Verbeck Research

MEMS (Micro Electro Mechanical Systems) Mass Spectrometry and Ion Optics: Miniature analytical devices have recently become a growing area to produce handheld, field-portable instrumentation. Because of the difficulty to micromachine optical components and features with small aberrations, it is necessary to incorporate new doped silicon micro-electro-mechanical system (MEMS) methods. This technique allows for precise manufacturing of small electrical and mechanical device assemblies.

The micromechanical spectrometers and ion optical components are fabricated using deep reactive ion etching (DRIE) on highly n-doped (0.01 ohm-cm) silicon-on-insulator (SOI) wafers to form the micromechanical and electromechanical structures. The wafer is then diced and flip-chip bonded to an insulating substrate for components that operate at high voltages (>1 kV). An automated and directed pick and place microassembly assembly tool with MEMS end-effectors and high precision robotics is used to assemble the micro ion-optical devices. This assembly system provides a high degree of flexibility in terms of three-dimensional assembled structures and assembly precision. Ion and electron-optical assemblies are tested for electrical breakdown from 760 to 1x10^-7 torr. The mass spectrometers and ion lens assemblies are then tested for ion manipulation accuracy.

 

 

Bradbury-Nielsen Gate

Rectangular Lens Assembly

Rectangular Lens Assembly

Grids Lens

 We have created and tested ten new MEMS based ion optical assemblies. This list includes the Bradbury-Nielsen Gate, cylindrical ion trap, time-lag focusing TOF, reflectron optics, einzel lens, electron beam collimator, periodic focusing, and ion mobility. Data has been presented showing the resolution, attenuation, and performance of each of these devices. With the ability to utilize multiple substrates such as Pyrex, sapphire, and aluminum nitride, we can make ion lenses that can withstand an applied potential >2kV before breakdown. These devices have been created with <5um feature sizes and <250nm position accuracy. The angular alignment of the assembled structures is shown to be less than 1 degree.

Microscale Analysis Utilizing Micromanipulation Coupled with Nanospray Mass Spectrometry: Direct sampling of materials and surfaces using mass spectrometry has been an important development over the past decade. We have coupled a fine positioner with nanospray mass spectrometry to develop a new method for direct sample analysis. Traditional methods of mass spectrometry rely on larger sample sizes; however, electrospray ionization mass spectrometry can utilize a smaller volume of solution to compete analysis. Nanospray can also accomplish this, but to an even greater degree, by using even smaller volumes of relatively low concentrations. Nanomanipulation allows for a more direct extraction of a particular sample (i.e. forensic trace analysis, cell analysis). This can be used in direct connection with nanospray through analysis with the tip, or capillary flow into the nanospray source. This coupling of nanomanipulation with nanospray will allow for accurate placement of the sampling probe and mass spectrometry imaging of small samples.

 

 

Zyvex L200 Nanomanipulator with Nikon TE2000 Inverted Scope

Proexon Nanospray Unit Affixed to Thermo's DECA

 The nanomnaipulator (L-200, Zyvex, Richardson, TX) is a set of four positioners that sit directly on top of the stage of the inverted microscope(Nikon TE2000U). The positioners consist of two Tungsten probes (10nm resolution) and two glass capillaries attachements (1um resolution). The probes and capillaries can be manually landed onto the sample, than manipulated electronically using a joystick to control the probe location.