Wearable low-cost moisture sensor

Aantal studenten: 1 of 2
Aantal masterproeven: 1
Promotor 1: Erwin Bosman
Promotor 2: Jan Vanfleteren

Begeleider 1: Wim Christiaens (Quad industries)

Begeleider 2: Thomas Vervust

Contactpersoon: Erwin Bosman

Trefwoorden: sensing, sensor, antenna, moisture, printed electronics, flexible

Problem statement:

Most of the sensor-driven wearables today are aimed at data-gathering on activities like fitness. Not because the customer has a medical need to, more because he likes playing with data. But of course wearable sensors have bags of potential to be very practical. One of them can fix a real-world problem: moisture sensors for use in babies diapers, or for older people suffering incontinence disorders. The basic problem is that it’s inconvenient to have to keep checking whether a diaper needs changing. The reusable moisture sensor, positioned inside the diaper, can communicate with the outer world by means of alert generations and can store and deliver the measurement history on demand.

Apart from this dedicated application, many other application domains exist for these low-cost communicative moisture sensors of which food monitoring, building health monitoring and general product storage are just a few.

Traditional moisture indicators are often chemical-based, resulting in some kind of irreversible change in characteristics (e.g. color change), as such “storing” the moisture exposure history of a product, but these indicators lack the generation of more detailed information like moisture exposure duration, frequency and total moisture uptake. As a consequence, products can be tagged as “moisture exposed” and are thrown away no matter if the moisture uptake was detrimental for the product or not.

Quad Industries has manufactured a low cost disposable temperature logging label (joint development between NXP and Enfucell) using a logging integrated chip, flexible batteries and a printed NFC antenna. The low cost printed device has basically similar functionality of the envisaged abovementioned sensor, but for temperature sensing instead of moisture. Quad industries wishes to extend its technology to moisture exposure logging by developing a moisture sensing technique based on a similar build-up of printed polymer and conductive layers as the rest of the device. Since no additional process steps are needed, the additional process cost to the device would be neglectable.

Figure 1: A low cost disposable temperature logging label manufactured by Quad Industries


Goals of the thesis

During the thesis, the candidate will develop a sensing technology and a sensor design to measure moisture exposure on a flexible lowcost PET foil. This design and technology will make use of the benefits of the well-established technology platform of printed electronics at Quad industries. The thesis will give the candidate the opportunity to work bilaterally with the company on achieving this goal.

The candidate will perform a literature study on the present state-of-the-art on wearable electronics and moisture sensors and will derive potential moisture sensing approaches with printed electronics. Based on the approach, multiple designs can be made by the candidate. The fabrication of the devices can be performed in the CMST cleanrooms and  at Quad industries. The prototypes will be characterized for their sensitivity, hysteresis behavior and reliability.

Depending on the interest of the candidate, the focus of the thesis can be positioned more on the design aspect or more on the manufacturing technologies.

The work is divided in the following parts:

- Design/modeling/simulation of different sensing mechanisms
- Fabrication of multiple prototypes.
- Demonstration of the devices and characterisation.

Locatie: Ardoyen (clean rooms) en thuis