Fig. 3: Characterization of freeform functional fibres.

a Optical attenuation of blue light (470 nm) along the length of optical fibres. The loss due to diverting light at the contact site is indicated in red (n = 5). b Optical photographs, demonstrating light emission from a straight terminated optical fibre and an optical fibre terminated with a contact site. Fibres are immersed in a solution of colloidal particles (milk). c Impedance spectra of printed electrodes immersed in phosphate-buffered saline (PBS) (n = 5). d Scanning electron micrograph (top view) of the contact site of a typical printed electrode. e Hydrostatic resistance of a printed microfluidic fibre. Fibre length and lumen diameter are 44 mm and 135 µm, respectively (n = 5). f Micrographs of various fluidic fibre designs. Cross-section of a fluidic fibre illustrates the characteristic pyramidal shape of the structure (i). Freestanding fibres can be printed in curved shapes and support laminar flow inside the lumen (ii). Demonstration of a bifurcated microfluidic fibre eluting food dye from two outlets (iii) and a T-shaped junction for production of micro-droplets (iv).