Carboxylic SWCNTs, EDC (20mM), sulfo-NHS (20mM), PBS buffers (100 mM, pH7.4), MES buffer (100 mM, pH 5.5), HBsAg standard solutions and anti-HBsAg monoclonal antibody (ab) were used to synthesize the SWCNT-ab composite through the EDC-NHS activation in MES to form amine-reactive NHS-ester and then reacted with a protein in PBS. Then the composite was formulated with optimal ink formulation (0.5wt% Tween20, 1% CMC) in 10mM Tris buffer at pH of 7.4. Ink was then prepared at ~ 1 mg-SWCNT/mL and gently sonicated for 10 min and 5 min 1500 rpm centrifuge to obtain the supernatant to avoid jetting nozzle clogging. After printing, the device was baked at 220C to remove the additives and formed secure electrical networking and electrode connections. All materials from Sigma Aldrich unless stated otherwise. Ink surface tension and ink viscosity were measured with Cahn Instrument and RFS, respectively.