Scaffold techniques include the use of solid scaffolds, hydrogels and other materials. Peptide aptamer scaffolds are typically small, ordered, soluble proteins. An emerging field is to use DNA strands as scaffolds for metallic nanowire synthesis. Phase separation is a widely used technique for creating highly porous nanofibrous scaffolds with ease. EAM is also used in prototyping scaffolds for medical tissue engineering applications. PDGF has been shown to stabilize vascularisation in collagen-glycosaminoglycan scaffolds. The microfibril scaffolds and organizes the deposition of amorphous elastin. Solvent properties influence morphology of the scaffolds. Freeze-drying by itself is also a commonly employed technique for the fabrication of scaffolds. However, there are many other methods for forming nanofibrous scaffolds. The asymmetric coupling of azanorbornene scaffolds has also been successful. In addition, 3D bioprinting has begun to incorporate the printing of scaffolds. In general these requirements also apply to other types of working scaffolds. The European Standard sets out performance requirements for working scaffolds. State militia with fixed bayonets surrounded the prisons and the scaffolds.