Draftsight

Using DraftSight (v. 2017.1, Dassault Systèmes, Vélizy-Villacoublay, France), co-flow and flow-focusing devices with three inlets (1 mm wide circle and 200 µm wide channels), a 100 µm wide serpentine channel, and one outlet were designed. The two outer inlets were used for the external phase, the PVA solution, while the center inlet was used for the internal phase, the silk solution. Photolithography and soft lithography techniques were used to make the reproducible devices [45 (link)]. First, a master silicon wafer was fabricated using photolithography. The wafer was coated with a 100 µm thick high contrast negative photoresist layer (SU8 2035) (MicroChem, Westborough, MA, USA), covered with a photomask of desired features, and cured using UV rays. After fabricating the master wafer, soft lithography was used to make the individual PDMS devices. PDMS (Sylgard^TM 184, Dow Corning, Midland, MI, USA) was cured on the wafer and the individual devices cut out. These PDMS devices were plasma bonded onto glass slides and incubated at 60 °C overnight to restore the hydrophobicity of the PDMS.