According to the paper, the metal membranes capping each reservoir are patterned on the array for directing electrical current to the top of the membranes. The membranesmultiple layers of titanium and platinumare realized by post-IC photolithography and lift-off processes while the cavities for reservoirs are formed by CMOS compatible post-IC deep dry etching from the backside of the die.
The paper notes that titanium and platinum are CMOS compatible, having been used in standard CMOS process for metal silicides or diffusion barrier. The materials are also biocompatible, according to the paper, which cites research published in a biomedical materials journal.
The paper proposes a rechargeable lithium-ion nanowire battery with a capacity of 223mAh as the power source for drug-delivery assembly and a miniature (3x3mm2) square spiral inductor to pick up energy from external sources as well as a loop antenna to receive wireless command signals. The whole drug delivery assembly can
be encased in a biocompatible PDMS package , the paper states.
During operation, an external OOK command signal in RS232 format is wirelessly transmitted to the SoC and then received and demodulated by the OOK receiver, the paper states. According to the demodulated command, the integrated MCU activates the selected drug cell by applying current to its membrane through a switch, leading to the rupture of membrane and the release of drug, it states.
Research has shown that the membrane failure which releases the drug occurs about 50 milliseconds after the activation current is applied.
The full paper by researchers at National Taiwan University is available at TechOnline.