Surgical needles are commonly used by medical professionals to reach target locations inside of the body for disease diagnosis or other medical interventions — such as biopsy, brachytheraphy, thermal ablation, and drug delivery [1, 2]. The effectiveness of these procedures depends on the accuracy with which the needle tips reach the targets, such as tumors or certain organs/tissues. In procedures, such as deep brain stimulation and prostate brachytheraphy, it is impossible to reach the surgical sites via simple needle trajectory because of anatomical constraints. Although needles are considered minimally invasive devices, needle insertion still causes tissue damage of varying degrees so it is desirable to reach multiple targets, or multiple sites on a single target, to obtain multiple high-quality biopsy samples with each insertion [1, 2].

Recently there has been a substantial and growing interest in the medical community to develop innovative surgical needles for percutaneous interventional procedures. The answer to the challenge of developing advanced surgical needles could be found in nature. Insects such as honeybees (Fig. 1), mosquitos, and horse flies have sophisticated sting mechanics and stinger structures, which they use to steer their stingers to a specific target, such as a human, and to release their venom in a certain path in skin [3]. We are studying these mechanisms, evolved in nature over millions of years, as a basis to develop bioinspired needles.

Surgical needles are typically consisted of a hollow cylindrical component (cannula) and an inner solid cylindrical component (stylet). Our hypothesis is that a surgical needle (stylet) that mimics insect stinger mechanics and structures can be easily controlled for sophisticated needle steering during surgery and can result in more effective and less invasive percutaneous procedures. The focus of this work is to mimic honeybee stinger such as shown in Fig. 1 to design innovative surgery needles.

One of the critical issues in designing surgery needles is the insertion force required to penetrate and to navigate the needle inside the tissue [2]. Larger insertion forces increase tissue damages thus may result in a more painful procedure [2]. Another consideration is the needle trajectory path (needle tip deflection) and the difficulty to control the needle path. The needle deviates from the target and thus it is very difficult to navigate the needle in the tissue. There is a need to design advanced surgery needles that provide smaller insertion force. This can lead to a less invasive procedure, in other words, less tissue damage and pain [3]. The needle trajectory path of these new needle designs must be understood for the needle design optimization.

As stated previously, it is hypothesized that a honeybee-inspired needle can be utilized to reduce the insertion force. In this work, the experimental work to understand the mechanics of bioinspired needles is presented. 3D printing of the needles and their insertion tests are performed to investigate the effect of the needle designs on the insertion force and the needle deflection (trajectory path) curves. Understanding these factors should shed some lights on some design parameters to develop innovative surgery needles.

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