A high-precision bendable ophthalmic microinjection needle fabricated by polypropylene-fiber-templated electroplating: process design and ex vivo validation.

Intravitreal and subretinal drug delivery require slender injection tools that reduce tissue trauma while maintaining lumen patency and mechanical reliability. This study describes a bendable ophthalmic microinjection needle fabricated using a polypropylene-fiber sacrificial template and nickel electroplating process. High-gloss polypropylene fibers defined the inner lumen, a graphene conductive layer enabled nickel deposition, and laser bevel cutting combined with supported thermal pre-bending produced straight or 15° bent working tips. The target working geometry for the ex vivo tests was an outer diameter of 130 μm, an inner diameter of 80 μm, a wall thickness of 25 μm and a working length of 4 mm. The fabricated needles showed an inner-wall roughness of Ra = 0.04 μm and a product yield of 97.5%. In mechanical tests, the proposed needles showed lower puncture force than conventional drawn needles (0.087 ± 0.012 N for straight needles and 0.102 ± 0.015 N for 15° bent needles versus 0.153 ± 0.021 N for drawn needles) and higher summarized bending strength (245.3 ± 15.6 MPa versus 132.7 ± 24.3 MPa). In an ex vivo porcine eye model, the 15° bent needle achieved 93.3% subretinal injection accuracy and a tissue injury score of 0.27 ± 0.46. These results support the feasibility of the manufacturing route for preclinical ophthalmic microdevices. Biological validation was limited to ex vivo eyes; in vivo biocompatibility, nickel ion release, sterilization stability, particulate/endotoxin control and same-dimension comparator studies remain necessary before clinical translation.