Daraio Research Group Caltech



Our group and labs are hosted in the Gates-Thomas building at Caltech. Our lab is composed of four mains spaces: (i) Materials synthesis and facrication; (ii) Mechanical testing; (iii) Multifuntional properties testing (temperature sensitivity elceltrical responsivity, chemical stability, etc.); (iv) Plant growth and plant-cell culture biolab. Our fabrication tools include different advanced manufacturing systems (3D printers, SLA printers, etc.), chemical vapour deposition and chemical benches. The mechanical testing area is equipped with state of the art facilities for mechanical testing of materials, including the static and dynamic domain, with tension-compression tools that can characterize materials from the micro- to the macro-scopic scales. We also have tools to test the response of materials to impact, structural vibrations and sound. We have a number of devices for the multifuntional characterization of materials, which include thermal cameras, electronic platforms with controlled environments, DIC systems, high speed cameras and laser vibrometers/interferometers, optical microscopes.


3D Printing

3D printing

3D printers are used for additive manufacturing, a process where three dimensional solid objects are printed from a digital model. 3D printing is used in both pre-production (rapid prototyping) and full-scale production (rapid manufacturing) with applications in aerospace, automotive, engineering, medicine, architecture, fashion and beyond. Our group manages a number of 3D fabrication tools: E.g., a Connex-Triplex, two FromLab printers and a MakerBot printer. These printers allow us to fabricate instrument casings, robot models, structured polymeric materials with optimized geometries, and polymeric matrices to host and support samples.

The Connex printer builds models using variety of polymeric materials with a range of moduli from 30 MPa (similar to soft rubber) to 3500 MPa (like a hard plastic). This instrument can print multiple materials simultaneously with a 16 micron layer thickness and a precision of 100 microns.

For more information on our 3D printing capabilities, please contact Osama Bilal or Kirsti Pajunen.

3D Photolitography

3D photolithography
We use the commercial 3D-Photolitography Nanoscribe system to create microstructures with submicron resolution. To fabricate microstructures a laser beam is guided through a microscope optic and focused within liquid or solid photoresist. Polymerization occurs at the focal point of the laser due to two-photon absorption. By 3D scanning of the focal point through the resist fully three-dimensional structures can be fabricated. The scanning of the laser is done by movement of a high-resolution piezo-stage or by changing the incident angle of the laser beam at the microscope objective with a galvo-scanner. The latter is mainly used due to the lower moving mass, which allows for higher writing speeds up to 50.000 um/s. We use different negative tone photoresist, both from Nanoscribe (IP-L, IP-G, IP-Dip, IP-S) and other suppliers (Ormocer, SU-8). The Nanoscribe polymers are optimized for the use with the machine and offer the highest resolution (down to 200nm line width). Additionally IP-S is suited for writing large structures due to an increased proximity effect. The hybrid polymer Ormocer is especially interesting for biomedical applications due to its biocompatibility, whereas SU-8 offers a slightly higher stiffness around 5 GPa compared to the IP-Resists (2-3 GPa). To adapt to different resolution requirements a range of microscope objectives (25x, 63x, 100x) can be used. Using algorithms developed in the group, it is possible to write structures up to mm3 or cm2 areas within 12 - 24 h writing time while still maintaining a submicron resolution.

Polymer-Nanostructures Fabrication

3D photolithography
Facilities include polymer processing equipment for the assembly of nanocomposites. We use a Laurell WS-400B-6NPP/LITE spin-coater, with speeds up to 10,000 rpm and capacity for wafers up to 150 mm (5.9 inches). Our lab also has a vacuum chamber, hot plate, and fume hoods available for this type of synthesis. Additional resources at the Caltech Kavli Nanotechnology Institute are used for the construction and characterization of our nanomaterials.

Dynamic Measurement Technology

High-Speed Imaging

3D printing
Our lab has two high-speed cameras available (a PHANTOM V12.1 and v1610) for imaging dynamic events. Both cameras can operate at high-definition, 1280x800, and have a maximum acquisition speed of 1,000,000 fps. The shutter speed is 1ms when in standard mode, but can be programmed to sub-μs if required. The cameras also have high time resolution, ~20 ns, and an extreme dynamic range, with two different exposures within the same frame.

High Power Laser Excitation System

3D photolithography
Our lab has two high-speed cameras available (a PHANTOM V12.1 and v1610) for imaging dynamic events. Both cameras can operate at high-definition, 1280x800, and have a maximum acquisition speed of 1,000,000 fps. The shutter speed is 1ms when in standard mode, but can be programmed to sub-μs if required. The cameras also have high time resolution, ~20 ns, and an extreme dynamic range, with two different exposures within the same frame.

High Resolution Optical Detection

3D photolithography
Three laser vibrometers (Polytec, two OFV-534 units and one OFV-2500) can each measure the projected component of an object's surface vibration vector along the direction of the incident laser beam. The noncontact measurements can resolve the displacement amplitudes to as small as 0.1 pm, with a frequency range from near DC to 24 MHz. An integrated CCD camera is used for monitoring of the measurement volume. With the aid of microscope objectives, measurements can be performed on micron-sized objects.

Dynamic testing with Moire interference pattern

3D photolithography
The dynamic impact testing system built in our laboratory is capable of measuring the dynamic force and dynamic displacement directly. It consists of a striker impact subsystem with a dynamic force sensor (to generate impact and measure the force) and an optical subsystem (to measure the displacement). The dynamic force is measured by commercial dynamic force sensor and the dynamic displacement measurement subsystem works based on the method of geometric moire interferometry. This experimental set up is currently used for the dynamic characterization of carbon nanotube arrays subjected to strain rates varying between 1000-10000 /s.

Testing Tank with Scanning Hydrophone

3D photolithography
Our test tank (dimensions of 1 m x 0.75 m x 0.75 m) is used for measurements and mapping of acoustic fields in water. Measurements are made with a Precision Acoustics 4 mm needle hydrophone probe with a submersible preamplifier mounted onto a 3-axis positioning arm. The positioning arm is controlled by UMS3 scanning system that automates the repetitive tasks associated with the acquisition, display, storage and computation of data.

Quasi-static Measurement Technology

Instron E3000

3D printing
The Instron E3000 is our instrument of choice for low strain rate mechanical measurements of bulk materials. Its fully electric system makes for low maintenance and ease of use, and it can be setup for either tension or compression tests. The displacement resolution is 1 μm and the maximum load is 3000 N. It is ideal for quasistatic tests with displacement rates less than a few millimeters per second and for long-lasting measurements of low rate phenomena such as creep and stress relaxation. The E3000 can be coupled with our electronic and optical equipment for in situ measurements during sample deformation.

Electrical Measurements

3D photolithography
We perform electrical measurements using a Keithley 2635 source-meter. Four-probe tests allow for accurate measurement of electrical resistance, with current as low as pA and voltage as low as μV. This system is routinely coupled with the Instron E3000 to obtain in situ electrical measurements during deformation of materials.

Optical Characterization

3D photolithography
Optical characterization is performed using a Nikon Eclipse LV100 microscope, with several objective lenses up to 100x.

A CCD camera is used to capture images or video to computer for image analysis using NIS Elements software. The CCD can also be decoupled from the microscope to be used with standalone optics. This allows in situ optical measurements of material being deformed by the Instron E3000.

For large working area requirements (e.g. for high precision electrical measurements), a Leica S6D optical stereo microscope is also available, with a 6-36x magnification.