shown in figure 4.

Figure 6 .
Figure 6.SEM image of fibers with dominant orientation.Detected lines are highlighted in blue (Edited from [29]).

Table 1 .
Pre-calibration pumped volumes, flow rates, their respective absolute deviations δ from the expected flow rate, and calibration radii.

Table 2 .
Post-calibration pumped volumes, flow rates, and their respective absolute deviations δ from the expected flow rate.