Neuromorphic sensing of biomolecules covalently immobilised on polydimethyl glutarimide

Polydimethyl glutarimide (PMGI) layers with sub-micron thicknesses have been modified in a 2.5 kV Ar plasma immersion ion implantation (PIII) process to introduce free radical covalent binding sites. The surface roughness of the PMGI increased after the PIII treatment but no through-layer defects were observed. When applied to the treated PMGI, horseradish peroxidase (HRP) enzyme remained bound to the surface after extended immersion in sodium dodecyl sulfate solution (SDS). Hence, covalent binding between the activated surface and enzyme was confirmed. This covalent binding was achieved up to 24-h after the PIII process. The treated PMGI was then incorporated as a gate dielectric layer within a lateral three-terminal electrolyte-gated device. The device output characteristics resembled those of post-synaptic outputs; as successive (pre-synaptic) voltage pulses were applied to the gate, paired pulse depression and spike rate dependent plasticity were observed in the source-drain (post-synaptic) current. These characteristics were altered by the presence of HRP immobilised on the plasma-modified PMGI gate dielectric layer thus providing readout detection. These results and preliminary device characteristics show the potential for the plasma functionalized PMGI as a sensitive and reproducible biosensing technology.