For comprehensive removal of even trace organic residues, we turned to semiconductor photolithographic cleaning processes: the venerable "RCA clean" performs mechanical degreasing by ultrasonic-induced cavitation in increasingly polar solvents, namely trichloroethylene (TCE), acetone, isopropyl alcohol (IPA), and finally aqueous-based solutions . We began by choosing an appropriate solvent from these -water-based cleaners were excluded since surfactants in the analyte would rapidly cause uncontrollable foaming. We sought a semi-polar solvent and conveniently found this in isopropyl alcohol (IPA) with a polarity index of 3.9 vs. 10.2 for water. We found that reactant residues soaked in IPA swelled upon immersion, while agitating the residues did not cause foaming. Since cleaning generates large amounts of chemical waste, the low toxicity and ease of disposal also made IPA a good choice as the cleaning agent. As shown in Figure , we positioned our IPA cleaning bath at the rear of the stage such that it could be refilled easily. To avoid dripping residue while translating the probe head, we programmed movements to the cleaning bath along designed tracks that would not cross over the adjacent sample containers.