Microforce

[Coleman John]

Icame into possession of an analog microforce v+f when I purchased my XTR Prod a few months back. The unit didn't come with the articulating arm or the rock n' roller to attach the microforce to a tripod arm and I'm not currently willing to spend $1500 for those parts on something I wouldn't be able to collect much on rentals for within my kit. The unit does have a small dovetail plate on it though which made me wonder if there is an alternative way that I can connect it but I haven't had much luck in figuring out what that part would be. I've attached a photo and if anyone has any thoughts or ideas to DIY a solution, I'd be incredibly grateful!

Dom, that is exactly what I was looking for! I know the chances of it showing up somewhere are probably somewhat low but I'll take a look. This particular one says Panavision on the side. Thanks again. If anyone should come across one, feel free to reach out.

When microscopic objects cannot reliably detect contact forces, they are easily damaged. Traditional microforce sensors based on Micro Electromechanical Systems (MEMS) are limited by their large size, low detection accuracy, and susceptibility to electromagnetic interference.

Wang et al. utilize femtosecond laser-induced two-photon polymerization (TPP) 3D nanoprinting technology with mechanical metamaterials to fabricate the microcantilever tip of a fiber-optic microforce sensor. This sensor can measure the mechanical properties of heterogeneous materials such as cells, useful for biological sample detection and material research.

Optical fiber sensors in the place of traditional MEMS allow for high sensitivity and resistance to electromagnetic interference, without the bulky size required for the complex optical paths in conventional sensors.

The microcantilever tip integrated into the fiber optic sensor uses such metamaterials. The cantilever beam must be accurately aligned to the fiber end face, which is achieved using femtosecond laser-induced TPP 3D nanoprinting. Since the technology is based on the manufacturing principle of layer-by-layer stacking, it dramatically improves the flexibility and formation of microstructure designs.

Benefiting from the great advances of the femtosecond laser two-photon polymerization (TPP) technology, customized microcantilever probes can be accurately 3-dimensional (3D) manufactured at the nanoscale size and thus have exhibited considerable potentials in the fields of microforce, micro-vibration, and microforce sensors. In this work, a controllable microstructured cantilever probe on an optical fiber tip for microforce detection is demonstrated both theoretically and experimentally. The static performances of the probe are firstly investigated based on the finite element method (FEM), which provides the basis for the structural design. The proposed cantilever probe is then 3D printed by means of the TPP technology. The experimental results show that the elastic constant k of the proposed cantilever probe can be actively tuned from 2.46 N/m to 62.35 N/m. The force sensitivity is 2.5 nm/N, the Q-factor is 368.93, and the detection limit is 57.43 nN. Moreover, the mechanical properties of the cantilever probe can be flexibly adjusted by the geometric configuration of the cantilever. Thus, it has an enormous potential for matching the mechanical properties of biological samples in the direct contact mode.

Conflict of Interest Yiping WANG is an editorial board member for Photonic Sensors and was not involved in the editorial review, or the decision to publish this article. All authors declare that there are no competing interests.

Permissions All the included figures, tables, or text passages that have already been published elsewhere have obtained the permission from the copyright owner(s) for both the print and online format.

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Mechanical metamaterials can adjust mechanical properties of structures flexibly through a mechanical structural design based on the premise that the materials remain unchanged. Here, a cantilever probe microstructure is designed using mechanical metamaterials for an optical fiber microforce sensor tip that can be prepared by femtosecond laser-induced two-photon polymerization. The elastic constant k of the fabricated fiber-optic microforce sensor has been adjusted by two orders of magnitude from 0.165 to 46 N/m, and the geometric configuration of the cantilever beam can be tailored to match the mechanical properties of biological specimens. This fiber microforce sensor shows an ultra-high force sensitivity of 154 nm/N and a force resolution of up to 130 pN. The optical fiber microforce sensor that shows the lowest force resolution in a direct-contact mode has high potential for biosensing applications, and the results reveal a potential design strategy for special scanning tunneling microscope probes with unique physical properties.

