A system to apply energy to a targeted tissue region, comprising: instructions for using the system to treat an axilla, an applicator including an applicator interior carrying at least one energy emitter, a tissue-applicator interface sized and configured to be attached to the applicator for use in operative association with the energy emitter and to be detached from the applicator after use, the tissue-applicator interface comprising a bio-barrier system that, when the tissue applicator interface is attached to the applicator, isolates the applicator interior from contact with physiologic liquids in the targeted tissue region, the bio-barrier system including a first bio-barrier component having a prescribed conductivity to pass energy from the energy emitter to the targeted tissue region without substantial interference and loss of power, wherein the energy emitter is sized and configured to emit microwave energy, wherein the prescribed conductivity comprises a loss tangent tan δ of not greater than 0.1, where tan δ = σ/ωε, where σ is the conductivity of the first bio-barrier component, ω is the frequency of the energy emitted by the energy emitter, and ε is the permittivity of the first bio-barrier component, wherein the tissue-applicator interface includes a tissue acquisition chamber that acquires tissue in the targeted tissue region for application of energy in response to negative pressure generated by an external source and conveyed into the tissue acquisition chamber, wherein the bio-barrier system includes a second bio-barrier component separate from the first bio-barrier component, the second bio-barrier being substantially permeable to air to balance negative pressure between the tissue acquisition chamber and the applicator interior when the tissue-applicator interface is attached to the applicator, the second bio-barrier component also being substantially impermeable to liquids to isolate the applicator interior from contact with physiologic liquids in the targeted tissue region while balancing the negative pressure, and wherein the first bio-barrier component is substantially impermeable to air. instructions for using the system to treat an axilla, an applicator including an applicator interior carrying at least one energy emitter, a tissue-applicator interface sized and configured to be attached to the applicator for use in operative association with the energy emitter and to be detached from the applicator after use, the tissue-applicator interface comprising a bio-barrier system that, when the tissue applicator interface is attached to the applicator, isolates the applicator interior from contact with physiologic liquids in the targeted tissue region, the bio-barrier system including a first bio-barrier component having a prescribed conductivity to pass energy from the energy emitter to the targeted tissue region without substantial interference and loss of power, wherein the energy emitter is sized and configured to emit microwave energy, wherein the prescribed conductivity comprises a loss tangent tan δ of not greater than 0.1, where tan δ = σ/ωε, where σ is the conductivity of the first bio-barrier component, ω is the frequency of the energy emitted by the energy emitter, and ε is the permittivity of the first bio-barrier component, wherein the tissue-applicator interface includes a tissue acquisition chamber that acquires tissue in the targeted tissue region for application of energy in response to negative pressure generated by an external source and conveyed into the tissue acquisition chamber, wherein the bio-barrier system includes a second bio-barrier component separate from the first bio-barrier component, the second bio-barrier being substantially permeable to air to balance negative pressure between the tissue acquisition chamber and the applicator interior when the tissue-applicator interface is attached to the applicator, the second bio-barrier component also being substantially impermeable to liquids to isolate the applicator interior from contact with physiologic liquids in the targeted tissue region while balancing the negative pressure, and wherein the first bio-barrier component is substantially impermeable to air.