Category Archives: Microfluidics

Microfluidics

Microfluidic Manifolds

3D Structuring

MEMS_Sandwiches_Variants

 

GeSiM offers different approaches for micromachining of 3D structures. Microfluidic devices are easily made from silicon/glass sandwiches. However, many applications require optical transparent channel structures. Glass/glass sandwiches are precise but more expensive and give high accuracy (see next menu point).

 

PDMS microfluidics keeps prices close to disposables but requires more initial instrumentation. Please refer to the GeSiM MicCell or even the Micro-Contact-Printers. The latter one prints your microfluidic devices (NIL – Nano-Imprint-Lithography) but manage sample handling too by onboard pipettors.

 

Right: Different sandwich methods for microfluidic devices.

Manufacturing Technologies

3D Microfluidics from Hard Materials

  • Anisotropic wet-chemical etching of Si with KOH: inexpensive batch process, smooth surface, side wall angle depends on crystal orientation
  • Anisotropic plasma-enhanced dry Si etching (ASE/Bosch process): single wafers, dense structures, vertical side walls
  • Super-rough surfaces by etching in SF6/C4F8 plasma
  • Isotropic wet etching of glass with HF: round channels, 3 – 700 µm deep
  • Ultrasonic drilling and micro-blasting for 150 – 1000 µm thick glass, Si, quartz
REM_Images

a) Etched channel structure of a micromachined device, b) Micro pores, realized by ASE at presence of insulated platinum electrodes, c) Etched sieve structure, d) GeSiM dispenser structure: View from the pump chamber of the fluid inlet (From left to right)

 

Thin Film Services

Coating Technologies

GeSiM offers the deposition of conducting and insulating films by

  • Physical Vapor Deposition
  • Plasma-Enhanced Chemical Vapor Deposition
  • Screen Printing

 

Physical Vapor Deposition (PVD) by Magnetron Sputtering and Electron Beam Deposition

Can be applied to different materials:

  • Conductive materials: Aluminum (Al), titanium (Ti), platinum (Pt), tantalum (Ta):- Thickness from 0 to 200 Nanometers.
    – Resistance in the micro ohm range.
    – Patterning by lift-off and etching technologies.
    – Single-layer or multi-layer coating of these materials.
  • Conductive and transparent material ITO-90/10 (90% indium oxide In2O3 and 10% tin oxide SnO2):
    – Thickness from 20 to 200 Nanometers.
    – Resistance from 30 to 50 Ohm.
    – Patterning by lift-off and etching technologies.
  • Evaporated quartz SixOy, coated at 150° C.
Thin-Film_Examples-1

a) Platinum electrodes on glass, b) Thin film platinum resistors on a cantilever silicon nitride membrane, c) Aluminum metallization on a silicon chip, d) Gold electrodes on glass (From left to right)

 

Plasma Enhanced Chemical Vapor Deposition (PECVD)

  • Silicon oxide SiO2, silicon nitride Si3N4 and low stress oxinitride SixOyNz as alternative insulator materials:- Thickness from 20 Nanometers to 1.5 Microns.

    – Patterning by RIE dry etching and wet chemical etching.

  • Hydrofluorocarbon CxFy layers. Material similar to Teflon®:
    – Thickness range from 50 Nanometers to 2 Microns.
    – Patterning by O2 RIE plasma etching.

PVD and PECVD applies to all kind of substrates up to 4 inch diameter.

 

Screen Printing

  • Dispensing of the state of the art adhesives on printed circuit boards and micro system substrates for surface mounted device packaging.
  • Dispensing of silicon rubber.
  • Includes sieve design and production.
  • Typical thickness of printed materials in the range of 15 to 35 Microns.

 

Bonding

Connecting Microfluidic Chips with and without Glue

In order to achieve closed fludic channels MEMS technologies offers different – material dependent – methods. The GeSiM engineering service covers:

  • Anodic bonding
  • Silicon fusion bonding
  • Die bonding using adhesives
  • Wire bonding

 

Anodic Bonding

This process generates very tightly connected layers, produced by the application of high voltage and high temperature, and is ideal for the irreversible covering of microfluidic channels.

