miniature torque sensor that leverage MEMS technology exhibit high sensitivity and resolution, as documented in the literature, functioning on the principle of mode-localization in Weakly Coupled Resonators (WCRs) . In mode-localization sensors, even small structural irregularities within identical WCRs can confine vibrational energy, resulting in modifications to both vibrational amplitude and resonant frequency. Li et al. introduced a novel electric current sensor based on two WCRs utilizing silicon-based microfabrication methods, capable of measuring sub-microampere currents [24]. A computational study by Lyu et al. explored high order mode localization in weakly coupled microbeams, developing a reduced-order model to assess how coupling strength, mode, and actuation forces affect the system's dynamics [27].
Robot-assisted surgeries have become the preferred method over traditional procedures as they allow access to internal organs through small cuts, offering benefits such as quicker recovery times, reduced trauma, and fewer post-surgical infections [1]. Yet, despite the impressive capabilities of robotic surgical systems, a significant drawback remains: the lack of haptic feedback for surgeons. This absence can result in excessive force applied by surgical tools, potentially harming tissues and organs [2]. To address this issue, tactile sensors are commonly integrated into surgical instruments to monitor the interaction between tools and tissues during procedures. These small-scale devices assess various contact characteristics, including force, roughness, texture, temperature, and shape. Specifically, tactile sensors that gauge the force at the contact point are referred to as tactile force sensors [3].
Their load cell manufacturers can range from micrometers to millimeters, depending on the intended application. Tactile sensors come in different forms, such as high spatial resolution arrays, expansive tactile sensors, and single-point contact sensors [4]. For applications like assessing tissue hardness and performing tissue palpation, single-point contact tactile force sensors are advantageous due to their minimal contact area, which is suitable for delicate tissues, and their reduced need for calibration. Presently, various types of tactile sensors have been proposed for numerous robotic surgical tasks, including assessing soft tissue stiffness, providing force feedback in cardiovascular surgery, localizing lumps, tissue palpation, heart ablation, and vitreoretinal microsurgery [5], [6], [7], [8], [9], [10].
Current studies on 3D flexible piezoresistive sensors are concentrating on the materials used for conductivity and the design of their structures [1]. These conductive materials encompass metal nanostructures [12], carbon-based substances [13], and conductive polymers [14], all of which fulfill the needs for flexible electrodes. The design of 3D force sensor structures exhibits notable spatial geometric properties but can differ based on detection methods [[15], [16], [17], [18]].
A widely adopted configuration for 3D force sensors involves a four-element sensing system, where a bump at the top transfers force to the four sensing units. The variations in signals from adjacent sensors help determine the force's direction [10,19,20]. To enhance sensor sensitivity, micro-structured components have been designed for pressure detection. For instance, sensing materials like bucky paper (made from carbon nanotubes, CNTs) [15], graphene foam [21], and graphene on micro-pyramids [22] have been placed on the surfaces of flexible platforms to capture directional pressure differences. Additionally, sensing units can also be positioned on the sides of the bump, such as interlocked CNTs/PDMS microspheres [23], allowing for the separation of normal pressure and shear force without cross-talk. Due to their intricate sensing configurations, most of these sensors are produced using various compatible technologies. The primary challenges limiting the use of flexible 3D force sensors include the need for miniaturization, extensive area arraying, and cost reduction [24,25].
In this study, micro force sensor present a design featuring a three-element interlocked hemisphere structure aimed at achieving 3D force detection via contact deformation. The interlocking hemispheres focus stress on micro-contact areas, which enhances the sensitivity for multi-directional sensing.
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• Certified AS9100D (which includes ISO9001:2015)
• Compliant with NIST 800-171
• Adherence to J-STD-001, including Space Addendum
• Force Calibration and Testing linked to NIST, with optional ANSI Z-540 compliance
• Procurement from a vetted “Approved Vendor List”
• Compliance with International Traffic in Arms Regulations (ITAR)
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