{'fraction_non_alphanumeric': 0.029874213836477988, 'fraction_numerical': 0.01729559748427673, 'mean_word_length': 5.595854922279793, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Flexible, transparent, sub-100 µm microfluidic channels with fused deposition modeling 3D-printed thermoplastic polyurethane

The need for accessible and inexpensive microfluidic devices requires new manufacturing methods and materials that can replace traditional soft lithography and polydimethylsiloxane (PDMS). Here, we use fused deposition modeling (FDM) 3D printing to create transparent, flexible, and biocompatible microfluidic devices with channel dimensions consistently under 100 µm and as small as 40 µm. Channels consistently printed about 100 µm smaller than designed, but were repeatable and predictable. We demonstrate that thermoplastic polyurethane (TPU) has properties that may be useful for microfluidic applications, while remaining cost-efficient (~$0.01 per device) and optimal for rapid prototyping (fabrication time  <  25 min). FDM printing of TPU was shown to be able to produce high aspect ratio channels. Methods to compensate for sagging of bridging layers are provided. The 3D printed TPU was shown to be 85% transparent, durable, flexible, robust, and capable of withstanding high pressures when compared with PDMS. 3D printed TPU was also found to be compatible with cell culture, suggesting its usefulness in many biological applications.