Toothbrush-Driven Handheld Droplet Generator for Digital LAMP and Rapid CFU Assays.

Area of Science:

• Microfluidics
• Biotechnology
• Assay Development

Background:

• Traditional droplet microfluidics requires expensive, bulky equipment, limiting accessibility.
• Existing systems often rely on precision-fabricated chips and external pumps.
• There is a need for portable, low-cost droplet generation for field applications.

Purpose of the Study:

• To develop a handheld, low-cost vibrational droplet generator.
• To demonstrate its utility in biological assays like digital loop-mediated isothermal amplification and colony-forming unit counts.
• To provide an accessible 'lab-in-hand' solution.

Main Methods:

• Repurposed an electric toothbrush motor and modified disposable pipette tip.
• Used a 3D-printed adapter and adjustable counterweight to control vibration amplitude.
• Generated water-in-oil droplets (100-300 µm diameter) at ~100 droplets/sec.

Main Results:

• Achieved nearly monodisperse droplets with coefficients of variation below 5%.
• Successfully performed digital loop-mediated isothermal amplification (LAMP) for feline parvovirus detection.
• Demonstrated uniform microbial colony distribution using the device as a droplet spreader for *Escherichia coli*.

Conclusions:

• The toothbrush-based vibrational generator is inexpensive, easy to assemble, and minimizes reagent use and contamination.
• It offers a practical and scalable method for droplet assays in resource-limited or educational settings.
• Vibrational actuation provides a viable alternative to conventional microfluidic pumps for portable diagnostics.