Decontaminating surfaces with atomized disinfectants generated by a novel thickness-mode lithium niobate device.

We evaluated the ability of a novel lithium niobate (LN) thickness-mode device to atomize disinfectants and reduce microbial burden on model surface materials. A small-scale plastic model housed the LN thickness-mode device and circular coupon surface materials including polycarbonate, polyethylene terephthalate, stainless steel, borosilicate glass, and natural rubber. Coupon surfaces were coated with methicillin-resistant Staphylococcus aureus (MRSA) or multidrug-resistant (MDR) strains of Gram-negative bacterial pathogens (Klebsiella pneumoniae, Escherichia coli, and Acinetobacter baumannii), atomized with disinfectant solutions of varying viscosity (including 10% bleach, 70% ethanol (EtOH), or 25% triethylene glycol (TEG)) using the LN thickness-mode device, and assessed for surviving bacteria. The LN thickness-mode device effectively atomized disinfectants ranging from low viscosity 10% bleach solution or 70% EtOH to highly viscous 25% TEG. Coupons harboring MDR bacteria and atomized with 10% bleach solution or 70% EtOH were effectively decontaminated with ~ 100% bacterial elimination. Atomized 25% TEG effectively eliminated 100% of K. pneumoniae (CRE) from contaminated coupon surfaces but not MRSA. The enclosed small-scale plastic model established proof-of-principle that the LN thickness-mode device could atomize disinfectants of varying viscosities and decontaminate coupon surface materials harboring MDR organisms. Future studies evaluating scaled devices for patient rooms are warranted to determine their utility in hospital environmental decontamination.

Planar microfluidic drop splitting and merging.

Open droplet microfluidic platforms offer attractive alternatives to closed microchannel devices, including lower fabrication cost and complexity, significantly smaller sample and reagent volumes, reduced surface contact and adsorption, as well as drop scalability, reconfigurability, and individual addressability. For these platforms to be effective, however, they require efficient schemes for planar drop transport and manipulation. While there are many methods that have been reported for drop transport, it is far more difficult to carry out other drop operations such as dispensing, merging and splitting. In this work, we introduce a novel alternative to merge and, more crucially, split drops using laterally-offset modulated surface acoustic waves (SAWs). The energy delivery into the drop is divided into two components: a small modulation amplitude excitation to initiate weak rotational flow within the drop followed by a short burst in energy to induce it to stretch. Upon removal of the SAW energy, capillary forces at the center of the elongated drop cause the liquid in this capillary bridge region to drain towards both ends of the drop, resulting in its collapse and therefore the splitting of the drop. This however occurs only below a critical Ohnesorge number, which is a balance between the viscous forces that retard the drainage and the sufficiently large capillary forces that cause the liquid bridge to pinch. We show the possibility of reliably splitting drops into two equal sized droplets with an average deviation in their volumes of only around 4% and no greater than 10%, which is comparable to the 7% and below splitting deviation obtained with electrowetting drop splitting techniques. In addition, we also show that it is possible to split the drop asymmetrically to controllably and reliably produce droplets of different volumes. Such potential as well as the flexibility in tuning the device to operate on drops of different sizes without requiring electrode reconfiguration, i.e., the use of different devices, as is required in electrowetting-therefore makes the present method an attractive alternative to electrowetting schemes.