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Fabrication and evaluation of atomic force microscope probes with detachable and re-usable tips

Primary Information

Domain

Manufacturing

Project No.

7133

Sanction and Project Initiation

Sanction No: F.No.3-18/2015-TS-TS.I

Sanction Date: 29/11/2016

Project Initiation date: 29/11/2016

Project Duration: 36

Partner Ministry/Agency/Industry

Department of Scientific and Industrial Research

 

Role of partner:Financial support up to 50 percent of approved budget

 

Support from partner:50 percent

Principal Investigator

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G. R. Jayanth
Indian Institute of Science

Host Institute

Co-PIs

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Prof. Rudra Pratap
Indian Institute of Science

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Dr. Vijay Mishra
Indian Institute of Science

 

Scope and Objectives

The objectives of this proposal are to (a) batch fabricate array of detachable probe-tips at significantly greater densities than in batch-fabricated conventional AFM probes (b) batch fabricate tip-less AFM probes capable of picking up the probe-tips with precise control of their position and orientation by employing a liquid-meniscus micro-gripper (c) evaluate AFM tip pick-up, gripping and re-use (d) perform high-resolution AFM imaging in contact-mode and dynamic-mode AFM of nano-materials using detachable tips and (e) demonstrate automatic detection of tip wear and replacement of worn-out tips during AFM imaging.

Deliverables

Detachable AFM probe tips batch fabricated from Silicon or silicon nitride AFM micro-cantilever beams without tips of rectangular geometry batch fabricated from Silicon or silicon nitride A procedure to detach AFM tips from the array of the fabricated detachable tips and attach it on the microcantilever beams

 

Scientific Output

Three specific aims are proposed for fabrication and evaluation of AFM probes with detachable and re-usable tips. The first aim is the design and batch fabrication of an array of detachable AFM tips along with fabrication of tip-less AFM probes. The second aim is the evaluation of AFM probes with detachable tips, wherein a liquid-meniscus based micro-gripper would be integrated with the tip-less probe and demonstrated to pick up, grip, detach, and re-use AFM tips. The third aim is the demonstration of detachment of the tip upon detection of tip wear or tip damage, and demonstration of tip re-use for purposes of 3D nano-metrology. The tasks proposed to achieve each aim are outlined below. Aim#1. Design and batch fabrication of AFM probes with detachable tips Task#1.1. In this task, an array of probe-tips that can be readily detached from the substrate would be designed and batch-fabricated. Each detachable tip would be connected to the substrate by a slender beam. In order to detach the tip, the beam is fractured. The tip would be rigidly attached to a tip-head, which, in turn, would be compatible with being precisely picked up by a liquid-meniscus based micro-gripper. Task#1.2. In this task, AFM probes without a tip would be designed and batch-fabricated. The design of the probe would ensure compatibility with integrated liquid-meniscus based micro-grippers. The stiffness of the probe would be comparable to that of conventional contact-mode and dynamic mode AFM probes. Its design also enables the probe to pick up tips from the fabricated array of detachable tips. Task#1.3. In this task, an alternate design for the AFM probe would be investigated, wherein the batch fabricated probes would possess integrated micro-heaters and the liquid-droplets would be replaced by solid materials that can be temporarily melted by application of heat, such as polymers and wax. Task#1.4. In this task, the liquid-droplet based micro-gripper would be integrated to the fabricated tip-less AFM probe and would be demonstrated to detach and pick-up AFM tips from the fabricated tip array. The precision and repeatability with which the tips can be picked up would be quantified. Aim#2: Evaluation of AFM probes with detachable tips Task#2.1: In this task, the AFM probe carrying the detached tip would be evaluated for its performance in both contact-mode and dynamic-mode AFM by imaging calibration gratings first and subsequently other samples such as metal nanoparticles. Task#2.2: In this task, the probe would be employed in combination with an automated tip-replacement and re-use system that is currently under development in our laboratory to demonstrate tip re-use capability. Aim#3: Demonstration of applications of the fabricated probes with detachable and re-usable tips Task#3.1: Material characterization requires indenting the surface of the material, by means of the AFM probe. This renders the tip especially vulnerable to fracture. In this task, in-situ replacement of the damaged tip would be demonstrated during material characterization experiments.

