TMD

 Understanding tissue thickness and compressibility is crucial for proper surgical staple formation. If tissue is too thick for a given staple size, staples will not fully form, leading to tissue bruising and bleeding. If tissue is too thin, staples will either over-form or not provide an adequate seal.

The TMD (Tissue Thickness Measuring Device) was designed to aid clinical engineers in understanding tissue thickness and compressibility with respect to staple formation. In a nutshell, the device applies a constant pressure of 8 g/mm^2 (the industrial standard) to the tissue and readouts the corresponding tissue thickness. I designed this device as a 2016 summer intern at Intuitive Surgical. The device is still used as of November 2019 in official FDA validation testing of all surgical stapler products.

Design Requirements

• Ergonomic (one-handed)

• ± 0.05mm accuracy

• Sterilizable

Mechanical Design

The TMD is held via an ergonomic handle. The user opens the device’s jaws by pressing down a plunger. Once the jaws are around the target tissue, the plunger is released. A linear magnetic spring supplies compression on the tissue. Modified calipers that rest on an interior sleeve/slide readout tissue thickness. A cover protects the sensor, which can ultimately be removed during sterilization.

User Testing

Throughout the design process, I worked closely with the clinical engineers- the primary users of the device- to gain their input and validation, ensuring that the device is something they would use and prefer to the current method (a two-handed cumbersome process that utilizes a dial indicator and force gauge). The various prototypes were tested in clinical labs on porcine to evaluate the efficacy, ergonomics, and measurement accuracy.