BathMat

The BathMat is an inflatable device designed to simplify the repositioning of proned ICU patients with Acute Respiratory Distress Syndrome (ARDS) by supporting the torso of the patient while nurses reposition them. While proning significantly improves survival rates, it increases pressure sore risk, requiring repositioning every 2-4 hours under NHS guidelines.

Traditional repositioning is labour-intensive, requiring 5-7 staff members for over 30 minutes per procedure. 16,500 patients are proned annually in the NHS and ARDS-related pressure injuries alone cost the NHS an estimated £105 million per year. The BathMat's controllable inflatable system makes repositioning faster and safer for both patients and staff. The device is currently undergoing trials across four UK hospital trusts as of July 2025.

Since September 2024 I have been working in the BathMat team developing pneumatic controls, PCBs, inflatables, and more. This work has involved every stage of the design process: including talking to doctors and nurses to understand their needs, system-level design of pneumatic and electronic control, detailed design of PCBs and pneumatic connectors, verification testing to meet MHRA approval, and managing small-scale production of 20 prototype systems delivered to 4 hospitals.

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For my individual final year design project (Oct 2024 - May 2025) I was also working with the BathMat team on integrating pressure mapping capabilty into future iterations of the device. Pressure mapping data could be valuable for bedside staff to indicate where potential pressure concentrations might cause bed sores to form. This project involved extensive research into pressure mapping technology, and ultimately prototyping a large flexible pressure sensor array with a custom PCB to read the 64 x 64 sensor array.

The pressure sensor is a passive matrix design formed of long horizontal and vertical electrodes sandwiching a piezoresistive polymer layer. Passive matrix sensors suffer from crosstalk due to parasitic current paths, so a signal isolation circuit was implemented on a custom PCB to filter the data. The sensor driving firmware is run by an Arduino Nano, which can scan the 64x64 matrix at 2 Hz. The Arduino sends data over serial to a visualisation python script running on a PC.

Using a second Arduino I also implemented basic automatic control of the inflatable using the live pressure sensor data. This was set to inflate the section of the mat which had the lowest pressure.

This was a really interesting project from start to finish; involving PCB design, data visualisation and processing, and pneumatics. As part of my work with the BathMat team since graduating I have been further exploring integrating pressure mapping technology into the BathMat. My prototype was a success, but it was very labour intensive to make, not integrated into the inflatable, and the data visualisation was basic.

This is supported by a £200k grant from the UKRI to continue development and commercialisation of the BathMat pressure sensing technology, while the main BathMat project undergoes medical trials. Over the last few months I have been collaborating with specialist ink suppliers on screen-printing conductive silver electrodes to better integrate the sensor with the inflatable.