Introduction Mechanically actuated robotic capsule endoscopes for active locomotion have demonstrated considerable clinical potential for conducting biopsies or therapeutic intervention in human gastrointestinal (GI) tract.1 Nevertheless, the research began to slow down owing to on-board power limitations and mechanical complexity in miniaturising electronic elements incorporated in the capsule body.2 Ideally, such swallowable capsules should be self-powered in vivo by converting the numerous GI-providing energy, such as the energy from the peristalsis near gastroesophageal junction and the high shear intestinal fluid flow.3
Methods Graphene nanoplatelet (GNP), consisting of stacked layers of graphene to enable the delivery of a broad range of therapeutics, was pre-mixed and then melt blended with poly (vinylidene fluoride) (PVDF). The as fabricated binary composites were crystallised at pressure with a piston-cylinder apparatus.
Results Controllable rapid growth of unique self-powering 3 D hybrid nanoarchitectures, assembled from 1 D PVDF micro/nanowires on GNPs, was achieved by the pressure crystallisation of GNP/PVDF composites (Figure 1 a-c). By controlling the crystallisation conditions, the PVDF nanowires, with piezoelectric crystalline beta phase, were obtained respectively with folded- and extended-chain lamellae as their substructures. The GNPs may play the role as a catalyst in the composite system, due to their size effect, which catalysed the self-assembly of the PVDF molecules into nanowires and then resulted in the radial nanowire clusters. Although the original surfaces of GNP/PVDF composites were high hydrophobic, they were successfully converted into hydrophilic surfaces through the pressure treatment followed by appropriate etching process (Figure 1 d and e).
Conclusion The pressure crystallised GNP/PVDF composites may permit niche applications in the fabrication of a new-generation of self-powering robotic capsule endoscopes to meet the environmental conditions of each section of GI tract for energy scavenging. This study was funded by the National Natural Science Foundation of China (51373139).
References 1 Munoz F, Alici G, Li WH. Adv Drug Deliver Rev 2014;71:77–85.
2 Slawinski PR, Obstein KL, Valdastri P. World J Gastroentero 2015;21:10528–41.
3 Wang ZL, Song J. Science 2006;312:242–6.
Disclosure of Interest None Declared