Femtosecond-laser microprinting of fiber-tip clamped-beam probe for high-sensitivity micro-force measurements

Micromanipulation and biological, material science, and medical applications often require direct or indirect control and measurement of forces asserted on small objects. Here, we demonstrate − for the first time the microprinting of a novel fiber-tip-polymer clamped-beam probe micro-force sensor for the examination of biological samples. The proposed sensor consists of two bases, a clamped beam, and a force-sensing probe, which were developed using a femtosecond-laser-induced two-photon polymerization technique. A miniature all-fiber micro-force sensor of this type exhibited an ultrahigh force sensitivity of 1.51 nm/μN, a detection limit of 54.9 nN, and an unambiguous sensor measurement range of approximately 2.9 mN. The Young's modulus of polydimethylsiloxane, a butterfly feeler, and human hair were successfully measured with the proposed sensor. To the best of our knowledge, this fiber sensor has the smallest force-detection limit reported to date, comparable to that of an atomic force microscopes (AFM). As such, we believe that this device will be beneficial for high-precision biomedical and material science examination.