Herein, we combine the femtosecond laser-induced TPP 3D nanoprinting technology with mechanical metamaterials to fabricate the fiber end for a fiber-optic microforce sensor. The microcantilever beam constructed from the mechanical metamaterial shows good force sensitivity. The static mechanical properties of the proposed structure are analyzed by applying the finite element method (FEM) to the honeycomb structure of the cantilever beam. The elastic constant k of the fiber-optic microforce sensor can be adjusted by two orders of magnitude, from 0.165 to 46 N/m, and the cantilever geometry can be tailored to vary the mechanical properties of the probe and match the mechanical properties of relevant biological specimens. The resulting force resolution ranges down to 130 pN, which is much lower than the resolution of any other optical fiber microforce sensors reported to date. In addition, the optical fiber microforce sensor shows an ultra-high sensitivity of 154 nm/N and thus has immense potential for use in biomechanics and materials measurement applications.

Honeycomb is a magical product of nature, with the largest available space, which can minimize the amount of material used, thereby achieving minimum weight and showing great mechanical potential. The structure of the cantilever beam adopts the metamaterial of honeycomb structure. The metamaterial of honeycomb structure is a new type of porous topological material, which has the advantages of variable topological structure, high specific stiffness, and high resilience.37,38 By introducing it into the cantilever structure, the stiffness coefficient of the cantilever beam can be tuned in a wide range. By adopting the control variable method, the details of the microcantilever beam with a honeycomb structure are completely consistent except that the side length (a) and length of the cantilever beam (L) are different, as shown in Fig. 2. The cross-sectional area of the base under the cantilever beam is 60 60 m2, which can improve adhesion with the end face of the glass insert. By keeping the thickness to 5 m, the side length of the honeycomb cell in the microcantilever beam increases from 0.5 to 15 m and the beam length increases from 60 to 200 m. The sensor design details are presented in the supplementary material, S1.

To determine the mechanical properties of the fiber-optic microforce sensor, a nano-indenter (Hysitron TI980) is used. A cone tip (tip radius: 10 m) of this nano-indenter pushes and pulls at the center of the probe at a constant speed of 400 nm/s. The effects of the side length of the honeycomb cell and the beam length on the mechanical properties of the microcantilever structure are studied. The honeycomb cell side length is increased from 0.5 to 15 m initially, and as shown in Fig. 3(i), the force curves of six sets of microcantilevers show well-separated line shapes. Figure 3(g) shows that the elastic constant k ranges from 0.98 to 46 N/m. As can be seen in Fig. 3(i), the elastic constant k (46 N/m) is the highest and the displacement is the shortest when the honeycomb cell side length is 0.5 m. The main reason is that the smaller the honeycomb cell side length, the larger the effective width of the microcantilever beam and the larger the elastic constant k. The k value of the microcantilever is related to the sensitivity, and a smaller k value indicates higher sensitivity. In fact, k can be adjusted by two orders of magnitude by varying the honeycomb cell side length a, and the mechanical properties of the microforce sensor can also be optimized by adjusting the length L to match the mechanical properties of biological samples. In the next step, L is increased from 60 to 200 m, and as shown in Fig. 3(k), the elastic constant k decreases gradually with the length L when the size of hexagonal honeycomb elements in the microcantilever beams remains constant. Figure 3(l) shows that the first-order elastic constant k ranging from 0.165 to 0.98 N/m is also observed. It can be seen from Fig. 3(k) that the elastic constant k (0.98 N/m) is the highest and the displacement is the shortest when L = 60 m. Furthermore, the smallest elastic constant k (0.165 N/m) is close to the minimum value for the AFM tip, and the range realized for the overall elastic constant k basically covers that of a typical commercial AFM probe.40,41 Finally, the stability of the microcantilever beam is evaluated by repeating the experiments above five times. Figures 3(m) and 3(n) show that the force curves of these five cycles overlap each other and that k remains constant (6.9 0.2 N/m). The small fluctuations observed in the sensitivity confirm that the structure has excellent mechanical stability and resilience under compression conditions. All the k values are designated as linear fitted values for the structural compression process. Compared with the simulation results in Figs. 2(b) and 2(d), the k value measured in the experimental results is larger, which is mainly caused by the dimensional error of the preparation. This dimensional error is mainly caused by layer-by-layer printing and followed by structural shrinkage or deformation in development, which depends on the used laser power, scanning speed, surface tension of photoresist, and developer volatilization. Thus, these above fabrication parameters need to be repeatedly optimized to improve the printing quality.

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