Ultra-low power sensors and actuators
Small, low power sensors and actuators are vital for systems of all kinds to interact with their environment. Holst Centre and its partners are developing ultra low power (bio)chemical sensors, actuators and signal acquisition / conditioning ICs that can be implemented in standard CMOS processes.
Systems for monitoring medical conditions in a non-invasive and potentially inexpensive way mark a new frontier in medical diagnostics. Low-cost, rapid point-of-care diagnostics has emerged as a major new thrust area in lab-on-a-chip technology, and portable devices capable of measuring chemical markers in external bodily fluids and breath have recently started to attract attention.
Ideally, wireless (bio)chemical sensors for wellbeing, lifestyle and medical diagnostics need to be autonomous, portable and/or wearable – so they should be small and low power while maintaining high selectivity and sensitivity.
Reducing the sensor system’s overall power consumption is a key factor. This extends system lifetime or increases the range of sensor functionalities that can be implemented. Holst Centre’s Sensors and Actuators program is developing transducer concepts that provide ultra low power solutions for (bio-)chemical sensor.
Electrical conductance transducers
Sensors based on changes in electrical conductance provide easy interfacing with read-out circuitry. The challenge is to create low-power systems with a strong response to specific gas molecules in breath or the personal environment. In this context, low power room temperature approaches based on functionalized vertical nanowires and room temperature metal-oxide thin film FETs are shown to enable ppb-level NOx and ppm-level CO2 monitoring.
Electrochemical transducers
Electrochemical detection systems are of special interest due to their good detection limits, wide linearity, quick response and low cost which open the possibility of mass production. Electrochemical sensors have one of the lowest power budgets for transducers and are presently being implemented for pH sensing in bodily fluids and nitric oxide (NO) sensing for asthma monitoring.
Holst Centre is also testing novel designs for a miniaturized reference electrode. An indispensable part of electrochemical cells, this helps enable scalable sensors for sweat and saliva analysis.
Optical transduction
Optical sensors are well known for high selectivity and sensitivity. However, light sources and detection instruments are typically bulky, high-power, and difficult to miniaturize. Holst Centre is developing low power approaches that tackle these issues. These include label free sensing by using nanoparticles and miniaturized SPR-based systems that operate without needing a bulky prism.
MEMS transducers
Micromechanical systems, such as cantilevers and doubly clamped beams, are ideal for making miniaturized sensor arrays. Traditionally, mass-increase induced resonance shifts in cantilevers are employed for bio-molecule detection. However, this effect is not directly transferable to sensing of volatile organic compounds, where the target molecules are significantly smaller.
To tackle this more challenging objective, Holst Centre has developed an array of doubly clamped beams that will be individually integrated with read-out/driver circuitry using ink-jet printing of a number of different sensitive coatings.
The program bridges the worlds of academia and industry. It features people with a wide range of expertise, from quantum physics and chemistry to IC design and manufacturing processes. Industrial partners include semiconductor, electronics and medical systems companies, and the program also has links with manufacturing equipment suppliers.