The CSMwear patch was fabricated using advanced MEMS metallization techniques in the Georgia Tech Inorganic Cleanroom. Computational and analytical studies were conducted to optimize the device mechanics to match the human skin. Examples of the devices on the sternum are shown in a and b.

The patch contains a high-resolution accelerometer (ADXL-355), photoplethysmography (PPG) sensor (MAX30105) and electrocardiography amplifier (MAX-30003) along with microfabricated ECG electrodes and communicates wirelessly via bluetooth, as shown in c. The device without top substrate and the electrodes are shown in d and e, respectively. These sensors allow for a thorough characterization of how the heart responds to stress.

The patch’s soft mechanics allow it to detect minute heart vibrations that correspond to crucial timing parameters, like valve openings. In f and g, the collected vibrations are compared to clinical echocardiography mapping of the aortic valve, and the results clearly show that the CSMwear patch can record aortic opening timings. Example signals for the PPG and ECG sensors are shown in h as well.


Furthermore, the device mechanics were investigated to determine the ability of the device to capture the heart vibrations. In a, an image of the device bending to 180⁰ with a radius of 3mm is shown, and the data quality during 100 rounds of cyclic bending with same parameters is shown in b.

Next, the device was placed along with a rigid comparison breakout board on a biomimetic elastomer substrate connected to a speaker. Data was collected with each device during various frequency sinusoidal excitations with 30mg amplitudes, and the resultant waveforms are shown in Fig c. The signal to noise ratios (SNR) is provided in Fig d, showing the clear advantage of the soft device.

In addition, zoomed in waveforms during various excitations are shown in e-f, demonstrating the serious distortion caused by traditional electronics.

Finally, the signal spectral contents are provided in Fig 2g, showing how the spectral peaks are degraded in the rigid comparison.