Date Published: May 02, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Xudong Ji, Pengcheng Zhou, Ling Zhong, Aimin Xu, Anderson C. O. Tsang, Paddy K. L. Chan.
Organic field‐effect transistors (OFETs)‐based sensors have a great potential to be integrated with the next generation smart surgical tools for monitoring different real‐time signals during surgery. However, allowing ultraflexible OFETs to have compatibility with standard medical sterilization procedures remains challenging. A novel capsule‐like OFET structure is demonstrated by utilizing the fluoropolymer CYTOP to serve both encapsulation and peeling‐off enhancement purposes. By adapting a thermally stable organic semiconductor, 2,10‐diphenylbisbenzothieno[2,3‐d;2′,3′‐d′]naphtho[2,3‐b;6,7‐b′]dithiophene (DPh‐BBTNDT), these devices show excellent stability in their electrical performance after sterilizing under boiling water and 100 °C‐saturated steam for 30 min. The ultrathin thickness (630 nm) enables the device to have superb mechanical flexibility with smallest bending radius down to 1.5 µm, which is essential for application on the highly tortuous medical catheter inside the human body. By immobilizing anti‐human C‐reactive protein (CRP) (an inflammation biomarker) monoclonal antibody on an extended gate of the OFET, a sensitivity for detecting CRP antigen down to 1 µg mL−1 can be achieved. An ecofriendly water floatation method realized by employing the wettability difference between CYTOP and polyacrylonitrile (PAN) can be used to transfer the device on a ventricular catheter, which successfully distinguishes an inflammatory patient from a healthy one.
Fabrication of OFET Device: First, 180 nm PAN was spin‐coated on precleaned glass substrate from its DMF solution (30 mg mL−1) followed by baking at 90 °C for 30 min. Then 2.25 wt% CYTOP solution was spin‐coated on PAN thin film with a thickness 70 nm followed by 100 °C baking for another 30 min. 50 nm aluminum (Al) gate electrode was deposited onto PAN/CYTOP hybrid substrate (250 nm) by thermal evaporation through a shadow mask. A 10 nm thick alumina layer was formed through anodization process with a current density 0.7 mA cm−2.39 The substrate was then immersed in a 2‐propanol solution of ODPA (2 × 10−3m) to form a SAM on the surface of the oxidized gate. A 30 nm thick film of DPh‐BBTNDT was then deposited through a shadow mask by thermal evaporation with substrate temperature 100 °C, followed by the deposition of 50 nm thick gold through another shadow mask to define the source/drain contacts. Finally, 4.5 wt% CYTOP solution was spin‐coated to form a 240 nm encapsulation followed by 100 °C baking for 1 h.
The authors declare no conflict of interest.