Scaffold fabrication
A polymer solution is pumped to a charged needle; the field draws a jet that whips, stretches and dries on its way to a grounded collector, laying down a non-woven mat of fine fibres. Solution properties, field and flow set the diameter and whether beads form.
Our ruleSimulations prepare you for the bench but don't replace hands-on practice.
Electrospinning
A polymer solution is pumped to a charged needle; the field draws a jet that whips, stretches and dries on its way to a grounded collector, laying down a non-woven mat of fine fibres. Solution properties, field and flow set the diameter and whether beads form.
How it differs from the standard method
- A rotating mandrel aligns fibres; a flat plate gives a random mat.
- Coaxial and emulsion spinning load drugs or proteins into the fibre core.
- Mat pores are only a few microns, so cells mostly stay on the surface.
1Building the space cells live in
A scaffold is a porous three-dimensional structure that holds cells in place, lets nutrients and waste move, carries load while tissue forms, and ideally degrades as the tissue takes over. What matters about it is mostly architecture: how much of it is empty (porosity), how big the pores are and whether they connect, and the size of the struts or fibres that cells touch.
Electrospinning
A high voltage draws a charged polymer jet that whips, stretches and dries into fibres tens of nanometres to a few microns across, mimicking collagen fibrils.
Salt leaching
Polymer is cast around salt crystals that are then dissolved away; the pores copy the crystals, and they connect only if the crystals touched.
Freeze-drying
Ice crystals grow in a frozen polymer solution and are sublimed off; freezing rate and temperature set the pore size.
3D bioprinting
An ink, often carrying cells, is extruded strand by strand into a designed lattice; the ink's flow behaviour decides what can be printed.
2What controls the architecture
In electrospinning, fibre diameter rises steeply with polymer concentration and more gently with flow rate, and falls with field strength; below the concentration where chains entangle, surface tension breaks the jet into beads. In salt leaching, porosity follows the salt volume fraction, but only salt that forms a continuous network can be leached, so salt fractions below about 80 wt% leave closed pores and trapped salt.
3Common failures
- Beaded or fused electrospun fibres from too dilute a solution, a weak or unstable field, slow solvents or a humid room.
- Closed pores, a polymer skin and residual salt in leached foams; collapse when a foam is dried above its glass transition.
- Inks that are too warm spread into puddles, inks that are too cold clog; mismatched pressure and speed give fat or broken strands.
- Fine needles at high pressure that shear cells to death even when the lattice looks perfect.
Key terms
Practise these as flashcards →The fraction of a scaffold's volume that is empty space.
Whether pores open into each other, which decides whether cells and fluid can travel through the scaffold.
The conical meniscus at the needle tip from which an electrospinning jet is drawn.
The polymer concentration above which chains overlap and entangle enough to hold a jet together as a fibre.
A sacrificial particle, such as salt or sugar, that templates pores and is removed afterwards.
L²/16A of a printed pore: 1 for a perfect square, lower when pores round off.
Viscosity falling as shear rate rises, which lets an ink flow through a needle and then hold its shape.
The stress on cells at the needle wall, ΔP·R/2L, the main cause of cell death during extrusion.
When to use it
- Electrospinning for thin, fibrous, high-surface-area mats such as wound dressings, vascular grafts or aligned nerve and tendon guides.
- Salt leaching or freeze-drying for simple, highly porous foams from synthetic or natural polymers without special equipment.
- 3D bioprinting when the shape, pore layout or placement of several cell types has to follow a design.
- Any of them when you need to control pore size for a target tissue, such as larger pores for bone ingrowth.
Compared with alternatives
When cells should be embedded in a nanoporous gel rather than seeded into macropores.
SEM, FTIR and degradation testing to confirm what the fabrication actually produced.
The next step: getting cells evenly into the finished scaffold.
Measures an ink's shear thinning and recovery before it is printed.
Checks the stiffness and strength the porous architecture leaves.
Sub-techniques
Choosing one here switches the whole page, including the protocol and the lab, to it.
A polymer solution is pumped to a charged needle; the field draws a jet that whips, stretches and dries on its way to a grounded collector, laying down a non-woven mat of fine fibres. Solution properties, field and flow set the diameter and whether beads form.
- A rotating mandrel aligns fibres; a flat plate gives a random mat.
- Coaxial and emulsion spinning load drugs or proteins into the fibre core.
- Mat pores are only a few microns, so cells mostly stay on the surface.