  • Bonding of double and triple sandwiches of silicon and Pyrex glass
  • Maximal substrate diameter: 4 inches (10 cm)
  • Process temperature between 300°C and 450°C.
  • Bonding with or without prealignment. Aligning accuracy ≥ 5 microns.
  • Bonding of insulator (Silicon oxide SiO2 or Silicon nitride Si3N4) silicon surfaces.

 

Silicon Fusion Bonding

  • Adhesive bonding after wet chemical pretreatment of substrates in strong acids
  • For double sandwiches of (micro-machined) silicon
  • Maximal substrate diameter: 4 inches (10 cm)
  • Process temperature between 950°C and 1100°C under nitrogen atmosphere

 

Die Bonding Using Adhesives

  • Computer Aided Design and sieve production for screen printing of adhesives
  • CAD and preparation of polymer spacers
  • Adhesive die bonding on whole wafers or on single chips
  • Aligning accuracy ≥ 5 microns
  • Usage of conductive adhesives to interconnect electrodes of top and bottom substrate of the die bonded sandwich
Bonding-Examples-2

a) Silicon-glass sandwich, b) Glass-silicon-glass sandwich (Patent 01993578.2-1524), c) 35 µm thick polymer layer on top of a glass wafer with SiO2– insulated platinum electrodes, d) Glass-polymer-glass flow through cell, assembled by die bonding using photolithographically patterned polymer spacer and screen printed adhesive Patent PCT/DE 01/03324) (From left to right)

Wire Bonding

  • On or between glass, silicon, ceramic, printed circuit boards with metal bond pads.
  • Wire material AlSi1, diameter: 25 microns.
  • Minimal bond pad area 30 x 30 microns².
  • Sealing of bond wires with epoxy.

 

 

Wafer Dicing Service

From the Batch Process to tiny Pieces

GeSiM accepts flat wafers with diameters up to 6 inch, furthermore tubes and objects of other geometries (please ask).

 

Substrate Materials

  • Silicon (up to 2 mm thick)
  • Different glasses (up to 1.5 mm thick)
  • Different Ceramics (up to 1.5 mm thick)
  • Stainless Steel (up to 1.0 mm thick)

 

Support

  • Pressure sensitive tapes
  • UV-curing tapes
  • Dicing wax
a) Glass capillary, diced into pieces of 1.5 mm length, b) Miniature mirrors, diced from a metallized 4 inch glass wafer, c) TEM cross section of a diced piece

a) Glass capillary, diced into pieces of 1.5 mm length, b) Miniature mirrors, diced from a metallized 4 inch glass wafer, c) TEM cross section of a diced piece (From left to right)

 

Instrumentation Service for R/D

Integrating the Worlds of Micro and Macrotechnology

The exchange of material and information with MEMS is more complex than with standard microelectronic chips. GeSiM offers customized solutions for packaging, liquid handling and instrument design.

  • Hybrid integration of Si or glass chips in ceramic of other wire bonding mounts,
  • Innovative electrical, fluidic and mechanical joining technology,
  • Integration of macrofluidic components (E.g. valves, pumps) or custom-specific parts,
  • Development of hard- and software,
  • Customization of GeSiM standard instruments.
Syringes_with_flowsensors

Multi-channel syringe module with flow sensors for supplying/removing fluids from microfluidic chips

 

 

Miscellaneous

Further MEMS Services

Microgalvanics

Galvanic deposition of thick layers of Ni (70 µm), Au (70 µm), Au (10 µm), after lift-off microstructuring

 

Screen Printing

  • Printing of SMD adhesives or silicone rubber on PCBs and microsystem substrates
  • Including sieve design and production
  • Typical thickness: 15 – 35 µm

 

Services

Photoemulsion Masks with your Design

Cleanroom facility at GeSiMCleanroom facility at GeSiM

 

We supply cost effective photo emulsion masks for patterns down to 25 microns. Smaller features are available with chrome masks from an external source. The photo emulsion masks are based on glass substrates 5″ x 5″ as well as on films of diverse sizes.