 

Results and outcome till date

1. Design and batch fabrication of AFM probes with detachable tips (Aim#1) - A Project Assistant has been hired, with his tenure beginning on 1st May 2017, to assist in the implementation of the project. Literature survey was performed in order to develop a suitable recipe to fabricate detachable AFM probes and probes without AFM tips. - A recipe was developed for batch fabrication of tip-less AFM probes. Suitable masks were designed and fabricated. Subsequently, batch fabrication of tip-less AFM probes has been successfully completed. The probes were fabricated using Silicon-on-insulator wafers by employing a combination of dry etching and wet etching. - AFM tips have been fabricated on a substrate with the help of dry etching techniques - New masks have been designed and fabricated for AFM cantilevers and the batch fabrication process of AFM probes with tips has begun - Masks have been designed for batch fabrication of detachable tips and the batch fabrication process has been started. - Investigation of an alternate design for the AFM probe has been undertaken, wherein the AFM probes would pick up tips by employing solid materials that can be temporarily melted by application of heat. Two materials were successfully evaluated for this capability, namely, paraffin wax and polycaprolactone (PCL). Centrifugal atomization has been employed to generate wax microspheres. The heating was provided by a green laser diode (wavelength 532nm) of power about 6mW focused on a tip-less micro-cantilever beam.

2. Evaluation of AFM probes with detachable tips (Aim#2) - A Vibration Isolation Table has been purchased for development of an AFM with automatic tip-exchange capability - Automated tip pick-up been experimentally demonstrated. - Automated tip detachment has been demonstrated. - The tips picked up as part of Aim#1 were evaluated by imaging a standard calibration grating in both contact mode and tapping modes of operation. The evaluation was done in commercial AFM. Further, they were evaluated both in air and in water. In all cases the image obtained was found to be identical to that obtained using a conventional AFM. - To showcase the fact that the image quality is preserved even when lateral feature-sizes are small, a DVD grating was also imaged.

3. Demonstration of applications of the fabricated probes with detachable and re-usable tips (Aim#3) - The automated tip-exchange module has been successfully demonstrated to replace tips during nano-indentation experiments. - An artifact that enables determination of the sharpness of the AFM tip has been employed to detect tip quality and subsequently initiate automatic tip exchange

 

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Societal benefit and impact anticipated

The Atomic Force Microscope is widely used for material characterization, surface imaging and for nanometer scale manipulation. It is presently the only technology that enables performing all these tasks in-situ, and is of central importance to development of nanotechnology. The proposed system significantly reduces the running cost of the instrument and allows a larger range of nano-probes to be employed, for more advanced applications.

Next steps

1. Fabrication of the detachable AFM tips
2. Automated replacement of detachable AFM tips

Publications and reports

K. S. Vikrant and G. R. Jayanth, "An AFM tip-replacement system compatible with all media and operation modalities", Ultramicroscopy, Vol. 196, pp. 136 (2019)

Patents

Nil

Scholars and Project Staff

Mr. Hari Prasanna (project assistant) Mr. Vikrant Kumar Singh (PhD Scholar)

Challenges faced

Optimization of fabrication parameters using wet-etching was found to be difficult. Hence after a few attempts where the fabricated parts were sub-optimal in quality, dry etching was adopted.

Financial Information

  • Total sanction: Rs. 3615000

  • Amount received: Rs. 2514000

  • Amount utilised for Equipment: Rs. 580087

  • Amount utilised for Manpower: Rs. 571667

  • Amount utilised for Consumables: Rs. 345769

  • Amount utilised for Contingency: Rs. 58077

  • Amount utilised for Travel: Rs. 27500

  • Amount utilised for Other Expenses: 0

  • Amount utilised for Overheads: Rs. 418000

Equipment and facilities

 

Vibration isolation table (Thorlabs)