BogazIcI UnIversIty

MIcro Electro MechanIcal Systems

(BUMEMS)

Shining polymer LED examples

Text Box: Turkiye’s first 16x16 passive matrix flexible polymer LED display fully fabricated and successfully tested in BUMEMS lab on May 4th, 2008.
Text Box: Turkiye’s first digital polymer circuits  fabricated in BUMEMS lab on May 15th, 2008.

Welcome to the website of the Bogazici University Micro Electro Mechanical Systems (BUMEMS) laboratory.

The aim of this laboratory is to do research on MEMS, circuits, MEMS-circuit integration and polymer microfabrication including organic / polymer electronics and microfluidics. The main focus of the lab is on polymer microfabrication, organic electronics and microfluidics and its applications to MEMS and electronic circuitry since it involves relatively cheaper and easier fabrication methods and equipment.

In-house polymer MEMS fabrication capabilities are developed in this lab. These polymer microfabrication capabilities have led to the fabrication of polymer electronics, polymer light emitting diodes and microfluidic devices. Recently, novel devices have been shown by integrating organic electronics to MEMS and microfluids.

The efforts to build the BUMEMS laboratory at the department of electrical and electronics engineering started on September 2005. Lab is under constant development. Building a laboratory is a dynamic (a progressive) process. This website shows current progress of the lab. It gives information on acquired fabrication and testing capabilities and purchased and installed equipment. Summaries of the most recently published research work are also given here. This website also includes details of funded projects and research assistant positions.

 

Detailed view of the fabricated Polymer IC showing metal layers and vias.

Ids-Vds Curve of a fabricated PFET

Layout of a Polymer Digital IC designed using IC tools

Picture of a Fabricated Polymer IC

Examples of Our Polymer / Organic Electronics

Examples of Polymer Light Emitting Diodes

Successfully generated MEMS display image examples (2009). (a) no actuation and no modulation  (b) actuated but no modulation (c) PLED array is modulated to give a checker board image (d) pattern obtained by selectively turning off several PLEDs. (In collaboration with A.D. Yalcinkaya)

For the first time, a fire resistant 4 (FR4) actuator suspended with two springs at the anchoring regions and an array of polymer light emitting diodes (PLEDs) placed on the actuator surface are integrated to form a polymer display. Slow-scan movement of the MEMS actuator and the electronic modulation of the LEDs form virtual pixels and thus generate a two-dimensional image.   (In collaboration with A.D. Yalcinkaya)

 

Examples of Polymer LED Integrated Polymer Scanner

Microheater Matrix Using Polymer Semiconductor Diodes for Thermal Patterning

Thermal pictures of the 16x16 heater matrix taken by an infrared thermal imaging camera. An area consisting of 4x4 heaters are selected and current densities of a) 0, b) 1, c) 2 and d) 3 mA/mm2 are applied.

Thermal patterns generated by the heater matrix on a thermal paper.

For the first time, polymer semiconductor diode matrix is used for thermal patterning. The system can generate thousands of individually addressable hotplates (diodes) to generate thermal gradients or hot spots  for chemical and biological reactions.

Generated patterns on the wall using steel scanner (In collaboration with A.D. Yalcinkaya)

Experimental Setup for the steel scanner (In collaboration with A.D. Yalcinkaya)

Examples of Steel Micro Scanners

Fabricated two-axis steel scanner

Realization  of Charge Pump Circuits Using Polymer Diodes

Schematic representation of a single stage AC to DC charge pump

DC Vout vs. frequency plots for various AC Vin values.

 

Polymer diodes made of P3HT are used to build an AC to DC charge pump circuit. Circuit’s  frequency response and charge-up time is measured. 

Solution State Diode Using Semiconductor Polymer Nanorods with Nanogap Electrodes

Certain semiconductor polymers such as P3HT stay as nanorods inside its solvent. These nanorods  are used inside its solution with electrodes, which have nanogaps that are longer than the lengths of the nanorods. This forms a diode with a higher mobility since intra-chain conduction dominates instead of hopping enabled inter-chain conduction.

