The Heartivity device is fabricated through a streamline process called "Cut-Solder-Paste". We take a copper foil (17 um) and laminate it on thermal release tape (TRT). We put it through a cutting device (LPKF U4 ProtoLaser) and remove the excess Cu foil. Next, we transfer it to Kapton and water soluble tape (WST). Finally, we solder on all our components and transfer to final substrate. This gives us a tattoo device on 3M Tegaderm.

 

We can see that our device consists of 4 layers; Near Field Communication (NFC) rechargeable layer, Bluetooth Low Energy (BLE) layer, readout circuit layer and disposable electrode layer. The BLE layer also has the x, y and z-axis accelerometer. In our case, the readout circuit layer consists of an ECG chip and a highly sensitive accelerometer to obtain the z-axis movement of the chest for the SCG signal.

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Our in-house app is available for Android devices. It displays the ECG signal on the top window and the SCG on the second window. The third, fourth and fifth window display the x, y and z-axis motion of the BLE accelerometer respectively. The app uses formulas to obtain the respiratory rate, RAC time interval, Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP). These are displayed in the top two windows numerically.