Babur B. Hadimioglu

Acoustic printheads with optical alignment

Acoustic printheads having an optically transparent substrate, at least two optical lenses, which may be part of the substrate, and a first structure, which may also be part of the substrate. The optical lenses focus light which irradiates the substrate into optical focal points at known locations relative to the first structure. The first structure may be part of an acoustic droplet ejector which includes an acoustic lens that is fabricated on the optically transparent substrate. The optical focal points can be used to precisely align the first structure with another structure.

Moving Liquids with Sound: The Physics of Acoustic Droplet Ejection for Robust Laboratory Automation in Life Sciences.

Liquid handling instruments for life science applications based on droplet formation with focused acoustic energy or acoustic droplet ejection (ADE) were introduced commercially more than a decade ago. While the idea of “moving liquids with sound” was known in the 20th century, the development of precise methods for acoustic dispensing to aliquot life science materials in the laboratory began in earnest in the 21st century with the adaptation of the controlled “drop on demand” acoustic transfer of droplets from high-density microplates for high-throughput screening (HTS) applications. Robust ADE implementations for life science applications achieve excellent accuracy and precision by using acoustics first to sense the liquid characteristics relevant for its transfer, and then to actuate transfer of the liquid with customized application of sound energy to the given well and well fluid in the microplate. This article provides an overview of the physics behind ADE and its central role in both acoustical and rheological aspects of robust implementation of ADE in the life science laboratory and its broad range of ejectable materials.

Near-field acoustic microscopy (Invited Paper)

We have integrated silicon micromachining techniques with piezoelectric thin film deposition to make a near-field acoustic microscope. A piezoelectric zinc oxide (ZnO) transducer is deposited on a substrate of 7740 glass. A sharp tip is formed in a silicon wafer which is anodically bonded to the glass substrate. A sample is attached to substrate of glass with a receiving ZnO transducer. The transducer on the tip excites an ultrasonic beam which passes from the tip to the sample and is detected by the receiving transducer. A feedback signal is generated to keep the transmitted amplitude constant as a sample is raster scanned. The feedback signal is applied to a tube scanner and is also used to modulate the intensity of a display monitor. We find that the instrument has a vertical height sensitivity of about 20 angstroms, and a lateral resolution of better than 800 angstroms.

Acoustic microscopy beyond the diffraction limit: an application of microfabrication

The critical components of a scanning near-field acoustic microscope have been microfabricated. A ZnO ultrasonic transducer is used to launch 175 MHz acoustic waves down a sharp silicon tip. Imaging can be done by raster scanning the tip over a sample while monitoring the transmitted acoustic signal. Initial experiments indicate the height sensitivity of the microscope is approximately 20 AA. One-dimensional scans show that the lateral resolution is approximately 800 AA. The exact nature of the interaction of the tip and sample is not well understood but repeated scans over the same region of a sample do not result in noticeable sample damage. The authors intend to use this microscope to image samples such as organic films and microfabricated structures.<<ETX>>