Shown above: the SmartHeat SLT heater materials stack-up. The patented inner layer makes every point on its surface a heater, a sensor, and a controller with no external components.
To reduce the risks of medical devices overheating in the field, Minco Products Inc. has just launched its SmartHeat SLT (Self-Limiting Technology) line of thin-film heaters suitable for a range of constant-temperature applications. Healthcare uses include IV fluid heating, diagnostic reagent heating, oxygen humidifiers for surgery, saline heaters for sleep apnea devices, and other home health devices. The thin film—measuring just 0.0013 in. thick—can be cut out, sized, and wrapped around items for lining tanks and tubes. It can even survive being cut, torn, or punctured in the field, with some exceptions.
Made up of multiple film layers between two outer layers of polyimide, the SmartHeat heaters rely on a novel silicone matrix at the center of the material stack-up to generate the heat. This extruded silicone matrix contains conductive carbon particles, says Brian Williams, Minco’s thermal solutions product manager.
The conductive particles operate through thermal expansion. “These particles are irradiated so that they expand and contract around a certain temperature,” he tells MD+DI. “When these particles are cold, they’re tightly packed together and begin conducting electricity.” As they heat up, they begin to expand, and once they hit their target temperature, they’re too far apart from each other and can no longer conduct any more electricity, so they stop heating.
Shown above: Carbon particles diffused through a silicone matrix move apart due to thermal expansion of the matrix, increasing electrical resistance and reducing power flow.
Williams likens the heating process to cruise control in a car, in which the engine speeds up to reach the desired speed and throttles back to avoid going faster.
To develop the SmartHeat SLT heaters, Minco partnered with a university that patented the carbon-infused silicone matrix. “They approached us for a joint venture,” Williams says. “We now buy the silicone matrix to make the thin-film heaters.”
The result, says Williams, are heaters that offer simplicity, safety, and stability:
Simplicity. Because the particles self-limit their temperature, there’s no need for on-board electronics, sensors, or software, minimizing device size and cost. A standard power supply—a hard bore plug in 12 to 240 volts—is all that’s needed. “You can plug in the heater and walk away,” he says. “You don’t need separate thermocouples for feedback or software to analyze performance.”
Safety. Because of such self-control, the heaters cannot damage expensive reagents or other products contained in reservoirs, he says.
Stability. The carbon particles are always in tune with a dynamic environment,” Williams adds. “If the door of a unit is opened and cold air rushes in, the particles draw more power to get back to the target temperature. You don’t need eight different sensors or complex software to control all inputs.”
And the technology could offer such performance for years. “Other SLTs can work as heaters for a long time, but they can lose their self-limiting feature after 2 or 3 years,” he said. “Our heaters have been through accelerated testing for 2 years, and based on the algorithms we feel that they could last 20 years.”
Shown above is a potential application: Respiratory humidification warming.
Minco has provided thermal solutions for more than 60 years, and Williams, who’s been at the company since 1991, calls the SmartHeat SLT technology “the best material solution we have qualified in the last 20 years of investigating self-limiting material options.”
Williams expects the healthcare system could benefit from the SmartHeat SLT technology given the value placed on long-lasting durable medical equipment. Self-limiting heaters could also bring diagnostics and other devices closer to the point of use.
For more information, visit www.minco.com/SmartHeat to view a product demonstration video, watch a webinar, or download product literature.
Minco will be exhibiting in Booth #1468 at MD&M West 2018 February 6-8, 2018, in Anaheim, CA.
Correction: An earlier version of this article described the technology as using a silicon matrix, when in fact it is a silicone matrix. The editors apologize for this error.