Measurements were made using a commercial research quartz
2.5. Sensor response in biomolecule mass loading
The sensor was characterized under conditions where biomolecule adsorption to a functionalized surface occurred in aqueous solution. Initially, phosphate buffer (50 mM phosphate, CAY10650 7.40) was introduced at 24 μL/min in both inlets to establish a baseline. A 7 mM solution of hexanethiol in phosphate buffer was introduced over the surface for 1+ hour to establish a monolayer in both streams of the device. Buffer was used to wash unbound hexanethiol out of the flow cell. BSA protein at concentrations from 5 to 15 μM in phosphate buffer was injected for 20 min to observe binding, followed by rinsing with phosphate buffer. Mass calculations for bottlenecks experiments were carried out as previously described  and , using a mass sensitivity of 164 Hz/μg.
2.6. Sensor response in mineral mass loading
3. Results and discussion
3.1. Sensor design and flow analysis
3.2. Sensor response in no mass loading