Scaffold Techniques and Designs in Tissue Engineering Functions and Purposes: A Review

Table 2

The method for fabricating bioactive PEEK/HA bone scaffolds.

Step	Process	Diagram	Method
1	Preparation of ceramic paste		Adhesive binder polyvinyl butyral (PVB) and plasticizer polyethyleneglycol (PEG) are fully dissolved in propan-2-ol solvent with the ratio of 75% (w/v) PVB and 25% (w/v) PEG. HA ceramic powder is then added to the solution (with 60% (v/v) of ceramic based on the dried paste) and stirred for 2 hours to achieve a well-dispersed solution
2	Solvent evaporation		Excess solvent is evaporated by fast stirring and blowing hot air (such as using hair dryer) until a viscous ceramic paste is achieved
3	3D printing		Ceramic paste is loaded into a syringe for 3D printing. The extrusion process forms lattice-shaped 3D scaffolds by incrementing regularly arranged 2D layers in the vertical axis
4	Drying, debinding, and sintering of the scaffold		The scaffold is left at room temperature for 24 hours to allow evaporation of excess solvent and subsequently to place the scaffold in an oven for debinding and sintering. Different heating procedures can be applied depending on the type of ceramic, such as the maximum sintering temperature for HA is 1300°C with a dwelling time of two hours. The bioceramic scaffold is then obtained
5	Compression moulding of PEEK powder into the HA scaffold	Using both static and dynamic loads to produce a PEEK/HA composite	Static loading: the mould is heated up to 250°C and then load is applied until the temperature reaches 400°C, maintained for a further 20 minutes (dwelling time) and then heating is stopped, and the mould is left to cool under pressure. Dynamic loading: the mould is heated up to 400°C and maintained for 20 minutes. Load is applied for 5 seconds before heating is stopped and then the mould is left to cool under pressure, whereby the PEEK matrix crystallized and solidified
6	Obtaining bioactive PEEK/HA composite		Composites are removed from the mould when the temperature has fallen to just below the glass transition temperature (143°C), followed by cooling to room temperature, thus mitigating thermal stress and cracking