March R&D Round Up

E-mail Melanie Martella

Spring is, at least theoretically, on its way. To celebrate, how about some intriguing research developments? This month we have a new type of sensor that uses hydrogels to accurately sense pH and an ultra-low-power biomedical signal processor.

A Novel Chemical/Biomedical Sensor
A team under Cagri Savran, associate professor of mechanical engineering at Purdue University, in collaboration with researchers led by Babak Ziaie, professor of electrical and computer engineering and biomedical engineering at Purdue, have created a novel sensor that reacts based on the acidity of its environment, enabling it to resolve pH changes smaller than 1/1000 on the pH scale.

To create the sensor, a series of fine stripes of hydrogel are laid down to form a diffraction grating. The top of the stripes and the spaces between the stripes are then coated with gold. Because the hydrogel stripes swell or shrink based on the acidity of the sensor's environment, shining a laser onto the sensor will create reflections from the spaces and the stripes that interfere with each other to create a diffraction pattern. Because the diffraction pattern is affected by the degree of swelling of the hydrogel stripes, it can be used to provide a reading of the local acidity and very precise measurement of pH.

Because the sensor has a fairly simple design, it could be far easier and cheaper to manufacture and more straightforward to use than more complicated devices. To read more and to see a diagram of the device, read Emil Venere's article, "Hydrogels used to make precise new sensor".

An Ultra-Low-Power Signal Processor for BANs
It sounds like something out of a science fiction movie, but the goal of a body area network (BAN) is to create a nonintrusive system of small wireless sensor nodes that are worn by a person and that continuously monitor various bodily parameters such as heart rate and blood pressure and whatnot. By enabling a more holistic view of how a person's body behaves, the BAN enables better, more efficient healthcare.

Key to these wearable biomedical sensor systems is the need for processors (and sensors) that consume very small amounts of power during operation, such that the BAN could be powered for months by either energy harvesting or very small batteries. As another step toward this goal, researchers from imec, Holst Centre, and NXP have developed the CoolBio. Based on NXP's CoolFlux DSP baseband core, the CoolBio is a C-programmable biomedical signal processor that consumes 13pJ/cycle when running a complex ECG (electrocardiogram) algorithm at 1 MHz and at an operating voltage of 0.4 V. The device supports a frequency range of 1–100 MHz and an operating voltage from 0.4 to 1.2V.

Rather than sending the data from the sensor nodes to some central location for processing, the more energy-efficient approach is to process and compress the data locally, on the BAN node, thus limiting the amount of power required to transmit data wirelessly, since wireless transmission tends to be the largest consumer of power.