A printer adapted to make nonwoven fabric by electrospinning
Electrospinning produces very thin fibers by stretching a polymer solution with an electric field. If the point where those fibers land moves in a controlled way, the process starts to look like a printer. This project built a prototype around that idea: a needle that travels on the carriage of an office printer and a cylindrical collector that rotates. It was used to deposit a polyester nonwoven fabric, and its fibers were compared with commercial fibers under an electron microscope.
Context
A nonwoven fabric is a sheet of fibers bonded together without weaving or knitting. In electrospinning, a drop of polymer solution at the tip of a needle is held at several kilovolts relative to a collector. When the electric force exceeds surface tension, the drop deforms into a cone (the Taylor cone) and emits a jet that thins and dries in flight. What reaches the collector is a fiber at the micro or nanometer scale.
Fiber diameter and quality depend on the concentration and conductivity of the solution, the voltage, the flow rate, the needle-to-collector distance and ambient humidity. Because these variables interact, the process is tuned largely by experiment.
Setup
The process was first reproduced on a bench setup to verify fiber formation.
Bench setup for the initial electrospinning tests
The prototype integrates three elements:
- A high-voltage supply designed and built in a parallel project in the group.
- A metal cylindrical collector driven by a stepper motor.
- A needle holder mounted on the translation mechanism of a Lexmark printer, which travels along the collector's axis.
Top view of the prototype: rotating collector and needle carriage
Collector rotation combined with needle translation spreads the fibers over the whole surface. The collector is covered with aluminum foil so the fabric can be removed.
Fiber deposition on the foil-covered collector
Results
Samples were observed in a scanning electron microscope and compared with commercial polyester filling fibers.
Commercial polyester fibers, about 50 μm in diameter
Fiber obtained with the prototype, about 13 μm in diameter
The fibers obtained are about 13 μm in diameter, with tips thinning down to about 5 μm, against 50 μm for the commercial ones. Their surface is more irregular and there are regions where the polymer did not form a fiber, which is consistent with a solvent that does not fully evaporate in flight.
Defect on an electrospun fiber
Overview of deposited fibers
What is missing
The process works but is not under control. The high-voltage supply could not sustain continuous operation and had to be switched off and on, which changes conditions during deposition. Solution flow was not regulated by a pump, and the acetone used as solvent proved too volatile. With a single needle, forming a fabric also takes a long time.
The author recommends a commercial supply, a syringe pump, humidity control and several needles in parallel.
How it fits in Robiolab
This work belongs to the digital-fabrication line through which the group built its manufacturing capability, together with the DLP stereolithography printer. Its connection to soft robotics is direct: electrospun fiber mats can serve as reinforcement layers that limit an elastomer's deformation in one direction, or as a substrate for flexible sensors.