Demonstration of the device. P3HT nanorods in solution forms a diode between electrodes with nanogap

SEM picture of Al and Si electrodes with nanogap formed by SiO2.

Setup for the experiments. Dipping the electrodes with nanogap into the solution is enough to form a diode.

I-V curve of a diode is seen only when the electrodes with nanogap are dipped into the polymer solution, not in air or in solvent.

Planar Water Gated Organic Field Effect Transistor Using Hydrophilic Polythiophene for Improved Digital Inverters

Operation of a planar water gated OFET is demonstrated for the first time. P3HT is functionalized with poly(ethylene glycol) to make it more hydrophilic. Double layer gate capacitance increases 1.8 times with hydrophilic polythiophene. Transconductance triples by using 100 mM NaCl solution instead of DI water. Inverters are build with a gain of 10 V/V using OFETs with best transconductances.

Hydrophilic

P3HT-co-P3PEGT

Planar Water Gated OFET Structure

Photograph of a fabricated planer water-gated OFET

Molecular structures of P3HT-co-P3PEGT

Voltage transfer characteristics of fabricated inverter utilizing P3HT-co-P3PEGT for different electrolyte solutions

Hexyl side chain

Polyethylene glycol (PEG) side chain

Light Emitting Diode as a Power Supply for Wireless and Batteryless Microsystems

A light emitting diode (LED) is used as a power supply to a wireless and batteryless microsystem for the first time. Three different application specific integrated circuits (ASIC) are designed, were manufactured and tested for this purpose. The microsystem can be powered optically through LED and  transmit its data optically using the same LED. This work is published in JMEMS.

Photo of an implemented microsystem

Optically received data from 10 cm, using a transimpedance amplifier based photodetector circuit built in-house.

Conceptual representation of the optically powered and optically transmitting microsystem using a single light emitting diode.

We made a presentation at ISSCC 2016:

ISSCC (International Solid-State Circuits Conference) is the flagship conference of the IEEE Solid-State Circuits Society. The semiconductor industry generated about $290 billion in sales in 2012. ISSCC is one of the premier technical forum for presenting advances in solid-state circuits and systems. Around 3000 people from academia and industry attend ISSCC. Corporate attendees from the semiconductor and system industries typically represent around 60% of the attendees.

I. Haydaroglu, M. Ozgun, Senol Mutlu, Presentation, 2016 International Solid State Circuits Conferene (ISSCC) Student Research Preview session (Student work in progress), Jan. 31-Feb. 4, San Francisco, CA.

We designed and tested a wireless and batteryless IC that uses a single light emitting diode (LED) to efficiently harvest optical energy and transmit data concurrently. LED voltage is sufficient to sustain continous opetation at 6 uW. A switched capacitor boosting driver pulses current through the LED to transmit data with 1 nJ/bit, recorded by an on-chip temperature sensor. This can be received externally from a 10 cm distance using an external  photodetector with transimpedance amplifier.

 

Current density vs voltage plots for commercial silicon PIN diode, 770 nm LED, and silicon photodiode under 68 mW/mm2 (120 mW power with a spot size of 1,5 mm diameter) 680 nm laser illumination. Corrected for effective device area; 1.2mm2 for s2386, 0.12mm2 for s5973 and 0.1mm2 for LED.

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Published in Nature.com/Scientific Reports: Water-Gated Field Effect Transistor (WG-FET) Using 16-nm-Thick Mono-Si Film

We introduced a novel water-gated field effect transistor (WG-FET) which uses 16-nm-thick mono-Si film as active layer. WG-FET devices use electrical double layer (EDL) as gate insulator and operate under 1 V without causing any electrochemical reactions.  Best on/off ratios are measured for probe-gate devices as 23,000 A/A and 85,000 A/A with insulated and uninsulated source-drain electrodes, respectively.

Photo of an implemented microsystem

A micrograph of a fabricated WG-FET device with planar-gate topology and Experimental setup for current-voltage measurements.

An illustration of a WG-FET device with source-drain electrode insulation

IDS-VDS measurement results for probe gate setup without source-drain electrode insulation. VGS is swept from 0 V to -1 V.