A high-precision bendable ophthalmic microinjection needle fabricated by polypropylene-fiber-templated
Qiangsheng Fu1, Xianshan Jin2, Gang Chen3
1Department of Information Center, Key Laboratory of Artificial Organs and Computational Medicine in Zhejiang Province, Shulan (Hangzhou) Hospital, Shulan International Medical College, Zhejiang Shuren University, Hangzhou, 310022, P. R. China.
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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.
