Wearables Hardware Intern | Sandeep Ramlochan

overview

The Sempionatto Lab makes wearable sensors that read your body chemistry straight from sweat. No blood draw, no lab. I worked on the whole stack over the summer: printing electrodes onto flexible Kapton film, checking them under a digital microscope, designing the analog circuitry in KiCad, and writing the firmware to pull readings off the sensors. The goal was a patch you could stick on your wrist and get continuous biomarker data from without having to do anything.

electrode fabrication

Carbon electrodes screen-printed onto flexible Kapton in separate passes for working, reference, and counter. Ion-selective membranes go on top after.

Array of screen-printed electrodes before membrane deposition

Five carbon electrode strips after printing

Two rows of finished electrode arrays on substrate

Flexible electrode strip showing printed carbon traces

Yellow Kapton electrode strips on the bench

Hexagonal sensor assembly taped to glass for testing

characterization

VHX digital microscope to check electrode geometry and surface quality before and after membrane application. You can see a lot go wrong at this step.

VHX microscope grid view of six electrode dots

VHX close-up of electrode edge and membrane interface

VHX microscope showing electrode degradation under sweat exposure

flexible assemblies

Multi-electrode arrays on flexible Kapton, thin enough to sit flat against skin.

Seven-electrode flexible array on Kapton substrate in Petri dish

Completed flexible biosensor circuit with gold traces on Kapton

circuit design

Analog front-end for ion-selective electrodes: INA333 instrumentation amps, DAC-driven reference bias, analog mux, ESP32 for wireless, and a boost plus LDO power path off a 3.7 V LiPo.

KiCad schematic showing dedicated lactate, potassium, and sodium electrode channels