If desired we also offer CAD services for your particular application.

 

Design Guidelines

Technical Information on the GeSiM Mask Service

We accept CAD data accordingly to the following rules, as well as create plot files based on your specs.

Photoemulsion mask on glass

Photoemulsion mask on glass

 

 

Supported data formats

 

  • AutoCAD™ DXF up to release 12 (preferred),
  • Gerber RS 274X,
  • GDS-II, CIF.

 

 

 

 

 

 

 

Design guidelines

For 5” masks, the plotting area is restricted to 100 mm x 100 mm. For a centered image on the mask, the outer dimensions of the drawing must be exactly 100 mm x 100 mm. Placing of four small squares (e.g. 50 microns x 50 microns) in the corners of the layout supports this contraint.

In DXF files, please use only solids, circles and closed polylines with a width of zero. These patterns will be filled by our software. Do not try to fill them with the hatch command. Avoid “islands”, try to split complex figures in separate parts instead. For text information, use only the text command, never dtext or mtext. Please set the font to txt.shx.

 

Download our sample file as a design template.

 

Organs on a Chip

Design and Prototyping of a novel “Organs-on-a-Chip” Bioreactor System for Substance Testing

This work was conducted by
Fraunhofer IWS Dresden, TU Berlin, ProBioGen AG Berlin, GeSiM mbH

 

Introduction

The prototype of this “organs-on-a-chip” (OOC) platform is supposed to enable studies of the interaction of consumer-relevant synthetic or natural substances with the human body in its typical environments and with its individual genotypic specificities. It has been designed for the long-term culture of human sub-organoids in small cavities of a microfludic flow-through cell.

 

Design of the Multi-Bioreactor Chip

A double sided micromachined silicon chip at the size of a standard glass slide is the heart of the bioreactor. It contains the growth segments and the cavities for the stem cells. The silicon chip is than enhanced with a PDMS layer shaping fluidic structures for supply and removal of reagents.

 

Features:

- Standard microscope slide format
- Six identical micro-bioreactor systems per chip
- Common central medium reservoir
- Live tissue imaging
Each micro-bioreactor consists of

- Three ogan growth segments
- A stem cell niche cavity
- Three behavior sensors
- Three waste reservoirs
Multi Organchip

Multi Organchip

Bioreactors on the Multi-Organ-Chip

Bioreactors on the Multi-Organ-Chip

 

 

 

 

 

LayerMaterialTechnologyFunctions 
1PDMS (2000 µm)CastingChannels and reservoirs
Cross section of the Multi-Bioreactor-Chip

Cross section of the Multi-Bioreactor-Chip

2Glass (200 µm)Lithography, LaserClosing layer
3Silicon (400 µm)Lithography, LaserChannels, organ growth segments & stem cell niche
4Glass (200 µm)Sensors and heatersSensors and heaters

The micromachining department at GeSiM contributed to the development by:

  • Lithography and mask design
  • Development of a new deep RIE etching process for micro patterning of silicon wafers
  • Adaptation of the PDMS casting technology for the fluidic reservoirs (Layer 1)
  • Development of a three layer glass/silicon/glass sandwich with embedded heater/sensor arrays (Accuracy of temperature control 0.1 K)

 

Instrumentation

GeSiM developed a docking station for unattended operation of the bioreactor chip. Laboratory compatibility was ensured by sticking to the common micro titer plate format (Approx. 125 mm x 83 mm). Therefore the bioreactor docking station fits to common laboratory robots, shakers, incubators, microscope stages and others.

Features:

  • Data exchange with PC
  • Battery based operation for at least 2 hours
  • Automatic charging in the docking station
  • Data acquisition and logging for at least 14 days (E.g. temperature)
  • Monitoring and alerting function for limit values