Disclosed herein are methods, devices, compositions, and systems for providing an interface between medical instrumentation and a patient. In various embodiments, the interface provides a sterile barrier, acoustic coupler, and thermal insulator between the patient and a medical instrument. In some embodiments, an acoustic coupler interface is used between an ultrasound instrument and a patient. In some embodiments, the acoustic coupler comprises a thermoplastic elastomer (“TPE”) and in particular oil-enhanced or gelatinous TPEs that can be used in diagnostic and therapeutic (HIFU) ultrasound procedures.