Meandering Spring Force Disc for 3D Piconewton Measurement
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Solution Overview
Problem
Existing methods for measuring cell forces in the pico- to micronewton range, especially for micrometer-sized adhesive samples and living systems such as cells or bacteria, are limited by a lack of comprehensive, quantitative, three-dimensional force measurement capabilities, often requiring complex setups or high costs.
Innovation Solution
A novel mechano-optical microsensor system with a force-measuring disc and planar arrangement of cells, utilizing biocompatible materials and meandering springs for precise, three-dimensional force measurement, combined with digital holographic microscopy and digital image correlation for cost-effective and sensitive readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional force measurement methods (PDMS microcolumns, TFM, MEMS) are used, then force measurement capability is provided, but measurement precision and force resolution are limited due to sensor element dimensions larger than cell dimensions
Solution Approach 1:
The force measuring disc is segmented into multiple independent force measuring cells, each with its own surface element and spring system. This segmentation allows each sensor element to be optimized for high resolution while maintaining overall system functionality. The disc can be divided into any number of cells depending on measurement requirements, enabling precise local force measurements without increasing overall device complexity.
Solution Approach 2:
The invention transitions from conventional planar or single-axis force sensors to a three-dimensional force measuring system. Each surface element can detect forces in three spatial dimensions (x, y, z directions) through the spring-mounted configuration, enabling full 3D force vector measurement. This dimensional enhancement provides comprehensive force resolution without requiring larger sensor elements.
2Adaptability or versatility
If existing techniques combine multiple physical phenomena (piezoelectric resistance and capacitance) for 3D measurements, then three-dimensional force measurement capability is achieved, but device complexity and size increase
Solution Approach 1:
Each surface element in the force measuring disc serves multiple functions simultaneously: it acts as a force sensor in three dimensions, an optical reflector for deflection detection, and a mechanical element with defined spring constants. This multi-functionality eliminates the need for separate sensing mechanisms for each spatial dimension, reducing overall device complexity while maintaining full 3D measurement capability.
Solution Approach 2:
The invention replaces complex multi-physical sensing systems with a simplified mechano-optical system. Instead of combining piezoelectric, capacitive, and other physical phenomena, the solution uses purely mechanical spring elements coupled with optical detection of surface element deflections. This substitution reduces device complexity while achieving equivalent or superior 3D measurement performance.
3Reliability
If PDMS microcolumns or hydrogel membranes are used for force sensing, then force measurement is enabled, but reliability is reduced due to inhomogeneities in polymerization or hydrogel softness
Solution Approach 1:
The invention changes the material parameter from soft, polymerization-dependent materials (PDMS, hydrogel) to rigid, metallurgical materials with well-defined and controllable elastic properties. The spring constants of the metal springs can be precisely controlled during manufacturing through parameters like wire diameter, coil geometry, and material selection, ensuring high reliability and reproducibility without the inhomogeneity problems of polymer-based systems.
Solution Approach 2:
The force measuring disc employs composite construction with a rigid base material (metallurgical disc) providing structural stability and precise spring mounting, combined with spring elements that provide controlled elasticity. This composite approach separates the structural support function from the elastic sensing function, ensuring that the spring constants remain well-defined and reliable while maintaining ease of manufacture through standard metallurgical processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables simultaneous, quantitative three-dimensional force measurements in the pico- to micronewton range, providing accurate and biocompatible force detection with modifiable force ranges and reduced complexity.
Implementation Method 1
each surface element can be elastically deflected in three spatial directions under the influence of a force via the springs without tilting significantly, with deflection and force being linearly related
Implementation Method 2
means for optically measuring the three-dimensional deflections of the surface elements of the at least one force measuring disc
Data Source
Figure 1~3
Figure 4
AI summary
The invention relates to a force measuring disc having a planar regular arrangement of force measuring cells, wherein a force measuring cell is formed in a hole in the force measuring disc, in which hole precisely one planar element which is secured by springs in a self-supporting fashion is arranged and is oriented so as to run parallel to the force measuring disc, wherein each spring is connected in a materially joined fashion at a first end to the edge of a hole and at a second end to the edge of a planar element, wherein a. the force measuring disc, the springs and the planar elements are formed from the same material, b. the springs are embodied as elongate meandering structures with more than two meandering periods, and c. each planar element is surrounded by four springs arranged in a rotationally symmetrical fashion, and d. each planar element can be elastically deflected in three spatial directions under the effect of a force, wherein there is a linear relationship between the deflection and the force. In addition, the invention relates to a device for determining forces in the piconewton to nanonewton ranges.