As the core component of the biopsy instrument’s interaction with biological tissue, the needle tip’s geometry not only affects the smoothness of the puncture process and the integrity of the sample structure, but also directly impacts the patient’s pain experience, the extent of bleeding, and the degree of tissue damage during surgery. Modern biopsy needle design requires a precise balance between puncture sharpness, mechanical strength, and operational controllability during the design phase. From traditional single-bevel structures to modern multi-faceted cutting edge designs, each geometry represents an engineering solution tailored to specific tissue characteristics and clinical scenarios.

The Classic Beveled Tip

As the oldest and most fundamental configuration used in biopsy, the beveled needle tip employs a design scheme where a single-plane beveled cut forms an acute angle at the tip. This classic structure effectively reduces puncture resistance when entering soft tissue, allowing the needle to smoothly pass through skin, subcutaneous tissue and muscle layers while preserving the integrity of the sample. However, the inherent drawback of single-bevel needles is that the cutting edge is prone to deflection after encountering denser tissue (such as fibrous or cartilaginous tissue), making it difficult to maintain directional stability throughout the puncture process.

Beveled needles have undergone continuous optimization and improvement. Modern beveled tips use a more precise bevel angle, a smoothly polished cutting edge and a high-precision grinding technique to minimize puncture trauma and reduce sample fragmentation. In addition, some beveled needles incorporate a micro-serrated edge design, which effectively increases cutting capacity when dealing with certain fibrotic tissues without significantly increasing insertion resistance.

Multi-Faceted Cutting Edge Design

To meet the complex needs of modern biopsy procedures, multi-faceted cutting edge designs have emerged. These needles usually employ two or more beveled planes at the tip to form multiple cutting edges. The purpose is to distribute puncture pressure across multiple surfaces, thereby reducing tissue damage at each contact point, while ensuring that the needle remains stable under uneven tissue conditions and maintains accurate puncture trajectory.

In a commonly used dual-bevel structure, the primary bevel is responsible for providing main cutting capacity, and the secondary bevel, located opposite the primary bevel, helps guide the needle through the tissue, maintaining the puncture direction and reducing lateral deviations. Triple-bevel designs further subdivide the force distribution, allowing the needle tip to balance the cutting effect more delicately as it passes through different layers of tissue.

Needles with multi-faceted cutting edges typically require more complex grinding and polishing processes, and the precision of the bevel angle between each plane directly determines the overall mechanical performance. Improper bevel matching may cause a sudden increase in resistance or unpredictable steering during puncture, thereby affecting the accuracy of the tissue sample.

Material Selection and Manufacturing Process

The material selection for biopsy needles is critical for ensuring their mechanical strength, biocompatibility, and corrosion resistance. Common materials include stainless steel, nickel-titanium alloys and polymer composites. Stainless steel needles offer a high cost-performance ratio and good mechanical properties; nickel-titanium alloys have excellent elasticity and super-elasticity, which can reduce deformation and improve puncture stability; polymer composites can reduce MRI artifacts and provide improved image quality in imaging-guided biopsies.

Manufacturing processes include precision grinding, electrochemical polishing and laser cutting. Precision grinding ensures the geometric accuracy of the cutting edge; electrochemical polishing can reduce surface roughness and eliminate micro-burrs; laser cutting technology can be used to create micro-serrations or textured surfaces, thereby improving needle penetration efficiency and sample retention capacity.

Clinical Applications and Optimization Directions

Different biopsy needle tip geometries correspond to various clinical applications. Fine-needle aspiration is often used for cytological sampling of thyroid, lymph nodes and soft tissue masses; core needle biopsy is often used for histological sampling of liver, kidney, breast and lung; vacuum-assisted biopsy can provide larger continuous tissue samples and is often used in breast lesion diagnosis and treatment.

With the development of precision medicine and minimally invasive surgery, biopsy needle tip design is moving towards personalization and specialization. With more accurate imaging guidance and navigation technology, the requirements for needle tip trajectory control and positioning accuracy become higher, and new designs will focus on how to further reduce tissue damage and improve sampling quality.

In addition, the integration of sensors is a future development direction. Embedding tiny sensors at the needle tip can measure tissue hardness, temperature and electrical properties in real time, providing physicians with more feedback information and assisting in determining tissue types and lesion margins.

Conclusion

The geometric design and manufacturing of biopsy needle tips is an interdisciplinary field that integrates mechanical engineering, materials science, biomedical engineering and clinical medicine. Whether it is the classic beveled tip or the modern multi-faceted cutting edge, the goal of needle tip design remains the same: to obtain sufficient high-quality samples with minimal patient trauma. Through continuous technological innovation and clinical feedback, the future biopsy needle tip will become more precise, intelligent and personalized, providing more accurate diagnostic and therapeutic solutions for clinical work.