Open Source Quartz Crystal Microbalance with dissipation monitoring

The dissipation factor and subsequently the characterization of the viscoelasticity of deposition films have become crucial for the study of biomolecular adsorption. Most of the commercial quartz crystal microbalance (QCM) systems offer this feature, but it has not been incorporated in open source systems. This article describes the design, construction, and simulation of an open source QCM module for measuring dissipation factor. The module includes two blocks: switch and envelope detector. The switch rapidly disrupts the excitation of the crystal, and connects the output to the envelope detector which demodulates the amplitude of the signal. Damped sinusoidal exponential signals with different time constant were used for simulating viscosity interfaces. The incorporation of few elements facilitated a double-faced PCB design with reduced dimensions. The results from simulation show that the system has a good performance in the range of the biomolecular processes; greater relative error are observed for time constant lower than 1 μs. In conclusion, a dissipation module has been developed for calculate dissipation factor using QCM, which is compact and shows great performance for use in biomolecular adsorption. **Keywords (as stated in the article):** Dissipation, QCM, viscoelastic, envelope.