We present an integrated circuit/microfluidic chip that traps and moves individual living biological cells and chemical droplets along programmable paths using dielectrophoresis (DEP). Our chip combines the biocompatibility of microfluidics with the programmability and complexity of integrated circuits (ICs). The chip is capable of simultaneously and independently controlling the location of thousands of dielectric objects, such as cells and chemical droplets. The chip consists of an array of 128 x 256 pixels, 11 x 11 microm(2) in size, controlled by built-in SRAM memory; each pixel can be energized by a radio frequency (RF) voltage of up to 5 V(pp). The IC was built in a commercial foundry and the microfluidic chamber was fabricated on its top surface at Harvard. Using this hybrid chip, we have moved yeast and mammalian cells through a microfluidic chamber at speeds up to 30 microm sec(-1). Thousands of cells can be individually trapped and simultaneously positioned in controlled patterns. The chip can trap and move pL droplets of water in oil, split one droplet into two, and mix two droplets into one. Our IC/microfluidic chip provides a versatile platform to trap and move large numbers of cells and fluid droplets individually for lab-on-a-chip applications.

An areal density of 1.6 Tbits/in. 2 has been achieved by anodically oxidizing titanium with the atomic force microscope ͑AFM͒. This density was made possible by ͑1͒ single-wall carbon nanotubes selectively grown on an AFM cantilever, ͑2͒ atomically flat titanium surfaces on ␣-Al 2 O 3 ͑1012͒, and ͑3͒ atomic scale force and position control with the tapping-mode AFM. By combining these elements, 8 nm bits on 20 nm pitch are written at a rate of 5 kbit/s at room temperature in air.

Alkyl and fluorinated alkyl monolayers covalently bonded to the silicon (111) surface have been prepared by UV illumination of the H-Si(111) surface while immersed in a solution of olefin precursor under high vacuum. An alkoxy monolayer covalently bonded to the silicon (111) surface is formed by the reaction of the H-Si(111) surface with a heated solution of primary alcohol precursors under high vacuum. Ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy are used to characterize the three monolayers. The alkyl monolayer is measured to have the largest number of organic adsorbates per surface silicon atom. Properties of the monolayers on the silicon surface are probed by cyclic voltammetry. The hydrophobic alkyl monolayer slows the oxidation of the silicon surface by water. The three monolayers also slow the rate of electron transfer across the silicon-electrolyte interface by acting as a tunneling barrier. The alkyl monolayer in tetrahydrofuran exhibits a large and reproducible blocking of the electron transfer.

Positioning single cells is of utmost importance in areas of biomedical research as diverse as in vitro fertilization, cell-cell interaction, cell adhesion, embryology, microbiology, stem cell research, and single cell transfection. Here we describe dielectrophoretic tweezers, a sharp glass tip with electrodes on either side, capable of trapping single cells with electric fields. Mounted on a micromanipulator, dielectrophoresis tweezers can position a single cell in three dimensions, holding the cell against fluid flow of hundreds of microns per second with more than 10 pN of force. We model the electric field produced by the tweezers and the field produced by coaxial microelectrodes. We show that cells are trapped without harm while they divide in the trap. In addition, dielectrophoretic tweezers offer the possibility for trapping, electroporating, and microinjecting a single cell with one probe.

A hybrid integrated circuit (IC) / microfluidic chip is presented that independently and simultaneously traps and moves microscopic objects suspended in fluid using both electric and magnetic fields. This hybrid chip controls the location of dielectric objects, such as living cells and drops of fluid, on a 60 × 61 array of pixels that are 30 × 38 μm2 in size, each of which can be individually addressed with a 50 V peak-to-peak, DC to 10 MHz radio frequency voltage. These high voltage pixels produce electric fields above the chip’s surface with a magnitude , resulting in strong dielectrophoresis (DEP) forces . Underneath the array of DEP pixels there is a magnetic matrix that consists of two perpendicular sets of 60 metal wires running across the chip. Each wire can be sourced with 120 mA to trap and move magnetically susceptible objects using magnetophoresis (MP). The DEP pixel array and magnetic matrix can be used simultaneously to apply forces to microscopic objects, such as living cells or lipid vesicles, that are tagged with magnetic nanoparticles. The capabilities of the hybrid IC / microfluidic chip demonstrated in this paper provide important building blocks for a platform for biological and chemical applications.