From medical robotics to handheld tools, healthcare today is using smarter surgical devices that give force and pressure feedback. Load cells help in many applications such as providing haptic feedback for robotics or handheld instruments used in minimally invasive surgery, pressure sensing for catheter tip steering and ablation, torque sensing of rotary tools, and more. These high value instruments are too expensive for single use and require autoclave sterilization for reuse. Until recently, autoclavable sensors have required complex, expensive packaging to ensure survivability and reliability. SMD now offers autoclavable strain gauge technology on all standard and custom sensors. These harsh environment sensors are completely hermetic, survive 100% humidity, PH of 11, and temperatures up to 200 °C.
Autoclaving is a sterilization process that uses steam at high temperature and pressure to kill bacteria, viruses and fungi and prevent patient infection (see figure 1). A typical process consists of a 20-minute soak with saturated steam at 134°C and 15 psi and some cycles may include detergents, as well. This harsh process can damage sensitive strain gauges and ruin the organic adhesives used to bond traditional strain gauges to a substrate. This can result in dramatic zero balance or span instability and lead to catastrophic failure. Industry focus has been to better protect the strain gauge from this harsh environment. A natural solution to this is using glass-to-metal headers and a welded hermetic body. However, this solution is complex, expensive, and inflexible – holding back creative solutions to emerging smart surgical tools.
Strain Measurement Devices, Inc. forgoes the use of organics entirely by using a high energy thin film sputter deposition process to bond strain gauges to a substrate (see figure 2). This batch-controlled process reliably, repeatably, and efficiently produces accurate and stable force sensors – ultimately lowering production costs when compared to bonding individual strain gauges, without compromising performance. Because our process lacks organic layers that break down at high temperatures and pressures, our load cells are naturally well suited for harsh environments.
To address industry demands for autoclavable force sensors, we took our thin film process to the next level by sputtering a protective inorganic encapsulation and changing our masking process to enable soldering directly to the thin film. We produce the same underlying reliable strain gauge, but with autoclave survivability inherently built in and no organic interlayer – reliability from the bottom up. This patented “case hardened” autoclavable load cell has been field tested for 10 years and hundreds of autoclave cycles. The design is not limited by packaging or next assembly constraints and can be applied to any of our standard force and pressure sensors as well as OEM sensors with specific requirements i.e., redundant bridges for even more resilient systems in critical sensing applications. Lastly, this technology is not limited to autoclavable surgical tools.
The SMD engineering and design team will work with you to meet almost any set of specifications. Whether you need a resilient solution for your autoclavable surgical tool or have a different harsh environment application, SMD can work with you to meet your needs. SMD sensors are skillfully engineered to seamlessly integrate with your device, resulting in a safer, reliable, and more effective products (see figure 3).
