Conformal Esophageal Catheter Balloon with On-Surface Fully Printed Electronics Fabricated by Cylindrical Coordinate-Based Aerosol Jet Printing

Barrett’s Esophagus (BE), a precursor to esophageal cancer (EsC), is a condition of the lower esophagus that causes the esophageal lining to inflame and thicken as the normal epithelial tissue is replaced with metaplastic intestinal tissue. BE is caused by stomach acid reflux into the esophagus, occurring as a complication of gastroesophageal reflux disease (GERD), which affects ~30 million people in North America. If left untreated, BE can continue to spread by causing more tissue erosion and the formation of precancerous lesions at both the epithelial surface and within the nonvisible mucosal layer. These lesions can then further deteriorate into adenocarcinomas, which have become the most common form of EsC with a 5-year survival rate of only 20%. Currently, the most prominent treatment for BE involves the use of an esophageal catheter to radiatively ablate affected tissue; however, this technique lacks precision in localized heating and control in terms of monitoring thermal impact on the tissue during treatment. These issues can easily lead to incomplete treatment of the BE lesions, especially those deep in the mucosal layer, requiring the endoscopic procedure to be repeated. Consequently, it is of great importance to develop an esophageal catheter that overcomes these deficiencies to provide precise ablation with tissue temperature dosimetry to ensure full treatment with minimum procedures.<br/>In this work, we demonstrate the design, fabrication, and testing of an esophageal catheter system that is capable of high precision radiative heating and real-time temperature monitoring of surrounding material. These advanced capabilities are achieved by the design of a dual-mode antenna that can create localized heating when radiating and can measure thermal body radiation when receiving. By transmitting higher frequency microwave energy, as opposed to typical radio frequency-based ablators, our device offers more precise heating due to the smaller resolution of the applied wavelength. This precision is then reciprocally utilized in the receiving mode of the antenna to accurately quantify the volume-averaged temperature of encompassing materials. To accomplish the fabrication of this antenna and accompanying sensors onto the complex 3D surface of our soft-material catheter, we developed a custom aerosol jet printer attachment for converting rectangular coordinate-based planar printing to a cylindrical coordinate-based printing approach. This innovative mechanism enables material deposition onto nonplanar surfaces of revolution, thus providing a simple platform to manufacture and rapidly prototype the design of printed bioelectronics directly on the curved surface of our catheter. The main body of the catheter, which is made of polyurethane, is a balloon that inflates to the shape of the esophagus ensuring conformal contact with the esophageal lining. Using our cylindrical coordinate-based printing method, we print highly conductive silver nanowire and graphene inks onto the circumference of this balloon in an inflated state to fabricate a temperature sensor, a pressure sensor, and the ground plane for our dual-mode microwave antenna. Both sensors utilize the environmentally sensitive properties of graphene to individually monitor temperature on the tissue lining and pressure as the inflated balloon achieves contact with the esophagus. The printed ground plane, which wraps around the circumference of the balloon, operates in tandem with a coaxially mounted monopole in the center of the balloon as the dual-mode antenna. Then as a final step, these surface mounted bioelectronics are covered in a biocompatible encapsulation layer to protect the patient as well as the deposited material. Ultimately, with real-time quantification of tissue temperature and the ability to precisely tune ablation, our esophageal catheter system will enable innovative endoscopic treatment to treat BE fully from the epithelium down to the mucosal tissue layer.